Comparison between steady and unsteady double-entry turbine performance using the quasi-steady assumption
Copeland, C., Martinez-Botas, R. and Seiler, M., 2009. Comparison between steady and unsteady double-entry turbine performance using the quasi-steady assumption. In: ASME Turbo Expo 2009. ASME, pp. 1203-1212.
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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, non-dimensional parameters in order to allow a point-by-point comparison with the instantaneous unsteady operation. As an average, the quasi-steady assumption generally under-predicted 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.
|Item Type||Book Sections|
|Creators||Copeland, C., Martinez-Botas, R. and Seiler, M.|
|Departments||Faculty of Engineering & Design > Mechanical Engineering|
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