The Pulsating Flow Field in a Mixed Flow Turbocharger Turbine: An Experimental and Computational Study

Palfreyman, D.; Martinez-Botas, Ricardo

doi:10.1115/1.1812322

Cited by 71 publications

(27 citation statements)

References 9 publications

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“…However, the current investigation shows that the flow field changes drastically with pulsating boundary conditions compared to static boundary conditions. The performance of a downstream located turbocharger depends on the quality of the inflow conditions to the turbocharger [34]. Hence, a parameter expressing the flow conditions upstream of the turbocharger inlet would be suitable to asses the performance of the energy recuperation device.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Flow effects due to pulsation in an internal combustion engine exhaust port

Semlitsch¹,

Wang²,

Mihăescu³

2014

Energy Conversion and Management

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In an internal combustion engine, the residual energy remaining after combustion in the exhaust gasses can be partially recovered by a downstream arranged device. The exhaust port represents the passage guiding the exhaust gasses from the combustion chamber to the energy recovering device, e.g. a turbocharger. Thus, energy losses in the course of transmission shall be reduced as much as possible. However, in one-dimensional engine models used for engine design, the exhaust port is reduced to its discharge coefficient, which is commonly measured under constant inflow conditions neglecting engine-like flow pulsation. In this present study, the influence of different boundary conditions on the energy losses and flow development during the exhaust stroke are analyzed numerically regarding two cases, i.e. using simple constant and pulsating boundary conditions. The compressible flow in an exhaust port geometry of a truck engine is investigated using three-dimensional Large Eddy Simulations (LES). The results contrast the importance of applying engine-like boundary conditions in order to estimate accurately the flow induced losses and the discharge coefficient of the exhaust port. The instantaneous flow field alters significantly when pulsating boundary conditions are applied. Thus, the induced losses by the unsteady flow motion and the secondary flow motion are increased with inflow pulsations. The discharge coefficient decreased about 2% with flow pulsation. A modal flow decomposition method, i.e. Proper Orthogonal Decomposition (POD), is used to analyze the coherent structures induced with the particular inflow and outflow conditions. The differences in the flow field for different boundary conditions suggest to incorporate a modeling parameter accounting for the quality of the flow at the turbocharger turbine inlet in one-dimensional simulations.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Flow effects due to pulsation in an internal combustion engine exhaust port

Semlitsch¹,

Wang²,

Mihăescu³

2014

Energy Conversion and Management

View full text Add to dashboard Cite

show abstract

“…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%

“…As a result, the turbine cycle-averaged efficiency dropped 4%-25%. Subsequently, Palfreyman [19] carried out a 3-D unsteady computational study on the same mixed-flow turbine. It showed that the flow field within the turbine stage was highly disturbed and influenced primarily by the pulsating inlet condition.…”

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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“…The operation of mixed flow turbines under such flows has been assessed by numerous authors. 3–5 Understanding the performance implication of such flows is essential to improve future designs. As the rotor is fed by the volute which directs and accelerates the flow into the rotor, the volute design can significantly impact stage performance.…”

Section: Introductionmentioning

confidence: 99%

Analysis of leading edge flow characteristics in a mixed flow turbine under pulsating flows

Lee

Jupp

Barrans

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part A:

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Current trends in the automotive industry towards engine downsizing means turbocharging now plays a vital role in engine performance. A turbocharger increases charge air density using a turbine to extract waste energy from the exhaust gas to drive a compressor. Most turbocharger applications employ a radial inflow turbine. However, to ensure radial stacking of the blade fibers and avoid excessive blade stresses, the inlet blade angle must remain at zero degrees, creating large incidence angles. Alternately, mixed flow turbines can offer non-zero blade angles while maintaining radial stacking of the blade fibers and reducing leading edge separation at low velocity ratios. Furthermore, the physical blade cone angle introduced reduces the blade mass at the rotor outer diameter reducing rotor inertia and improving turbine transient response. The current paper investigates the performance of a mixed flow turbine under a range of pulsating inlet flow conditions. A significant variation in incidence across the LE span was observed within the pulse, where the distribution of incidence over the LE span was also found to change over the duration of the pulse. Analysis of the secondary flow structures developing within the volute shows the non-uniform flow distribution at the volute outlet is the result of the Dean effect in the housing passage. In-depth analysis of the mixed flow effect is also included, showing that poor axial flow turning ahead of the rotor was evident, particularly at the hub, resulting in modest blade angles. This work shows that the complex secondary flow structures that develop in the turbine volute are heavily influenced by the inlet pulsating flow. In turn, this significantly impacts the rotor inlet conditions and rotor losses.

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The Pulsating Flow Field in a Mixed Flow Turbocharger Turbine: An Experimental and Computational Study

Cited by 71 publications

References 9 publications

Flow effects due to pulsation in an internal combustion engine exhaust port

Flow effects due to pulsation in an internal combustion engine exhaust port

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

Analysis of leading edge flow characteristics in a mixed flow turbine under pulsating flows

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