An internal combustion engine may include one or more turbochargers for compressing a fluid which is supplied to one or more combustion chambers within corresponding combustion cylinders. Each turbocharger typically includes a turbine driven by exhaust gases of the engine and a compressor which is driven by the turbine. The compressor receives the fluid to be compressed and supplies the fluid to the combustion chamber. The fluid which is compressed by the compressor may be in the form of combustion air or a fuel and air mixture.
During low load conditions such as an idle condition in a diesel engine, the exhaust gases do not drive the turbocharger at a rotational speed which is sufficient to significantly compress the combustion air. In fact, under low load conditions the turbocharger can act as a restriction to the combustion air which is transported to the intake manifold. It is thus possible that under certain low load conditions the turbocharger may in fact impede the efficient operation of the internal combustion engine.
It is also known that a turbocharger in an internal combustion engine may undergo a surge condition, during which the volumetric flow rate to the compressor is too low and the pressure ratio is too high. Thus, the flow can no longer adhere to the suction side of the blades of the compressor wheels and the discharge process is interrupted. The air flow through the compressor is reversed until a stable pressure ratio with positive volumetric flow rate is reached, the pressure builds up again and the cycle repeats. It is known to sense the impending or actual occurrence of a surge condition associated with a compressor and bleed off compressed gas within the compressor to alleviate the surge condition. It is also known to bleed off compressed gas within the compressor upon the occurrence of other operating conditions, such as a high pressure condition, etc. An example of a compressor in a turbocharger which bleeds off high pressure gas from the compressor is disclosed in U.S. Pat. No. 3,044,683 (Woollenweber).
The present invention is directed to overcoming one or more of the problems as set forth above.