Automotive compressor: effect of an electric throttle in the upstream circuit on the surge limit

Abstract

On vehicles equipped with a turbocharged engine, there is a risk of compressor surge. This surge generates instabilities that lead to driving inconvenience, or even mechanical failure of the supercharging system. In general, the surge appears rather in transient operation: sudden closing of the throttle valve on gasoline engine, regulation of the EGR on diesel engine linked also to turbine regulation (VNT device or Waste Gate). On a turbocharger test stand, we set up the surge line in a “conventional way”: stationary experiments. Then we set up this line in transient conditions for different positions of an electric throttle placed upstream the compressor. It appears that: the surge limit is pushing back to lower flow rates when it is determined in transient; the surge limit is pushing back to lower flow rates when closing the throttle valve. The tests were carried on by the transient analysis of the surge during a quick closing-opening of the electric throttle valve.

Compressor Surge Mitigation in Turbocharged Spark-Ignition Engines without an Anti-Surge Control System during Load-Decrease Operation

“…However, this limit is not reliable once the turbocharger is coupled to the engine, because surge appearance is affected by the piping geometry around the compressor [19][20][21][22][23][24] and engine pulsation [25,26], as stated before. Besides, the surge margin may be modified under transient flow conditions [29]. Instead, the compressor outlet pressure (p 2 ) signal, acquired with a sampling of 0.2 crank-angle degrees, and its first derivative were used for surge detection.…”

“…The following two strategies were studied: the optimization of throttle closure and the application of different closings on the intake flap, located upstream of the compressor, to increase EGR rate. Podevin et al [29] already demonstrated, via experiments in a turbocharger test rig, that the surge area can be decreased by up to 60% by applying a certain closing on an electric throttle at the compressor inlet. In order to evaluate both strategies, a series of tip-outs under the most critical surge conditions was tested, and the filtered crank-angle resolved pressure signal at the compressor outlet and its time derivative were analyzed for surge detection.…”