Gasoline dithering for spark-ignited gaseous fuel internal combustion engine

Abstract

An internal combustion engine system of the present application includes a spark-ignited internal combustion engine that is powered by a gaseous fuel. The engine system also includes an exhaust system that is in exhaust gas receiving communication with the internal combustion engine. The exhaust system includes an exhaust treatment component. Additionally, the exhaust system includes a liquid fuel injection system in liquid fuel injecting communication with the exhaust system to inject liquid fuel into exhaust gas upstream of the exhaust treatment component.

What is claimed is: 
     
         1 . An internal combustion engine system, comprising:
 a spark-ignited internal combustion engine powered by a gaseous fuel;   an exhaust system in exhaust gas receiving communication with the internal combustion engine, the exhaust system comprising an exhaust treatment component; and   a liquid fuel injection system in liquid fuel injecting communication with the exhaust system to inject liquid fuel into exhaust gas upstream of the exhaust treatment component.   
     
     
         2 . The internal combustion engine system of  claim 1 , wherein the gaseous fuel comprises natural gas. 
     
     
         3 . The internal combustion engine system of  claim 1 , wherein the liquid fuel comprises gasoline. 
     
     
         4 . The internal combustion engine system of  claim 1 , wherein the liquid fuel injection system injects liquid fuel into the exhaust gas based on an air-to-fuel ratio of the exhaust gas generated by the spark-ignited internal combustion engine. 
     
     
         5 . The internal combustion engine system of  claim 1 , wherein the spark-ignited internal combustion engine generates exhaust gas with an air-to-fuel ratio above 1.0. 
     
     
         6 . The internal combustion engine system of  claim 1 , wherein the exhaust treatment component stores oxygen, and wherein the liquid fuel injection system injects liquid fuel into the exhaust gas based on an oxygen storage capacity of the exhaust treatment component. 
     
     
         7 . The internal combustion engine system of  claim 1 , wherein the liquid fuel injection system injects liquid fuel into the exhaust gas during a cold start of the spark-ignited internal combustion engine. 
     
     
         8 . The internal combustion engine system of  claim 1 , wherein the exhaust system comprises an exhaust manifold coupled to the spark-ignited internal combustion engine, and wherein the liquid fuel injection system injects liquid fuel into the exhaust manifold. 
     
     
         9 . The internal combustion engine system of  claim 1 , further comprising a gaseous fuel injection system in gaseous fuel injecting communication with the spark-ignited internal combustion engine, wherein the liquid fuel injection system injects liquid fuel into the exhaust gas independently of the injection of gaseous fuel injected into the engine by the gaseous fuel injection system. 
     
     
         10 . The internal combustion engine system of  claim 1 , wherein quantity and timing of the injection of liquid fuel into the exhaust gas by the liquid fuel injection system is based solely on conditions of the internal combustion engine system downstream of the spark-ignited internal combustion engine. 
     
     
         11 . The internal combustion engine system of  claim 1 , wherein the exhaust treatment component comprises an oxidation catalyst. 
     
     
         12 . The internal combustion engine system of  claim 1 , wherein the exhaust treatment component comprises a three-way catalyst. 
     
     
         13 . The internal combustion engine system of  claim 1 , wherein the liquid fuel injection system comprises a retrofitted diesel exhaust fluid injection system. 
     
     
         14 . The internal combustion engine system of  claim 1 , wherein the exhaust treatment component comprises a nitrogen oxide reduction catalyst. 
     
     
         15 . The internal combustion engine system of  claim 1 , wherein the gaseous fuel comprises substantially solely natural gas. 
     
     
         16 . An electronic control module for a spark-ignited internal combustion engine powered by a gaseous fuel, comprising:
 an exhaust system condition module that determines a condition of an exhaust system in exhaust gas receiving communication with the spark-ignited internal combustion engine; and   a liquid fuel control module that commands the dithering of a liquid fuel into the exhaust system based on the condition of the exhaust system.   
     
     
         17 . The electronic control module of  claim 16 , wherein the exhaust system comprises an oxidation catalyst, and wherein the condition of the exhaust system comprises an oxygen storage capacity of the oxidation catalyst. 
     
     
         18 . The electronic control module of  claim 16 , wherein the condition of the exhaust system comprises an air-to-fuel ratio of exhaust gas generated by the spark-ignited internal combustion engine. 
     
     
         19 . The electronic control module of  claim 16 , wherein the condition of the exhaust system comprises an exhaust gas temperature below a minimum threshold. 
     
     
         20 . A method for dithering a liquid fuel into an exhaust system in exhaust receiving communication with a spark-ignited internal combustion engine powered by a gaseous fuel, the method comprising:
 determining a condition of the exhaust system; and   injecting a liquid fuel into exhaust gas flowing through the exhaust system based on the condition of the exhaust system.