Aerodynamic Improvement of Centrifugal Compressors

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A step improvement in aero-engine technology will be crucial for the air transport industry to confront the inevitable increase in fuel prices, competition and environmental pressures. The centrifugal compressor, which has far superior pressure ratio per stage than axial compressors currently used in most aircraft engines, can play a major role in this improvement. Indeed, the replacement of many axial compressor stages by a single centrifugal compressor stage will result in simpler, shorter and lighter aero-engines. However, the aerodynamic performance and technology of centrifugal compressors must be brought close to that of axial compressors. The proposed research will build on experience and developments in axial compressor technology to significantly improve the aerodynamics of centrifugal compressors for wider use in aero-propulsion. It will seek to improve the adiabatic efficiency and stall margin of centrifugal compressors as well as reduce the degradation of these parameters with engine age. It is proposed to do so through investigation and understanding of the flow physics and developing effective design and flow control strategies by using a pioneering cost-effective approach that takes advantage of the rapid evolution in additive manufacturing (3D printing) technology. First, additive manufacturing technology allows for the exploration highly complex designs that were not practical or possible with standard manufacturing technology. In addition, polymer 3D printing technology allows for fast fabrication of relatively inexpensive test rigs. The proposed research will rely on low-cost fully instrumented rotating centrifugal compressor rigs custom designed and built with 3D printing by large teams of senior undergraduate students in a two-semester final-year design project course that has successfully produced compressor rigs for three years. The test data obtained from the first new rig will serve to validate a computation fluid dynamics (CFD) simulation tool to capture the complex flow field in centrifugal compressors. This simulation tool will be used, along with analytical modelling, by graduate students to elucidate/understand the flow mechanisms associated with the three aspects studied and predict the effect of aerodynamic improvement strategies. The second new rig will then serve to experimentally validate these strategies. In doing so, this research will provide cost-effective training of a large number of HQP in all three aspects of engineering (analytical/numerical/experimental) and provide industry with sought-after experts in centrifugal compressor technology not only for aeronautics but also for the very wide variety of industries that use this technology.