Brett Peter Dewar

Abstracts

1 Computational Fluid Dynamics Simulation and Design Optimisation of a Triple Exit Volute for High Speed Centrifugal Compressor

Authors: Brett Peter Dewar

Abstract:

The key elements of a whole compressor system are inlet, impeller, diffuser, and volute. It is perhaps the volute that is the least well understood. Early simulation efforts have, justifiably, focused mostly on the impeller. As compressor speeds become higher, increased performance is demanded (particularly with regard to efficiency), and space, where compressors are housed, becomes tighter non-traditional volute designs are being studied. One such design is to have a volute with multiple outlets. Such a design has the potential to decrease the flow path length of individual fluid parcels from inlet to outlet, thus reducing total pressure loss for comparable static pressure rise. These designs also allow for the working fluid to be separated for different applications in the system as a whole, such as to different reservoirs, engine banks, or heat exchangers. These designs do, however, introduce more complicated geometry, particularly the addition of extra volute tongues; this can mitigate any gains in performance if the design is not carefully simulated and optimised. This works details the design, optimisation, and simulation process of a triple exit volute for a high speed air compressor. A detailed explanation of the CFD methodology is given, including boundary conditions and mesh verification. The volute geometry is evaluated in terms of different profile shapes and their hydraulic diameter gradient with regard to circumferential position. Cross section profiles are also allowed to change for each outlet, i.e., the design is not restricted to one volute simply mirrored three times. Objective functions are presented in terms of static pressure rise, total pressure loss, and circumferential velocity component at each cross section and compared against hydraulic diameter as a function of circumferential position. Finally, an analysis of any differences at the three volute tongues is presented.

Keywords: Turbomachinery, Computational Fluid Dynamics, Optimisation, ANSYS

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