Lean burn active ignition engine with aftertreatment system and method

Abstract

An engine system including a lean burn active ignition engine and aftertreatment system, and a method for operating such a system, are disclosed. In a representative embodiment, the lean burn active ignition engine includes an engine block including plural cylinders, an intake manifold adapted to provide charge air to the cylinders, an exhaust manifold, an active ignition source; and fuel and air handling systems that provide fuel/charge air mixture such that an air-to-fuel ratio of the mixed charge air and fuel in each of the engine cylinders is substantially greater than a stoichiometric quantity to achieve a lean burn condition. An exhaust gas aftertreatment system is fluidly coupled to an outlet of the exhaust manifold and includes an oxidation-reduction catalyst, and a selective catalytic reduction (SCR) catalyst fluidly coupled to the oxidation-reduction catalyst and positioned downstream of the oxidation-reduction catalyst.

1 . An engine system, comprising:
 a lean burning active ignition internal combustion engine, comprising:
 an engine block including plural cylinders; 
 an air handling system including an intake manifold adapted to provide charge air to the cylinders; 
 an exhaust manifold; 
 an active ignition source; and 
 a fuel injection system, which together with the air handling system is adapted to provide a mixture fuel from the injection system and charge air from the intake manifold such that an air-to-fuel ratio of the charge air/fuel mixture in each of the engine cylinders is substantially greater than a stoichiometric quantity to achieve a lean burn condition; and 
   an exhaust gas aftertreatment system fluidly coupled to an outlet of the exhaust manifold, said aftertreatment system including an oxidation-reduction catalyst and a selective catalytic reduction (SCR) catalyst fluidly coupled to the oxidation-reduction catalyst and positioned downstream of the oxidation-reduction catalyst.   
     
     
         2 . The engine system of  claim 1 , further comprising an energy conversion device fluidly connected to an outlet of the exhaust manifold and adapted to convert energy of an exhaust stream from the exhaust manifold to compress ambient air for said charge air. 
     
     
         3 . The engine system of  claim 2 , wherein the energy conversion device is a turbocharger including a turbine fluidly connected to an outlet of the exhaust manifold and adapted to turn with an exhaust stream from the exhaust manifold, and a compressor mechanically linked to the turbine and configured to provide the compressed ambient air with the turbine turning. 
     
     
         4 . The engine system of  claim 1 , further comprising a knock suppressant doser provided at the intake side of the engine block, said knock suppressant doser adapted to inject a knock suppressant into the charge at a quantity sufficient to reduce engine operating temperature with said lean burn condition. 
     
     
         5 . The engine system of  claim 4 , wherein the knock suppressant is at least one of exhaust gas recirculation (EGR) gas, alcohol, fuel or water. 
     
     
         6 . The engine system of  claim 1 , wherein the fuel injection system is one of direct injection or port fuel injection system. 
     
     
         7 . The engine system of  claim 1 , wherein the oxidation-reduction catalyst is a three-way catalyst. 
     
     
         8 . The engine system of  claim 1 , further comprising a particulate filter, wherein the oxidation-reduction catalyst is integrated with the particulate filter. 
     
     
         9 . The engine system of  claim 1 , further comprising a controller monitoring plural conditions of the engine and requests for power and adapted to communicate a signal to the fuel injection system in response to said monitored conditions and/or said request for power, said signal indicating to inject a quantity of fuel such that that the engine operates at a lean burn condition when the engine load is less than a predetermined threshold, and said signal indicating to inject a quantity of fuel such that that the engine operates substantially at a stoichiometric condition when the engine load is greater than a predetermined threshold. 
     
     
         10 . The engine system of  claim 9 , wherein the exhaust gas aftertreatment system includes a valve fluidly connected downstream from the oxidation-reduction catalyst, said valve controllable to route the exhaust gas through the SCR under said lean burn operating condition, and to route the exhaust gas to bypass the SCR under said stoichiometric operating condition. 
     
     
         11 . A method of operating an engine system including a lean burning active ignition internal combustion engine and an aftertreatment system, said engine including an engine block including plural cylinders, an intake manifold for providing charge air to the cylinders, an exhaust manifold, and at least one active ignition source for igniting a charge air and fuel mixture in each cylinder, and said aftertreatment system including an oxidation-reduction catalyst and a selective catalytic reduction (SCR) catalyst, comprising:
 injecting a metered amount of fuel at high pressure into each cylinder of the engine block to mix with charge air in the cylinder such that the air-to-fuel ratio of the mixed charge air and fuel is substantially greater than a stoichiometric quantity to achieve a lean burn condition upon combustion;   for each cylinder, combusting the mixed charge air and fuel in the cylinder by operating the at least one active ignition source; and   providing an exhaust gas stream resulting from said combustion though the aftertreatment system including an oxidation-reduction catalyst and a selective catalytic reduction (SCR) catalyst fluidly coupled to the oxidation-reduction catalyst and positioned downstream of the oxidation-reduction catalyst.   
     
     
         12 . The method of operating a lean burning active ignition internal combustion engine according to  claim 11 , further comprising converting energy of the exhaust gas stream to compress ambient air for said charge air. 
     
     
         13 . The method of operating a lean burning active ignition internal combustion engine according to  claim 11 , further comprising injecting a knock suppressant into the charge at a quantity sufficient to reduce engine operating temperature during said lean burn condition. 
     
     
         14 . The method of operating a lean burning active ignition internal combustion engine according to  claim 13 , wherein the step of injecting the knock suppressant includes monitoring plural conditions of the engine and requests for power, and determining whether a current or requested operating condition is a lean burn operating condition at which an operating a temperature would cause engine knock. 
     
     
         15 . The method of operating a lean burning active ignition internal combustion engine according to  claim 13 , wherein the knock suppressant is at least one of exhaust gas recirculation (EGR) gas, alcohol, fuel or water. 
     
     
         16 . The method of operating a lean burning active ignition internal combustion engine according to  claim 11 , wherein one of direct injection system or port fuel injection system injects the metered amount of fuel. 
     
     
         17 . The method of operating a lean burning active ignition internal combustion engine according to  claim 11 , wherein the oxidation-reduction catalyst is a three-way catalyst. 
     
     
         18 . The method of operating a lean burning active ignition internal combustion engine according to  claim 11 , further comprising filtering particulate matter from the exhaust stream in the aftertreatment system. 
     
     
         19 . The method of operating a lean burning active ignition internal combustion engine according to  claim 11 , further comprising:
 monitoring plural conditions of the engine and requests for power;   communicating a signal to a fuel injection system injecting said metered amount of fuel, said signal based on said monitored conditions and/or said request for power; and   if the engine load is less than a predetermined threshold, indicating in the signal to inject a quantity of fuel such that that the engine operates at a lean burn condition; and   if the engine load is greater than or equal to a predetermined threshold, indicating in the signal to inject a quantity of fuel such that that the engine operates substantially at a stoichiometric condition.   
     
     
         20 . The method of operating a lean burning active ignition internal combustion engine according to  claim 19 , further comprising:
 providing the exhaust gas through the SCR catalyst if the engine is operating in said lean burn condition; and   providing the exhaust gas to bypass the SCR catalyst if the engine is operating in said stoichiometric condition.   
     
     
         21 . A method of operating an engine system including a lean burning active ignition internal combustion engine and an aftertreatment system, comprising:
 providing exhaust gas from the lean burning active ignition internal combustion engine through a three way catalyst (TWC) in the aftertreatment system to produce ammonia during operation of the engine under stoichiometric conditions; and   storing the ammonia for additional NOx reduction during lean conditions.   
     
     
         22 . The method of operating a lean burning active ignition internal combustion engine according to  claim 21 , wherein the method further comprises providing the exhaust gas through a selective catalytic reduction catalyst downstream of the TWC, where said ammonia storage takes place.