Heating exhaust gas for diesel particulate filter regeneration

Abstract

An electrically heated element within the exhaust system of a diesel engine raises the exhaust temperature sufficiently at idle or similar low exhaust flow/low exhaust temperature conditions to the point where the DOC is activated to burn fuel. As soon as the catalyst within the DOC housing is active, the DPF regeneration can be initiated. The electrically heated element can be provided within the exhaust pipe between the turbine outlet of turbocharged diesel engines and the DOC housing inlet. The electrically heated element can be powered from the engine alternator and activated when needed by the engine electronic control module.

1 . An exhaust system for a diesel engine, the diesel engine generating exhaust from the combustion of fuel, comprising:
 an exhaust path receiving exhaust from the diesel engine;   a diesel oxidation catalyst (DOC) housing within the exhaust path;   a diesel particulate filter (DPF) within the exhaust path downstream of the DOC housing; and   an electric heating element within the exhaust path upstream of the DOC housing, the electric heating element configured to raise the temperature of exhaust gas entering the DOC housing.   
     
     
         2 . The exhaust system according to  claim 1 , comprising an engine control and a relay having a signal side that is signal-connected to the engine control and a power side connected between engine electric power and the electric heating element, the engine control triggering the relay to provide electric power to the electric heating element when exhaust temperature must be raised for sufficient DOC activation for effective DPF regeneration. 
     
     
         3 . The exhaust system according to  claim 2 , wherein the exhaust path comprises a turbine upstream of the DOC housing and the electric heating element is arranged between the turbine and the DOC housing. 
     
     
         4 . The exhaust system according to  claim 3 , wherein the electric heating element is arranged at the inlet of the DOC housing. 
     
     
         5 . The exhaust system according to  claim 1 , wherein the electric heating element is sized to heat exhaust gas to about 250° C. 
     
     
         6 . In a vehicle powered by a diesel engine, the diesel engine providing mechanical power to drive an electrical power generator, the diesel engine having a turbocharger that includes a compressor and an exhaust-driven turbine, the turbine having an exhaust outlet that is flow connected to a diesel oxidation catalyst (DOC) housing that is flow-connected to a diesel particulate filter (DPF), and an engine electronic control unit that receives engine sensor signals and sends engine control signals to change engine controllable parameters to control engine emissions, the improvement comprising:
 an electric heating element arranged in a flow path between the turbine and the DOC housing, the electric heating element being signal-connected to the engine electronic control unit and powered by the electrical power generator when the engine electronic control unit requests a higher exhaust gas temperature into the DOC housing.   
     
     
         7 . The improvement according to  claim 6 , comprising a relay having a signal side connected to the engine electronic control module and a power side connected between the electrical power generator and the electrical heating element. 
     
     
         8 . The improvement according to  claim 7 , wherein the electrical heating element is located within an exhaust pipe between a turbine outlet and a DOC housing inlet. 
     
     
         9 . The improvement according to  claim 8 , comprising a temperature sensor arranged between the DOC housing and the electric heating element. 
     
     
         10 . A method of initiating diesel particulate filter (DPF) regeneration for a diesel engine having an exhaust path that includes a diesel oxidation catalyst (DOC) upstream of a DPF comprising the steps of:
 determining if regeneration is required; and   heating the exhaust gas in communication with the DOC using an electric heating element in heat transfer communication with the exhaust gas.   
     
     
         11 . The method according to  claim 10 , wherein the step of heating the exhaust gas is further defined by the steps of:
 sensing the temperature of the exhaust gas in communication with the DOC; and   only if the temperature of the exhaust gas is below a required DOC activation temperature, undertaking the heating of the exhaust gas.   
     
     
         12 . The method according to  claim 11  wherein the step of heating the exhaust gas is further defined by the step of:
 generating the electric power required for the electric heating element by converting engine mechanical power to electrical power.