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Research Papers: Gas Turbines: Turbomachinery

A Detailed Comparison on the Influence of Flow Unsteadiness Between the Vaned and Vaneless Mixed-Flow Turbocharger Turbine

[+] Author and Article Information
M. H. Padzillah

UTM Centre for Low Carbon
Transport in Cooperation,
Imperial College London,
Universiti Teknologi Malaysia,
Johor Bharu 81310, Malaysia
e-mail: mhasbullah@utm.my

S. Rajoo

UTM Centre for Low Carbon
Transport in Cooperation,
Imperial College London,
Universiti Teknologi Malaysia,
Johor Bharu 81310, Malaysia

R. F. Martinez-Botas

Department of Mechanical Engineering,
Imperial College London,
Exhibition Road,
London SW7 2AZ, UK

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 15, 2017; final manuscript received August 1, 2017; published online October 31, 2017. Assoc. Editor: Riccardo Da Soghe.

J. Eng. Gas Turbines Power 140(4), 042601 (Oct 31, 2017) (15 pages) Paper No: GTP-17-1066; doi: 10.1115/1.4038076 History: Received February 15, 2017; Revised August 01, 2017

A turbocharger is a key enabler for lowering CO2 emission of an internal combustion engine (ICE) through the reutilization of the exhaust gas energy that would otherwise have been released to the ambient. In its actual operating conditions, a turbocharger turbine operates under highly pulsating flow due to the reciprocating nature of the ICE. Despite this, the turbocharger turbines are still designed using the standard steady-state approach due to the lack of understanding of the complex unsteady pressure and mass propagation within the stage. The application of guide vanes in a turbocharger turbine stage has increased the complexity of flow interactions regardless of whether the vanes are fixed or variable. Although it is enticing to assume that the performance of the vaned turbine is better than the one without (vaneless), there are currently no tangible evidences to support this claim, particularly during the actual pulsating flow operations. Therefore, this research looks into comparing the differences between the two turbine arrangements in terms of their performance at flow field level. For this purpose, a three-dimensional (3D) “full-stage” unsteady turbine computational fluid dynamics (CFD) models for both volutes are constructed and validated against the experimental data. These models are subject to identical instantaneous inlet pressure profile of 60 Hz, which is equivalent to an actual three-cylinder four-stroke engine rotating at 2400 rpm. A similar 95.14 mm diameter mixed-flow turbine rotor rotating at 48,000 rpm is used for both models to enable direct comparison. The complete validation exercises for both steady and unsteady flow conditions are also presented. Results have indicated that neither vaned nor vaneless turbine is capable of maintaining constant efficiency throughout the pulse cycle. Despite that, the vaneless turbine indicated better performance during peak power instances. This work also showed that the pulsating pressure at the turbine inlet affected the vaned and vaneless turbines differently at the flow field level. Furthermore, results also indicated that both the turbines matched its optimum incidence angle for only a fraction of pulse cycle, which is unfavorable.

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References

Baines, N. C. , and Lavy, M. , 1990, “ Flows in Vaned and Vaneless Stators of Radial-Inflow Turbocharger Turbines,” International Conference on Turbochargers and Turbocharging, London, May 22–24, pp. 7–12.
Spence, S. W. , Rosborough, R. S. , Artt, D. , and McCullogh, G. , 2007, “ A Direct Performance Comparison of Vaned and Vaneless Stators for Radial Turbines,” ASME J. Turbomach., 129(1), pp. 53–61. [CrossRef]
Karamanis, N. , Palfreyman, D. , Arcoumanis, C. , and Martinez-Botas, R. F. , 2006, “ Steady and Unsteady Velocity Measurements in a Small Turbocharger Turbine With Computational Validation,” J. Phys. Conf. Ser., 45(1), pp. 173–173. [CrossRef]
Yang, M. Y. , Padzillah, M. H. , Zhuge, W. L. , Martinez Botas, R. F. , and Rajoo, S. , 2014, “ Comparison of the Influence of Unsteadiness Between Nozzled and Nozzleless Mixed Flow Turbocharger Turbine,” 11th International Conference on Turbochargers and Turbocharging, London, May 13–14, pp. 333–345.
Lam, J.-W. , Roberts, Q. D. H. , and McDonnel, G. T. , 2002, “ Flow Modelling of a Turbocharger Turbine Under Pulsating Flow,” Seventh International Conference on Turbochargers Turbocharging, London, May 14–15, pp. 181–197.
Palfreyman, D. , and Martinez-Botas, R. F. , 2005, “ The Pulsating Flow Field in a Mixed Flow Turbocharger Turbine: An Experimental and Computational Study,” ASME J. Turbomach., 127(1), pp. 144–155. [CrossRef]
Karamanis, N. , Martinez-Botas, R. F. , and Su, C. C. , 2001, “ Mixed Flow Turbines: Inlet and Exit Flow Under Steady and Pulsating Conditions,” ASME J. Turbomach., 123(2), pp. 359–371. [CrossRef]
Copeland, C. D. , Newton, P. , Martinez-Botas, R. F. , and Seiler, M. , 2012, “ A Comparison of Timescales Within a Pulsed Flow Turbocharger Turbine,” Tenth International Conference on Turbochargers and Turbocharging, London, May 15–16, pp. 389–404.
Newton, P. , Martinez-Botas, R. , and Seiler, M. , 2014, “ A Three-Dimensional Computational Study of Pulsating Flow Inside a Double Entry Turbine,” ASME J. Turbomach., 137(3), p. 031001. [CrossRef]
Greitzer, E. M. , Tan, C. S. , and Graf, M. B. , 2004, Internal Flow, Concepts and Applications, Cambridge University Press, Cambridge, UK. [CrossRef]
Padzillah, M. H. , Yang, M. , Zhuge, W. , and Martinez-Botas, R. F. , 2014, “ Numerical and Experimental Investigation of Pulsating Flow Effect on a Nozzled and Nozzleless Mixed Flow Turbine for an Automotive Turbocharger,” ASME Paper No. GT2014-26152.
Dale, A. , and Watson, N. , 1986, “ Vaneless Radial Turbocharger Turbine Performance,” Third International Conference on Turbocharging and Turbochargers, London, May 6–8, pp. 65–76.
Rajoo, S. , 2007, “ Steady and Pulsating Performance of a Variable Geometry Mixed Flow Turbocharger Turbine,” Ph.D. thesis, Imperial College of Science, Technology and Medicine, London. https://spiral.imperial.ac.uk/handle/10044/1/39159
Szymko, S. , 2006, “ The Development of an Eddy Current Dynamometer for Evaluation of Steady and Pulsating Turbocharger Turbine Performance,” Ph.D. thesis, Imperial College of Science, Technology and Medicine, London. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436123
Pesiridis, A. , and Martinez-Botas, R. , 2005, “ Experimental Evaluation of Active Flow Control Mixed-Flow Turbine for Automotive Turbocharger Application,” ASME Paper No. GT2005-68830.
Chiong, M. S. , Rajoo, S. , Romagnoli, A. , Costall, A. W. , and Martinez-Botas, R. F. , 2014, “ Integration of Meanline and One-Dimensional Methods for Prediction of Pulsating Performance of a Turbocharger Turbine,” Energy Convers. Manage., 81, pp. 270–281. [CrossRef]
Padzillah, M. H. , Rajoo, S. , Yang, M. , and Martinez-Botas, R. F. , 2015, “ Influence of Pulsating Flow Frequencies Towards the Flow Angle Distributions of an Automotive Turbocharger Mixed-Flow Turbine,” Energy Convers. Manage., 98, pp. 449–462. [CrossRef]

Figures

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Fig. 1

The schematic of the cold-flow turbocharger test facility in Imperial College London

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Fig. 2

The 36 grid hotwire measurement location in the flow duct [13]

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Fig. 3

Components of the turbine stage that include the volute, pivoting mechanism, lean vanes and adjustment ring

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Fig. 4

Experimental setup that shows (a) vaneless turbine and (b) vaned turbine

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Fig. 5

Main components of the eddy current dynamometer [14]

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Fig. 6

The generated profile lines for Rotor A

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Fig. 7

Assembly of the meshed geometries for (a) vaneless and (b) vaned

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Fig. 8

Comparison between CFD and experimental data of (a) MFP against pressure ratio and (b) total-to-static efficiency against velocity ratio (VR) for vaned volute configuration

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Fig. 9

Comparison of instantaneous mass flow rate between CFD and experimental data

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Fig. 10

Comparison of instantaneous torque between CFD and experimental data

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Fig. 11

Plot of instantaneous efficiency against incidence angle for vaned and vaneless turbine arrangement

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Fig. 12

Plot of absolute flow angle at volute exit and rotor inlet for vaned and vaneless turbine configuration

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Fig. 13

The plot of instantaneous absolute flow angle for vaned and vaneless volute during (a) pressure rise instance and (b) pressure decline instance

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Fig. 14

Plot of instantaneous mass flow parameter against pressure ratio for vaned and vaneless turbine arrangements

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Fig. 15

Measurement locations within the computational domain

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Fig. 16

Instantaneous static pressure trace at 60 deg, 180 deg and 240 deg of volute centroid for both vaned and vaneless configuration

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Fig. 17

The contour plot of instantaneous static pressure distribution within the vaned and vaneless volute during (a) pressure rise instance and (b) pressure decline instance

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Fig. 18

The plot of instantaneous static pressure trace at 180 deg volute centroid, volute exit, and rotor inlet

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Fig. 19

The plot of instantaneous static pressure contour at the peak cycle pressure

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Fig. 20

The plot of instantaneous static pressure distribution at ∅ = 274 deg

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Fig. 21

Comparison of averaged parameters for vaned and vaneless volute arrangements

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