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  • 1.
    Tian, Simeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Petrie-Repar, Paul
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Sun, Tianrui
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    CFD-Aided Design of a Transonic Aeroelastic Compressor Rig2019In: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 141, no 10, article id 101003Article in journal (Refereed)
    Abstract [en]

    This paper presents the results of computational fluid dynamics (CFD)-aided design calculations of a transonic linear cascade wind tunnel. The purpose of the wind tunnel is to generate data for the validation of numerical methods employed to calculate aerodynamic damping for forced response cases in transonic compressors. It is common for transonic wind tunnels to use transonic walls (perforated walls with controlled suction) to adjust the transonic flow in the experiment. Unfortunately, perforated walls are difficult to model in CFD simulations, and they complicate the validation process. One of the goals of the new tunnel is not to use perforated walls. The main difficulty in the design of a transonic linear cascade is achieving periodic flow for the central blades due to shock reflections from the side walls and the sensitivity of transonic flow to small changes in geometry. Other design constraints are the maximum available mass flow of 4.5 kg/s and the minimum required blade thickness of 2 mm for instrumentation. The purpose of the current CFD simulations is to determine the optimum geometry (sidewalls, tailboards, and throttle) of the tunnel with the goal of achieving near periodic flow conditions for the central blade channels at the similar condition in a typical transonic compressor.

  • 2.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Bartelt, Michael
    Vogt, Damian
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aeroelastic Properties of Combined Mode Shapes in an Oscillating LPT Cascade2009Conference paper (Refereed)
  • 3.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Tavera Guerrero, Carlos
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gutierrez, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aeroelastic Response of a Transonic Compressor Cascade at High Reduced Fequencies2022In: Proceedings of ISUAAAT16, 2022Conference paper (Refereed)
    Abstract [en]

    The present work focuses on experimental and numerical investigations of the unsteady response in a transonic compressor cascade oscillating at high-reduced frequencies. An attempt is made to highlight the main features that drive the unsteady response on the cascade blades. The operating point set in the rig is representative for modern transonic compressors, with a supersonic inflow and oblique shock waves forming at the leading edge of the blades. The cascade consisting of five blades, has been operated in the influence coefficient domain, where the central blade 0 is excited to oscillate in its natural modes of vibration. The investigated modes are mode 3, 4 and 7, with a reduced frequency ranging from 2.08 to 4.55. Steady aerodynamics in the rig has been assessed by measuring the static pressure distributions on the blade and Laser-Two-Focus (L2F) flow field measurements within the central two passages of interest. The aeroelastic testing data indicated that the unsteady blade surface pressure response is mainly driven by the position and relative motion of the shock waves, caused by the blade oscillation. Unsteady response distributions are fairly similar for modes 3 and 4, with some observed differences when compared to mode 7 response. The preliminary results from unsteady simulations qualitatively correspond quite well to the test data, and the main trends are overall well captured both in amplitude and phase. The parametric studies on sensitivity of the numerical solution are ongoing.

  • 4.
    Chalke, Akshay Prafulla
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gutierrez, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aeroelastic Tailoring of Compressor Blades2022In: ICAS PROCEEDINGS of 33th Congress of the International Council of the Aeronautical Sciences, Stockholm, Sweden, Stockholm, 2022Conference paper (Refereed)
    Abstract [en]

    Paper explores the potential of using carbon-fibre reinforced composites for designing low-pressure compressor blades with improved aeroelastic performance. Comparison between the blades with different laminate  stackups is made with respect to the modal behaviour and aerodynamic damping. It is found that if carefully designed, the composite blades can provide higher aeroelastic stability than the reference metallic blade. At the same time the results reveal that a laminate stackup with stabilizing behaviour in one mode could have a destabilizing effect for the other mode. The dependency on ply angle and arrangement of plies in laminates is observed to be complex and furtheri nvestigations and experimental validation is therefore deemed necessary.

  • 5.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Tavera Guerrero, Carlos
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gutierrez, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Blade oscillation mechanism for aerodynamic damping measurements at high reduced frequencies2022In: E3S Web Conf.Volume 345, 2022XXV Biennial Symposium on Measuring Techniques in Turbomachinery (MTT 2020), 2022, Vol. 345, article id 03002Conference paper (Refereed)
    Abstract [en]

    Accurate prediction of aerodynamic damping is essential for flutter and forced response analysis of turbomachinery components. Reaching a high level of confidence in numerical simulations requires that the models have been validated against the experiments. Even though a number of test cases have been established over the past decades, there is still a lack of suitable detailed test data that can be used for validation purposes in particular when it comes to aero damping at high reduced frequencies which is more relevant in the context of forced response analysis. A new transonic cascade test rig, currently undergoing commissioning at KTH, has been designed with the goal to provide detailed blade surface unsteady pressure data for compressor blades profiles oscillating at high reduced frequencies. The paper provides an overview of the blade actuation system employed in the test rig and presents the result of a series of bench tests characterizing the blade vibration amplitudes achieved with this actuation system.

  • 6.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gutierrez, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Franke, Daniel
    Technical University of Darmstadt Darmstadt, Germany.
    Tavera Guerrero, Carlos
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Klausmann, Fabian
    Technical University of Darmstadt Darmstadt, Germany.
    Bringing turbomachinery aeromechanics research closer to education2022In: ISUAAAT16, 2022, no 10Conference paper (Refereed)
    Abstract [en]

    The paper presents experiences from an international student project course in turbomachinery aeromechanics, which has been established within the framework of the H2020 research project ARIAS (“Advanced Research Into Aeromechanical Solutions”). The main activities, challenges, and lessons learned from the students’ feedback and instructors’ experience from 2020 to 2022 are presented from an educational point of view. A key goal of the aeromechanic project course (APC) is to strengthen the link between education and research based on multinational collaborative work. The course focuses on gradually enabling the students to perform a forced response analysis within one academic semester. This is achieved by providing the necessary fundamentals as well as training and application of interdisciplinary tools to investigate structural and aerodynamic effects. The course is based on online lectures, tool-specific tutorials, literature reviews, and guest lectures. The students work via web-based communication in international teams conducting various numerical analyses to determine distinct influences on forced response phenomena at the ARIAS TUDa transonic compressor. Metrics regarding the course structure, quality, project rating, and students’ feedback are obtained via an anonymous survey. The shown collaborative results and conclusions presented by the students display that the gap between theoretical knowledge and application is reduced.

  • 7.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Vogt, Damian
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical investigation of mistuned aerodynamic influence coefficients in an oscillating LPT cascade2012In: Proceedings of the ASME Turbo Expo, New York: American Society of Mechanical Engineers , 2012, p. 1355-1367Conference paper (Refereed)
    Abstract [en]

    The effect of aerodynamic mistuning on the aerodynamic damping in an oscillating Low-Pressure Turbine (LPT) cascade is investigated. The considered aerodynamic mistuning is caused by blade-to-blade stagger angle variations. The study is carried out experimentally and numerically by employing the influence coefficient method. On the experimental side a sector cascade is used where one of the blades is made oscillating in three orthogonal modes. The unsteady blade surface pressure is acquired on the oscillating blade and two neighbour blades and reduced to aeroelastic stability data. By gradually de-staggering the oscillating blade, aerodynamically mistuned influence coefficients are acquired. On the numerical side full-scale time-marching RANS CFD simulations are performed using nominal and de-staggered blades. The study shows that variations in blade-to-blade stagger angle affect the aerodynamic influence coefficients and as a consequence overall aeroelastic stability. Whereas discrepancies are found in the exact prediction of mistimed influence coefficients compared to measured, the overall magnitude and trends are well captured.

  • 8.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Vogt, Damian
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Influence of Tip Clearance Modelling in Predictions of Aeroelastic Response in an Oscillating LPT Cascade2012Conference paper (Refereed)
    Abstract [en]

    The present study investigates the influence of tip clearance modelling in predictions of the aeroelastic response in an oscillating Low-Pressure Turbine (LPT) cascade. The study was carried out through validation of different numerical models against experimental data. On the experimental side a sector cascade was used, where one of the blades was oscillated in axial bending mode. Unsteady pressure measurements were performed at several spanwise positions on the non-oscillating blades and at mid-span of the oscillating blade. On the numerical side full-scale time-marching RANS CFD simulations were performed employing models with and without tip clearance. The study showed that the model without tip clearance provides reliable result up to 70%. In the near-tip region difference induced due to the absence of tip clearance in the model amounts to about 25% of minimum stability value, relative to the nominal tip clearance model. It has also been shown that the resolution of the tip clearance mesh in spanwise direction of the gap might have a considerable impact of prediction accuracy. Imposed small variations in the tip clearance size have not led to substantial changes in predicted aeroelastic response of the cascade.

  • 9.
    Grönstedt, Tomas
    et al.
    Chalmers University of Technology, Sweden.
    Xisto, Carlos
    Chalmers University of Technology, Sweden.
    Zhao, Xin
    Chalmers University of Technology, Sweden.
    Jonsson, Isak
    Chalmers University of Technology, Sweden.
    Reinap, Avo
    Lund University, Sweden.
    Genrup, Magnus
    Lund University, Sweden.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gutierrez Salas, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Lejon, Marcus
    GKN Aerospace, Sweden.
    Avellán, Richard
    GKN Aerospace, Sweden.
    Mårtensson, Hans
    GKN Aerospace, Sweden.
    MULTIDISCIPLINARY ASSESSMENT OF A YEAR 2035 TURBOFAN PROPULSION SYSTEM2022In: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022, International Council of the Aeronautical Sciences , 2022, p. 4981-4990Conference paper (Refereed)
    Abstract [en]

    A conceptual design of a year 2035 turbofan is developed and integrated onto a year 2035 aircraft model. The mission performance is evaluated for CO2, noise and NOx and is compared with a notional XWB/A350-model. An OGV heat exchanger is then studied rejecting heat from an electric generator, and its top-level performance is evaluated. The fan, the booster and the low-pressure turbine of the propulsion system are subject to more detailed aero design based on using commercial design tools and CFD-optimization. Booster aerodynamic modelling output is introduced back into the performance model to study the integrated performance of the component. The top-level performance aircraft improvements are compared to top-level-trends and ICAO estimates of technology progress potential, attempting to evaluate whether there is some additional margin for efficiency improvement beyond the ICAO technology predictions for the same time frame.

  • 10. Lejon, M.
    et al.
    Grönstedt, T.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Petrie-Repar, Paul
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Genrup, M.
    Mann, A.
    Multidisciplinary design of a three stage high speed booster2017In: Proceedings of the ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, GT 2017, ASME Press, 2017, Vol. 2B, article id UNSP V02BT41A037Conference paper (Refereed)
    Abstract [en]

    The paper describes a multidisciplinary conceptual design of an axial compressor, targeting a three stage, high speed, high efficiency booster with a design pressure ratio of 2.8. The paper is outlined in a step wise manner starting from basic aircraft and engine thrust requirements, establishing the definition of the high speed booster interface points and its location in the engine. Thereafter, the aerodynamic 1D/2D design is carried out using the commercial throughflow tool SC90C. A number of design aspects are described, and the steps necessary to arrive at the final design are outlined. The SC90C based design is then carried over to a CFD based conceptual design tool AxCent, in which a first profiling is carried out based on a multiple circular arc blade definition. The design obtained at this point is referred to as the VINK compressor. The first stage of the compressor is then optimized using an in-house optimization tool, where the objective functions are evaluated from detailed CFD calculations. The design is improved in terms of efficiency and in terms of meeting the design criteria put on the stage in the earlier design phases. Finally, some aeromechanical design aspects of the first stage are considered. The geometry and inlet boundary conditions of the compressor are shared with the turbomachinery community on a public server. This is intended to be used as a test case for further optimization and analysis.

  • 11.
    Tavera Guerrero, Carlos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mårtensson, Hans
    GKN Aerospace Sweden AB, Trollhättan, Sweden.
    STEADY-STATE AERODYNAMICS TIP GAP INFLUENCE IN A TRANSONIC LINEAR CASCADE AT NEAR STALL2022In: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022, International Council of the Aeronautical Sciences , 2022, p. 2131-2140Conference paper (Refereed)
    Abstract [en]

    A comparison of steady-state aerodynamics for two tip gap configurations in the KTH transonic linear cascade is presented. The experimental campaign is performed for 1% and 2% tip clearances. The operational point is representative of an open-source virtual compressor (VINK) operating near stall at part speed. The inlet Mach number (M ≈ 0.81) is above its airfoil critical value with a high incidence angle, producing a leading-edge separation bubble. The measurement plane is at 85% span for each tip gap configuration. Steady-state aerodynamic measurements are presented at the passage and downstream the blades. The blade loading at the passages of interest is mapped by a set of instrumented blades containing 15 pressure taps. The downstream conditions are reconstructed by five-hole probe measurements. Numerical results are computed by the commercial software ANSYS CFX. A comparison of experimental and numerical data is presented to identify correlations and limitations. The scope of this paper is to experimentally and numerically determine the influence of tip gap variation in the steady-state aerodynamics in a transonic linear cascade where leading-edge separation occurs.

  • 12.
    Tavera Guerrero, Carlos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Hans, Mårtensson
    GKN Aerospace Sweden AB.
    Steady-state aerodynamics tip gap influence in atransonic linear cascade at near stall2022Conference paper (Refereed)
    Abstract [en]

    A comparison of steady-state aerodynamics for two tip gap configurations in the KTH transonic linear cascade is presented. The experimental campaign is performed for 1% and 2% tip clearances. The operational point is representative of an open-source virtual compressor (VINK) operating near stall at part speed. The inlet Mach number (Mach 0:81) is above its airfoil critical value with a high incidence angle, producing a leading edge separation bubble. The measurement plane is at 85% span for each tip gap configuration. Steady-state aerodynamic measurements are presented at the passage and downstream the blades. The blade loading at the passages of interest is mapped by a set of instrumented blades containing 15 pressure taps. The downstream conditions are reconstructed by five-hole probe measurements. Numerical results are computed by the commercial software ANSYS CFX. A comparison of experimental and numerical data is presented to identify correlations and limitations. The scope of this paper is to experimentally and numerically determine the influence of tip gap variation in the steady-state aerodynamics in a transonic linear cascade where leading edge separation occurs.

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  • 13.
    Vogt, Damian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    The Effect of Unsteady Aerodynamic Asymmetric Perturbations on the Mode Shape Sensitivity of an Oscillating LPT Cascade2009Conference paper (Refereed)
  • 14.
    Tavera Guerrero, Carlos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Groth, Pieter
    GKN Aerospace Sweden AB, Trollhättan, Sweden.
    Validation of Steady-State Aerodynamics in a Transonic Linear Cascade at Near Stall Conditions2022In: Proceedings of the ASME Turbo Expo, ASME International , 2022Conference paper (Refereed)
    Abstract [en]

    A new set of steady-state aerodynamics data from the recently build KTH transonic linear cascade (TLC) is presented. The operational point is representative of an open source virtual compressor (VINK) operating near stall at 70% speed line. The inlet Mach number (M = 0.81) is above its airfoil critical value with high incidence angle, producing a leading edge separation bubble. The test object in the TLC has a 2% tip gap, and the reference measurement plane is at 85% span. Results show repeatability, and periodicity. Upstream flow field was mapped by a non-intrusive, Laser-2-Focus (L2F) method. The blade loading was recovered by a set of pressure taps. Flow field properties downstream the test section were recovered by a five-hole probe. A flow structures comparison was performed between numerical and experimental data. Numerical results were obtained from the commercial software Ansys CFX, where different turbulence models were tested: SST, SST with reattachment method (RM) and SST with turbulent transition (γ - θ). The closest match to the experimental data was recovered by SST-γ - θ RM. Separation onset and flow properties downstream are strongly affected by the selected turbulence transition model. The results are aimed to work as step towards validation for CFD in separated regions. These data is the first of a series of test campaigns for experimental validation for aerodynamic damping in separated flows. 

  • 15.
    Tavera Guerrero, Carlos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gutierrez, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mårtenson, Hans
    GKN Aerospace Sweden AB.
    Validation of unsteady aerodynamics in a transonic linear cascade at first flex modeshape at near stall conditions2022Conference paper (Refereed)
    Abstract [en]

    Experimental and numerical, are presented in the transonic linear cascade (TLC) at KTH. Numerical results are recovered by SST turbulence model with a reattachment modification (RM) from commercial software Ansys CFX. This paper aims to compare the current numerical methods as a step towards producing open data for validation purposes. The operational point is representative of an open source virtual compressor (VINK) operating near stall at part speed, with an induced leading edge separation bubble at an inlet Mach number of 0.81. Steady-state results consists of Laser-2-Focus anemometer (L2F), blade loading, flow visualization and five-hole probe measurements. Steady-state numerical results indicate an over prediction of low momentum regions in the passages and under prediction of a separation bubble. The cascade operates in the influence coefficient domain, where the central blade vibrates in its first natural mode shape with 0.69 reduced frequency. Unsteady pressure coefficients display an amplitude discrepancy between methods. Numerically, the unsteady pressure content at the measurement plane (85% span) is dominated by the oscillation of the tip leakage vortex, which is not observed from experimental data. Despite a qualitative mismatch with the unsteady  pressure amplitude, the phase- lag shows good agreement between both methods, which is of high relevance when predicting the aerodynamic damping.

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  • 16.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Sensitivity of Aeroelastic Properties of an Oscillating LPT Cascade2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Modern turbomachinery design is characterized by a tendency towards thinner, lighter and highly loaded blades, which in turn gives rise to increased sensitivity to flow induced vibration such as flutter. Flutter is a self-excited and self-sustained instability phenomenon that may lead to structural failure due to High Cycle Fatigue (HCF) or material overload. In order to be able to predict potential flutter situations, it is necessary to accurately assess the unsteady aerodynamics during flutter and to understand the physics behind its driving mechanisms. Current numerical tools used for predicting unsteady aerodynamics of vibrating turbomachinery components are capable of modeling the flow field at high level of detail, but may fail in predicting the correct unsteady aerodynamics under certain conditions. Continuous validation of numerical models against experimental data therefore plays significant role in improving the prediction accuracy and reliability of the models.

     

    In flutter investigations, it is common to consider aerodynamically symmetric (tuned) setups. Due to manufacturing tolerances, assembly inaccuracies as well as in-service wear, the aerodynamic properties in a blade row may become asymmetric. Such asymmetries can be observed both in terms of steady as well as unsteady aerodynamic properties, and it is of great interest to understand the effects this may have on the aeroelastic stability of the system.

     

    Under certain conditions vibratory modes of realistic blade profiles tend to be coupled i.e. the contents of a given mode of vibration include displacements perpendicular and parallel to the chord as well as torsion of the profile. Current design trends for compressor blades that are resulting in low aspect ratio blades potentially reduce the frequency spacing between certain modes (i.e. 2F & 1T). Combined modes are also likely to occur in case of the vibration of a bladed disk with a comparatively soft disk and rigid blades or due to tying blades together in sectors (e.g. in turbines).

     

    The present investigation focuses on two areas that are of importance for improving the understanding of aeroelastic behavior of oscillating blade rows. Firstly, aeroelastic properties of combined mode shapes in an oscillating Low Pressure Turbine (LPT) cascade were studied and validity of the mode superposition principle was assessed. Secondly, the effects of aerodynamic mistuning on the aeroelastic properties of the cascade were addressed. The aerodynamic mistuning considered here is caused by blade-to-blade stagger angle variations

     

    The work has been carried out as compound experimental and numerical investigation, where numerical results are validated against test data. On the experimental side a test facility comprising an annular sector of seven free-standing LPT blades is used. The aeroelastic response phenomena were studied in the influence coefficient domain where one of the blades is made to oscillate in three-dimensional pure or combined modes, while the unsteady blade surface pressure is acquired on the oscillating blade itself and on the non-oscillating neighbor blades. On the numerical side, a series of numerical simulations were carried out using a commercial CFD code on a full-scale time-marching 3D viscous model. In accordance with the experimental part the simulations are performed using the influence coefficient approach, with only one blade oscillating.

     

    The results of combined modes studies suggest the validity of combining the aeroelastic properties of two modes over the investigated range of operating parameters. Quality parameters, indicating differences in mean absolute and imaginary values of the unsteady response between combined mode data and superposed data, feature values that are well below measurement accuracy of the setup.

     

    The findings of aerodynamic mistuning investigations indicate that the effect of de-staggering a single blade on steady aerodynamics in the cascade seem to be predominantly an effect of the change in passage throat. The changes in steady aerodynamics are thereby observed on the unsteady aerodynamics where distinctive effects on flow velocity lead to changes in the local unsteady pressure coefficients. In order to assess the overall aeroelastic stability of a randomly mistuned blade row, a Reduced Order Model (ROM) model is introduced, allowing for probabilistic analyses. From the analyses, an effect of destabilization due to aero-asymmetries was observed. However the observed effect was of moderate magnitude.

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  • 17.
    Tian, Simeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Gutierrez Salas, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Tavera Guerrero, Carlos
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Design, Optimization and Evaluation of a Transonic AeroelasticrigManuscript (preprint) (Other academic)
    Abstract [en]

    Modern transonic compressors face challenges in the forced response investigations due to the lack of experimental validations. A new transonic aeroelastic rig was built to validate simulations on aerodynamic damping predictions at high-reduced frequencies. For simplicity, the transonic linear compressor cascade uses the influence coefficient vibration method where only one blade vibrates in a controlled manner. The design introduces the whole iteration process, starting from the initial design ideas to the evaluation, where reassess on modifications are also considered. The design has led to a test section designed with CFD-aided optimizations, a transonic nozzle based on the Foelsch method, a mechanical design obtained with experimental data input, and a vibration setup with piezoelectric actuators. Additionally, a promising periodic flow was obtained in the optimal design, and the impact of different factors of the test rig was analyzed. The evaluation section contains the discussion on the unsteady performance, on the lateral walls, tailboards, and around each blade, due to three different mode shapes oscillating at their frequency. The unsteady evaluation also provides several recommendations on the rig design and testing.

  • 18.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Deshpande, Srikanth
    GKN Aerospace AB.
    Gallardo Antolin, Juan Manuel
    ITP Aero.
    Setchfield, Richard
    Rolls Royce plc.
    D'Ettole, Antonio Giuseppe
    Avio Aero.
    ARIAS project- Summary of project results2023Other (Other academic)
    Abstract [en]

    The present report contains the summary of project activities and main achievements of the ARIAS project. It starts with a brief overview of the project goals and objectives, breaking these down on a WP level. A description of each subtask in the work package with its specific objectives is included, providing the necessary background for the interpretation of the results. The main results and achievements of each project's tasks are thereafter highlighted.

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  • 19.
    Vedin, Felix
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Sandström, Camilla
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    A comparison study of PV and battery technologies for EWB off-grid electrification projects in Sub-Saharan Africa2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Only 10 % of the rural population in Sub-Saharan Africa has access to electricity. At the same time the Sub-Saharan countries are close to the equator and get many sun hours a day, leading to a huge potential for solar energy. This report aims to compare different PV system components for use in Sub-Saharan Africa to facilitate EWB for their work in electrification projects in the areas. The PV system will be compared with the following factors: economic, adoptability, scalability, environmental impact and efficiency, weighed in that order. A case simulation was made for a village around Nairobi were 20 households would be supplied with solar power. Both Polycrystalline silicon cells and thin filmed CIGS were simulated were the Poly c-Si cell was both the cost-efficient and scalable choice. Poly c-Si cells was also concluded to be advantageous of the crystalline cells by the chosen factors. Pb-acid batteries are best suited for off grid PV systems in rural areas. Different types of Pb-acid batteries can be used depending on the area’s typology. Off grid solar powered microgrids could be the solutions for an increased socioeconomic wellbeing for communities in rural areas.

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  • 20.
    Stjernquist, Marie
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    A study on the placement of turbines downstream of a hydroelectric power station2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Human energy related activity has increased the carbon dioxide concentration in the atmosphere by 40 % since the preindustrial area. A leading contributor to this is the burning of fossil fuels in order to extract energy. Due to this, we are today facing many issues following climate change and global warming. The search for renewable energy sources is therefor of outmost importance. The biggest renewable energy source today is hydropower. It is big in newly industrialized countries such as China and Brazil, where in the latter it covers over 70% of the electricity supply. A relatively unexplored area is the implementation of turbines in the downstream of a hydroelectric power station. The risk here is that the turbine[s] will increase the water depth and hence impact the hydraulic head i.e. the potential power of the hydro power station negatively This report explores the potential and optimal placement of a turbine/ turbine fences in the downstream by using the Bernoulli equation. Two different cases are examined. The geometry in the first one is a finite uniform channel whereas in the second one it is a finite divergent channel. The equations for the two different cases will also vary, mainly in the expression of the friction loss. It is shown that the choices of expression for the friction loss and geometry are important for the results as the two cases gave different results. However, the second approach is supposed more accurate and shows that the closer the beginning of the channel the more power can be extracted but this also means an increase in water depth. For some flows and turbine diameters a turbine fence was also placed further on, hence departed from the expected result. This shows the complexity of the problem and the importance of an optimization model.

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  • 21.
    Dass Naidu, Aravin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    AERODYNAMIC FORCING & DAMPING COMPUTATIONS IN A TRANSONIC AXIAL TURBINE OF A TURBOCHANRGER USING TIME & FREQUENCY DOMAIN FLOW TRANSFORMATION TECHNIQUES2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The current report discusses efficient and accurate numerical techniques to evaluate aerodynamic disturbance and damping forces based on investigations carried out at ABB Turbo System AG. The test turbomachine comprises a single-stage transonic axial turbine analysed with the fluid dynamic software ANSYS CFX 17.0 and post-processing tool Matlab. In the first stage, the 23 unequally spaced stators 33 rotors turbine configuration was scaled to two configurations with 22 and 24 equally spaced stators respectively and 33 rotors. These configurations permit integer reduction of blade count across adjacent blade rows and as such a reduced computational domain. An innovative time domain signal patching routine was implemented to recover the original 23 stators 33 rotors blade forces in the cylindrical direction and generalised force from the 22 and 24 stators configurations with reasonable accuracy. Computational savings of 57.5% were enabled with such an approach. To further reduce computational demand, the two configurations with 22 and 24 equally spaced stators were simulated with time domain flow field transformation methods; profile transformation, time inclination and Fourier method. A comparison of total blade and midspan forces in cylindrical direction, generalised force and local unsteady pressures demonstrated the capacity of the time inclination and Fourier methods to capture harmonic data within an accuracy of 15%. Moreover these time domain flow field transformation methods when used in conjunction with the signal patching routine allowed for computational savings larger than 93%. In the second stage, two different strategies to extract aerodynamic damping forces were compared. The first termed aerodynamic influence coefficient method (AIC) takes into account the aerodynamic influence of an oscillating blade on neighbouring blades in a blade row was introduced. This approach enables a single numerical simulation for the construction of an aerodynamic damping curve. The second approach involves simulating each travelling wave mode and extracting the corresponding unsteady aerodynamic work for damping derivation termed as the energetic approach (EA). An evaluation into the accurate set-up of the AIC method indicated the need to run a full 33 rotors simulation without the assignment of spatial periodic boundaries to limit false boundary settings. Moreover, the influence across 23 of the blades needed to be asses to obtain an accurate aerodynamic damping curve. The energetic approach was carried out using a simple transient method, the time domain flowfield transformation Fourier method and the time/frequency domain flowfield transformation harmonic balance method. Both the Fourier and harmonic balance methods predicted identical aerodynamic damping values to the transient case at three interblade phase angles with large computational savings. However, instabilities at backward travelling waves for the harmonic balance limited its application. Identical aerodynamic damping predictions with the AIC method, energetic approach with Fourier method and harmonic balance methods verified three numerical aerodynamic damping prediction approaches. A comparison of computational cost however suggests that the Fourier and harmonic balance methods are more efficient techniques for future damping computations.

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  • 22.
    Citoleux, Lucas
    KTH, School of Industrial Engineering and Management (ITM).
    Aerodynamic studies of the flutter behavior of a compressor jet engine: Establishment of 1D criteria for the appearance of flutter within low pressure compressors2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Turbojet compressors are subject to numerous vibration phenomena that limit their good operability. Among these different phenomena, flutter is a major concern during the study and design phase. This aeroelastic instability can have an impact on the correct operation of the compressor. The precise reasons for the appearance of this phenomenon remain relatively unknown today. 

    This thesis aims to study the flutter phenomenon in turbojet compressors. The objective set for this internship is to reproduce the stationary aerodynamic configurations observed during turbomachinery compressor tests using 2D and 3D computer calculation tools. A first phase of bibliographic research was done to know more on the theory of flutter in compressors as well as to highlight the already existing works on the subject. Then, computer modeling was carried out on a compressor testing that showed flutter. Thanks to these simulations, different criteria were defined from the calculations and the analysis of results. 

    The final objective of this internship is therefore to know more precisely the various factors of appearance of the self-induced flutter within the compressors, in order to introduce and/or improve criteria to avoid this phenomenon in the future when designing new compressors.

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  • 23.
    Lamouroux, Julien
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aeroelastic forced response of a bladed drum from a low pressure compressor2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this master thesis is to provide a reliable methodology to predict the forced response of a monoblock bladed drum from a low pressure compressor. Pre-test forced response calculations have already been made at Techspace Aero in 2013. Now that experimental data are available, the methodology has to be adapted to ensure the best numerical-experimental correlation possible. The final goal is that, at the end of the thesis, engineers at Techspace Aero will be able to launch reliable forced response simulations within a short amount of time. For the sake of confidentiality, some data are not revealed, such as the engine name, some numerical values (forced response, aerodynamic damping, frequency of the mode etc…) and axis scales.

    In this paper, the study focuses on the forced response of a rotor blade from the first stage under the excitation from the upstream stator. The mode under investigation is the 2S2, the one that responded during the experiment. The TWIN approach is used to compute the forced response of the rotor blade. With this approach, a steady stage computation has first to be carried on as an initialization. Then two unsteady computations are necessary. The first, without blade motion, will provide the excitation aerodynamic forces. The aerodynamic damping will be extracted from the second one, where the motion of the blade is imposed on a given eigenmode. The forced response can then be computed with these two results and some additional structural data.  The results will be compared to the experimental value.

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  • 24.
    VILLENEUVE, Baptiste
    KTH, School of Industrial Engineering and Management (ITM).
    Aeroengine transients in altitude test facility2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Altitude test facilities offer a safe and reliable way to perform a wide variety of tests on aircraft engine. Among them, aeroengine transients represent a necessary step in the certification and qualification of engines. Mission requirements for military aircraft impose fast variations of the engine regime requiring large and complex testing facilities. These facilities are expected to allow large variations of mass flow rate in a short period: from 25 𝑘𝑔/𝑠 to about 100 𝑘𝑔/𝑠 in less than 10 seconds. Besides, the facilities must perform these fast transients at pressure conditions above and below atmospheric pressure, thus requiring large industrial equipment and machinery. 

    In this context, this study aims to create a physical model of the air network at Direction Générale de l’Armement Essais Propulseurs (DGA EP) to replicate aeroengine transient testing of a military aircraft engine, using a 0D/1D simulation software: Simulink. The model relies on the geometry of the network, previous studies carried out on the centre and test data provided by DGA EP. Elements of the upstream part of the test bed (pipes, bends, grid…) and the regulation system (valves, bypass network) are represented in the model. The modelling of Plenum C is put aside because of the complex phenomena occurring inside, which would be too demanding considering the time allowed for this project.

     A two-dimensional axisymmetric geometry of a test bed was created and a transient manoeuvre is finally simulated using Computational Fluid Dynamics (CFD) to observe other aerodynamic phenomena occurring during testing. Results are compared with the 0D/1D simulation software to assess the validity of the linearization of fluid mechanics equations done by Simulink. The independence of the position of the sensors inside Plenum A is also shown in this study.

     This project has shown the ability to reproduce test data during aeroengine transient manoeuvres using Simulink. Further work on the model could allow making predictions on the behaviour of the network leading to improvements in transient testing at DGA EP by adapting regulation strategies.

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  • 25.
    Trellu, Antonie
    KTH, School of Industrial Engineering and Management (ITM).
    Analysis of vibration stability phenomena in jet engines2024Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This degree project, conducted at SAFRAN AIRCRAFT ENGINES in France, focuses on vibration phenomena in aircraft engines. Rotor parts of jet engine rotate at high speeds and generate considerable vibrations to the structure. Overall mechanics studies the dynamic behavior of the whole engine with regard to safety and performance criteria.

    For an engine in particular, bi-stability was observed. This phenomenon refers to the appearance of two stable vibratory states, with a high and a low state, at a given engine speed. This behavior can generate alarms when it exceeds the tolerated thresholds.

    In this study, test data will be analyzed to determine the parameters responsible for the appearance of this phenomenon. Then, a scenario will be proposed to finally model this phenomenon using numerical tools. Harmonic and transient calculations will be carried out to reproduce the phenomenon seen in tests.

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  • 26.
    Yang, Shu
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    CFD Investigation of aeromechanic FORCING sensitivity for a generic transonic turbine2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Aeromechanic problems occur in various disciplines, the research here is focused on turbomachinery.  Advanced design criteria and accurate prediction methods for aeromechanic problems such as forced response and flutter become increasingly important with the present demand in turbomachine engine development towards lighter, cheaper, more efficient and reliable turbomachines. The aeromechanic analysis made at a late stage in the design process plays a crucial role to avoid failures. The present work aims at getting a better understanding of the aerodynamic mechanisms in transonic turbine stages and further development of numerical methods for stator-rotor interaction predictions.

     

    In this work standard industry tools are used for forced response computations for a one stage transonic high pressure turbine. Different configurations namely a tip shroud cavity, a hub cavity and external purge flow have been studied numerically to evaluate the influences on blade forcing predictions. CFD results are compared for all the cases with different features in both steady and unsteady state. Blade loading and integrated blade forcing are examined and physical interpretations of flow field features are given.

     

    The investigation shows that including detailing features has a significant influence on the aerodynamic forcing. Leakage flow going through the tip shroud cavity is approximately 4.0% of the main passage flow. The first harmonic of rotor circumferential forcing is reduced by 19.8% when including the hub cavity. The tip shroud cavity feature tends to increase the unsteady aerodynamic forcing for the rotor blade despite of the slightly different operating conditions. The external purge flow has been proven to have a relative difference of 1.1% on the rotor blade forcing. The change in forcing is considered to arise from the interaction between the cavity flow and the main passage flow. 

  • 27.
    Kumlu, Armagan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    CFD INVESTIGATION OF IMPELLER DIFFUSER INTERACTION EFFECTS ON RADIAL COMPRESSOR STAGE2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The effects of impeller-diffuser interaction are investigated through numerically simulating the modified wedge vane profiles. Steady and time-accurate, 3D- viscous RANSsolver is used to perform flow field computations.

    The original design is modified to obtain better aerodynamic performance. Five morechanges are made to the leading edge profile of the new design, in order to assess different degrees of unsteadiness. These changes show that their contribution on stageefficiency is rather minor, while they have a huge reduction on blade loadings. Moreover, it is shown that the shorter radial distance of vaneless space does not necessarilymean an increased loading thanks to the eliminating in-phase fluctuations on pressureand suction sides.

    It is found that the impeller reacts to the upstream static pressure disturbance, whichis caused by the applied geometry change and its resultant flow field in the wedge diffuser, but not to the radial location of a certain profile. In addition, the results indicatethat the wedge diffuser aerodynamic performance is driven by time-averaged flow fieldbehaviour.

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  • 28.
    Lucio, César
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Design of a High Subsonic Nozzle for a Transonic Linear Cascade Operating at Near Stall Conditions2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis presents the results of computational fluid dynamics (CFD) design calculations of a subsonic nozzle operating at Mach number 0.85 in a transonic linear cascade wind tunnel. The purpose of the nozzle is to accelerate a fluid by decreasing the pressure energy and raising the kinetic one. The challenge in a nozzle design is to obtain uniform flow at the desired velocity. This parameter is examined in this project measuring the total pressure loss, boundary layer thickness, and exit flow angle. These measures have been the drivers for the present nozzle design. A quasi-one-dimensional approach implemented in Python programming was performed for the first design phase of the project. Subsequently, a mesh independence study was done and five wall contours were tested using the software package from ANSYS (ICEM CFD & CFX). The purpose of the CFD simulations was to determine the nozzle's optimum geometry to achieve flow uniformity in the nozzle outlet. It was found that the 5th order polynomial wall contour proposed by NASA was the best one concerning flow uniformity. Afterwards, the drawings and CAD model of the selected nozzle was produced with Autodesk Inventor. Finally, a turbulence model comparison among SST and k—ε  is presented. It was confirmed that k—ε can be used for saving computational resources without loosing significant accuracy in the CFD simulation results.

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  • 29.
    Björkman, Joel
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Molinder, Jesper
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Design pre-study of a linear cascade test rig for turbine components2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the modern society different gas turbine applications play a major role such as power generation and the jet engine. To achieve higher efficiency for the gas turbine cycle experimental heat-transfer and aerodynamic research is necessary. The division of Heat and Power Technology at KTH has recently invested in a linear cascade test rig for turbine components. To receive reliable results from future experiments it is important that the flow pattern in the cascade correspond to the flow pattern inside a real turbine. The test section is affected by both up- and downstream phenomenon and therefore the design of the inlet and outlet of the test section is of great importance. A Computational Fluid Dynamics (CFD) analysis of the test rig is necessary to find a suitable geometry. The aim over the cascade is to achieve periodicity, for example, when the pressure distribution is repeated over the section of blades used in the cascade.

     

    A model of the inlet to the test section and the test section itself has been created. The domain has been discretized into finite volumes by applying a mesh and then solved with the commercial CFD package, ANSYS CFX14, to predict behavior of the fluid along the test rigs different parts.

     

    Two different geometries of the inlet were analyzed, one with a short transaction and the other with a longer transaction. The present work indicates that a transaction with a longer duct has a more uniform velocity- and pressure profile downstream. The solution for the fluid behavior inside the test section did not converge and the results are not reliable. However the results indicate that; some periodicity is achieved over the section of blades, transonic velocities occur and a high level of vortices further downstream the cascade is located. The reason why the solution did not converge and is unreliable could be numerous, one major impact may be that the underlying mesh isn’t good enough and does not resolve the aerodynamic phenomena that occur correctly.

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  • 30.
    Cellier, Antony Hermann Guy
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Detection and Identification of Instability and Blow-off/Flashback Precursors in Aeronautical Engines using Deep Learning techniques2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The evolution of injection processes toward more fuel efficient and less polluting combustion systems tend to make them more prone to critical events such as Thermo-Acoustic Instabilities, Blow-Off and Flash-Back. Moreover, the addition of Di-Hydrogen as a secondary or as the main fuel is in discussion by aeronautical engines manufacturers. It drastically modifies the stability of the system and thus raise several interrogations concerning the multiplicity of its use. Being able to predict critical phenomena becomes a necessity in order to efficiently operate a system without having to pre-test every configuration and without sacrificing the safety of the user. Based on Deep Learning techniques and more specifically Speech Recognition, the following study presents the steps to develop a tool able to successfully detect and translate precursors of instability of an aeronautical grade swirled injector confined in a tubular combustion chamber. The promising results obtained lead to proposals for future transpositions to real-size systems.

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  • 31.
    Kapekov, Ali
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Development of an innovative cooling concept for turbofan engines2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper is submitted in support of a candidature for the Double Degree in Vehicle Engineering with a specialization in Aerospace between KTH Royal Institute of Technology, Sweden, and Ecole Centrale Lyon, France.

    The present report emphasizes a research project for current or next generation turbofan engines used in civil aviation, and especially its equipment integration from a thermal management point of view. The cooling and ventilation of such equipment in the core compartment is especially harsh. Its optimization had been considered through a complete analysis described in an exhaustive paper which is only available internally at Airbus or for thesis examiners because of confidentiality issues.

    Considering only Two-Phase flow heat transfer, the heat pipes are deeply explained in order to familiarize the reader. An achievable heat pipe is modelled help to a 1D simulation software called LMS Imagine.Lab AMESim (Siemens PLM). The modelling is illustrated and correlated with experimental values for commercial heat pipes.

    Finally two other two-phase flow heat transfer systems are duly noted, with a short description of the theory that led to model adaptation and GUIs development using Matlab.

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  • 32.
    Lennie, Matthew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Technical University of Berlin.
    Development of the QFEM Solver: The Development of Modal Analysis Code for Wind Turbine Blades in QBLADE2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Wind Turbine industry continues to drive towards high market penetrationand profitability. In order to keep Wind Turbines in field for as long as possiblecomputational analysis tools are required. The open source tool QBlade[38] softwarewas extended to now contain routines to analyse the structural properties of WindTurbine blades. This was achieved using 2D integration methods and a Tapered Euler-Bernoulli beam element in order to find the mode shapes and 2D sectional properties.This was a key step towards integrating the National Renewable Energy LaboratoriesFAST package[32] which has the ability to analyse Aeroelastic Responses. The QFEMmodule performed well for the test cases including: hollow isotropic blade, rotatingbeam and tapered beam. Some improvements can be made to the torsion estimationof the 2D sections but this has no effect on the mode shapes required for the FASTsimulations.

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  • 33.
    Gagne, Anton
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Effects of Asymmetry and Other Non-Standard Excitations on Structural Dynamic Forced Response Analysis of Turbomachinery Flow-Path Components2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A recent paper explored a potential deficiency in the single frequency harmonic response structural dynamic analysis approach typically used to assess a resonant condition in turbomachinery flow path components. This deficiency is prevalent in supersonic flow conditions when non-adjacent stages are present. The previous investigation demonstrated other excitation sources present in complex or supersonic flows could be missed using the typical analysis approach, in some cases leading to large under-prediction of structural response when compared with a baseline transient analysis. This paper presents the results of a follow on study, in which the inclusion of these effects in dynamic analyses is investigated. A representative rotor was created and analyzed for forced response characteristics when individual and combined unsteady content was present. A simple shell and beam 2D model was used to study the forced response behavior using transient and harmonic analyses. The results showed a significant contribution from non-integer forcing as well as from certain integer order forcing. A 3D model was also created for future analysis but did not display the sideband characteristics similar to flow seen in the previous investigation.

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  • 34.
    Broliden, Caroline
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Hellstadius, Emma
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Electricity Generation from Geothermal Energy in Australia2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis aims to investigate the economical and technical prerequisites for electricity generation from geothermal energy in Australia. The Australian government has increased the pressure on the energy sector to decrease the emissions of greenhouse gases. Today, a major part of the electricity production is generated from fossil fuels, and an increased focus on renewable energy resources have emerged in recent years.

    Geothermal energy is thought to have great potential in Australia due to the high abundance of so-called hot rocks. However, it is still a relatively new technology that has not yet been proved to be economically viable at commercial scale in Australia.

     

    The study will investigate both the technical and economical aspects of geothermal energy as a resource for electricity production. The technical investigation is based mainly on identifying which technologies are suitable for use in Australia, as well as which factors that have the greatest impact on plant capacity. In the economical section of the literature review the costs and economical factors affecting the plant profitability will be discussed. Based on the literature review, an economical model is developed to estimate the profitability of a so-called enhanced geothermal system (EGS) with a binary power plant. The net present value, internal rate of return as well as levelized cost of electricity is calculated for a base case scenario. The base case scenario is based on the current exploratory progress of EGS in Australia to date. The base case is then used as a reference scenario when varying the parameters to determine the effect on plant profitability as well as the sensitivity of the model.

     

    The results of the calculations show that with the current conditions in Australia, electricity generation from geothermal EGS is not viable. The costs are still too high and the amount of electricity that can be produced is limited by a few key parameters. If the obstacles are overcome, geothermal energy could have a great potential as a source for electricity production in Australia.

     

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  • 35.
    Eriksson, Kristina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Persson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Energi - och ekonomipotential för solceller i Hållbara Järva2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    One of the city of Stockholm’s main objectives is to have a society completely free from fossil fuels. To achieve this, several investments regarding improvements in energy efficiency and renewable energy are currently being planned or implemented. One of these investments is a project called Hallbara Jarva which is located in the suburbs of Stockholm.

     

    The purpose of this thesis is to examine the prospects of an investment in photovoltaic cells from an energy-saving and economical point of view. The analysis is limited to three buildings within Hallbara Jarva and is intended for the property owner. 

     

    Solar energy is a type of renewable energy source and is commonly divided into solar heating and solar power. This thesis introduces both techniques but the calculations are limited to solar power.  The many types of technical solutions for photovoltaic cells all derives from the same phenomena. In commercial applications The photovoltaic cells are connected with a power inverter to form a power providing system. To approach the issue an analysis of three main areas is made.

     

    Primarily the photovoltaic system is sized based on the electricity consumption in the buildings. Furthermore an assessment is made whether or not the photovoltaic system is a profitable investment. Lastly a comparison between the output of the analysis and the main renewable energy objectives for Hallbara Jarva is made.

     

    The final result is obtained which states that the photovoltaic system yields a sufficient amount of electricity during the summer, to meet the electricity requirements in the buildings. The system should be sized so that the monthly electricity production never exceeds   the demand. An evaluation of this particular investment determines that it yields a small profit.

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  • 36.
    Papavramidis, Konstantinos
    KTH, School of Industrial Engineering and Management (ITM).
    Evaluation of Potential Propulsion Systems for a Commercial Micro Moon Lander2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the advent of Space 4.0 era with the commercialization and increased accessibility of space, a requirement analysis, trade-off options, development status and critical areas of a propulsion system for a Commercial Micro Moon Lander is carried out. An investigation of a suitable system for the current mission is examined in the frame of the ASTRI project of OHB System AG and Blue Horizon. Main trajectory strategies are being investigated and simulations are performed to extract the ∆V requirements. Top-level requirements are extracted which give the first input for the propulsion design. An evaluation of the propulsion requirements is implemented which outlines the factors that are more important and drive the propulsion design. The evaluation implements a dual comparison of the requirements where weighting factors are extracted, resulting the main drivers of the propulsion system design. A trade-off analysis is performed for various types of propulsion systems and a preliminary selection of a propulsion system suitable for the mission is described. A first-iteration architecture of the propulsion, ADCS and GNC subsystems are also presented as well as a component list. A first approach of the landing phase is described and an estimation of the required thrust is calculated. A unified Bipropellant propulsion system is proposed which fills out most of the mission requirements. However, the analysis shows that the total mass of the lander, including all the margins, exceeds a bit the mass limitations but no the volume limitations. The results shows that a decrease in payload capacity or the implementation of a different trajectory strategy can lower the mass below the limit. In addition, further iterations in the lander concept which will give a more detailed design, resulting to no extra margins, can drive the mass below the limit. Finally, a discussion on the results is done, addressing the limitations and the important factors that need to be considered for the mission. The viability of the mission due to its commercial aspect is being questioned and further investigation is suggested to be carried out on the ”micro” lander concept.

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  • 37.
    Costanzo, Anthony
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental Investigation of Shock Wave-Boundary Layer Interaction on a Generic Oscillating Bump2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The presented research investigates the effects of shock wave boundary layer interaction on the unsteady pressure response of the surface of an oscillating structure. A simplified structure, a 2D prismatic bump, located in a straight channel is used to better understand the bending flutter phenomenon. Time-resolved measurements of the unsteady surface pressures and the instantaneous model geometry measurements are performed in order to study the effect of the shock wave on the aerodynamic load acting over the flexible generic bump. The bump is oscillated in a controlled manner with amplitude of ±0.5mm for four reduced frequencies ranging from k=0.123 to k=0.492. The experiments are performed for a transonic flow operating point characterized by an inlet Mach number of 0.69 and a total inlet pressure of 160 kPa, with an outlet Mach number and outlet static pressure of 0.79 and 106 kPa, respectively. The unsteady pressure measurements were performed using recessed mounted pressure transducers with Kulite fast response sensors. The presented results demonstrate that the shock wave induces a strong amplification of the unsteady pressure at the foot of the shock. This amplification was shown to decrease with the increase in reduced frequency, specifically between k=0.123 and k=0.246.

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    Costanzo Anthony EGI-2014-107MSC EKV1068
  • 38.
    Jonsson, Oskar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fan Blade Vibrations in Synchronous Machines2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The design of a fan structure should be made in relation to both an aerodynamic aspect as well as a structural point of view to avoid both self-excited vibrations and forced response. If the blades start to vibrate it can cause high cycle fatigue until they break and cause severe damage. Research in the aerodynamic area is moving forward with an increase in computer power. It is however difficult and very time demanding to calculate the behavior of complex structures.Using an analytical approach on the other hand may lead to a very conservative design. This work has its focus on the structural point of view with a design of the blades towards best aerodynamic stability and to make the design procedure at ABB better towards an optimization. The theory describes the aerodynamic phenomena, structural dynamics as well as analyzing techniques to avoid high cycle fatigue.The analyzing techniques described in the theory have been applied to two different fan geometries used by ABB today. A new design procedure has been made to get a higher degree of freedom for more machine sizes as well as to save material and to get a safer structure.

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  • 39.
    Bernardi, Giacomo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Feasibility Study of a 3D CFD Solution for FSI Investigations on NREL 5MW Wind Turbine Blade2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the increase in length of wind turbine blades flutter is becoming a potential design constrain, hence the interest in computational tools for fluid-structure interaction studies. The general approach to this problem makes use of simplified aerodynamic computational tools. Scope of this work is to investigate the outcomes of a 3D CFD simulation of a complete wind turbine blade, both in terms of numerical results and computational cost. The model studied is a 5MW theoretical wind turbine from NREL. The simulation was performed with ANSYS-CFX, with different volume mesh and turbulence model, in steady-state and transient mode. The convergence history and computational time was analyzed, and the pressure distribution was compared to a high fidelity numerical result of the same blade. All the model studied were about two orders of magnitude lighter than the reference in computation time, while showing comparable results in most of the cases. The results were affected more by turbulence model than mesh density, and some turbulence models did not converge to a solution. In general seems possible to obtain good results from a complete 3D CFD simulation while keeping the computational cost reasonably low. Attention should be paid to mesh quality.

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  • 40.
    Ricquemaque, Lore
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    FEM model of impacts on blades2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In-service support engineers often have to answer derogations requests regarding impacts on compressor blades. The stress concentration factor is a physical quantity helping them to take the decisions : it is a measure of the local increase of the stress due to the impact. Several techniques already exist to derive it like Petersons' abaci giving it regarding the geometrical parameters of the impact. They are user friendly but conservative in practice. The most accurate method is zoom-calculation : a Finite Element Model is created to precisely measure the stress concentration factor. This effective approach is however very time-consuming. In between, Snecma engineers developed a few years ago a law on the form of abaci derived from a zoom-calculation results database. The main purpose of this thesis is to create laws regarding new geometrical parameters and increase the size of the database following on from the work already carried out. FEM models depending on various parameters are thus created to derive stress concentration factors. A deep difference from what has been done before rests on the method : a calculation chain is developed to get results on different sets of impact parameters. It enables to easily and quickly update the mesh on the models and thus to consider numerous defect geometries. The final results of the study are a set of abaci giving the stress concentration factor due to the impact regarding its geometrical parameters.

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  • 41.
    Ozturk, Utkudeniz
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    FLUTTER ANALYSES VIA DIFFERENT SOLVERS AND VALIDATION WITH EXPERIMENTAL DATA2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the desire of increasing the performance and power to weight ratio (for aero engines), the gas and steam turbine blades are becoming slimmer and exposed to higher loads. Together with this, different physics underlying the blade failures became stimulated. Flutter is one of the instabilities that lead failure and design against flutter is still a challenge. Validated, trustable Computational Fluid Dynamics (CFD) tools are believed to be the ultimate key towards the design of flutter-free turbomachines.

    This work is dedicated to flutter analyses via different CFD solvers and comparison of the calculated results with the experimental data. The experimental data was produced in previous studies with the flutter test rig situated at The Royal Institute of Technology (KTH). This test rig is a unique, controlled flutter testing setup with an annular cascade.

    Classical time marching approach (influence coefficients-INFC) and Transient Blade Row (TBR) approach (traveling wave mode-TWM) in ANSYS-CFX are tested in this study. Also some comparisons are made between these and in-house harmonic solver TF3D.

    From the steady state perspective there are two design and two off-design operating points. In addition to this, three different reduced frequencies and three different oscillation modes (axial, circumferential, torsion) make up nine unsteady operating points. A number of combinations of the steady and unsteady operating points are investigated.

    INFC and TWM results are compared with the experimental data at 10, 50 and 90% spans in terms of unsteady Cp properties (phase and amplitude) around the blade circumference. Finally, the stability curves obtained via INFC are compared on their own to point out operational differences. Stability curves for a selected operating point from INFC, TBR (TWM) are compared.

  • 42.
    Chitrakar, Sailesh
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Kathmandu University.
    FSI analysis of Francis turbines exposed to sediment erosion2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sediment erosion is one of the key challenges in hydraulic turbines from a design and maintenanceperspective in Himalayas and Andes. Past research works have shown that the optimization of theFrancis turbine runner blade shapes can decrease erosion by a signicant amount. This study conductedas a Master's Thesis has taken the proposed designs from past works and conducted a CFDanalysis on a single passage of a Francis runner blade to choose an optimized design in terms of erosionand eciency. Structural analyses have been performed on the selected design through one-way andtwo-way FSI to compare the structural integrity of the designs.Two types of cases have been considered in this thesis work to dene the boundary condition of thestructural model. In the rst case, a runner blade is considered to have no in uence of the joint andother stier components. In the second case, a sector of the whole runner has been modeled withnecessary boundary conditions. Both one-way and two-way FSI have been performed on the casesfor the designs. Mesh independent studies have been performed for the designs, but only for the rstcase, whereas in the second case, a ne mesh has been used to make the analysis appropriate.The loads have been imported into the structural domain from the uid on the interfaces for one-wayFSI. In the case of two-way FSI, the Multi-Field Solver (MFX) supported by ANSYS has been usedto solve the coupled eld analysis. A fully coupled FSI in ANSYS works by writing an input le inthe structural solver containing the information about the interfaces in the structural domain, whichis imported in the uid solver. The interaction between the two domains is dened in ANSYS-CFX,including the mesh deformation and solver setups. The results have been post-processed in CFX-Post,where the results from both the elds are included. It has been found that the structural integrity ofthe optimized design is better than the reference design in terms of the maximum stress induced inthe runner. The two-way FSI analysis has been found as an inevitable part of the numerical analysis.However, with the advancement of the computational capability in the future, there could be a greatscope in the research eld to carry out a fully-coupled transient simulation for the whole runner toget a more accurate solution.

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  • 43.
    Lions, Alexandre
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    IMPROVING THE REPRESENTATION OF 1D PERFORMANCE COMPRESSOR MODEL2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thesis project was carried out at SAFRAN AIRCRAFT ENGINES in France with goal to check the feasibility of implementing 1D validated aerodynamic models into the engine performance models. It is a part of a wider project of improving the representation of transient and steady effects that are missing in 0D representations. The main difficulty is to implement this 1D model in the PROOSIS performance software. The focus of the project was to implement the subsonic to choke range of operating conditions consistently within the PROOSIS solver. Therefore, using only simplified aerodynamics, a first instance of the model was programmed. A second instance of the model was able to take into account the choking phenomena. The solution found works in the PROOSIS tool which is a non-causal programming software and manage to unite the subsonic to choke operating range in a single physical system. The model once enriched with the right correlations will be able to be used in a performance model, replacing the compressor maps.

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  • 44.
    Wang, Haotian
    KTH, School of Industrial Engineering and Management (ITM).
    Influence on tip leakage flow in a compressor cascade with plasma actuation2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As one of the key components of aero engines, compressor is required to endure higher pressure,  possess  higher  efficiency  and  wider  operating  range. Intensive studies have been made on tip leakage flow and researchers find that by reasonably organizing tip leakage flow, aero engines are  more likely to achieve better performance and reliability. Conventional flow controlling methods  like casing treatment and micro jet could substantially modify tip leakage flow, unfortunately with  a price of additional loss, not to mention the difficulty in manufacturing such structure. Whereas  plasma actuation  flow control method  uses  plasma actuators,  such equipment is easy  to  build,  responses  fast  and  has  a  wide  excitation  bandwidth.  This  method  has  become  a  new  trend  in  internal flow active control field. 

    In this research, a phenomenological model is adopted to simulate DBD plasma actuation in the  flow field inside a compressor cascade. The aim is to find out how plasma actuation will influence  tip  leakage  flow.  Meanwhile  possible  means  to  improve  plasma  actuation  performance  are  discussed. 

    First of all, numerical simulation of flow inside a compressor cascade without plasma actuation is  conducted to validate accuracy of the numerical methodology adopted and then determine one  numerical  approach  that  satisfies  specific  needs  sufficiently.  Meanwhile,  influence  of  casing  movement on tip leakage flow as well as possible mechanism of tip leakage vortex core generation  is investigated in detail. The results indicate:   

    1. Generating position of tip leakage vortex moves towards leading edge with increasing moving  speed of shroud. 

    2. As shroud moving speed increases, trajectory of tip leakage vortex moves away from suction  side of blade and closely towards shroud. 

    3. Casing movement  tends  to  transform  tip leakage vortex  from  circular  to  oval  shape  due  to  circumferential shearing. 

    4. Casing  movement  has  little  influence  on  total  pressure  field  concerning  absolute  pressure  value. While total pressure loss does reduce slightly with increasing moving speed of shroud. 

    5.Vorticity  transport  from  tip  clearance  into  passage  may  be  contributing  significantly  to  generation of tip leakage vortex inner core. 

    Secondly, a simplified model of DBD plasma actuation based on literature [1] is derived and applied  through  UDF  function  of  commercial  software  Fluent  into  the  flow  field.  Different  actuation  positions,  voltages  and  frequencies  are  applied  in  simulation  and  compared.  After  that  casing  movement is included. Main conclusions are as follow:   

    6. Plasma  actuation  shows  significant  suppressing  effect  on  tip  leakage  vortex  on  both  size,  trajectory and strength. 

    7. The suppressing effect on tip leakage vortex grows stronger as actuator moves towards leading  edge. 

    8. Increasing actuation voltage results in stronger suppressing effect on tip leakage vortex. 

    9. Plasma actuation can effectively improve total pressure loss situation near shroud region with  increasing actuation power. 

    10. Increasing actuation frequency results in stronger suppressing effect on tip leakage vortex as  well. Additionally, frequency performs slightly better than voltage.

    11. Casing  movement  tends  to  weaken  suppressing  effect  of  tip  leakage  vortex  by  plasma  actuation. More  actuation  power  is  needed  to  achieve  sufficient  suppressing  effect  in  real  compressors. 

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  • 45.
    Jazzar, Jacques
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Methods of post-treatment of aerodynamic tests of engine boosters2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Aerodynamics studies in a booster such as analysis of the flow through the whole component or study of local turbulent phenomenon constitute a crucial part of its development in order to get better overall performances, like efficiency of the compressor and compression ratio. In order to put in perspective the computational predictions, it is critical to obtain sets of data from tests to caliber numerical analyses and to assure the booster respects design specifications. Aerodynamics testing is then an important part of the development of a compressor. However, it is complicated to obtain such values for many reasons: time constraints, problems regarding support, important costs etc. Thus, it is important to get as much information as possible from these tests data in a limited period in order to spend more time in results interpretation and less in treating raw data. Thus, an optimized tool of treatment to first deduce results from test data; and then to compare different engines or different sets of tests data, to get a wider state of the art and to avoid time-consuming analyses was needed. In order to do so, the first part of the development consists in investigating the existing methods to extract and analyze data from tests already used, and then deducing a general methodology to obtain from raw measures the performances of the studied booster compared to other available data. Once the methods have been set up and validated, the tool in itself was implemented in a practical way. Then, it was important to validate it on real tests values and to observe if it was adjustable for all kind of aerodynamics tests.

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  • 46.
    Grassart, Pierre
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Monitoring of the lubrication system of an aircraft engine through a Prognostic and Health Monitoring approach2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
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  • 47.
    Stasolla, Vincenzo
    KTH, School of Industrial Engineering and Management (ITM).
    Numerical analysis of aerodynamic damping in a transonic compressor2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Aeromechanics is one of the main limitations for more efficient, lighter, cheaper and reliable turbomachines, such as steam or gas turbines, as well as compressors and fans. In fact, aircraft engines designed in the last few years feature more slender, thinner and more highly loaded blades, but this trend gives rise to increased sensitivity for vibrations induced by the fluid and result in increasing challenges regarding structural integrity of the engine. Forced vibration as well as flutter failures need to be carefully avoided and an important parameter predicting instabilities in both cases is the aerodynamic damping.

    The aim of the present project is to numerically investigate aerodynamic damping in the first rotor of a transonic compressor (VINK6). The transonic flow field leads to a bow shock at each blade leading edge, which propagates to the suction side of the adjacent blade. This, along with the fact that the rotating blade row vibrates in different mode shapes and this induces unsteady pressure fluctuations, suggests to evaluate unsteady flow field solutions for different cases. In particular, the work focuses on the unsteady aerodynamic damping prediction for the first six mode shapes. The aerodynamic coupling between the blades of this rotor is estimated by employing a transient blade row model set in blade flutter case. The commercial CFD code used for these investigations is ANSYS CFX.

    Aerodynamic damping is evaluated on the basis of the Energy Method, which allows to calculate the logarithmic decrement employed as a stability parameter in this study. The least logarithmic decrement values for each mode shape are better investigated by finding the unsteady pressure distribution at different span locations, indication of the generalized force of the blade surface and the local work distribution, useful to get insights into the coupling between displacements and consequent generated unsteady pressure. Two different transient methods (Time Integration and Harmonic Balance) are employed showing the same trend of the quantities under consideration with similar computational effort. The first mode is the only one with a flutter risk, while the higher modes feature higher reduced frequencies, out from the critical range found in literature. Unsteady pressure for all the modes is quite comparable at higher span locations, where the largest displacements are prescribed, while at mid-span less comparable values are found due to different amplitude and direction of the mode shape. SST turbulence model is analyzed, which does not influence in significant manner the predictions in this case, with respect to the k-epsilon model employed for the whole work. Unsteady pressure predictions based on the Fourier transformation are validated with MATLAB codes making use of Fast Fourier Transform in order to ensure the goodness of CFX computations. Convergence level and discrepancy in aerodamping values are stated for each result and this allows to estimate the computational effort for every simulation and the permanent presence of numerical propagation errors.

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  • 48.
    Boccadamo, Danilo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Numerical investigation of a transonic nozzle guide vane under elevated loading2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Despite many new investigations over the last years, there is no indication that alternative energy conversion technologies will overtake the place of turbomachinery. Hence thermal turbines are still the most dominant movers for electricity generation.Although this leadership in the energy production does not seem to be in danger, the current drivers in turbomachinery industry are to work towards both less fuel consumption and less pollution. In order to meet the future economic and environmental goals, researchers press towards highly loaded vanes and blades. This has to be performed at maintained or improved aerodynamic performances. Increased performances and blade loading lead in turn to increased velocities and larger regions of supersonic fluid velocities and consequently general increasing of shock intensities. The biggest problem dealing with supersonic flow and high shock intensities is that the boundary layer, when walking through these regions, experiences strong pressure gradients and intense shock-boundary layer interaction. This may lead the blade to stall meaning detachment of both boundary layer and cooling-film from the wall. These effects can evidently lead to catastrophic consequences since nowadays the materials used in turbomachinery applications have temperature strengths much lower than those coming from the combustion chamber. This thanks to very complex blade and vane cooling systems.There are even other features that may take benefit from increased velocities such as an attenuation in the boundary layer growth and the static pressure distribution on the blade surface. For helping researchers studying these new geometries, a cold air annular test rig designed by “Siemens Industrial Turbomachinery AB”, it has been built and placed at “Division of Heat and Power Technology” at KTH.The present thesis has the goal to provide a numerical model for CFD calculations, optimized for boundary layer studies, able to give a good prediction of detachment of the boundary layer and losses for different working cases. A previous model was provided with a commercial software for both ideal vane and real test rig. Recover of results and adaptions of the model were performed with a new version of the same software starting from the previous model. A comparison between numerical and experimental results have shown a good match for the subsonic and transonic case. Instead, problems were met for the supersonic case. Many attempts of different boundary condition at the inlet have been run. No reliable solution has been reached with realistic pressure profile at inlet while realistic results have been found using the mass flow rate as Inlet boundary condition. At the end, an analysis of shock and detachment is provided in terms of density gradient and static entropy distribution through the blade passage. Future works may aim to solve the “supersonic problem”.

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  • 49.
    Dargahi, Borzou
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Numerical Investigation of Various Modelling Strategies for Throttling a Transonic Compressor Rig Diffuser2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The concern of this study is modeling of the flow field in the diffuser of a 1.5 stage compressor test rig in which the mass flow is constrained at the exit of the diffuser. Constraining method is is applied through, throttling by means of a slab at the exit of the diffuser, where the flow enters the exit volute. Mass flow constraining enables achieving different mass flow rates through the machine. For this reason, modeling of the flow field in the diffuser during the throttling stages and how the compressor will be affected by that, is the question this study is answering. In attempt to answer the research questions, Ansys CFX platform has been used for numerical investigation. Various geometries of the diffuser are studied to examine the sensitivity of outflow to modelling strategies of the upstream diffuser and how the flow parameters at the outlet of the upstream compressor stage would change accordingly. In this study various geometry designs are considered including simplification of geometry according to flow behaviour in the diffuser, horizontal nozzle diffuser and annular diffuser design including slab with three sizes of outlet area.. From the model setup it is realized that extending the height of the outlet of diffuser has a significant effect on the model stability although changing the outlet area does not impact the results in terms of mass flow rate and inlet pressure profile. In addition transient studies were carried out to assess how the outlet flow is changing with the variations in the flow field at the inlet. The results indicate that the fluctuations die out before reaching the slab and do not affect the outlet flow.

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  • 50.
    Ridard, Mathilde
    KTH, School of Industrial Engineering and Management (ITM).
    NUMERICAL STUDY OF TWO-PHASE FLOWS FOR PERFORMANCES IN SOLID ROCKET PROPULSION2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
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