Diesel Engine With In-Cylinder Soot and NOx Control Using Water or Aqueous Injection

Abstract

A method of controlling emissions in the exhaust gas of a diesel engine, the engine having one or more combustion cylinders that each generates a combustion jet having a soot region. A water injector is operable to inject a spray of water or aqueous solution into the combustion jet, specifically toward the area of highest soot concentration. This water injection is timed to occur at or immediately before the combustion phase in which the soot reaches its greatest concentration. The size and shape of the spray are such that the majority of the spray reaches the area of greatest soot concentration.

What is claimed is: 
     
         1 . A method of controlling emissions in the exhaust gas of a diesel engine, the engine having one or more combustion cylinders that each generates a combustion jet having a soot region, comprising:
 modeling the combustion jet to determine a soot region within the combustion jet and an area of highest soot concentration in the combustion jet;   installing a water injector operable to inject a spray of water or aqueous solution into the combustion chamber,   wherein the direction of the spray is different from the direction of the combustion jet;   during engine operation, receiving data representing the combustion phase of the engine's combustion cycles;   injecting the spray into the combustion jet in response to the data;   wherein the injecting step is performed by timing injection of the spray so that it occurs at or immediately before the combustion phase in which the soot reaches its greatest concentration, and by directing the size and shape of the spray so that the majority of the spray reaches the area of greatest soot concentration.   
     
     
         2 . The method of  claim 1 , wherein the soot region is generally conical, and wherein the area of highest soot concentration is at the end of the soot region distal to the fuel injection. 
     
     
         3 . The method of  claim 1 , wherein the timing step is further performed to correspond with a mixing-controlled phase of combustion. 
     
     
         4 . The method of  claim 1 , wherein the installing step is performed such that the water spray enters the combustion chamber in a direction perpendicular to the direction of fuel injection. 
     
     
         5 . The method of  claim 1 , further comprising receiving data representing the amount of fuel injected during the engine's combustion cycles, and further comprising determining an amount of spray to inject based on the amount of fuel injected. 
     
     
         6 . The method of  claim 1 , wherein the amount of water injected is in a range of 0% to 50% of the amount of injected fuel. 
     
     
         7 . The method of  claim 1 , wherein the installing, receiving, timing and directing steps are performed for each cylinder of the engine. 
     
     
         8 . The method of  claim 1 , wherein the timing step is based on crank angle data. 
     
     
         9 . The method of  claim 1 , further comprising receiving engine load data, and wherein the injecting step is performed or not performed based on the load data. 
     
     
         10 . A system for controlling emissions in the exhaust gas of a diesel engine, the engine having one or more combustion cylinders that each generates a combustion jet in a combustion chamber, comprising:
 a water injector operable to inject a spray of water or aqueous solution into the combustion chamber,   wherein the water injector is positioned so that the direction of the spray is different from the direction of the combustion jet;   a control unit programmed to perform the following tasks during engine operation: receiving data representing the combustion phase of the engine's combustion cycles, and delivering control signals for injecting the spray into the combustion jet in response to the data;   wherein the injecting is performed by timing injection of the spray so that it occurs at or immediately before the combustion phase in which the soot reaches its greatest concentration, and by directing the size and shape of the spray so that the majority of the spray reaches the area of greatest soot concentration.   
     
     
         11 . The system of  claim 10 , wherein the timing step is further performed to correspond with a mixing-controlled phase of combustion. 
     
     
         12 . The system of  claim 10 , wherein the water spray enters the combustion chamber in a direction perpendicular to the direction of fuel injection. 
     
     
         13 . The system of  claim 10 , wherein the control unit is further programmed for receiving data representing the amount of fuel injected during the engine's combustion cycles, and for determining an amount of spray to inject based on the amount of fuel injected. 
     
     
         14 . The system of  claim 10 , wherein the amount of water injected is in a range of 0% to 50% of the amount of injected fuel. 
     
     
         15 . The system of  claim 10 , wherein the injection timing is based on crank angle data. 
     
     
         16 . The system of  claim 10 , wherein the control unit is further programmed for receiving engine load data, and wherein the injecting step is performed or not performed based on the load data.