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  • 1.
    Lim, Shyang Maw
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Aerothermodynamics and exergy analysis in turbocharger radial turbine2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Coupling of turbomachine to reciprocating automotive engine in turbocharging leads to complex fluid flow and thermal characteristics in the turbine. Some undesirable characteristics include heat transfer, flow pulsation and secondary flow due to the complex geometry of the upstream exhaust manifold. The performed literature review exposed that there is a need for an enhanced understanding of the thermo-fluid physics of a turbocharger turbine operating under realistic on-engine conditions, and on quantifying the impact on the performance. Often, simplified set-ups and geometries are employed, neglecting the heat transfer.

    This dissertation aimed to improve the quality of heat transfer analysis in a turbocharger turbine, and to enhance the understanding of aerothermodynamic effects due to heat transfer on the performance under engine-like pulsatile flow scenarios. Firstly, a flow exergy based analysis was developed to be used with the input provided by three-dimensional flow field data predicted by Detached Eddy Simulation (DES). Its applicability to identify and to quantify the aerothermodynamic related losses due to heat transfer was thoroughly investigated with a set-up replicating a hot gas stand continuous flow scenario. Next, the developed methodology was applied to engine-like pulsatile flow scenarios, to investigate the effects of flow pulsation and the influences of upstream exhaust manifold on the heat transfer and turbine performance. For the investigated geometry and specified boundary conditions, this dissertation mainly concluded that 1) The most sensitive measures associated with heat loss are the flow exergy lost via heat transfer and the thermal irreversibilities. The influence of heat loss on turbine power reduction is small in a relative sense, and 2) Although the exhaust manifold characteristics govern the fundamental flow physics and heat transfer in the scroll, its impact on the turbine power seems to be small relatively. 

    The contributions with this dissertation were mainly twofold. Firstly, it contributes to a deeper understanding of the thermo-fluid physics of a turbocharger turbine operating under engine-like pulsating flow scenario. This knowledge might be useful for industrial product development in the future. Secondly, from academic perspective, the flow exergy budget analysis could potentially serve as a practical example to students in connecting the dots between classroom theory and real life engineering application.

  • 2.
    Lim, Shyang Maw
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. Competence Center for Gas Exchange (CCGEx), Linné FLOW Centre.
    Flow and heat transfer in a turbocharger radial turbine2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    In the past decades, stricter legislation has been imposed to improve fuel economy and to reduce tail-end emissions of automotive vehicles worldwide. One of the important and effective technologies adopted by the automobile manufacturers to fulfill legislation requirements is the turbocharger technology. As unavoidable large temperature gradients exists in an automotive turbocharger, heat transfer is prominent. However, the effects of heat loss on the turbocharger turbine performance is unclear, i.e. there is no consensus about its effects among researchers. Therefore, the objective of the licentiate thesis is to investigate the effects of heat transfer on an automotive turbocharger radial turbine performance. Furthermore, the thesis also aims to quantify the heat transfer related losses in a turbocharger turbine. Both gas stand (continuous flow) and engine-like (pulsating flow) conditions are considered. By using Detached Eddy Simulation (DES), the flow field of the targeted turbocharger turbine is computed under adiabatic and non-adiabatic conditions. Energy balance and exergy concept are then applied to the simulations data to study the effects of heat loss on performance and to quantify the heat transfer related losses. The main findings of the licentiate thesis are 1) Pressure ratio drop in turbine is less sensitive to heat loss as compared with turbine power. Hence there is a risk of making wrong conclusions about the heat transfer effects on the turbine performance by just comparing the measured pressure ratio under adiabatic and non-adiabatic scenarios; 2) It is possible to quantify heat transfer related losses in a turbocharger turbine. This quantification allows understanding on how well the turbine system utilizes the available energy, and assisting identification of the system component that is sensitive to heat transfer; 3) Heat loss has insignificant effect on turbine power under the investigated engine-like pulsating flow condition; and 4) Even under unavoidable non-adiabatic conditions, much of the exergy discharged out to the environment and more effort could be done to recover the wasted exergy as useful turbine work in the current turbine system. The outcomes of the licentiate thesis naturally lead to the main focus of future work, i.e. exploring different exhaust valve strategies to minimize losses and to optimize flow exergy extraction as useful turbine work for better exhaust gas exergy utilization.

  • 3.
    Lim, Shyang Maw
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Dahlkild, Anders
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Mihaescu, Mihai
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Aerothermodynamics and exergy analysis of a turbocharger radial turbine integrated with exhaust manifold2018In: Institution of Mechanical Engineers - 13th International Conference on Turbochargers and Turbocharging 2018, 2018Conference paper (Refereed)
    Abstract [en]

    Large temperature gradients are associated with automotive turbocharger and thus the turbine experiences significant heat loss. Currently, the investigation of aerothermodynamic effects as a result of heat loss in turbine is commonly done by looking at the global performance parameters, i.e. pressure ratio and efficiency. This study aims to investigate the aerothermodynamic effects of heat transfer on a radial turbine operating under engine-like pulsating flow condition by identifying and quantifying the loss mechanisms via an exergy-based method using Detached Eddy Simulation data. Major findings with this study are: 1) Although exergy lost via heat transfer and internal irreversibilities could be as much as the turbine power, the drop of turbine power is only 4% as compared to an adiabatic turbine;2) Only about 12% of the available exhaust energy is extracted by the investigated turbine.

  • 4.
    Lim, Shyang Maw
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Mechanics.
    Dahlkild, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Influence of Upstream Exhaust Manifold on Pulsatile Turbocharger Turbine Performance2019In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 141, no 6Article in journal (Refereed)
    Abstract [en]

    This research was primary motivated by limited efforts to understand the effects of secondary flow and flow unsteadiness on the heat transfer and the performance of a turbocharger turbine subjected to pulsatile flow. In this study, we aimed to investigate the influence of exhaust manifold on the flow physics and the performance of its downstream components, including the effects on heat transfer, under engine-like pulsatile flow conditions. Based on the predicted results by detached eddy simulation (DES), qualitative and quantitative flow fields analyses in the scroll and the rotor's inlet were performed, in addition to the quantification of turbine performance by using the flow exergy methodology. With the specified geometry configuration and exhaust valve strategy, our study showed that (1) the exhaust manifold influences the flow field and the heat transfer in the scroll significantly and (2) although the exhaust gas blow-down disturbs the relative flow angle at rotor inlet, the consequence on the turbine power is relatively small.

  • 5.
    Lim, Shyang Maw
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Dahlkild, Anders
    KTH, School of Engineering Sciences (SCI), Centres, Faxén Laboratory. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Mihaescu, Mihai
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Mechanics of Industrial Processes.
    Influence of upstream geometry on pulsatile turbocharger turbine performance2018Report (Other academic)
    Abstract [en]

    This research was primary motivated by limited efforts to understand the effects of secondary flow and flow unsteadiness on the heat transfer and the performance of a turbocharger turbine subjected to pulsatile flow. In this study, we aimed to investigate the influence of exhaust manifold on the flow physics and the performance of its downstream components, including the effects on heat transfer, under engine-like pulsatile flow conditions. Based on the predicted results by Detached Eddy Simulation (DES), qualitative and quantitative flow fields analyses in the scroll and the rotor’s inlet were performed, in addition to the quantification of turbine performance by using the flow exergy methodology. With the specified geometry configuration and exhaust valve strategy, our study showed that 1) The exhaust manifold influences the flow field and the heat transfer in the scroll significantly, and 2) Although the relative inflow angle at the rotor’s inlet is significantly affected by the initial exhaust gas blow down from the exhaust manifold, the consequence on the turbine power is relatively small.

  • 6.
    Lim, Shyang Maw
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Dahlkild, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Influence of upstream geometry on pulsatile turbocharger turbine performance2018In: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines, ASME Press, 2018, Vol. 8Conference paper (Refereed)
    Abstract [en]

    Unlike conventional turbomachinery, an automotive turbocharger's turbine is operated under unsteady hot and pulsatile flow due to the inherent nature of reciprocating engine. Although the turbine is integrated with exhaust manifold in real application, some experiments and numerical studies ignore its presence. In this study, we aimed to investigate the effects of upstream complex exhaust manifold on the prediction of pulse flow turbine performance via Detached Eddy Simulation (DES). Heat transfer was incorporated and the exergy based approach was used to quantify the heat transfer associated losses. Our primary results showed that under the investigated turbine stage, although the presence of exhaust manifold influences the prediction of heat transfer and internal irreversibilities in the scroll significantly, it does not significantly affect the prediction of turbine power, heat transfer and irreversibilities at the downstream components.

  • 7.
    Lim, Shyang Maw
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Dahlkild, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Wall Treatment Effects on the Heat Transfer in a Radial Turbine Turbocharger2016In: Springer Proceedings in Physics, Springer Science+Business Media B.V., 2016, p. 439-447Conference paper (Refereed)
    Abstract [en]

    Contradicting results about heat transfer effects on the performance of turbine turbocharger motivated this study. It was aimed to assess the effects that the wall treatment in a numerical sense has on the performance of a radial turbine of automotive turbocharger operating under a continuous flow condition. Adiabatic and non-adiabatic conditions were analyzed by using Unsteady Reynolds Averaged Navier-Stokes (URANS), Large Eddy Simulations (LES) and Detached Eddy Simulations (DES) approaches. When considering heat transfer, heat transfer loss at various locations is highly dependent on the near-wall modelling approach employed. Development of thermal boundary layer in the upstream region of turbine affects how the gas is convected in the downstream components, such as the scroll and the rotor. As long as the deviation in predicting thermal boundary layer does not affect the prediction of gas temperature at the inlet and outlet of the rotor, the difference in turbine power prediction by different near-wall modelling approaches was found to be small.

1 - 7 of 7
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  • fi-FI
  • nn-NO
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