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Gas Turbines: Vehicular and Small Turbomachines

Contribution to the Modeling and Understanding of Cold Pulsating Flow Influence in the Efficiency of Small Radial Turbines for Turbochargers

[+] Author and Article Information
J. R. Serrano, F. J. Arnau, P. Fajardo, M. A. Reyes Belmonte

 Universidad Politécnica de Valencia, CMT Motores Térmicos, Camino de Vera s/n, 46022, Valencia, Spain

Fabrice Vidal

 PSA Peugeot Citroën, DRIA, Route de Gisy, 78943 Vélizy, Villacoublay Cedex, France

J. Eng. Gas Turbines Power 134(10), 102701 (Aug 14, 2012) (11 pages) doi:10.1115/1.4007027 History: Received June 18, 2012; Revised June 20, 2012; Published August 14, 2012; Online August 14, 2012

In the present paper, an unsteady approach to determine the performance of a small radial inflow turbine working under cold pulsating flow is presented. It has been concluded that a reasonably good characterization of turbine behavior working with pulsating flow can be obtained using, in a quasi-steady way, models of the turbine isentropic efficiency and turbocharger mechanical efficiency. Both models have been fitted using data obtained from a steady flow characterization procedure. Turbocharger-measured parameters from the cold pulsating flow campaign have been compared with the ones obtained from one-dimensional gas dynamics computational modeling. The modeling approach is based on quasi-steady isentropic and mechanical efficiency models. Reasonably good accuracy in compressor and turbine variables prediction has been obtained for most of the operative conditions. Influence of amplitude and frequency of the pulsating flow over the instantaneous and average turbine efficiency has been studied to put some light on the analysis of the involved physical phenomena. The main conclusion is that the biggest effect of unsteady flow on turbine efficiency is through the influence on blade jet to speed ratio. It has been also concluded that, for the same average blade jet to speed ratio, pulses’ amplitude does not influence turbine efficiency when it is closed, but does at other variable geometry turbine (VGT) positions. The effect of pulses’ frequency is less evident and only influences VGT performance at the highest VGT openings.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Layout of the facility

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Figure 2

Rotary valve used in test campaign and two different plates

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Figure 3

Pulses of a two- and three-cylinder engine

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Figure 4

Test campaign in compressor and turbine maps

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Figure 5

Characterization of turbine efficiency

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Figure 6

OpenWAMTM turbocharger model

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Figure 7

Compressor map validation per each VGT opening: (a) 0%, (b) 50%, (c) 100% opening. Imposed turbocharger speed.

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Figure 8

Errors in compressor parameters when turbocharger speed is let free, (a) 0%, (b) 50%, (c) 100% VGT opening

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Figure 9

Errors in turbine mass flow parameter and turbocharger speed when the second is let free, (a) 0%, (b) 50%, (c) 100% VGT opening

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Figure 10

Errors in turbine outlet temperature when turbocharger speed is let free, (a) 0%, (b) 50%, (c) 100% VGT opening

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Figure 11

Modeling example, (a) 0%, (b) 50%, (c) 100% VGT opening

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Figure 12

Average ηTs for free speed simulations

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Figure 13

Average ηmech for free speed simulations

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