Experimental Investigation on Surge Phenomena in an Automotive Turbocharger Compressor

Paper #:
  • 2018-01-0976

  • 2018-04-03
Downsizing and turbocharging are today considered an effective way to reduce CO2 emissions in automotive gasoline engines. To this aim, a deep knowledge of turbocharger behaviour could be a key solution to improve the engine-turbocharger matching calculation. The influence of the automotive intake circuit geometry on the compressor surge line position is an important aspect to take into account to guide the project of the intake manifold enlarging the compressor stable zone. This aspect has a considerable impact on engine performance, especially during transient conditions. The instability phenomenon of surge can seriously damage the compressor for vibrations and temperature stress. To avoid compressor damaging, the maximum boost pressure is generally limited with a by-pass system, reducing the engine mass flow rate. The deep knowledge of the surge phenomenon can help the automotive intake configuration maintaining the boost pressure at reasonable levels not compromising engine torque at different operating points and in transient conditions. A wide experimental investigation is carried out at the turbocharger test facility of the University of Genoa on a small turbocharger compressor coupled to different downstream circuits. A specific circuit adaptable in volume and length is used to study the effect of different configurations on steady compressor performance with special reference to the surge line position. Different instantaneous parameters are measured upstream and downstream the compressor. In particular, high frequency response transducers are adopted to measure instantaneous pressure signals and instantaneous turbocharger rotational speed. The system is also equipped with different dynamic sensors to measure noise and vibrations in both stable zone and surge operations. Structural measurements are performed using micro accelerometers located on the compressor housing. Sensor dynamic characteristics allowed to investigate frequency signals up to 50kHz in order to extend vibration investigation to the higher frequencies, in the range of blade pass frequency phenomena. Other accelerometers (with a dynamic up to 10 kHz) where located at the inlet and outlet compressor section, and at the plenum placed in the compressor line. Acoustic measurements are carried out with a pre-polarized microphone located at the compressor outlet section. In the paper, a description of the circuit made up for the surge phenomenon analysis is reported. The preliminary results of the experimental campaign are presented taking into account the influence of geometry variations on compressor map and surge phenomenon.
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