Computational modelling and assessment of supersonic flow in centrifugal compressors for aviation air-conditioning systems

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This research project aims to initiate a collaboration between Dr. Jeff Defoe at the University of Windsor and Dr. Matteo Pini at the Delft University of Technology in the Netherlands. The focus of the work is computer simulations of flow through centrifugal compressors in a novel application. Recent advances in high-speed electric motors have enabled the possibility of using such compressors for aircraft environmental control (air-conditioning) systems. This requires that the working fluid in the compressor is a refrigerant gas. Such refrigerants have much more complex behaviour than gases like air and so detailed thermodynamic models of the fluid are needed within the framework of computational predictions of flow. At the same time, all turbo-compressors are subject to limits on their ability to operate at flow rates lower than the design value due to flow instabilities. The most relevant of these is rotating stall, in which flow breaks down in the space between two blades of the compressor, and this disturbance spreads around the machine, leading to a large drop in pressure rise and flow rate. To computationally predict the onset of this phenomenon requires high-fidelity computations which are most efficiently run in parallel with a large number of computing cores. The open-source flow simulation code OpenFOAM is to be used for such computations in this project, but first a model for the behaviour of the refrigerant must be implemented into the code. Stall inception mechanism(s) will then be identified. The compressor design and fluid thermodynamic model will be provided by Dr. Pini's group, and Dr. Defoe's group will carry out the implementation and simulations in OpenFOAM. In turn, the results will enable Dr. Pini's group to carry out simulations quickly, and should lead to further collaboration between the two teams in the area of compressor behaviour in this novel application. Further advances may lead to adoption of such machines on aircraft, with a potential to reduce overall energy consumption and thus lower environmental impact.