The effect of unequal admission on the performance and loss generation in a double-entry turbocharger turbine

Colin D. Copeland, Peter J. Newton, Ricardo Martinez-Botas, Martin Seiler

Research output: Contribution to journalArticle

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Abstract

The current work investigates a circumferentially divided turbine volute designed such that each gas inlet feeds a separate section of the turbine wheel. Although there is a small connecting interspace formed between the nozzle and the mixed-flow rotor inlet, this design does well to preserve the exhaust gas energy in a pulsed-charged application by largely isolating the two streams entering the turbine. However, this type of volute design produces some interesting flow features as a result of unequal flows driving the turbine wheel. To investigate the influence of unequal flows, experimental data from the turbocharger facility at Imperial College have been gathered over a wide range of steadystate, unequal admission conditions. These test results show a significant drop in turbine performance with increasing pressure difference between inlets. In addition, the swallowing capacities of each gas inlet are interdependent, thus indicating some flow interaction between entries. To understand the flow physics driving the observed performance, a full 3D computational fluid dynamics (CFD) model of the turbine was created. Results show a highly disturbed flow field as a consequence of the nonuniform admission. From these results, it is possible to identify the regions of aerodynamic loss responsible for the measured performance decrease. Given the unequal flows present in a double-entry design, each rotor passage sees an abrupt change in flow conditions as it rotates spanning the two feeding sectors. This operation introduces a high degree of unsteady flow into the rotor passage even when it operates in steady conditions. The amplitude and frequency of this unsteadiness will depend both on the level of unequal admission and the speed of rotor rotation. The reduced frequency associated with this disturbance supports the evidence that the flow in the rotor passage is unsteady. Furthermore, the CFD model indicates that the blade passage flow is unable to fully develop in the time available to travel between the two different sectors (entries).
LanguageEnglish
Article number021004
Number of pages11
JournalJournal of Turbomachinery: Transactions of the ASME
Volume134
Issue number2
Early online date21 Jun 2011
DOIs
StatusPublished - Mar 2012

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Turbines
Rotors
Dynamic models
Wheels
Computational fluid dynamics
Flow interactions
Intake systems
Unsteady flow
Exhaust gases
Gases
Nozzles
Flow fields
Aerodynamics
Physics

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The effect of unequal admission on the performance and loss generation in a double-entry turbocharger turbine. / Copeland, Colin D.; Newton, Peter J.; Martinez-Botas, Ricardo; Seiler, Martin.

In: Journal of Turbomachinery: Transactions of the ASME, Vol. 134, No. 2, 021004, 03.2012.

Research output: Contribution to journalArticle

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