Regeneration of diesel particulate filters using lambda variation

Abstract

This invention provides a method of regenerating a diesel particulate filter in an exhaust-gas purification system of a diesel engine using lambda variation. During regeneration on demand, the ratio of air to fuel for the corresponding operating point of the diesel engine is adjusted so as to achieve the substantially highest possible exhaust-gas temperature. For this purpose, the ratio of air to fuel (lambda value) is preferably kept at a minimum and substantially constant over the major part of the load range so that the engine is operated at full load during the regeneration phases.

1 . A method of regenerating a diesel particulate filter in an exhaust-gas purification system of a diesel engine, wherein during regeneration the substantially highest possible exhaust-gas temperature for the corresponding operating point of the diesel engine is reached by adjusting the ratio of air to fuel.  
   
   
       2 . The method according to  claim 1 , wherein the ratio of air to fuel (lambda value) is minimized to achieve the highest possible exhaust-gas temperature.  
   
   
       3 . The method according to  claim 1 , wherein during regeneration the ratio of air to fuel is maintained substantially constant over the major part of the load range.  
   
   
       4 . The method according to  claim 1 , wherein during regeneration the engine is operated at full load.  
   
   
       5 . The method according to  claim 1 , wherein the engine is a diesel engine with or without supercharging.  
   
   
       6 . The method according to  claim 1 , wherein the adjustment of the ratio of air to fuel is performed by means of a throttle valve for the supply and intake air, respectively.  
   
   
       7 . The method according to  claim 6 , wherein the throttle valve restricts the air flow rate at partial load of the engine.  
   
   
       8 . The method according to  claim 5 , wherein the adjustment of the ratio of air to fuel in a super-charged diesel engine is further performed by a system for varying the boost pressure.  
   
   
       9 . The method according to  claim 1 , wherein the adjustment of the ratio of air to fuel in a super-charged diesel engine is performed by means of a regulating valve downstream of the supercharger, the regulating valve closing or restricting the air passage to the engine and simultaneously opening a passage to the environment.  
   
   
       10 . The method according to  claim 1 , wherein the entire air flow rate in a supercharged diesel engine is restricted upstream of the supercharger such that the resulting boost pressure is varied through the air flow entering the supercharger.  
   
   
       11 . The method according to  claim 1 , wherein the air flow supplied to the engine is heated.  
   
   
       12 . The method according to  claim 1 , wherein, in a supercharged diesel engine having an intercooler downstream of the supercharger, the intercooler is bypassed during regeneration.  
   
   
       13 . The method according to  claim 1 , wherein the diesel particulate filter is catalytically coated.  
   
   
       14 . Device for regenerating a diesel particulate filter in an exhaust-gas purification system of a diesel engine, particularly for performing the method according to  claim 1 , which is adapted to achieve the substantially highest possible exhaust-gas temperature for the corresponding operating point of the diesel engine during regeneration by adjusting the ratio of air to fuel.