Engine turbocompressor controllable bypass system and method

Abstract

A system for a turbocharged internal combustion engine includes an engine having a charge inlet connected to the compressor outlet and an exhaust outlet connected to the turbine inlet for driving the turbocharger with hot exhaust gas and supplying compressed air to the engine for combustion. A bypass duct connects the compressor outlet to the turbine inlet for diverting a portion of the compressed air around the engine to the turbine inlet. A control member selectively controls the diversion of air. An operating method for the system involves controlling surge in an engine turbocharger compressor by diverting a portion of compressed air to the turbine inlet to limit compressor air pressure and insure sufficient air flow to avoid compressor surge. Preferably, the diverted air enters a distal part of an engine exhaust header for mixing with the exhaust gases prior to passing into the turbine inlet. Other benefits are disclosed.

1 . A controllable bypass system for a turbocharged internal combustion engine, the system comprising: 
 an engine having a charge inlet and an exhaust outlet;    a turbocharger including a turbine driving a compressor, a turbine inlet connected to the engine exhaust outlet for driving the turbine with hot exhaust gas and a compressor outlet connected to the engine charge inlet for supplying compressed air to the engine for combustion;    a bypass duct connecting the compressor outlet to the turbine inlet for diverting a portion of the compressed air around the engine from the compressor outlet to the turbine inlet; and    a control member for selectively controlling the diversion of air through the bypass duct.    
     
     
         2 . A system as in  claim 1  wherein the control member is a control valve in the duct and is externally operable for controlling bypass air flow.  
     
     
         3 . A system as in  claim 2  wherein the control valve is operated by a controller responsive to air flow and pressure differential across the compressor to provide bypass air flow as required to avoid surge in the compressor air flow.  
     
     
         4 . A system as in  claim 1  including a charge air cooler in the engine charge inlet for cooling the compressed air prior to combustion in the engine.  
     
     
         5 . A system as in  claim 1  wherein the engine includes an exhaust manifold forming part of the engine exhaust outlet and the bypass duct is connected to the exhaust manifold at an end distal from the turbine inlet  
     
     
         6 . A method of controlling surge in an engine turbocharger compressor, the method comprising: 
 diverting a sufficient portion of the compressed air from the compressor outlet around the engine to the turbine inlet to limit compressor air pressure and insure sufficient air flow to avoid compressor surge conditions while utilizing the energy in the diverted air to maintain compressor speed.    
     
     
         7 . A method as in  claim 6  including passing the diverted air through an engine exhaust header for mixing with the exhaust gases prior to passing into the turbine inlet.  
     
     
         8 . A method of controlling NOx production in an engine having a turbocharger, the method comprising: 
 diverting a controlled portion of compressed air from the compressor outlet around the engine to the turbine inlet to limit oxygen content in the cylinders and thereby reduce NOx production in the cylinders while utilizing the energy in the diverted air to maintain compressor speed.    
     
     
         9 . A method as in  claim 8  including passing the diverted air through an engine exhaust header for mixing with the exhaust gases prior to passing into the turbine inlet.  
     
     
         10 . A method of controlling peak cylinder pressure in an engine having a turbocharger, the method comprising: 
 diverting a portion of the compressed air from the compressor outlet around the engine to the turbine inlet to limit oxygen content in the cylinders and reduce the combustion rate, thereby limiting peak pressures in the engine cylinders while utilizing the energy in the diverted air to maintain compressor speed.    
     
     
         11 . A method as in  claim 10  including passing the diverted air through an engine exhaust header for mixing with the exhaust gases prior to passing into the turbine inlet.