FLOW CHARACTERISTICS AND DESIGN METHODOLOGY FOR A CENTRIFUGAL COMPRESSOR VOLUTE

Throughout the years, many studies have been carried out on engines with every effort to save fuel, reduce emissions and produce more power. Turbochargers have been developed and installed in the exhaust system of an engine to use exhaust emissions for boosting power within an internal combustion engine, which would otherwise be wasted. The turbocharger characteristics are essential to determine its performance. There are three stages in a turbocharger, namely being, the turbine stage where energy is extracted from the exhaust gases; bearing housing where energy is being transferred to the compressor stage; and the compressor stage where ambient air is drawn in and compressed to increase the fluids density and pressure prior to being delivered into the intake system. The compressor stage consists of four main components, namely being, the inducer, impeller, diffuser and volute.

The volute of a turbocharger compressor is the third most important component within the compressor stage and has therefore, not received the attention that is needed. However, manufacturers are continuously seeking to obtain a realistic design methodology where variables exposed in real conditions, such as frictional effects are accounted for to minimise losses during performance. For this reason, it is essential to develop a thorough understanding of the flow phenomena the turbocharger compressor stage experiences under steady and transient conditions from a macroscopic level to a microscopic level. This creates a solid foundation for conducting the presented research.

In this study, a realistic design methodology for a turbocharger compressor volute has been presented. Detailed qualitative and quantitative flow field analyses of the turbocharger compressor stage have been numerically carried out under steady and transient flow conditions using Computational Fluid Dynamics (CFD) based techniques. The numerical investigations carried out in this study allow a clear visualisation of the flow structure within the turbocharger compressor stage volute, which makes it a cost effective method to undertake this research study. Approximations have been presented to design the symmetric and asymmetric type volutes, which have been applied into practice and analysed under steady and transient conditions to validate the presented compressor volute design methodology for turbocharging applications.