System and method for quantizing fuel dilution of engine motor due to post-injection fueling to regenerate an exhaust aftertreatment device

1. A method for quantizing fuel dilution of a supply of engine motor oil in a lubrication system of an internal combustion engine due to post-injection of fuel into a cylinder of the engine that occurs after a main injection to create rich exhaust leaving the cylinder, the method comprising:

in a data processing system associated with the engine, executing an algorithm for a) calculating a quantity of post-injected fuel that is retained in a film of engine motor oil on a wall of the cylinder and that, as a consequence of such retention and continuing operation of the engine, is returned to the engine motor oil supply, the algorithm comprising processing various data including data indicative of the quantity of post-injected fuel, data indicative of in-cylinder pressure at some point in the engine cycle that bears on the quantity of post-injected fuel retained in the film, data indicative of in-cylinder temperature at some point in the engine cycle that bears on the quantity of post-injected fuel retained in the film, and data indicative of engine speed, and b) using the calculated quantity of post-injected fuel that is retained in the film to quantize fuel dilution of the engine motor oil supply.

2. A method as set forth in claim 1 wherein the execution of the algorithm comprises using the data indicative of in-cylinder pressure and the data indicative of in-cylinder temperature to select from a look-up table containing data values, each correlated with a respective set of values of in-cylinder pressure data and in-cylinder temperature data, a data value correlated with the data indicative of in-cylinder pressure and the data indicative of in-cylinder temperature, and using the data value selected from the look-up table, the data indicative of the quantity of post-injected fuel, and the data indicative of engine speed to calculate the quantity of post-injected fuel that is returned to the engine motor oil supply as a consequence of being retained in the film of engine motor oil on the wall of the cylinder.

3. A method as set forth in claim 2 wherein the execution of the algorithm further comprises updating a data value quantizing fuel dilution of the engine motor oil supply by processing data indicative of temperature of the engine motor oil supply at a location external to the cylinder and a correlation function that correlates fuel evaporation from the engine motor oil supply with engine motor oil temperature at the location external to the cylinder to calculate a quantity of evaporative fuel from the engine motor oil supply, and adding to an earlier data value that quantizes fuel dilution of the engine motor oil supply, the difference between the calculated quantity of evaporative fuel from the engine motor oil supply and the calculated quantity of fuel returned to the engine motor oil supply as a consequence of being retained in the film of engine motor oil on the wall of the cylinder.

4. A method as set forth in claim 1 further including initiating execution of the algorithm in response to a request to regenerate an aftertreatment device in an exhaust system through which exhaust from the cylinder passes.

5. A method as set forth in claim 1 further including initiating execution of the algorithm in response to a request to regenerate a diesel particulate filter in an exhaust system through which exhaust from the cylinder passes.

6. An algorithm for calculating a quantity of post-injected fuel that is retained in a film of engine motor oil on a wall of a cylinder of an internal combustion engine into which fuel is injected and that, as a consequence of such retention and continuing operation of the engine, is returned to a supply of engine motor oil in a lubrication system of the engine, the algorithm comprising

processing various data including data indicative of engine speed, data indicative of in-cylinder pressure at some point in the engine cycle bearing on the quantity of post-injected fuel retained in the film of engine motor oil that is returned to the engine motor oil supply, data indicative of in-cylinder temperature at some point in the engine cycle bearing on the quantity of post-injected fuel retained in the film of engine motor oil that is returned to the engine motor oil supply, and data indicative of the quantity of post-injected fuel.

7. An algorithm as set forth in claim 6 comprising using the data indicative of in-cylinder pressure and the data indicative of in-cylinder temperature to select from a look-up table containing data values, each correlated with a respective set of values of in-cylinder pressure data and in-cylinder temperature data, a data value correlated with the data indicative of in-cylinder pressure and the data indicative of in-cylinder temperature, and using the data value selected from the look-up table, the data indicative of the quantity of post-injected fuel, and the data indicative of engine speed to calculate the quantity of fuel that is returned to the engine motor oil supply as a consequence of being retained in the film of engine motor oil on the wall of the cylinder.

8. A method as set forth in claim 7 wherein the algorithm further comprises updating a data value quantizing fuel dilution of the engine motor oil supply by processing data indicative of temperature of the engine motor oil supply at a location external to the cylinder and a correlation function that correlates fuel evaporation from the engine motor oil supply with engine motor oil temperature at the location external to the cylinder to calculate a quantity of evaporative fuel from the engine motor oil supply, and adding the difference between the calculated quantity of evaporative fuel from the engine motor oil supply and the calculated quantity of fuel returned to the engine motor oil supply as a consequence of being retained in the film of engine motor oil on the wall of the cylinder to an earlier data value quantizing fuel dilution of the engine motor oil supply.