Low temperature catalyst light-off

Abstract

A catalyst associated with an internal combustion engine can be heated to improve emissions performance of the engine. Hydrogen can be generated within the internal combustion engine by combusting a first combustion mixture having a first air-fuel ratio including excess fuel relative to a stoichiometric air-fuel ratio, such that a reforming reaction occurs during the combusting of the first combustion mixture. A second combustion mixture having a second air-fuel ratio including excess oxygen can be combusted within the internal combustion engine such that oxygen remains in second exhaust gases after the combusting of the second combustion mixture. The first exhaust gases and the second exhaust gases can be delivered to the catalyst and the catalyst is heated by reacting at least some of the hydrogen and at least some of the oxygen at the catalyst. Internal combustion engines, systems, vehicles engine management systems, and method are disclosed.

What is claimed is: 
     
         1 . A method for heating a catalyst associated with an internal combustion engine, comprising:
 generating hydrogen within the internal combustion engine, the generating of the hydrogen comprising combusting a first combustion mixture having a first air-fuel ratio, the first air-fuel ratio comprising an excess of fuel relative to a stoichiometric air-fuel ratio such that a reforming reaction occurs during the combusting of the first combustion mixture to generate the hydrogen in first exhaust gases;   combusting a second combustion mixture having a second air-fuel ratio within the internal combustion engine, the second air-fuel ratio comprising an excess of oxygen relative to the stoichiometric air-fuel ratio such that oxygen remains in second exhaust gases after the combusting of the second combustion mixture;   delivering the first exhaust gases and the second exhaust gases to the catalyst; and   heating the catalyst by reacting at least some of the hydrogen and at least some of the oxygen at the catalyst.   
     
     
         2 . The method of  claim 1 , further comprising:
 determining that a temperature of the catalyst is below a minimum target operating temperature of the catalyst; and   causing the generating of the hydrogen and the combusting of the second combustion mixture based on the determining.   
     
     
         3 . The method of  claim 1 , comprising bringing the at least some of the hydrogen and the at least some of the oxygen together at the catalyst. 
     
     
         4 . The method of  claim 1 , comprising adsorbing one or both of the at least some of the generated hydrogen and the at least some of the excess oxygen onto a surface in the flow path to facilitate delivery of the at least some of the hydrogen and the at least some of the oxygen to the catalyst. 
     
     
         5 . The method of  claim 1 , further comprising controlling the combusting of the first combustion mixture and the second combustion mixture, the controlling comprising manipulating at least one of a valve timing of the internal combustion engine; an operation of one or more fuel injectors or a carburetor of the internal combustion engine; a compression ratio of the internal combustion engine; and a spark timing of the internal combustion engine. 
     
     
         6 . The method of  claim 1 , wherein the combusting of the first combustion mixture occurs in a first cylinder of the internal combustion engine. 
     
     
         7 . The method of  claim 6 , wherein the combusting of the second combustion mixture occurs in a second cylinder of the internal combustion engine. 
     
     
         8 . The method of  claim 1 , wherein the combusting of the first combustion mixture and the combusting of the second combustion mixture occurs in a same engine cylinder. 
     
     
         9 . The method of  claim 8 , wherein the combusting of the first combustion mixture occurs in a first engine cycle and the combusting of the second combustion mixture occurs in a second engine cycle. 
     
     
         10 . The method of any of  claim 1 , wherein the internal combustion engine comprises an opposed-piston engine. 
     
     
         11 . The method of  claim 8 , wherein the combusting of the first combustion mixture and the combusting of the second combustion mixture occur at a temporal separation within an engine cycle. 
     
     
         12 . The method of  claim 11 , wherein the generating hydrogen comprises injecting a first quantity of fuel after combusting the second combustion mixture within the engine cycle. 
     
     
         13 . The method of  claim 12 , wherein the injecting of the first quantity of fuel occurs during an expansion stroke of the engine cycle. 
     
     
         14 . The method of  claim 12 , wherein the first quantity of fuel comprises approximately 20% of a second quantity of fuel present in the second combustion mixture. 
     
     
         15 . The method of  claim 11 , wherein the combusting of the second combustion mixture comprises providing approximately 20% excess air relative to a stoichiometric air-fuel ratio for the second quantity of fuel. 
     
     
         16 . An internal combustion engine comprising:
 a combustion mixture delivery system;   a controller configured to control the combustion mixture delivery system to provide a first combustion mixture having a first air-fuel ratio, the first air-fuel ratio comprising an excess of fuel relative to a stoichiometric air-fuel ratio, such that a reforming reaction occurs during combustion of the first combustion mixture to generate hydrogen in first exhaust gases, the controller being further configured to provide a second combustion mixture having a second air-fuel ratio, the second air-fuel ratio comprising an excess of oxygen relative to the stoichiometric air-fuel ratio such that oxygen remains in second exhaust gases after the combusting of the second combustion mixture; and   an exhaust system that delivers the first and second exhaust gases to a catalyst such that at least some of the delivered hydrogen reacts with at least some of the delivered oxygen, thereby heating the catalyst.   
     
     
         17 . A system comprising the internal combustion engine of  claim 16  and a catalyst arranged to receive the first and second exhaust gases. 
     
     
         18 . An engine management system comprising:
 computer hardware configured to perform operations comprising:   controlling a combustion mixture delivery system of an internal combustion engine to provide a first combustion mixture having a first air-fuel ratio, the first air-fuel ratio comprising an excess of fuel relative to a stoichiometric air-fuel ratio, such that a reforming reaction occurs during combustion of the first combustion mixture to generate hydrogen in first exhaust gases, and to provide a second combustion mixture having a second air-fuel ratio, the second air-fuel ratio comprising an excess of oxygen relative to the stoichiometric air-fuel ratio such that oxygen remains in second exhaust gases after the combusting of the second combustion mixture,   wherein the engine management system performs the controlling based on determining that a measured temperature of the catalyst is below a minimum target operating temperature of the catalyst.   
     
     
         19 . An internal combustion engine comprising the engine management system of  claim 18 . 
     
     
         20 . A computer program product comprising a computer-readable storage medium storing instructions that, when executed by a computing system comprising at least one programmable processor, cause the computing system to perform operations comprising:
 controlling a combustion mixture delivery system of the engine to provide a first combustion mixture having a first air-fuel ratio, the first air-fuel ratio comprising an excess of fuel relative to a stoichiometric air-fuel ratio, such that a reforming reaction occurs during combustion of the first combustion mixture to generate hydrogen in first exhaust gases, and to provide a second combustion mixture having a second air-fuel ratio, the second air-fuel ratio comprising an excess of oxygen relative to the stoichiometric air-fuel ratio such that oxygen remains in second exhaust gases after the combusting of the second combustion mixture.