Limiting nox emissions

Abstract

A method for controlling an internal combustion engine limits emission of undesirable compounds of nitrogen and oxygen and provides increased transient power.

1 . A method of operating a compression ignition engine to limit exhaust emissions during transient operation to increase engine power comprising:
 operating the engine at a first power output by providing a first air/fuel mixture to a combustion chamber of the engine;   receiving a request for an increased power output from the engine, that is greater than the first power output;   providing a second air/fuel mixture to the combustion chamber of the engine, the second air/fuel mixture comprising a greater amount of fuel than the first air/fuel mixture; and   treating a flow of exhaust gas with a non-urea aftertreatment to reduce a level of pollutant in the exhaust gas during a fuel enriched operation of the engine to invoke the real-time removal reduction of the pollutant while increasing engine power.   
     
     
         2 . The method of  claim 1 , wherein the pollutant is NOx. 
     
     
         3 . The method of  claim 2 , wherein the NOx is reduced to less than 0.2 gram per horsepower-hour work performed by the engine. 
     
     
         4 . The method of  claim 2 , wherein the NOx is reduced to less than 0.3 gram per horsepower-hour work performed by the engine. 
     
     
         5 . The method of  claim 1 , wherein the second air/fuel mixture is a substantially rich air/fuel condition. 
     
     
         6 . The method of  claim 5 , wherein the substantially rich air/fuel mixture has an air/fuel ratio within a range that includes a stoichiometric air/fuel ratio. 
     
     
         7 . The method of  claim 6 , wherein the range of substantially rich air/fuel condition is from about 95 percent to about 105 percent of the stoichiometric air/fuel ratio. 
     
     
         8 . The method of  claim 7 , wherein the range of substantially rich air/fuel condition is from about 90 percent to about 110 percent of the stoichiometric air/fuel ratio. 
     
     
         9 . The method of  claim 1 , wherein the first air/fuel condition is a substantially lean air/fuel mixture. 
     
     
         10 . The method of  claim 9 , wherein the substantially lean air/fuel mixture has an air/fuel ratio ranging from about 17:1 to about 20:1. 
     
     
         11 . The method of  claim 1  wherein the second air/fuel mixture is provided for a transient operation of the engine. 
     
     
         12 . The method of  claim 1 , wherein the aftertreatment contains a catalyst that is operative to reduce the pollutant when an oxygen concentration in the exhaust gas is at or below a predetermined level. 
     
     
         13 . The method of  claim 1 , further comprising reducing a flow of recirculated exhaust gas to the engine while providing the second air/fuel mixture in the combustion chamber of the engine. 
     
     
         14 . The method of  claim 1 , wherein the step of providing the first air/fuel mixture further comprises the step of estimating an oxygen concentration in the combustion chamber and controlling a flow of fuel in response to the estimated oxygen concentration. 
     
     
         15 . The method of  claim 14 , wherein the step of estimating the oxygen concentration in the combustion chamber further comprises the step of sensing the oxygen concentration in the exhaust gas using at least one sensor. 
     
     
         16 . The method of  claim 15 , wherein the at least one sensor is a lambda sensor. 
     
     
         17 . The method of  claim 1 , wherein the compression ignition engine is diesel fueled. 
     
     
         18 . The method of  claim 1 , wherein the compression ignition engine further comprises:
 a turbocharger, the turbocharger is driven by a flow of exhaust gas from the engine, provides a flow of compressed air to the engine, and   a controllable exhaust gas recirculation valve that controls a recirculation flow of exhaust gas from the flow of exhaust gas from the engine to the turbocharger into the flow of compressed air provided to the engine; and   wherein the step of providing a second air/fuel mixture to the combustion chamber of the engine further comprises closing the exhaust gas recirculation valve to increase the flow of exhaust gas to the turbocharger.   
     
     
         19 . The method of  claim 18  wherein:
 the turbocharger of the compression ignition engine has a variable nozzle through which the exhaust gas flow passes to drive the turbocharger, the variable nozzle causes the turbocharger to increase flow and compression of air to the engine and in doing so increases pressure of the exhaust gas flowing from the engine and the variable nozzle causes the turbocharger to decrease flow and compression of air to the engine and in doing so decreases pressure of the flow of exhaust gas flowing from the engine; and 
 wherein the step of providing a second air/fuel mixture to the combustion chamber of the engine further comprises controlling the variable nozzle of the turbocharger to increase flow of air to the engine. 
 
     
     
         20 . A method of operating a compression ignition engine to limit exhaust NO x  emissions during fuel enriched operation to increase engine power comprising:
 Injecting hydrocarbon into an exhaust stream from the compression ignition engine; and   treating the flow of exhaust gas with a non-urea aftertreatment to reduce a level of NO x  in the exhaust gas by combination with injected hydrocarbon during a fuel enriched operation of the engine to invoke a real-time reduction of NO x  while increasing engine power.   
     
     
         21 . A method of operating a compression ignition engine to limit exhaust emissions comprising:
 operating the engine using a first fuel injection pattern to inject fuel into a combustion chamber of the engine, wherein the first fuel injection pattern comprises at least one pilot injection and at least one main injection;   receiving a request for an increased power output from the engine;   operating the engine using a second fuel injection pattern to inject fuel into the combustion chamber in response to the request for the increased power output, wherein the second fuel injection pattern consists of main only injection; and   treating a flow of exhaust gas with a non-urea aftertreatment to reduce a level of at least one pollutant in the exhaust gas during a fuel enriched operation of the engine to invoke a real-time reduction of the pollutant while increasing engine power.   
     
     
         22 . The method of  claim 21 , wherein the pollutant is soot. 
     
     
         23 . A method for use in an exhaust system of a diesel engine, the method comprising:
 providing a flow of an exhaust gas from a compression ignition engine, wherein the exhaust gas includes NOx;   determining whether the compression ignition engine is being fueled by a rich a rich air/fuel mixture;   if the compression ignition engine is being fueled by a rich a rich air/fuel mixture, injecting hydrocarbon into the exhaust gas; and   providing the exhaust gas injected with the hydrocarbon to a three-way catalyst system.   
     
     
         24 . The method of  claim 23 , further comprising determining whether the injected hydrocarbon has reduced the NOx passing from the three-way catalyst system to a predetermined level. 
     
     
         25 . The method of  claim 23 , wherein the hydrocarbon is injected into the exhaust gas at a doser of the exhaust system. 
     
     
         26 . The method of  claim 23 , wherein the hydrocarbon is injected into the exhaust gas at a burner of the exhaust system. 
     
     
         27 . The method of  claim 23 , further comprising determining whether to elevate the amount of hydrocarbon injected into the exhaust gas to accommodate for aging deterioration of the three-way catalyst converter.