Influence of pulsating flow frequencies towards the flow angle distributions of an automotive turbocharger mixed-flow turbine

Padzillah, Muhamad Hasbullah; Rajoo, Srithar; Yang, Ming; Martinez-Botas, Ricardo

doi:10.1016/j.enconman.2015.03.028

Cited by 18 publications

(17 citation statements)

References 8 publications

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“…Based on the understanding of the unsteady turbine characteristics, a number of models were developed to capture the unsteady effects. These models are helpful in turbine preliminary design and performance evaluation [14][15][16][17][18][19][20][21]. Also, the performance of engines matched with different turbines can be predicted before the experiment.…”

Section: Introductionmentioning

confidence: 99%

Unsteady Flow Loss Mechanism and Aerodynamic Improvement of Two-Stage Turbine under Pulsating Conditions

Zhao

Zhuge

et al. 2019

Entropy

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The developments of two-stage turbocharging and turbocompounding promote the application of the two-stage turbine system in internal combustion engines. Since the turbine suffers from the pulsating exhaust, the performance deteriorates significantly from steady conditions. In the paper, the pulsating flow losses in the two-stage turbine are analyzed and a control method is proposed to improve the turbine performance. ANSYS CFX, which is a commercial software for computational fluid dynamic, is applied to resolve the three-dimensional unsteady flow problem. The accuracy of the simulation method is verified by the experimental data from each turbine. Firstly, the impacts of pulse amplitudes on transient loss of each component of the two-stage turbine are studied. Then flow field analysis is carried out to understand details of the unsteady flows. It is found that the variation of incidence angle at the low-pressure turbine (LPT) rotor tip is significantly larger than that at rotor hub, which causes severe flow loss near leading edge. As a result, the LPT performance drops down significantly. To improve the LPT performance, the blade shape at tip is modified. The aerodynamic performances of turbines with three different shapes under high- and low-load pulsating flow conditions are evaluated. It is found that increased inlet blade angle and medium thickness achieves good aerodynamic performance. The rotor averaged efficiency is improved by 2.27% under high-load pulsating condition.

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Section: Introductionmentioning

confidence: 99%

Unsteady Flow Loss Mechanism and Aerodynamic Improvement of Two-Stage Turbine under Pulsating Conditions

Zhao

Zhuge

et al. 2019

Entropy

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“…This is a state-of-the-art test facility capable to generate turbine maps three/four times wider than those obtained by using a compressor as loading device. Extensive explanation about the test-facility was previously published by the Imperial College London Turbocharger Research Group [29].…”

Section: Turbine Testingmentioning

confidence: 99%

“…The impact of the LPT installation on the engine is analyzed by comparing the amount of the recovered energy to the baseline engine Brake Specific Fuel Consumption (BSFC). The BSFC indicates the amount of fuel required producing 1 kW of engine power and it is given by Equation 29. …”

Section: Lpt Impact On Engine Performancementioning

confidence: 99%

Design methodology of a low pressure turbine for waste heat recovery via electric turbocompounding

Mamat

Martinez-Botas

Rajoo

et al. 2016

Applied Thermal Engineering

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This paper presents a design methodology of a high performance Low Pressure Turbine (LPT) for turbocompounding applications to be used in a 1.0 L “cost-effective, ultra-efficient heavily downsized gasoline engine for a small and large segment passenger car”. Under this assumption, the LPT was designed to recover the latent energy of discharged exhaust gases at low pressure ratios (1.05–1.3) and to drive a small electric generator with a maximum power output of 1.0 kW. The design speed was fixed at 50,000 rpm with a pressure ratio, PR of 1.08. Commercially available turbines are not suitable for this purpose due to the very low efficiencies experienced when operating in these pressure ratio ranges. By fixing all the LPT requirements, the turbine loss model was combined with the geometrical model to calculate preliminary LPT geometry. The LPT features a mixed-flow turbine with a cone angle of 40° and 9 blades, with an inlet blade angle at radius mean square of +20°. The exit-to-inlet area ratio value is approximately 0.372 which is outside of the conventional range indicating the novelty of the approach. A single passage Computational Fluid Dynamics (CFD) model was applied to optimize the preliminary LPT design by changing the inlet absolute angle. The investigation found the optimal inlet absolute angle was 77°. Turbine off-design performance was then predicted from single passage CFD model. A rapid prototype of the LPT was manufactured and tested in Imperial College turbocharger testing facility under steady-state and pulsating flow. The steady-state testing was conducted over speed parameter ranges from 1206 rpm/K0.5 to 1809 rpm/K0.5. The test results showed a typical flow capacity trend as a conventional radial turbine but the LPT had higher total-to-static efficiency, ηt-s in the lower pressure ratio regions. A maximum total-to-static efficiency, ηt-s of 0.758 at pressure ratio, PR ≈ 1.1 was found, no available turbines exist in this range as parameters. A validation of the predicted single passage CFD analysis for the off-design performance against the LPT test result found a minimum total-to-static efficiency Standard Deviation of ±0.026 points for the speed parameter of 1507 rpm/K0.5. A minimum Mass Flow Parameter Standard Deviation of ±0.091 kg/s K0.5 bar is found at 1206 rpm/K0.5

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“…Recent work by Copeland et al [5] utilized CFD approach in an attempt to characterize the level of 'unsteadiness' within the turbocharger turbine stage. This is done by defining a new parameter called 'lambda parameter' that represents the ratio of the time-averaged rate of change of the mass flow within the domain to the time-averaged of the through flow mass.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Flow Field Between Steady and Unsteady Flow of an Automotive Mixed Flow Turbocharger Turbine

2016

Self Cite

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Graphical abstract AbstractGlobal decarbonizing efforts in transportation industry have forced the automotive manufacturers to opt for highly downsized high power-to-weight ratio engines. Since its invention, turbocharger remains as integral element in order to achieve this target. However, although it has been proven that a turbocharger turbine works in highly pulsatile environment, it is still designed under steady state assumption. This is due to the lack of understanding on the nature of pulsating flow field within the turbocharger turbine stage. This paper presents an effort to visualize the pulsating flow feature using experimentally validated Computational Fluid Dynamics (CFD) simulations. For this purpose, a lean-vaned mixed-flow turbine with rotational speed of 30000 rpm at 20 Hz flow frequency, which represent turbine operation for 3-cylinder 4-stroke engine operating at 800 rpm has been used. Results indicated that the introduction of pulsating flow has resulted in more irregular pattern of flow field as compared to steady flow operation. It has also been indicated that the flow behaves very differently between pressure increment and decrement instances. During the pressure decrement instance, flow blockage in terms of low pressure region occupies most of the turbine passage as the flow exit the turbine.Keywords : Mixed-flow turbine, computational fluid dynamics, pulsating flow AbstrakUsaha mengurangkan pelepasan karbon secara global dalam industry pengangkutan telah menjadikan pengeluar kenderaan automotif memilih untuk menghasilkan enjin yang mempunyai nisbah kuasa-kepada-berat yang tinggi. Sejak penciptaannya, pengecas turbo masih kekal menjadi elemen penting untuk mencapai matlamat ini. Namun begitu, sungguhpun telah dibuktikan bahawa alat ini sentiasa beroperasi dalam keadaan aliran berdenyut, ianya masih lagi direka menggunakan andaian aliran mantap. Ini adalah kerana kurangnya kefahaman terhadap persekitaran aliran denyutan dalam pengecas turbo tersebut. Kertas kerja ini membentangkan satu usaha untuk memaparkan ciri-ciri aliran denyut menggunakan kaedah Pengiraan Dinamik Bendalir (CFD) yang telah disahkan secara uji kaji. Untuk tujuan ini, turbin aliran campuran dengan kelajuan putaran 30000 rpm pada frekuensi aliran 20 Hz, bagi mewakili operasi turbin pada enjin 3-silindir 4 lejang yang beroperasi pada 800 rpm telah digunakan. Keputusan menunjukkan bahawa pengenalan aliran berdenyut telah menyebabkan corak aliran yang lebih tidak teratur berbanding operasi aliran mantap. Keputusan juga telah menunjukkan bahawa corak aliran adalah sangat berbeza antara sewaktu tekanan sedang menaik dan menurun. Semasa tekanan sedang menurun, aliran didapati terganggudi mana kawasan tekanan rendah telahmeliputi sebahagian besar laluan turbin semasa aliran hamper dengan bahagian keluaran turbin.Kata kunci: Turbin aliran campuran, dinamik bendalir berbantukan komputer,

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Influence of pulsating flow frequencies towards the flow angle distributions of an automotive turbocharger mixed-flow turbine

Cited by 18 publications

References 8 publications

Unsteady Flow Loss Mechanism and Aerodynamic Improvement of Two-Stage Turbine under Pulsating Conditions

Unsteady Flow Loss Mechanism and Aerodynamic Improvement of Two-Stage Turbine under Pulsating Conditions

Design methodology of a low pressure turbine for waste heat recovery via electric turbocompounding

Comparison of Flow Field Between Steady and Unsteady Flow of an Automotive Mixed Flow Turbocharger Turbine

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