Research Papers: Gas Turbines: Turbomachinery

On the Design and Matching of Turbocharger Single Scroll Turbines for Pass Car Gasoline Engines

[+] Author and Article Information
Marc Gugau

BorgWarner Turbo Systems Engineering GmbH,
Marnheimer Straße 85/87,
Kirchheimbolanden 67292, Germany
e-mail: mgugau@borgwarner.com

Harald Roclawski

Department of Mechanical Engineering,
Institute of Fluid Mechanics
and Turbomachinery,
Technical University of Kaiserslautern,
Gottlieb Daimler Straße,
Kaiserslautern 67661, Germany
e-mail: roclawsk@mv.uni-kl.de

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received March 25, 2014; final manuscript received May 11, 2014; published online June 27, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(12), 122602 (Jun 27, 2014) (10 pages) Paper No: GTP-14-1165; doi: 10.1115/1.4027710 History: Received March 25, 2014; Revised May 11, 2014

With emission legislation becoming more stringent within the next years, almost all future internal combustion gasoline engines need to reduce specific fuel consumption, most of them by using turbochargers. Additionally, car manufactures attach high importance to a good drivability, which usually is being quantified as a target torque already available at low engine speeds—reached in transient response operation as fast as possible. These engine requirements result in a challenging turbocharger compressor and turbine design task, since for both not one single operating point needs to be aerodynamically optimized but the components have to provide for the optimum overall compromise for maximum thermodynamic performance. The component design targets are closely related and actually controlled by the matching procedure that fits turbine and compressor to the engine. Inaccuracies in matching a turbine to the engine full load are largely due to the pulsating engine flow characteristic and arise from the necessity of arbitrary turbine map extrapolation toward low turbine blade speed ratios and the deficient estimation of turbine efficiency for low engine speed operating points. This paper addresses the above described standard problems, presenting a methodology that covers almost all aspects of thermodynamic turbine design based on a comparison of radial and mixed-flow turbines. Wheel geometry definition with respect to contrary design objectives is done using computational fluid dynamics (CFD), finite element analysis (FEA), and optimization software. Parametrical turbine models, composed of wheel, volute, and standard piping allow for fast map calculation similar to steady hot gas tests but covering the complete range of engine pulsating mass flow. These extended turbine maps are then used for a particular assessment of turbine power output under unsteady flow admission resulting in an improved steady-state matching quality. Additionally, the effect of various design parameters like either volute sizing or the choice of compressor to turbine diameter ratio on turbine blade speed ratio operating range as well as well as turbine inertia effect is analyzed. Finally, this method enables the designer to comparatively evaluate the ability of a turbine design to accelerate the turbocharger speed for transient engine response while still offering a map characteristic that keeps fuel consumption low at all engine speeds.

Copyright © 2014 by ASME
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Fig. 1

Steady-state engine targets: (a) engine performance and (b) p3 and fuel consumption (“BSFC”)

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Fig. 2

Unsteady turbine inflow: (a) pulsating flow character and (b) pulse coefficient

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Fig. 3

CFD-model for map generation

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Fig. 4

Flow parameter map

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Fig. 5

Combined efficiency map

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Fig. 6

Turbine maps for different designs RFT/MFT at tip speed = 280 m/s; (a) FP and (b) efficiency

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Fig. 7

Change of turbine properties with diameter

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Fig. 8

Turbine efficiency maps at 1500

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Fig. 9

Engine pulse at 1500 and turbine work range

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Fig. 10

Turbine efficiency maps at 5000

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Fig. 11

Engine pulse at 5000 and turbine work range

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Fig. 12

Turbine efficiency work maps and power generation at 1500

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Fig. 13

Turbine efficiency work maps and power generation at 5000

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Fig. 14

Flow parameter of four test turbines

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Fig. 15

Design properties of test turbines

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Fig. 16

Combined efficiency of four test turbines

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Fig. 17

Power output and pulse C of four test turbines

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Fig. 18

Power and pressure p3 of four test turbines

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Fig. 19

Results for four test turbines: (a) acceleration and (b) mean efficiency




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