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Research Papers

Unsteady Effect in a Nozzled Turbocharger Turbine

[+] Author and Article Information
Srithar Rajoo

Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UKsrithar.rajoo@imperial.ac.uk

R. F. Martinez-Botas

Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UKr.botas@imperial.ac.uk

J. Turbomach 132(3), 031001 (Mar 24, 2010) (9 pages) doi:10.1115/1.3142862 History: Received July 25, 2007; Revised August 28, 2008; Published March 24, 2010; Online March 24, 2010

The unsteady behavior of a nozzled turbocharger turbine under pulsating flow conditions has been studied experimentally in a cold flow test facility that replicates engine pulses. The results presented are obtained at a turbine speed of 48,000 rpm for pulsating frequencies of 40 Hz and 60 Hz (which correspond to 1600 rpm and 2400 rpm in a twin turbocharger six cylinder internal combustion engine). The turbine unsteady behavior is compared for nozzle vane angles ranging between 40 deg and 70 deg. A nozzled turbocharger turbine is found to behave differently from a nozzleless turbine under pulsating flow. The existence of a nozzle ring “damps” the unsteady flow leading to a reduced level of flow dynamics affecting the turbine wheel for all vane angles. The bigger volume in the nozzled turbine is also another contributing factor to the observed characteristics. The results are more pronounced in the higher frequency and maximum vane opening condition. Given this “damping” behavior, the concept of unsteady efficiency is questioned. The level of unsteadiness in the flow is characterized by the relevant nondimensional parameters, and the onset of the unsteadiness in the flow and its effect on a nozzled turbocharger turbine is discussed. The onset of the unsteady effect is suggested to be at 40 Hz flow condition. However, the nozzled turbine exhibits more of filling and emptying characteristics for both the frequency conditions, especially at close nozzle position cases. The effect of unsteadiness on the instantaneous efficiency calculation is more pronounced in the nozzled turbine compared with a nozzleless turbine.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Meridional view of the mixed-flow turbine and the nozzle vane used in the current study

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Figure 2

Schematic of the turbocharger test facility and the measuring instruments

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Figure 3

Efficiency versus velocity ratio of the pivoting vane mixed-flow turbine

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Figure 4

Velocity triangle at the rotor inlet

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Figure 5

Mass flow parameter versus pressure ratio of the pivoting vane mixed-flow turbine

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Figure 6

Turbine’s instantaneous swallowing capacity at 60 deg vane angle, with 40 Hz and 60 Hz pulsating flows

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Figure 7

Turbine’s isentropic (a) and actual (b) power for 1 cycle of 40 Hz pulsating flow (nozzleless (8))

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Figure 8

Turbine’s isentropic (a) and actual (b) power for 1 cycle of 60 Hz pulsating flow (nozzleless (8))

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Figure 9

Turbine’s instantaneous swallowing capacity for different vane angles at 40 Hz pulsating flow

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Figure 10

Turbine’s instantaneous swallowing capacity for different vane angles at 60 Hz pulsating flow

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Figure 11

Turbine’s isentropic (a) and actual (b) power for a 40 Hz pulsating cycle at different vane angles

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Figure 12

Turbine’s isentropic (a) and actual (b) power for a 60 Hz pulsating cycle at different vane angles

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Figure 13

Cycle averaged velocity ratio (U/Cis) at different vane angles

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Figure 14

Measured instantaneous inlet static pressure at different vane angles

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Figure 15

Instantaneous efficiency of a nozzleless turbine (a) (8) and nozzled turbine with different vane angle settings at 40 Hz (b) and 60 Hz (c) pulsating flows

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Figure 16

Cycle averaged turbine power with different vane angle settings at 40 Hz and 60 Hz pulsating flows

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