On-Engine Performance Evaluation of New-Concept Turbocharger Compressor Housing Design

Following the market demands in finding the niche balance between engine performance and legislation requirement, a new compressor scroll has been designed for small to medium size passenger cars. The design adopts a slight deviation from the conventional method, thus resulting in broader surge margin and better efficiency at off-design region. This paper presents the design of the new compressor scroll and its performance validation. The new compressor scroll is coupled to a standard wheel and tested on the cold gas stand followed by the on-engine testing. The testing program focused on back-to-back comparison with the standard compressor scroll, as well as identifying on-engine operational regime with better brake specific fuel consumption (BSFC) and transient performance. A specially instrumented 1.6L gasoline engine was used for this study. The engine control unit configurations are kept constant for both the compressor testing. The intake and exhaust manifold has been customized to fit the turbochargers and kept identical between the standard and new compressor scroll installations. The turbocharger with new compressor scroll design is found to work at higher boost pressure and has better stage efficiency across most of the engine operating conditions. Largest efficiency difference was noted at part-load engine operation. In term of BSFC, 8-10% of improvement by the new compressor scroll has been recorded at high-load conditions. In order to understand the source of better on-engine compressor efficiency, the instantaneous pressure in both standard and new concept compressor housing has been experimentally measured during the testing. The pressure pulsation and pressure loss in the compressor scroll will be analysed and presented in this paper. At the same time, transient test at low-to-medium speed revealed that the new compressor scroll has improved the engine transient response across the board, but more pronouncedly at medium operating speed.