On-engine performance evaluation of a new-concept turbocharger compressor housing design

Abstract

Following market demands for a niche balance between engine performance and legislation requirement, a new-concept 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 performance evaluation of the new compressor scroll on the cold-flow 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 configuration is kept constant in 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 and low engine speed operation. In term of BSFC, 8-10% of improvement has been recorded with the new compressor scroll at high-load conditions. The compressor scrolls have been instrumented to measure instantaneous flow pressure in order to investigation potential reasons for performance improvement. The difference in efficiency between the compressor scrolls does not exhibit apparent trend with the scroll pulse pressure amplitude, but do show the likelihood of pulse flow and heat transfer effect. At the same time, the new compressor scroll was found to generally improve the engine transient response for the low-to-medium speed conditions. The transient gradient of the boost pressure for the new-concept compressor is noted to increase towards the end of the transient process, whereas the transient gradient of the engine brake torque is generally more linear.