Design and Performance Enhancement of a Gasoline Engine Turbocharger Compressor by Adopting RCT and Hybrid RCT

Abstract

The diesel engine used the turbocharger technology for a long period. To solve the compressor associated with surge unstable phenomena, the medium and large size turbocharger compressor used the RCT(recirculation casing treatment) also called ported shroud technology in a diesel engine. The RCT can decrease the vortex at the impeller part when the compressor is operated in the low mass flow rate working fluid. Due to the casting limitation, the small size compressor which the pressure ratio range from 1.2 to 2.5 is not easy to adopt the RCT technology. The 3D printer technology has been developing very quickly nowadays. It can also be used for the future compressor production. Recently, the turbocharger has been installed to the gasoline engine to increase the engine power and decrease the emission pollution. Most gasoline engine displacement is from 1.3L to 2.0L. Hence, it is essential to investigate the flow and performance of the small-sized gasoline engine turbocharger RCT compressor by using the CFD technology. Comparing the CFD results between the Non-RCT and RCT compressor model, the RCT compressor can increase the efficiency at the low mass flow rate, which improves the unstable flow performance. However, at the medium mass flow rate range, especially the mass flow rate of the gasoline engine at the highest power output point, the RCT compressor has the lower efficiency than the non-RCT compressor. A new Hybrid RCT has been designing by the author which has a small channel connecting the compressor volute downstream part and RCT inlet duct to improve the flow movement by overcoming the adverse pressure gradient. The CFD results showed that the Hybrid RCT compressor had a similar performance with the RCT compressor, but it could increase the efficiency than the RCT compressor at the medium mass flow range and showed higher efficiency in a certain region of compressor than the non-RCT compressor.