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  • 1. Adomavicius, A.
    et al.
    Belousov, A.
    Gylys, J.
    Jasiulevicius, Audrius
    KTH, Superseded Departments, Energy Technology.
    Kubarev, Andrej
    KTH, Superseded Departments, Energy Technology.
    Ognerubov, V.
    Ziedelis, S.
    The studies of RBMK-1500 reactor core behavior during abnormal operation transients2004In: Proceedings of the PHYSOR 2004: The Physics of Fuel Cycles and Advanced Nuclear Systems - Global Developments, 2004, p. 1035-1047Conference paper (Refereed)
    Abstract [en]

    This paper describes series of RBMK-1500 reactor transient investigations, performed with CORETRAN code. Aspects of the reactor core neutronic and thermal hydraulic behavior during postulated core transients were analyzed, hi particular, RBMK-1500 transients leading to changes in reactor power and core reactivity were considered. Three reactivity-initiated accident cases were addressed: a) spontaneous control rod bank withdrawal in the central part of the core; b) spontaneous control rod bank withdrawal in core periphery and c) release of one Shortened Absorber Rod from the reactor core. Reactor nominal power operation was used as the reference core state. Analysis was performed using data, obtained from the actual plant database recorded for Ignalina Nuclear Power Plant Unit 2 on 27th January 2001. The CORETRAN calculations were benchmarked against STEPAN code results.

  • 2.
    Alkan, Deniz
    KTH, Superseded Departments, Energy Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Investigating CVT as a Transmission System Option for Wind Turbines2013Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    In this study, an innovative solution is examined for transmission problems and frequency control for wind Turbines. Power electronics and the gear boxes are the parts which are responsible of a significant amount of failures and they are increasing the operation and maintenance cost of wind turbines. Continuously transmission (CVT) systems are investigated as an alternative for conventional gear box technologies for wind turbines in terms of frequency control and power production efficiency. Even though, it has being used in the car industry and is proven to be efficient, there are very limited amount of studies on the CVT implementation on wind turbines. Therefore, this study has also an assertion on being a useful mechanical analyse on that topic. After observing several different types of possibly suitable CVT systems for wind turbines; a blade element momentum code is written in order to calculate the torque, rotational speed and power production values of a wind turbine by using aerodynamic blade properties. Following to this, a dynamic model is created by using the values founded by the help of the blade element momentum theory code, for the wind turbine drive train both including and excluding the CVT system. Comparison of these two dynamic models is done, and possible advantages and disadvantages of using CVT systems for wind turbines are highlighted. The wind speed values, which are simulated according to measured wind speed data, are used in order to create the dynamic models, and Matlab is chosen as the software environment for modelling and calculation processes. Promising results are taken out of the simulations for both in terms of energy efficiency and frequency control. The wind turbine model, which is using the CVT system, is observed to have slightly higher energy production and more importantly, no need for power electronics for frequency control. As an outcome of this study, it is possible to say that the CVT system is a candidate of being a research topic for future developments of the wind turbine technology.

  • 3.
    Allegret-Bourdon, Davy
    KTH, Superseded Departments, Energy Technology.
    Experimental study of fluid-structure interactions oon a generic model2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    A new type of test facility is presented which allows theinvestigation of fluid-structure interactions using a genericflexible model. Rather than modelling the complex geometry of aturbomachine blade passage or blade row, this test facilityuses a two dimensional generic bump located in a straightchannel in order to reach a better understanding of the bendingflutter phenomenon. Thus, experimental campaigns are performedto observe and measure surface pressure fluctuations linked tothe interactions of a shock wave with the boundary layer formedover the oscillating structure. The new test facility modifiesan existing wind tunnel featuring a straight rectangular crosssection. The oscillating model used in the study is oftwo-dimensional prismatic shape and has been investigated inprevious studies, from which base case data are available. Inorder to introduce capabilities for the planned fluid-structureexperimental campaigns, a flexible version of the model hasbeen built. It is moulded of polyurethane at defined elasticityand hardness, and actuated by a novel type of fully integratedmechanical oscillating mechanism. A frequency controlled ACservomotor drives this oscillating mechanism. The whole drivetrain is able to produce an oscillation of the model atvariable amplitude and frequency up to 200Hz. At the same time,a one dimensional laser sensor measures precisely the wholemodel displacement through a top optical window. The flow inthe test section can be set at different operating conditions.Time-resolved pressure measurements are performed on theoscillating surfaceusing Kulite fast response transducerscoupled to an adapted long line probe technique. While theinstantaneous models shape is scanned using laser triangulationtechnique through the top window, unsteady Schlierenvisualization measurement are performed using the accessthrough two side windows. Similar coupling is also performedbetween unsteady flexible geometry measurements and unsteadypressure measurements. The mode shapes of this flexible bumpstrongly depend on the excitation frequency. It is consideredthat a first bending mode shape is obtained for reducedfrequencies up to 0.037. However, for reduced frequencieshigher than 0.037, the mode shapes are interpreted as higherharmonic stripe mode shapes. Thus a second order mode shape isreached for reduced frequencies between 0.037 and 0.074, and athird order mode shape is reached for reduced frequenciesbetween 0.074 and 0.294. In this experimental study, the modeloscillates at reduced frequencies from 0.015 to 0.294 attransonic flow condition characterized by an inlet Mach numberMiso1=0.69 and an outlet Mach number Miso2=0.80. Schlieren pictures as well as unsteadypressure repartitions are obtained for this operating flowcondition. The presented unsteady results demonstrate that thephase of shock wave movement towards bump local motion shows adecreasing trend for third bending mode shapes fluctuating withreduced frequencies higher than 0.074. At the pressure tapslocated after the shock wave formation, the phase of pressurefluctuations towards bump local motion present the samedecreasing trend for the same kind of mode shapes. However noconclusion can be drawn for this range of perturbationfrequencies at a non-fluctuating bending mode shape (a modeshape that remains the same in the whole perturbation frequencyrange). In conclusion, a new version of this generic bump willhave to be manufactured in order to perform similar experimentsat a non-rigid first bending mode shape.

  • 4. Amos, I. G.
    et al.
    Jablonowski, T.
    Rossi, E.
    Vogt, Damian M.
    KTH, Superseded Departments, Energy Technology.
    Boncinelli, P.
    Design and off-design optimisation of highly loaded industrial gas turbine stages2004In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 24, no 12-nov, p. 1735-1744Article in journal (Refereed)
    Abstract [en]

    A European collaborative project to investigate the design of advanced industrial gas turbine stages (DAIGTS) has now completed 30 months of a 36-month programme of work. The objectives of the project were to investigate advanced aerodynamic analysis of industrial gas turbine stages, off-design performance characteristics, prediction of aero-mechanical behaviour.This paper gives an overview of the technical progress made and includes a description of the rigs used in the study. Key results include the development of advanced CFD models to include cooling and real engine geometric features, off-design performance mapping of transonic industrial turbine stages and the development of a unique oscillating cascade rig.

  • 5.
    Anton Remirez, Raul
    et al.
    KTH, Superseded Departments, Energy Technology. University of Gävle, Sweden.
    Jonsson, Hans
    KTH, Superseded Departments, Energy Technology. University of Gävle, Sweden.
    Moshfegh, B.
    Modelling of EMC screens for radio base stations Part 1: Experimental parametric study2004In: ITherm 2004, Vol 1, IEEE , 2004, p. 463-470Conference paper (Refereed)
    Abstract [en]

    Enclosing electronics in sealed metal boxes provides good electromagnetic shielding, but evidently restricts the air movement necessary for adequate cooling. In order to meet ElectroMagnetic Compatibility (EMC) requirements, a perforated plate (an EMC screen) must be used. The design of this screen must provide a sufficient free area ratio for the adequate airflow, but at the same time the holes must be small enough to block electromagnetic radiation. An experimental set-up that represents a Radio Base Station (RBS) subrack was built inside a wind tunnel. The airflow pattern and pressure drop through the EMC screen were investigated experimentally for different subrack geometries, screen porosities and velocities, and the recirculation zones were identified. The study was performed by means of pressure and velocity measurements, together with smoke visualization under isothermal conditions.

  • 6. Badinand, T.
    et al.
    Fransson, Torsten H.
    KTH, Superseded Departments, Energy Technology.
    Radiative heat transfer in film-cooled liquid rocket engine nozzles2003In: Journal of thermophysics and heat transfer, ISSN 0887-8722, E-ISSN 1533-6808, Vol. 17, no 1, p. 29-34Article in journal (Refereed)
    Abstract [en]

    A radiation model has been implemented in a Navier-Stokes flow solver to investigate the importance of thermal radiation in film-cooled liquid hydrogen/liquid oxygen rocket engine thrust chambers. Two running conditions were computed: high-altitude and sea-level conditions. For high altitudes, the smalls are heated by radiation approximately 3 K, and the flow is not influenced. At sea level, the flow separates from the nozzle walls and a Mach disk is formed inside the nozzle. This extra source of radiation is clearly observable and, combined with the cold atmospheric air pocket created behind the separation, contributes importantly to the wall temperatures. An increase of up to 140 K is observed in the zone after the separation. Moreover, the position of the shock is slightly affected by radiative transfer. It is shown that radiative heat transfer does play an important role in the case of a shocked film-cooled nozzle. In the unshocked case, its effects are noticeable, but may be neglected.

  • 7.
    Badinand, Thomas
    KTH, Superseded Departments, Energy Technology.
    A complete procedure for modeling radiative heat transfer and spectral signature nongray participating media2000Licentiate thesis, comprehensive summary (Other scientific)
  • 8.
    Badinand, Thomas
    KTH, Superseded Departments, Energy Technology.
    Influence of thermal radiation in liquid rocket engines2002Doctoral thesis, comprehensive summary (Other scientific)
  • 9. Bednarski, M
    et al.
    Cholewa, W
    Frid, Wiktor
    KTH, Superseded Departments, Energy Technology.
    Identification of sensitivities in Bayesian networks2004In: Engineering applications of artificial intelligence, ISSN 0952-1976, E-ISSN 1873-6769, Vol. 17, no 4, p. 327-335Article in journal (Refereed)
    Abstract [en]

    This paper presents a methodology for sensitivity analysis that can be applied to Bayesian belief networks, i.e. analysis of the influence of the quality of network parameters (such as conditional and a priori probabilities) on the values of the hypothesis variable(s). The presented methodology makes use of one-way sensitivity analysis and makes it possible to apply a particular mathematical model for relations between the considered parameter and distribution of values in the node of interest (hypothesis node). The sensitivity analysis has been applied to a network describing a Nuclear Power Plant during fault conditions.

  • 10. Belico dos Reis, Lineu
    et al.
    Silveira, Semida
    KTH, Superseded Departments, Energy Technology.
    Energia Elétrica para o Desenvolvimento Sustentável2000Book (Other academic)
  • 11.
    Birru, Eyerusalem
    et al.
    KTH, Superseded Departments, Energy Technology.
    Erlich, Catharina
    KTH, Superseded Departments, Energy Technology.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Energy performance comparisons in the sugar cane industryManuscript (preprint) (Other academic)
    Abstract [en]

    Operation parameters of both traditional and modern sugar mills are analyzed and compared. Results show that the power-to-heat ratio of the modern and traditional mills lie in the ranges of 0.3-1 and 0.04-0.07, respectively. The three modifications made are: change to electric drives and higher capacity BPT (Case 1), HP boiler, CEST and electric drives (Case 2) and Case 2 plus bagasse drying (Case 3). The thermodynamic impact of these modifications on the traditional mills, shows more power is generated as the modification gets more advanced. The average increment in cogeneration efficiency values (as compared to base case) for Case 1, Case 2 and Case 3 are 4 %, 21 % and 31 %, respectively. The surplus power due to the modification made in Case 1 and Case 2 lies in the range 8-36 kWh/TC and 58-104 kWh/TC, respectively. For Case 3, the surplus power is the highest and the power generated lies in the range of 102-142 kWh/TC. The average LCOE value for Case 1 is 11 USD/MWh. For Cases 2 and 3 the average LCOE is 58 USD/kWh. The lowest average PBP values obtained are corresponding to the modification in Case 1. For the electricity prices of 0.04, 0.08 and 0.16 USD/kWh , the PBP for Case 1 are 7.5, 3 and 1 year. For Case 2 and Case 3, the lowest average PBP values obtained are corresponding to electricity price of 0.16 USD/kWh and these amount 6 and 5 years, respectively. 

  • 12. Bohdanowicz, P.
    et al.
    Simanic, B.
    Martinac, Ivo
    KTH, Superseded Departments, Energy Technology.
    Sustainable hotels – Eco-certification according to EU Flower, Nordic Swan and the Polish Hotel association2004Conference paper (Refereed)
    Abstract [en]

    Over their lifetime (including construction, operation, maintenance, and eventually demolition), buildings require appreciable amounts of energy, water and many other resources. The built environment is undoubtedly the origin of a considerable portion of the overall air, water and soil pollution, as well as waste generation in our society. Hotel buildings, due to their very specific and unique function and operational patterns, generally have a much larger ecological impact than other commercial buildings of similar size. At the same time, the well-being and development of the tourism and the hotel industry, relies heavily on the availability of a clean, natural environment. It is crucial for the sustainability of ecological systems, as well as business operations to ensure that hotel facilities are designed, constructed, operated and refurbished in a manner that is least harmful to the environment. If the environment is part of your business, protecting the environment means protecting your business. 2 For many years, the hotel industry was reluctant to acknowledge any significant influence on the natural surroundings. Recently, however, attitudes have started to change. In order to help hoteliers incorporate more environmentally sound practices into daily operations, branch associations, various NGOs, academic communities and hotel companies continue to develop guidelines and manuals. Industry self-regulation, in the form of certification and labelling schemes, has proved to be a valuable additional tool. Numerous certification and labelling schemes are offered internationally, nationally or locally by industrial organisations, as well as by governmental and non-governmental instit utions (EU Flower, Nordic Swan, Green Globe 21, Green Leaf, The Green Key, and others).

  • 13.
    Bohdanowicz, Paulina
    KTH, Superseded Departments, Energy Technology.
    A Study of Environmental Impacts, Environmental Awareness and Pro-Ecological Initiatives in the Hotel Industry2003Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Throughout the millennia commercial lodging establishmentshave evolved to what is today known as the hospitalityindustry. Hotels constitute one of the main, and stillexpanding, pillars of this sector and are highly unique amongother commercial buildings. They are designed to providecomfort and services twenty-four/seven. The success of tourism,and indirectly the hotel industry, largely depends on theavailability of a clean natural environment. At the same time,the environment is the major recipient of negative impactscreated by the construction and operation of hotel facilities.For many years, the industry was very reluctant to admit itsinfluence on the natural surroundings, but recently attitudeshave started to change.

    An e-mail based survey of environmental attitudes has beenperformed among more than 4000 European hoteliers, yielding 610responses. A similar questionnaire has further been distributedamong the guests of chosen hotels resulting in 141 answers fromfour Scandinavian hotels. Surveys revealed that both Europeanhoteliers and Scandinavian hotel guests perceive theenvironment as an important factor in the development andsuccess of tourism. Hoteliers are typically aware that theirfacilities influence the natural surroundings, a view sharedalso by hotel patrons, although the magnitude of the impacts isoften underestimated. Hotel managers and staff do have acertain (though varying) level of environmental knowledge andare generally aware of measures that can be taken towardsgreater environmental responsibility.

    Despite the fear shared by many hoteliers, thatenvironmental practices may negatively affect customer comfortand satisfaction, more than 75% of hotel guests interviewedexpressed their support and willingness to participate in manysuch initiatives. As hotel patrons are gradually demanding“green alternatives”, hoteliers are becomingincreasingly motivated and willing to take steps towardsgreater environmental responsibility. Almost 25% of hotelguests interviewed declared their willingness to pay more foraccommodation in an eco-certified facility.

    More than 70% of hotels investigated have already introducedpro-ecological initiatives, primarily in the areas of energyand water conservation, as well as responsible wastemanagement. The areas targeted are typically those, which canyield company benefits in a relatively short time.

    The results of the survey confirmed that the possibility ofa significant decreaseof the operational costs, and theexistence of an obvious and continuous customer demand, maylikely prompt hoteliers to respond with greater environmentalresponsibility. There is undoubtedly a great need for enhancingof education and environmental awareness among hotelrepresentatives and the general public. Given its profile thehotel industry can indisputably become a significant venue ofsuch education by communicating its environmental commitment tocustomers and inter-related industries.

    Keywords:hotels, environmental impacts, mitigationmeasures, survey, hoteliers, hotel customers, environmentalattitudes, environmental awareness, pro-ecological activities,incentives.

  • 14.
    Bohdanowicz, Paulina
    et al.
    KTH, Superseded Departments, Energy Technology.
    Martinac, Ivo
    KTH, Superseded Departments, Energy Technology.
    Attitudes towards sustainability in chain hotels – Results of a European survey2003In: Proceedings of the CIB International Conference on Smart and Sustainable Built Environment, 2003Conference paper (Refereed)
  • 15.
    Bohdanowicz, Paulina
    et al.
    KTH, Superseded Departments, Energy Technology.
    Simanic, Branko
    KTH, Superseded Departments, Energy Technology.
    Martinac, Ivo
    KTH, Superseded Departments, Energy Technology.
    Environmental education at Scandic hotels: approach and results2004In: Proceedings of the Regional Central and Eastern European Conference on Sustainable Building (SB04), 2004Conference paper (Refereed)
  • 16.
    Bohdanowicz, Paulina
    et al.
    KTH, Superseded Departments, Energy Technology.
    Zanki-Alujevic, Vlasta
    KTH, Superseded Departments, Energy Technology.
    Martinac, Ivo
    KTH, Superseded Departments, Energy Technology.
    Attitudes towards environmental responsibility among Swedish, Polish and Croatian hoteliers2004In: Proceedings of the BEST Sustainable Tourism Think Tank IV: Sustainability and mass destinations: Challanges and possibilities, 2004Conference paper (Refereed)
  • 17. Bron, O.
    et al.
    Fransson, Torsten
    KTH, Superseded Departments, Energy Technology.
    Ferrand, P.
    Experimental and Numerical Study of Non-Linear Interactions in Three-Dimensional Nozzle Flow2004Conference paper (Refereed)
  • 18.
    Bron, Olivier
    KTH, Superseded Departments, Energy Technology.
    Numerical and Experimental study of shock boundary layer interaction in unsteady transonic flow2003Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    A prerequisite for aeroelastic stability prediction inturbomachines is the understanding of the fluctuatingaerodynamic forces acting on the blades. Unsteady transonicflows are complex because of mutual interactions betweentravelling pressure waves, outlet disturbances, shock motion,and fluctuating turbulent boundary layers. Complex phenomenaappear in the shock/boundary layer region and produce phaselags and high time harmonics, which can give a significantcontribution to the overall unsteady lift and torque, andtherefore affect flutter boundaries, cause large localstresses, or even severely damage the turbomachine.

    The present research work is concerned with theunderstanding of phenomena associated with travelling waves innon-uniform transonic flows and how they affect the unsteadypressure distribution on the surface as well as the far fieldradiated sound. In similitude with turbomachines potentialinteraction, the emphasis was put on the unsteady interactionof upstream propagating acoustic waves with an oscillatingshock in 2D and 3D nozzle flows. Both numerical andexperimental studies are carried out and compared with eachother.

    Results shows that the unsteady pressure distribution, bothon the bump surface and within the channel, results from thesuperposition of upstream and downstream propagating waves. Itis believed that outlet pressure perturbations propagateupstream in the nozzle, interact in the high subsonic flowregion according to the acoustic blockage theory, and arepartly reflected or absorbed by the oscillating shock,depending on the frequency of the perturbations and theintensity of the SBLI. Furthermore the shock motion amplitudeis found to be related to the mean flow gradients and localwave length of the perturbations rather than to the shockboundary layer interaction. The phase angle between incomingpressure perturbations and the shock motion increases with theperturbation frequency but also depends on the intensity of theSBLI. Additionally the phase angle "shift" observed underneaththe shock location linearly increases with the perturbationfrequency and the shock strength. Such phase shift is criticalregarding aeroelastic stability and might have a significantimpact on the phase angle of the overall aerodynamic forceacting on the blade and shift the aerodynamic damping fromstable to exciting.

    Keywords:Shock Boundary Layer Interaction, ShockMotion, Unsteady Flows, Nozzle Flows, Potential Interaction,Back Pressure Perturbations.

  • 19.
    Bui Viet, Anh
    KTH, Superseded Departments, Energy Technology.
    Phenomenological and mechanistic modeling of melt-structure-water interactions in a light water reactor (LWR) severe accident1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Severe accidents in light water reactors have been the fotalpoint of much research, performed in the last two decades,aimed at understarrding the inherent physical phenomena and toevaluate proposed accident management schemes for mitigatingthe consequences of such accidents. Severe accident progressionand consequences, av the reactor core overheats and melts, areintimately related to the interactions of the melt with coolant(water) and structures.

    The objective of this work is to address the modeling of thethermal hydrodynamic phenomena and interactions, occurringduring the progression of reactor severe accidents. The maintheme of the present work is to integrate phenomenologicalmodeling with mechanistic modeling. Integrated phenomenologicalmodels are developed to describe the accident scenarios, whichtonsist of many processes, while mechanistic modeling,including direct numerical simulation, is carried out todescribe separate effects and selected physical phenomena ofparticular importance.

    Modeling of the in-vessel melt-structure interactions is thetopic of the first chapter. In its first part, models aredeveloped for the core debris heat up and the formation of amelt pool in the lower head of reactor vessel and the resultantthermal loads on the vessel. The heat transport andinteractions, occurring in this scenario, are representedthrough energy-conservation formulation. In order to describethe phase change associated with core debris and vessel wallmelting, a temperature-based enthalpy method is employed andthe initial energy-conservation equation is modified. Naturalconvection heat transfer inside the decay-heated melt pool isaccounted for in this work by an effective diffusivityconvectivity model. Its application has also been extended tothe case of metallit layers, heated from below and cooled fromtop and sides. These models, implemented in a computer codenamed MVITA, have becn applied to predict the vessel thermalloads during core debris heat up and melting in the reactorlower head. It was found that the formation of melt pool isquite coherent and large melt pool volumes result coherently.If the reactor vessel is not cooled from outside, the vesselmelt-through is inevitable. With vessel external cooling, themelt pool can be retained inside the vessel for moderate powerdensities (or reactor power level), even though partial wallmelting may occur. Modeling of the trust formation has beenincluded in the MVITA code. We believe that it is the firsttime that the melt pool, trust layers, metallit layer and thevessel have been described in an integrated two-dimensionalfashion and the results obtained showed that the vessel thermalloads are reduced dur to the 2D heat diffusion in thevessel.

    The second part of the first chapter deals with the issue oflocal vessel failureand its modeling. Specifically, theprocess of melt discharge from the local failure of the vesseland the dynamics of the failure enlargement caused by the meltdischarge process are considered. A general model, integratingmajor physical aspects of melt discharge and failure siteenlargement, is developed. Analysis, based on this integratedmodel, was performed to study the effects of various parameteruncertainties. It was shown that significant narrowing of theuncertainty range of the process important parameters, such asthe final size of the failure in the vessel and the meandischarge rate of the core melt to the containment, could beachieved when employing the new understarrding of hole ablationphenomenology.

    In the second chapter, modeling efforts are directed towardsinvestigating the phenomenology of the mixing of a corium meltjet, discharging from the reactor vessel, with water, presentin the BWR containment lower drywell. Particular attention isfocused on the break-up of the melt jet in water, the behaviorof the fragments, as well as on the dynamics of the mixing zoneand its feedback to the break-up process. Numerical methods,which allow solution of the mathematical models of themultiphase system with minimal numerical diffusion, aredeveloped and used to investigate relevant interfacialphenomena, such as Kelvin-Helmholtz instabilities and jet/dropfragmentation in a flow field. The development of surfaceinstabilities and fragmentation of melt jet or drops were foundto be affected strongly by the property variations in themelt-coolant system caused, e.g., by the melt solidificationand water vaporization. It was found that break-up of ahigh-density melt drop in the water flow field is dominated bythe shear break-up mode, except when the melt drop hss highviscosity. The break-up of a heavy melt at the leading edge dueto Rayleigh-Taylor instabilities was found to be governed bythe jet-water density ratio and jet velocity. An integratedmodel of melt-water interactions is also developed in thiswork, which takes into account major physical phenomena andinter-relations. Results of the analysis using this modelindicate the sensitivity of the general behavior of the melt,drop, and water fields on a number of key factors, e.g., theheat transfer regimes (film boiling and radiation), finalfragment size, dynamits of water vaporisation and steamcondensation, etc.

    The third chapter of the dissertation is devoted to theproblem of ex-vessel debris bed coolability, i.e., behavior ofa core debris bed, located on the containment floor, and theablation of containment concrete basemat. The relevant physicalprocesses are described by a simple model, which takes intoaccount the dynamits of trust growth and the physical-chemicalaspects of malten torium-concrete interactions. Stability ofthe trust layer, separating the melt pool portion of the debrisbed and the molten concrete, as well as the heat transferthroughthis layer (which is similar to that of film boiling)were found to be important factors for concrete ablation.Coolability of an ex-vessel core debris bed is determined bythe bed geomettical tonfiguration and straclure, which definethe area available for cooling from outside. If such cooling isinsufficient, concrete melt-through is feasible.

    Keywords:light water reactor, severe accidents,melt-structure-coolant interaction, melt pool formation, holeablation, jet fragmentation, drop breakup, premixing, debriscoolability, natural convection, heat transfer, instabifities,multiphase flow, phase change.

  • 20.
    Burt, Tyrrell S.
    KTH, Superseded Departments, Energy Technology.
    The sick buidling syndrome1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This investigation consisted of an intervention study of asingle officebuilding. In the first study, already reported, itwas concluded thatmicrobiological and chemical factors wereunlikely to be responsible forsymptoms of sick buildingsyndrome (SBS) in this building. The focus of theinvestigationtherefore narrowed down to the physical factors. Theseincludethe thermal aspects, and aspects relating to air quality,lighting and acoustics.

    This report contains the results of the second study,carried out after intervention measures had been implemented.The questionnaire usedpreviously was shortened and retested. Ascoring system was used to ratesymptoms and find associationswith SBS. The most prevalent physicalfactors were reports ofdry air, stuffy air and noise, but the factors moststronglyassociated with SBS symptoms were ventilation noise,staticelectricity and dust. The dust appears to be produced bythe supplyventilation system. The intervention measuresprovided the building withimproved thermal control. This hadsome effect on the perceived airquality, but the effect on SBSsymptoms was slight. Although air flows tothe rooms wereadequate, the distribution of supply air in the rooms was stillpoor after intervention.

    The acoustic environment was examined because of the strongassociationfound between complaints of ventilation noise andSBS symptoms.Measurements showed that many occupants were beingsubjected to over 70 dBof noise produced by the ventilationsystem. Much of this was in theinfrasound region below 20 Hzand inaudible. The biological effects ofinfrasound have beenreported to include symptoms such as headache,fatigue, nauseaand lack of concentration. The descriptions of these symptomsare very similar to the descriptions of some SBS symptoms.Theresults from this study showed that opening a window couldincrease levelsof infrasound. Reducing fans speeds providedsome noise reduction, althoughthe effects in the infrasoundregion were slight. Closing both windows and doors gave thebiggest reduction, but this adversely affects air qualityandinterferes with working routines.

    Other factors considered in this study are allergy,circadian rhythms,electromagnetic fields, individual controland lighting. The strongestassociation with SBS symptoms waswith atopic conditions of asthma,allergy, eczema and allergy.Evening types had more SBS than morning types,which is a newfinding in SBS studies. Working with computers had littleeffecton SBS in this study, and the literature suggests that theeffectsof electromagnetic fields in an office environment areslight. Individualcontrol over the work and the indoorenvironment appears to be associatedwith SBS. High levels oflighting were slightly associated with SBS.

    The most effective remedial measures in this building wouldbe to lower the supply air temperatures to give improved airdistribution, to filter theair at the supply terminals toreduce the dust, and to install an activenoise control systemto reduce levels of low frequency noise andinfrasound.

    KEYWORDS:Sick building syndrome, allergy, infrasound,air quality.

  • 21.
    Caraghiaur, Diana
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Frid, Wiktor
    KTH, Superseded Departments, Energy Technology.
    Tillmark, Nils
    KTH, Superseded Departments, Mechanics.
     Detailed pressure drop measurements in single- and two-phase adiabatic air-water turbulent flows in realistic BWR fuel assembly geometry with spacer grids2004In: The 6th International Conference on Nuclear Thermal Hydraulics, Operations and Safety (NUTHOS-6) Nara, Japan, October 4-8, 2004, 2004Conference paper (Refereed)
    Abstract [en]

    In recent years, advanced numerical simulation tools based on CFD methods have been increasingly used in various multi-phase flow applications. One of these is two-phase flow in fuel assemblies of Boiling Water Reactors. The important and often missing aspect of this development is the validation of CFD codes against proper experimental data. The purpose of the current paper is to present detailed pressure measurements over a spacer grid in adiabatic single- and two-phase flow, which will be used to validate and further develop a CFD code for BWR fuel bundle analysis. The experiments have been carried out in an asymmetric 24-rod sub-bundle, representing ¼ of Westinghouse SVEA-96 nuclear reactor fuel assembly. Single-phase measurements have been performed at superficial velocities comprised between jliq: 0.90 – 4.50 m/s and in the two-phase, which was simulated by air-water mixture, measurements have been performed at void fractions ranging from 4 to 12% and liquid superficial velocity jliq : 4.50 m/s. In order to increase the number of the measured points, five pressure taps were drilled in one of the rods, which was easily moved vertically by a traverse system, covering most of the points in axial direction. The possibility to substitute any of the rods in the fuel bundle by the pressure sensing rod and the possibility to change the pressure taps facing-angle provides more measuring points inside the subchannels. A detailed pressure distribution comparison between single- and two-phase flows for different subchannel positions and different flow conditions was performed over one of the spacers.  In addition, single-phase pressure drop measurements on the upper part of the test section comprising two spacer grids has been carried out.

  • 22.
    Chernysheva, Olga V.
    KTH, Superseded Departments, Energy Technology.
    Flutter in sectored turbine vanes2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In order to eliminate or reduce vibration problems inturbomachines without a high increase in the complexity of thevibratory behavior, the adjacent airfoils around the wheel areoften mechanically connected together with lacing wires, tip orpart-span shrouds in a number of identical sectors. Although anaerodynamic stabilizing effect of tying airfoils together ingroups on the whole cascade is indicated by numerical andexperimental studies, for some operating conditions suchsectored vane cascade can still remain unstable.

    The goal of the present work is to investigate thepossibilities of a sectored vane cascade to undergoself-excited vibrations or flutter. The presented method forpredicting the aerodynamic response of a sectored vane cascadeis based on the aerodynamic work influence coefficientrepresentation of freestanding blade cascade. The sectored vaneanalysis assumes that the vibration frequency is the same forall blades in the sectored vane, while the vibration amplitudesand mode shapes can be different for each individual blade inthe sector. Additionally, the vibration frequency as well asthe amplitudes and mode shapes are supposed to be known.

    The aerodynamic analysis of freestanding blade cascade isperformed with twodimensional inviscid linearized flow model.As far as feasible the study is supported by non-linear flowmodel analysis as well as by performing comparisons againstavailable experimental data in order to minimize theuncertainties of the numerical modeling on the physicalconclusions of the study.

    As has been shown for the freestanding low-pressure turbineblade, the blade mode shape gives an important contributioninto the aerodynamic stability of the cascade. During thepreliminary design, it has been recommended to take intoaccount the mode shape as well rather than only reducedfrequency. In the present work further investigation using foursignificantly different turbine geometries makes these findingsmore general, independent from the low-pressure turbine bladegeometry. The investigation also continues towards a sectoredvane cascade. A parametrical analysis summarizing the effect ofthe reduced frequency and real sector mode shape is carried outfor a low-pressure sectored vane cascade for differentvibration amplitude distributions between the airfoils in thesector as well as different numbers of the airfoils in thesector. Critical (towards flutter) reduced frequency maps areprovided for torsion- and bending-dominated sectored vane modeshapes. Utilizing such maps at the early design stages helps toimprove the aerodynamic stability of low-pressure sectoredvanes.

    A special emphasis in the present work is put on theimportance for the chosen unsteady inviscid flow model to bewell-posed during numerical calculations. The necessity for thecorrect simulation of the far-field boundary conditions indefining the stability margin of the blade rows isdemonstrated. Existing and new-developed boundary conditionsare described. It is shown that the result of numerical flowcalculations is dependent more on the quality of boundaryconditions, and less on the physical extension of thecomputational domain. Keywords: Turbomachinery, Aerodynamics,Unsteady CFD, Design, Flutter, Low-Pressure Turbine, Blade ModeShape, Critical Reduced Frequency, Sectored Vane Mode Shape,Vibration Amplitude Distribution, Far-field 2D Non-ReflectingBoundary Conditions. omain.

    Keywords:Turbomachinery, Aerodynamics, Unsteady CFD,Design, Flutter, Low-Pressure Turbine, Blade Mode Shape,Critical Reduced Frequency, Sectored Vane Mode Shape, VibrationAmplitude Distribution, Far-field 2D Non-Reflecting BoundaryConditions.

  • 23.
    ChungHong, Sheng
    KTH, Superseded Departments, Energy Technology.
    Some two-phase flow and boiling heat transfer characteristics in small diameter tubes2001Licentiate thesis, monograph (Other scientific)
  • 24.
    Claesson, Joachim
    KTH, Superseded Departments, Energy Technology.
    Literature Survey, relevant to compact brazed plate heat exchangers as evaporators in heat pump system2004Report (Other academic)
  • 25.
    Cronhjort, Björn
    et al.
    KTH, Superseded Departments, Energy Technology.
    Mörner, N. -A
    A question of vs. wet the case for dry rock disposal of nuclear waste2004In: Radwaste Solutions, ISSN 1529-4900, Vol. 11, no 3, p. 44-47Article in journal (Refereed)
    Abstract [en]

    Dry rock disposal (DRD) of nuclear waste in high-relief areas where the groundwater has been artificially drained is discussed. Disposal of high-level nuclear waste can involve multiple problems that put serious stress on society and environment. In US, the Department of Energy uses dry deposition at Yucca Mountain at a depth of 300 meters. The groundwater table is at a depth of 600 m. So, at the given climatic conditions, the Yucca Mountain repository at 300 m will be dry. In such cases the DRD method is found to be suitable.

  • 26. Dovic, D.
    et al.
    Palm, Björn E.
    KTH, Superseded Departments, Energy Technology.
    Svaic, S.
    Visualtization of one-phase flow in chevron-plate heat exchangers end their performance2000In: Strojniski vestnik, ISSN 0039-2480, Vol. 46, no 7, p. 429-435Article in journal (Refereed)
    Abstract [sl]

    Modern plate heat exchangers with chevron corrugation patterns are spread across a range of applications both in one- and two-phase flow regimes due to their compactness and superior thermal-hydraulic performance when compared to the other types of heat exchangers. Recently a limited number of experimental studies have been undertaken to understand the influence of corrugation angles and the ratio of corrugation depth to,wave length (b/l) On the flow pattern and in turn on the heat transfer and pressure drop. In order to clarify this complex issue, visualization tests have been performed on a model of a Plate heat exchanger (PHE) having only a single channel composed of one metal and one plastic transparent plate with identical corrugation.

  • 27.
    Duwig, Christophe
    KTH, Superseded Departments, Energy Technology.
    Numerical and experimental validation of gas turbine combustor design for gasified biomass combustion2000Licentiate thesis, comprehensive summary (Other scientific)
  • 28.
    Einberg, Gery
    KTH, Superseded Departments, Energy Technology.
    Ventilation and stable climate2001Licentiate thesis, monograph (Other scientific)
  • 29.
    Eriksson, Francis
    KTH, Superseded Departments, Energy Technology.
    Sorption av VOC på rumsytor och inredningsmaterial i ventilerade lokaler1998Licentiate thesis, monograph (Other scientific)
  • 30.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Han, Han
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Lundqvist, Per
    KTH, Superseded Departments, Energy Technology.
    The Solubility of Propane (R290) with Commonly Used Compressor Lubrication Oils2003In: Compressors and Their Systems, 2003, Vol. 4, p. 157-166Conference paper (Refereed)
    Abstract [en]

    An ongoing project called "Charge minimisation of a small capacity heat pump" is aimed to minimise the refrigerant charge in heat pumps, refrigeration and air-conditioning systems. The experimental heat pump was run with propane as refrigerant and the designed heat capacity (condenser capacity) was over 5kW. Tests were done to investigate the refrigerant charge distribution in different sections of the heat pump, while it was running. The experiments done so far have shown that the amount of refrigerant in the compressor is higher than expected.

    This paper presents the measured refrigerant masses in a hermetic scroll compressor together in suction line and the calculated refrigerant mass dissolved in the compressor lubrication oil at different evaporation temperatures. Finally, solubility tests of propane with different lubricating oils are presented. The tests show that the propane is more soluble in POE than PAG oils.

  • 31.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Andersson, Klas
    KTH, Superseded Departments, Energy Technology.
    Mini-Channel Aluminium Heat Exchangers with Small Inside Volumes2003In: Proc. 21st IIR International Congress of Refrigeration, Washington DC, August 17-22, 2003, 2003Conference paper (Refereed)
  • 32.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Samoteeva, Oxana
    KTH, Superseded Departments, Energy Technology.
    Anderson, Klas
    KTH, Superseded Departments, Energy Technology.
    The Behaviour of Small Capacity (5kW) Heat pump with Micro-Channelled Flat Tube Heat Exchangers2002Conference paper (Refereed)
  • 33.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Lundqvist, Per
    KTH, Superseded Departments, Energy Technology.
    Granryd, Eric
    KTH, Superseded Departments, Energy Technology.
    Propane Heat Pump with Low Refrigerant Charge: Design and Laboratory Tests2004In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 27, no 7, p. 761-773Article in journal (Refereed)
    Abstract [en]

    Independently of the choice of refrigerant, environmental and or safety issues can be minimised by reducing the amount of refrigerant charge per heat pump or refrigeration system. In the investigation reported here, a laboratory test rig was built, simulating a water-to-water heat pump with a heating capacity of 5 kW. The system was designed to minimize the charge of refrigerant mainly by use of mini-channel aluminium heat exchangers. It was shown that the system could be run with 200 g of propane at typical Swedish operating conditions without reduction of the COP compared to a traditional design. Additional charge reduction is possible by selecting proper compressor lubrication oils or by using a compressor with less lubrication oil.

  • 34.
    Fernando, W. Primal D.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Samoteeva, Oxana
    KTH, Superseded Departments, Energy Technology.
    Lundqvist, Per
    Palm, Björn
    KTH, Superseded Departments, Energy Technology.
    Charge Distribution in a 5kW Heat Pump Using Propane as Working Fluid: Part 1: Experimental Investigation2001In: Proc. 16. Nordiske Kølemøde og 9. Nordiske Varmepumpedage29.-31. August 2001, 2001, p. 299-Conference paper (Refereed)
  • 35.
    Fransson, Torsten H.
    et al.
    KTH, Superseded Departments, Energy Technology.
    Hillion, F. X.
    Klein, E.
    An international electronic and interactive teaching and life-long learning platform for gas turbine technology in the 21st century2001In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 123, no 3, p. 595-603Article in journal (Refereed)
    Abstract [en]

    An interactive learning platform which sets a new standard for electronic learning of gas turbine technology in a global life-long learning perspective is presented (Fig. I). The platform contains a theoretical section in the Sonn of several pages for each chapter available, with a significant number of related interactive simulations, movies, animations, virtual laboratory exercises, virtual study visits and realistic case studies. A significant background information related to historical development in the field, a display of existing components, nomenclature, multi-lingual dictionary and keywords, as well as questions for self-assessment and exams, an electronic communication group and a database of the user's ''successes and failures,'' enhance the learning process in a significant way. The program is intended as a platform for an international collaboration on learning heat and power technology. It can be used both in the classroom as well as for self-studies and is as such well adapted for both university and post-university learning, both on and off campus. Tools to facilitate the introduction of new material exist. It is thus hoped that teachers at different universities can join forces and in a noncompetitive way introduce material which can be shared, instead of developing similar simulations with somewhat different interfaces. The long-term goal of the learning platform is of course that users worldwide will have the possibility to access the best teaching material available from any specialist, and that this material will contain supplementary pedagogical information which will enhance the learning both at a university and a post-university level.

  • 36.
    Freudenreich, Kai
    KTH, Superseded Departments, Energy Technology.
    Experimental Investigation of Velocity Gust in High Pressure Turbines2001Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis investigates the unsteady three-dimensional gustfield in high subsonic and transonic turbine stages based onexperimental velocity data. The generation, propagation andinteraction mechanisms of the velocity gust in high pressureturbines are studied. Two approaches are followed: In aparametric study the tendencies of the velocity gust dependenton a number of stage parameters are examined. Secondly, theunsteady velocity flow field of one stage operating point iscarefully studied. This aims to receive a detailed picture ofvortical and potential velocity gust components, with andwithout shock contributions, and their interaction with therotor flow field.

    A three-dimensional Laser-two-Focus anemometer has been usedto measure the periodic three-dimensional velocity andturbulence intensity in subsonic and transonic turbine flow.The application of the measurement technique to the wind tunnelfor rotating annular cascades and the data evaluation aredescribed.

    For the parametric study the stator vane count, the axialgap between stator and rotor, the rotor turning frequency andthe flow regime subsonic vs. transonic have been changed. Thestator induced wake and shock propagate in different downstreamdirections. Dependent on the axial gap between stator and rotorthe rotor blades experience either two separated velocitydistortions or one superposed and re-enforced velocitydistortion. Accordingly, the computed blade surface pressureperturbations (not part of this thesis) show a differentweighting of the first andhigher harmonic amplitudes. At therotor exit the gust and the non time-resolved unsteadiness areclosely related to the stage loss. Highest unsteadiness andloss occur for strong negative off-design incidence, possiblydue to boundary layer separation on the rear blade suctionside. Lowest unsteadiness and loss occur not at design inletangle, but at strong positive off design. Data from stator onlyconfigurations represent the time-averaged rotor inlet flowfairly well. It might be used for simple gust computations tocalculate the unsteady rotor aerodynamics.

    The detailed flow field study shows the distribution of thegust components and the Mach number perturbation due to thestator induced wake and trailing edge shock. The computedunsteady pressure on the front blade suction side, the forcingfunction, is mainly affected by the pressure perturbations fromthe stator trailing shock, i.e. potential gust. This shock hasonly a minor influence on the velocity field. Furtherdownstream in the rotor passage the vortical gust near and theforcing function on the suction surface can be related to eachother. Closer to the casing and at lower Mach numbers increasedeffects by the stator wake and secondary vortices, resp.decreased stator shock effects are observed. The gust is alsosplit up into potential and vortical components using atwo-dimensional incompressible analysis using harmonicallydecomposed gust data. No reasonable results are obtained forthe potential gust component. This is attributed to the missingconsideration of compressibility effects and the pressure gust,especially at stator exit Mach numbers close to one.Qualitative agreement to the time-resolved analysis is foundfor the vortical gust distribution in the rear rotorpassage.

    A three-dimensional gust structure was examined, theinteraction of the stator wake with the relative eddy. Thegeneration of turbulence intensity due to the chopping ofstator wake and secondary vortices by the blades is described.Finally, stator trailing edge shocks and their time-dependentrelative strength to each other can be identified by the spaceand time-resolved turbulence intensity.

    Recommendations for future work are given.

    Keywords:turbomachinery, unsteady aerodynamics, gust,forcing function, forced response, transonic flow, annularcascade, Laser-Two-Focus Anemometer, experiments

  • 37.
    Granryd, Eric G.
    KTH, Superseded Departments, Energy Technology.
    Hydrocarbons as refrigerants - an overview2001In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 24, no 1, p. 15-24Article in journal (Refereed)
    Abstract [en]

    Possibilities and problems of using hydrocarbons as working fluids in refrigerating equipment are discussed. An overview of safety standards is given. Different hydrocarbon alternatives are listed and characteristics in terms of thermodynamic cycles as well as heat transfer are shown. The general conclusion is that hydrocarbons offer interesting refrigerant alternatives for energy efficient and environmentally friendly refrigerating equipment and heat pumps. However, safety precautions due to flammability must be seriously taken into account. For some applications this can be done without adding noticeably to the total installation cost, but not in the general case.

  • 38.
    Green, Jeff
    KTH, Superseded Departments, Energy Technology.
    Forced Response Predictions: Applications within the Design Process: (Dealing with Orientation Scatter in Single Crystal Blades)1999In: 4th US National Turbine Engine High CycleFatigue Conference, Monterey, California, USA. 1999, 1999Conference paper (Refereed)
  • 39.
    Green, Jeff
    et al.
    KTH, Superseded Departments, Energy Technology.
    Marshall, J.G:
    Forced Response Prediction within the Design Process1999In: 3rd European Conference on Turbomachinary - Fluid Dynamics andThermodynamics. 2-5 March 1999, London, UK. Reference: L07/C557 – 67., 1999Conference paper (Refereed)
  • 40.
    Gubaidullin, Askar
    KTH, Superseded Departments, Energy Technology.
    Natural Convection Heat Transfer in Two-Fluid Stratified Pools with Internal Heat Sources2001Doctoral thesis, comprehensive summary (Other scientific)
  • 41.
    Hansson Concilio, Roberta
    et al.
    KTH, Superseded Departments, Energy Technology.
    Park, Hyun Sun
    KTH, Superseded Departments, Energy Technology.
    Sehgal, Balraj
    KTH, Superseded Departments, Energy Technology.
    Evaluation of Quantitative Measurement by High-speed X-ray Radiography for Fragmented Particle Fraction2004In: Proc. of the 6th International Topical Meeting on Nuclear Reactor Thermal Hydraulics Operations and Safety (NUTHOS-6), 2004Conference paper (Refereed)
  • 42.
    Haraldsson, Haraldur Óskar
    KTH, Superseded Departments, Energy Technology.
    Breakup of jet and drops during premixing phase of fuel coolant interactions2000Doctoral thesis, comprehensive summary (Other scientific)
  • 43.
    Herbe, Lars
    KTH, Superseded Departments, Energy Technology.
    CFC and HCFC refrigerant retrofit: a theoretical, practical and environmental evaluation of alternatives1997Licentiate thesis, monograph (Other scientific)
  • 44.
    Hu, Jiasen
    KTH, Superseded Departments, Energy Technology.
    Turbulence and transition prodictions of internal flows2000Doctoral thesis, comprehensive summary (Other scientific)
  • 45.
    Högström, Carina
    KTH, Superseded Departments, Energy Technology.
    Värmepump med propan som köldmedium1999Licentiate thesis, monograph (Other scientific)
  • 46.
    Höhn, Wolfgang
    KTH, Superseded Departments, Energy Technology.
    Numerical investigation of blade flutter at or near stall in axial turbomachines2000Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    During the design of the compressor and turbine stages oftoday's aeroengines aerodynamically induced vibrations becomeincreasingly important since higher blade load and betterefficiency are desired. Aerodynamically induced vibrations inturbomachines can be classified into two general categories,i.e. selfexcited vibrations, usually denoted as flutter, andforced response. In the first case the aerodynamic forcesacting on the structure are dependent on the motion of thestructure. In the latter case the aerodynamic forces can beconsidered to be independent of the structural motion. In thisthesis the development of a method based on the unsteady,compressible Navier-Stokes equations in two dimensions isdescribed in order to study the physics of flutter for unsteadyviscous flow around cascaded vibrating blades at stall.

    The governing equations are solved by a finite differencetechnique in boundary fitted coordinates. The numerical schemeuses the Advection Upstream Splitting Method to discretize theconvective terms and central differences discretizing thediffusive terms of the fully non-linear Navier-Stokes equationson a moving H-type mesh. The unsteady governing equations areexplicitly and implicitly marched in time in a time-accurateway using a four stage Runge-Kutta scheme on a parallelcomputer or an implicit scheme of the Beam-Warming type on asingle processor. Turbulence is modelled using theBaldwin-Lomax turbulence model. The blade flutter phenomenon issimulated by imposing a harmonic motion on the blade, whichconsists of harmonic body translation in two directions and arotation, allowing an interblade phase angle betweenneighbouring blades. An aerodynamic instability is given whichcan lead to a flutter problem, if the computed unsteadypressure forces amplify the imposed blade motion.Non-reflecting boundary conditions are used for the unsteadyanalysis at inlet and outlet of the computational domain. Thecomputations are performed on multiple blade passages in orderto account for nonlinear effects. Unsteady boundary conditionsare developed considering primary and secondary gust effectstowards the investigation of the forced response problem withthe presented method.

    Subsonic massively stalled and transonic separated unsteadyflow cases in compressor and turbine cascades are studied. Theresults, compared with experiments and the predictions of otherresearchers, show good agreement for inviscid and viscous flowcases for the investigated flow situations with respect to thesteady and unsteady pressure distribution on the blade in thevicinity of shocks and in separated flow areas.

    The results show the applicability of the new scheme forstalled flow around cascaded blades. As expected the viscousand inviscid methods show different results in areas whereviscous effects are important, i.e. separated flow and shockwaves. In particular, different predictions for inviscid andviscous flow for the aerodynamic damping for the investigatedflow cases are found.

    Keywords: turbomachinery, flutter, forced response, gust,unsteady aerodynamics, Navier-Stokes equations, AdvectionUpstream Splitting Method, implicit scheme, non-reflectingboundary conditions, gust boundary conditions, parallelcomputing

  • 47.
    Jacoby, Jürgen
    KTH, Superseded Departments, Energy Technology.
    Catalytic combustion of gasified biomass in gas turbines1999Licentiate thesis, comprehensive summary (Other scientific)
  • 48.
    Jacoby, Jürgen
    KTH, Superseded Departments, Energy Technology.
    Experimental Investigation of Catalytic Combustion of Simulated Gasified Biomass for Gas Turbine Applications2001Doctoral thesis, comprehensive summary (Other scientific)
  • 49.
    Jasiulevicius, Audrius
    KTH, Superseded Departments, Energy Technology.
    Analysis methodology for RBMK-1500 core safety and investigations on corium coolabiblty during a LWR sever accidnet2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents the work involving two broad aspectswithin the field of nuclear reactor analysis and safety. Theseare: - development of a fully independent reactor dynamics andsafety analysis methodology of the RBMK-1500 core transientaccidents and - experiments on the enhancement of coolabilityof a particulate bed or a melt pool due to heat removal throughthe control rod guide tubes.

    The first part of the thesis focuses on the development ofthe RBMK-1500 analysis methodology based on the CORETRAN codepackage. The second part investigates the issue of coolabilityduring severe accidents in LWR type reactors: the coolabilityof debris bed and melt pool for in- vessel and ex-vesselconditions.

    The safety of the RBMK type reactors became an importantarea of research after the Chernobyl accident. Since 1989,efforts to adopt Western codes for the RBMK analysis and safetyassessment are being made. The first chapters of this Thesisdescribe the development of an independent neutron dynamics andsafety analysis methodology for the RBMK-1500 core transientsand accidents. This methodology is based on the codes HELIOSand CORETRAN. The RBMK-1500 neutron cross section library wasgenerated with the HELIOS code. The ARROTTA part of theCORETRAN code performs three dimensional neutron dynamicsanalysis and the VIPRE-02 part of the CORETRAN package performsthe rod bundle thermal hydraulics analysis. The VIPRE-02 codewas supplemented with additional CHF correlations, used inRBMK-type reactor calcula tions. The validation, verificationand assessment of the CORETRAN code model for RBMK-1500 wereperformed and are described in the thesis.

    The second part of the thesis describes the in- vesselparticulate debris bed and melt pool coolabilityinvestigations. The role of the control rod guide tubes (CRGTs)in enhancing the coolability during a postulated severeaccident in a BWR was investigated experimentally. Thisinvestigation is directed towards the accident managementscheme of retaining the core melt within the BWR lowerhead.

    The particulate debris bed coolability was also investigatedduring the ex-vessel severe accident situation, having a flowof non-condensable gases through the porous debris bed.Experimental investigations on the dependence of the quenchingtime on the non-condensable gas flow rate were carriedout.

    The first chapter briefly presents the status ofdevelopments in both the RBMK- 1500 core analysis and thecorium coolability areas.

    The second chapter describes the generation of the RBMK-1500neutron cross section data library with the HELIOS code. Thecross section library was developed for the whole range of thereactor conditions (i.e. for both cold and hot reactor states).The results of the benchmarking with the WIMS-D4 code andvalidation against the RBMK Critical Facility experiments isalso presented here. The HELIOS generated neutron cross sectiondata library provides a close agreement with the WIMS-D4 coderesults. The validation against the data from the CriticalExperiments shows that the HELIOS generated neutron crosssection library provides excellent predictions for thecriticality, axial and radial power distribution, control rodreactivity worths and coolant reactivity effects, etc. Thereactivity effects of voiding for the system, fuel assembly andadditional absorber channel are underpredicted in thecalculations using the HELIOS code generated neutron crosssections. The underprediction, however, is much less than thatobtained when the WIMS-D4 code generated cross sections areemployed.

    The third chapter describes the work, performed towards theaccurate prediction, assessment and validation of the CHF andpost-CHF heat transfer for the RBMK- 1500 reactor fuelassemblies employing the VIPRE-02 code. This chapter describesthe experiments, which were used for validating the CHFcorrelations, appropriate for the RBMK-1500 type reactors.These correlations after validation were added to the standardversion of the VIPRE-02 code. The VIPRE-02 calculations werebenchmarked against the RELAP5/MOD3.3 code. It was found thatthese user-coded additional CHF correlations developed for theRBMK type reactors (Osmachkin, RRC KI and Khabenskicorrelations) and implemented into the code by the author,provide a good prediction of the CHF occurrence at the RBMKreactor nominal pressure range (at about 7 MPa). Transition andfilm boiling are also predicted well with the VIPRE-02 code forthis pressure range. It was found, that for the RBMK- 1500reactor applications, EPRI CHF correlation should be used forthe CHF predictions for the lower fuel assemblies of thereactor in the subchannel model of the RBMK-1500 fuel assembly.RRC KI and Bowring CHF correlations may be used for the upperfuel assemblies. For a single-channel model of the RBMK-1500fuel channel, Osmachkin, RRC KI and Bowring correlationsprovide the closest predictions and may be used for the CHFestimation. For the low coolant mass fluxes in the fuelchannel, Khabenski correlation can be applied.

    The fourth chapter presents the verification of the CORETRANcode for the RBMK-1500 core analysis (HELIOS generated neutroncross section data, coupled CORETRAN 3-D neutron kineticscalculations and VIPRE-02 thermal hydraulic module). The modelwas verified against a number of RBMK-1500 plant data andtransient calculations. The new RBMK-1500 core model wassuccessfully applied in several safety assessment applications.A series of transient calculations, considered within the scopeof the RBMK-type reactor Safety Analysis Report (SAR), wereperformed. Several cases of the transient calculations arepresented in this chapter. The HELIOS/CORETRAN/VIPRE-02 coremodel for the RBMK-1500 is fully functional. The RBMK-1500 CPSlogic, added into the CORETRAN provides an adequate response tothe changes in the reactor parameters.

    Chapters 5 and 6 describe the experiments and the analysisperformed on the coolability of particulate debris bed and meltpool during a postulated severe accident in the LWR. In theChapter 5, the coolability potential, offered by the presenceof a large number of the Control Rod Guide Tubes (CRGTs) in theBWR lower head is presented. The experimental investigationsfor the enhancement of coolability possible with CRGTs wereperformed on two experimental facilities: POMECO (POrous MEdiumCOolability) and COMECO (COrium MElt COolability). Theinfluence of the coolant supply through the CRGT on the debrisbed dryout heat flux, debris bed and melt pool quenching time,crust growth rate, etc. were examined. The heat removalcapacity offered by the presence of the CRGT was quantifiedwith the experimental data, obtained from the POMECO and COMECOfacilities. It was found that the presence of the CRGTs in thelower head of a BWR offers a substantial potential for heatremoval during a postulated severe accident. Additional 10-20kW of heat were removed from the POMECO and COMECO testsections through the CRGT. This corresponds to the average heatflux on the CRGT wall equal to 100-300 kW/m2.

    In the Chapter 6 the ex-vessel particulate debris bedcoolability is investigated, considering the non-condensablegases released from the concrete ablation process. Theinfluence of the flow of the non-condensable gases on theprocess of quenching a hot porous debris bed was considered.The POMECO test facility was modified, adding the air supply atthe bottom of the test section, to simulate the noncondensablegas release. The process was investigated for both high and lowporosity debris beds. It was found that for the low porositybed composition the countercurrent flooding limit could beexceeded, which would degrade the quenching process for suchbed compositions. The experimental results were analyzed withseveral CCFL models, available in the literature.

    Keywords:RBMK, light water reactor, core analysis,transient analysis, reactor dynamics, RIA, ATWS, critical heatflux, post-CHF, severe accidents, particulate debris beds, meltpool coolability, BWR, CRGT, dryout, quenching, CCFL, crustgrowth, solidification, water ingression, heat transfer.

  • 50. Jocker, M.
    et al.
    Hillion, F. X.
    Fransson, Torsten H.
    KTH, Superseded Departments, Energy Technology.
    Wahlen, U.
    Numerical unsteady flow analysis of a turbine stage with extremely large blade loads2002In: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 124, no 3, p. 429-438Article in journal (Refereed)
    Abstract [en]

    This paper presents the detailed numerical analysis including parametric studies on the aerodynamic excitation mechanisms in a turbine stage due to the unsteady stator-rotor interaction, The work is part of the predesign study of a high-pressure subsonic turbine,for a rocket engine turbopump. The pressure level in such turbines can be remarkably high (in this case 54 MPa inlet total pressure). Hence, large unsteady rotor blade loads can be expected, which impose difficult design requirements, The parameter studies are performed at midspan with the numerical flow solver UNSFLO, a 2-D/Q3-D unsteady hybrid Euler/Navier-Stokes solver. Comparisons to 2-D and steady, 3-D results obtained with a fully viscous solver VOLSOL, are made. The investigated design parameters are the axial gap (similar to8-29 percent of rotor axial chord length) and the stator vane size and count (stator-rotor pitch ratio similar to1-2.75), For the nominal case the numerical solution is analyzed regarding the contributions of potential and vortical flow disturbances at the rotor inlet using rotor gust computations. It was found that gust calculations were not capable to capture the complexity of the detected excitation mechanisms, but the possibility to reduce excitations by enforcing cancellation of the vortical and potential effects has been elaborated. The potential excitation mechanism in the present turbine stage is found dominant compared to relatively small and local wake excitation effects. The parameter studies indicate design recommendations for the axial gap and the stator size regarding the unsteady rotor load.

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