Mixer for dedicated exhaust gas recirculation systems

Abstract

Systems, methods and techniques for exhaust gas recirculation are provided. The system includes mixing exhaust flow from at least one cylinder of an engine with air in an air intake system prior to combustion. The exhaust flow from the at least one cylinder is accumulated prior to mixing and distributed into the intake air system in a controlled manner.

What is claimed is: 
     
         1 . A method, comprising:
 operating an engine having a plurality of cylinders;   directing air into the plurality of cylinders from an air intake system;   combusting a mixture of air and fuel within the plurality of cylinders to generate a power output and a flow of exhaust;   directing a first portion of the flow of the exhaust to an aftertreatment system;   directing a second portion of the flow of the exhaust to an exhaust gas recirculation system to mix with the air in the air intake system prior to combustion, wherein the second portion of the flow of exhaust is created by combustion in at least one of the plurality of cylinders dedicated to providing the second portion of the flow of the exhaust; and   prior to mixing with the air in the air intake system, storing the second portion of the flow of the exhaust in an accumulator in the exhaust gas recirculation system, the accumulator extending between an inlet to the accumulator and a plurality of outlets from the accumulator into the air intake system, wherein the accumulator provides a stored supply of recirculated exhaust gas to the air intake system in response to air pulsation by the plurality of cylinders during operation of the engine.   
     
     
         2 . The method of  claim 1 , further comprising providing a plurality of flows of the second portion of the exhaust from the plurality of outlets of the accumulator into the air intake system. 
     
     
         3 . The method of  claim 2 , further comprising spacing the plurality of flows of the second portion of the exhaust at locations spaced apart from each other along the air intake system. 
     
     
         4 . The method of  claim 2 , wherein the plurality of flows of the second portion of the exhaust extend from the accumulator substantially orthogonally to a flow of the air in the air intake system. 
     
     
         5 . The method of  claim 1 , wherein the accumulator includes a storage volume between the inlet and the plurality of outlets, and the storage volume is sized as a function of a total number of the plurality of cylinders contributing to the second portion of the flow of exhaust to mix with air. 
     
     
         6 . The method of  claim 1 , further comprising:
 directing the first portion of the flow of the exhaust to a turbocharger; and   directing the second portion of the flow of the exhaust from the at least one of the plurality of cylinders only to the accumulator.   
     
     
         7 . The method of  claim 1 , further comprising a porous media defining the plurality of outlets that are spaced along a mixing chamber of the intake system where the outlets are connected to the intake system. 
     
     
         8 . The method of  claim 7 , wherein the accumulator is upstream of the porous media. 
     
     
         9 . A system, comprising:
 an engine including a plurality of cylinders;   an intake passage configured to direct combustion air to all of the plurality of cylinders;   an exhaust passage configured to receive exhaust from a first portion of the plurality of cylinders and direct the exhaust from the first portion to an aftertreatment system; and   an exhaust gas recirculation system configured to receive exhaust from a second portion of the plurality of cylinders and direct the exhaust from the second portion to the intake passage, wherein the exhaust gas recirculation system includes an accumulator having an inlet for receiving the exhaust gas from the second portion of the plurality of cylinders, a plurality of outlets along the intake passage that directly connect the accumulator to the intake passage, and a storage volume between the inlet and the plurality of outlets, the storage volume being sized as a function of the number of cylinders comprising the second portion of the plurality of cylinders.   
     
     
         10 . The system of  claim 9 , wherein the second portion of the plurality of cylinders are dedicated to providing exhaust to the exhaust gas recirculation system. 
     
     
         11 . The system of  claim 10 , wherein the first portion of the plurality of cylinders are dedicated to providing exhaust to a turbocharger system. 
     
     
         12 . The system of  claim 9 , wherein each of the plurality of outlets is fluidly connected with a mixing chamber of the intake passage. 
     
     
         13 . The system of  claim 12 , wherein each of the plurality of outlets includes a length of conduit extending from the storage volume to the mixing chamber, each of the conduits defining an inner dimension and including an orifice having an opening dimension that is less than the inner dimension. 
     
     
         14 . The system of  claim 9 , wherein the accumulator receives exhaust from a cooler in the exhaust gas recirculation system. 
     
     
         15 . The system of  claim 9 , wherein the second portion of the plurality of cylinders consists of one cylinder. 
     
     
         16 . The system of  claim 15 , wherein the first portion of the plurality of cylinders includes at least two cylinders. 
     
     
         17 . The system of  claim 9 , further including an exhaust manifold fluidly communicating the first group of the plurality of cylinders with a turbocharger. 
     
     
         18 . The system of  claim 9 , further including:
 a cooler located within the exhaust gas recirculation system; and   a valve located upstream of the cooler to regulate exhaust flow from the second portion of the plurality of cylinders through the exhaust gas recirculation system.   
     
     
         19 . The system of  claim 18 , wherein the valve is connected to the exhaust passage downstream of a turbocharger in the exhaust passage. 
     
     
         20 . The system of  claim 9 , wherein the storage volume comprises a porous media configured to spatially distribute the exhaust flow from the second portion of the plurality of cylinders, the porous media defining the plurality of outlets along the intake passage. 
     
     
         21 . A system, comprising:
 a combustion engine having a first group of cylinders and at least one second group of at least one cylinder;   an exhaust manifold configured to receive exhaust from the first group of cylinders;   a turbocharger configured to receive exhaust only from the exhaust manifold;   an intake system configured to direct combustion air to the first and second groups of cylinders;   an exhaust gas recirculation system configured to receive exhaust from only the second group of cylinders; and   an accumulator connecting the exhaust gas recirculation system to the intake system, the accumulator including an inlet and a plurality of separate exhaust outlets in flow communication with the intake system, wherein the accumulator is configured to accumulate exhaust in the exhaust gas recirculation system and provide a constant supply of recirculated exhaust gas to the intake system in response to air pulsation of the first and second groups of cylinders during operation of the combustion engine.   
     
     
         22 . The system of  claim 21 , wherein the accumulator defines a storage volume between the inlet and the plurality of outlets, and the storage volume is a function of a total number of cylinders in the second group. 
     
     
         23 . The system of  claim 21 , wherein the second group of cylinders consists of a single cylinder. 
     
     
         24 . The system of  claim 23 , wherein the first group of cylinders includes at least two cylinders. 
     
     
         25 . The system of  claim 21 , wherein the storage volume is comprised of a porous media and the porous media defines the plurality of outlets opening into a mixing chamber of the intake system. 
     
     
         26 . The system of  claim 21 , further comprising:
 a cooler situated to cool exhaust flowing through the exhaust gas recirculation system; and   a valve located upstream of the cooler to regulate the flow of exhaust through the exhaust gas recirculation system, wherein the accumulator is downstream of and receives exhaust from the cooler.   
     
     
         27 . The system of  claim 26 , further comprising an outlet conduit extending from the turbocharger to an aftertreatment system, wherein the valve is connected to the outlet conduit downstream of the turbocharger.