Method for operating a compression-ignition internal combustion engine

Abstract

In a method for operating a compression-ignition internal combustion engine, a mean gas temperature in the cylinder is determined during a combustion in the combustion chamber, and a gradient of the mean gas temperature is calculated. The untreated nitrogen oxide emission level from the internal combustion engine is then determined either from a value for the gradient of the mean gas temperature and/or from a maximum value for the mean gas temperature in the cylinder. Accordingly, the engine parameters are set so that a profile of the mean gas temperature is produced, at which NOx emissions are formed during combustion are reduced.

1 - 11 . (canceled)  
     
     
         12 . A method for operating a compression ignition internal combustion engine having a cylinder, in which a combustion chamber is defined between a piston and a cylinder head, an engine control device, an intake valve, an exhaust valve, a fuel feed device and a downstream exhaust gas aftertreatment system, said method comprising: 
 feeding combustion air to the combustion chamber via the intake valve;    metering a quantity of fuel as a function of an operating point of the engine during a working cycle;    determining a mean gas temperature in the cylinder during a combustion in the combustion chamber;    calculating a gradient of the mean gas temperature; and    determining an untreated nitrogen oxide emission level from the internal combustion engine, based on at least one of a value for the gradient of the mean gas temperature, and a position of the gradient of the mean gas temperature in the combustion chamber.    
     
     
         13 . A method for operating a compression ignition internal combustion engine having a cylinder in which a combustion chamber is defined between a piston and a cylinder head, an engine control device, an intake valve, an exhaust valve, a fuel feed device and a downstream exhaust gas aftertreatment system, said method comprising: 
 feeding combustion air to the combustion chamber via the intake valve;    metering a quantity of fuel as a function of an operating point of the engine during a working cycle;    determining a mean gas temperature in the cylinder during a combustion operation in the combustion chamber;    determining an untreated nitrogen oxide emission level of the internal combustion engine, based on at least one of a maximum value for the mean gas temperature in the combustion chamber, and a position of a maximum value for the mean gas temperature.    
     
     
         14 . A method for operating a compression-ignition internal combustion engine having a cylinder in which a combustion chamber is defined between a piston and a cylinder head, an engine control device, an intake valve, an exhaust valve, a fuel feed device and a downstream exhaust gas aftertreatment system, said method comprising: 
 feeding combustion air to the combustion chamber via the intake valve;    metering a quantity of fuel as a function of an operating point of the engine during a working cycle;    determining a mean gas temperature in the cylinder, in the combustion chamber;    determining an untreated nitrogen oxide emission level from the internal combustion engine based on at least one of a mean gas temperature when the intake valve is closed and a final compression temperature in the combustion chamber.    
     
     
         15 . The method as claimed in  claim 12 , wherein the mean gas temperature is determined within a defined crank angle range.  
     
     
         16 . The method as claimed in  claim 13 , wherein the mean gas temperature is determined within a defined crank angle range.  
     
     
         17 . The method as claimed in  claim 14 , wherein the mean gas temperature is determined within a defined crank angle range.  
     
     
         18 . The method as claimed in  claim 12 , further comprising: 
 determining a quantity of a reducing agent for downstream exhaust gas aftertreatment system based on the untreated nitrogen oxide emission level which has been determined.    
     
     
         19 . The method as claimed in  claim 13 , further comprising: 
 determining a quantity of a reducing agent for downstream exhaust gas aftertreatment system based on the untreated nitrogen oxide emission level which has been determined.    
     
     
         20 . The method as claimed in  claim 14 , further comprising: 
 determining a quantity of a reducing agent for downstream exhaust gas aftertreatment system based on the untreated nitrogen oxide emission level which has been determined.    
     
     
         21 . The method as claimed in  claim 12 , wherein the metered quantity of fuel is injected into the combustion chamber in such a manner that at least one of a predetermined gradient of the mean gas temperature in the combustion chamber, and a predetermined position of the maximum value for the mean gas temperature, is established in the combustion chamber.  
     
     
         22 . The method as claimed in  claim 13 , wherein the metered quantity of fuel is injected into the combustion chamber in such a manner that at least one of a predetermined gradient of the mean gas temperature in the combustion chamber, and a predetermined position of the maximum value for the mean gas temperature, is established in the combustion chamber.  
     
     
         23 . The method as claimed in  claim 14 , wherein the metered quantity of fuel is injected into the combustion chamber in such a manner that at least one of a predetermined gradient of the mean gas temperature in the combustion chamber, and a predetermined position of the maximum value for the mean gas temperature, is established in the combustion chamber.  
     
     
         24 . The method as claimed in  claim 12 , wherein the metered quantity of fuel is injected into the combustion chamber in such a manner that a combustion center of gravity is established at a defined crank angle position.  
     
     
         25 . The method as claimed in  claim 13 , wherein the metered quantity of fuel is injected into the combustion chamber in such a manner that a combustion center of gravity is established at a defined crank angle position.  
     
     
         26 . The method as claimed in  claim 14 , wherein the metered quantity of fuel is injected into the combustion chamber in such a manner that a combustion center of gravity is established at a defined crank angle position.  
     
     
         27 . The method as claimed in  claim 12 , wherein an exhaust gas recirculation quantity for setting a defined oxygen concentration in the combustion chamber is set as a function of a combustion center of gravity.  
     
     
         28 . The method as claimed in  claim 13 , wherein an exhaust gas recirculation quantity for setting a defined oxygen concentration in the combustion chamber is set as a function of a combustion center of gravity.  
     
     
         29 . The method as claimed in  claim 14 , wherein an exhaust gas recirculation quantity for setting a defined oxygen concentration in the combustion chamber is set as a function of a combustion center of gravity.  
     
     
         30 . The method as claimed in  claim 12 , wherein a drop in the oxygen concentration which is required for nitrogen oxide reduction is calculated from the calculated untreated nitrogen oxide emission level, so that an exhaust gas recirculation device is set such that, after combustion air has been mixed with recirculated exhaust gas, a defined oxygen concentration is produced in a cylinder charge upstream of or in the combustion chamber.  
     
     
         31 . The method as claimed in  claim 12 , wherein: 
 oxygen concentration of the combustion air before it enters the combustion chamber is measured by means of an oxygen sensor; and    a defined oxygen concentration of the combustion air upstream of or in the combustion chamber is set by means of the exhaust gas recirculation device as a function of the measured concentration.    
     
     
         32 . The method as claimed in  claim 12 , wherein: 
 oxygen concentration of the exhaust gases after the exhaust gases have emerged from the combustion chamber is measured by means of an oxygen sensor;    oxygen concentration of the combustion air before it enters the combustion chamber is calculated from this signal, an exhaust gas recirculation rate and a measured combustion air quantity; and    a defined oxygen concentration of the combustion air upstream of or in the combustion chamber is set by means of the exhaust gas recirculation device, as a function of the calculated concentration.