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

该研究项目旨在启动温莎大学的杰夫·笛福博士和荷兰代尔夫特理工大学的马泰奥·皮尼博士之间的合作。工作的重点是对离心式压气机在一种新型应用中的流动进行计算机模拟。高速电动马达的最新进展使将这种压缩机用于飞机环境控制(空调)系统成为可能。这就要求压缩机中的工质是制冷剂气体。这类制冷剂的行为比空气等气体复杂得多，因此需要在计算流动预测的框架内建立详细的流体热力学模型。与此同时，由于流动不稳定，所有涡轮压缩机在低于设计值的流量下运行的能力都受到限制。其中最相关的是旋转失速，在这一过程中，气流在压缩机两个叶片之间的空隙中破裂，这种扰动在机器周围传播，导致压力上升和流量大幅下降。要在计算上预测这种现象的发生，需要高保真的计算，这种计算最有效地与大量计算核心并行运行。本项目将使用开源流动模拟程序OpenFOAM进行此类计算，但首先必须在该程序中实现制冷剂行为的模型。然后将确定失速启动机制(S)。压缩机设计和流体热力学模型将由皮尼博士的团队提供，迪福博士的团队将在OpenFOAM中进行实施和模拟。反过来，结果将使皮尼博士的团队能够快速进行模拟，并应导致两个团队在这一新应用中压缩机行为领域的进一步合作。进一步的进展可能会导致在飞机上采用这种机器，有可能减少总体能源消耗，从而降低对环境的影响。

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.