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Research Papers

Comparison Between Steady and Unsteady Double-Entry Turbine Performance Using the Quasi-Steady Assumption

[+] Author and Article Information
Colin D. Copeland

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

Ricardo Martinez-Botas1

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

Martin Seiler

 ABB Turbo Systems Limited, Baden CH-5401, Switzerlandmartin.a.seiler@ch.abb.com

1

Corresponding author.

J. Turbomach 133(3), 031001 (Nov 11, 2010) (10 pages) doi:10.1115/1.4000580 History: Received July 21, 2009; Revised August 13, 2009; Published November 11, 2010; Online November 11, 2010

The experimental performance evaluation of a circumferentially divided, double-entry turbocharger turbine is presented in this paper with the aim of understanding the influence of pulsating flow. By maintaining a constant speed but varying the frequency of the pulses, the influence of frequency was shown to play an important role in the performance of the turbine. A trend of decreasing cycle-averaged efficiency at lower frequencies was measured. One of the principal objectives was to assess the degree to which the unsteady performance differs from the quasi-steady assumption. In order to make the steady-unsteady comparison for a multiple entry turbine, a wide set of steady equal and unequal admission flow conditions were tested. The steady-state data was then interpolated as a function of three, nondimensional parameters in order to allow a point-by-point comparison with the instantaneous unsteady operation. As an average, the quasi-steady assumption generally underpredicted the mass flow and efficiency loss through the turbine, albeit the differences were reduced as the frequency increased. Out-of-phase pulsations produced unsteady operating orbits that corresponded to a significant steady-state, partial admission loss, and this was reflected as a drop in the quasi-steady efficiency. However, these differences between quasi-steady in-phase and out-of-phase predictions were not replicated in the measured results, suggesting that the unequal admission loss is not as significant in pulsating flow as it is in steady flow.

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Figures

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Figure 1

Test facility layout

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Figure 2

Circumferentially divided, double-entry turbocharger turbine

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Figure 3

Equal admission, steady-flow, relative efficiency contours

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Figure 4

Unequal admission, steady-flow, relative efficiency contours: (a) top: U/Cis=0.8, (b) middle: U/Cis=0.65, and (c) bottom U/Cis=0.5

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Figure 5

Steady-flow, interpolated relative efficiency contours plotted in 3D space

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Figure 6

Steady-state efficiency contours, with unsteady operating traces superimposed: (a) 3D representation, (b) equal admission perspective, and (c) unequal admission perspective

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Figure 7

Steady-state efficiency contours, with unsteady operating traces superimposed: (a) 3D representation, (b) equal admission perspective, and (c) unequal admission perspective

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Figure 8

Dynamic behavior of speed and pressure ratios for 42 Hz and 84 Hz in-phase pulsations

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Figure 9

(a) Unsteady (US) and quasi-steady (QS) cycle-averaged efficiency and unsteady/quasi-steady ratios of averaged mass flow and power (IM and IP): (b) in-phase and (c) out-of-phase

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Figure 10

In-phase, isentropic, and actual power using unsteady and quasi-steady data

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Figure 11

In-phase, unsteady mass flow versus quasi-steady mass flow (outer entry)

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