Experimental Investigation on Surge Phenomena in an Automotive Turbocharger Compressor

Downsizing and turbocharging are today considered an effective way to reduce CO₂ emissions in automotive gasoline engines, especially for the European and US markets. In the broad field of research and development for engine boosting systems, the instability phenomenon of surge has gathered considerable interest in recent years, as the main limiting factor to high performance boosting and boost pressure control. To this extent, developing an in-depth knowledge of the surge dynamics and on the phenomena governing the transition from stable to unstable operation can provide very valuable information for the design of the intake system and boost pressure control algorithms, allowing optimal boost pressure without compromising the transient response. This paper describes an experimental study that aims at better understanding the phenomena leading to the inception of surge, and exploring the effects of the downstream circuit geometry on the compressor dynamic behavior in surge and prior to surge. A specific circuit adaptable in volume and length was designed to study the effect of different configurations on the steady flow compressor performance, with special reference to the surge line position. Instantaneous static pressures are measured in several locations upstream and downstream the compressor. Besides, dynamic sensors to measure noise and vibrations are also adopted. The preliminary results of the experimental campaign are presented, exploring the influence of geometry variations on the compressor map and surge dynamics.