Gasoline Particulate Reduction Using Optimized Port Fuel Injection Plus Direct Injection

Abstract

An optimized port plus direct injection (PFI+DI) fueling system for reducing DI-generated particulates from a spark ignition gasoline engine is disclosed. It uses information from a computational model that includes piston wetting. Means for DI particulate reduction include control of DI timing and duration as a function of various parameters. Illustrative computational results for decreasing particulates in various drive cycles are presented. These calculations illustrate large potential particulate reductions (e.g. 95%) that can be obtained relative to DI operation alone. The optimized PFI+DI system could provide DI generated particulate reduction, efficiency and cost advantages relative to operation of a DI alone engine with a gasoline particulate filter (GPF). Alternatively, it could be used in combination with a GPF to ease GPF operation requirements and provide additional particulate reduction. Techniques for reducing piston wetting generation of particles from use of DI alone are also described.

What is claimed is: 
     
         1 . A fuel management system for a spark ignition engine that is fueled with gasoline and uses port fuel injection and direct injection;
 wherein the use of port fuel injection is such as to reduce particulate emission by reducing the fraction of fuel in the engine that is directly injected;   and wherein during at least part of a drive cycle the fraction of fuel that is provided by direct injection is increased as torque is increased and wherein it is matched to that needed for preventing knock as engine torque and engine speed change;   and wherein reduction of particulate emission is obtained by use of port fuel injection to increase the fraction of directly injected fuel that is introduced between a selected first crank angle degree on the intake stroke and a selected second crank angle degree on the compression stroke;   and wherein particulate emission decreases when the directly injected fuel is introduced after the first crank angle and before the second crank angle;   and wherein at least one of the selected first and second crank angles are determined by at least one input to a control system.   
     
     
         2 . The spark ignition engine of  claim 1 , wherein the selected first crank angle is determined by at least one input to the control system. 
     
     
         3 . The spark ignition engine of  claim 1 , wherein the selected second crank angle is determined by at least one input to the control system. 
     
     
         4 . The spark ignition engine of  claim 1 , wherein the selected first crank angle is determined by temperature information that is used by the control system. 
     
     
         5 . The spark ignition engine of  claim 1 , wherein the selected second crank angle is varied based on temperature information that is used by the control system. 
     
     
         6 . The spark ignition engine of  claim 1 , wherein the direct injection is initiated within the crank angle range between the first and second crank angle; and
 wherein the initiation is within the first 25% of time that the piston is between the first and second crank angle degrees.   
     
     
         7 . The fuel management system of  claim 1 , wherein the selected first and/or second crank angles are based on a look up table that uses experimental data about particulate emissions. 
     
     
         8 . The spark ignition engine of  claim 1 , wherein information from a model for piston wetting is used. 
     
     
         9 . The spark ignition engine of  claim 1 , wherein for at least part of the first 100 seconds of engine operation, spark retard is used to enable operation with port fuel injection alone and wherein spark retard is less than 10 crank angle degrees. 
     
     
         10 . The spark ignition engine of  claim 1 , wherein during at least some time within the first 100 seconds of engine operation, the fraction of fuel that is directly injected is matched to that needed to prevent knock as torque varies and wherein the engine is operated using port fuel injection alone for at least part of the first 100 seconds of engine operation. 
     
     
         11 . The spark ignition engine of  claim 1  wherein during at least some time within the first 100 seconds of engine operation, the fraction of fuel that is directly injected is matched to that needed to prevent knock as torque varies;
 and wherein the engine is operated using port fuel injection for the first 100 seconds of engine operation; and wherein a spark retard of less than 10 crank angle degrees is employed during at least some time during the first 100 seconds of engine operation. 
 
     
     
         12 . A spark ignition engine that is fueled with gasoline and uses direct injection;
 wherein reduction of particulate emission is obtained by increasing a fraction of directly injected fuel that is introduced between a selected first crank angle degree that occurs on the intake stroke and a selected second crank angle degree that occurs on the compression stroke;   and wherein the selected first and/or second crank angles are varied with changing temperature.   
     
     
         13 . The spark ignition gasoline engine of  claim 12 , wherein the first crank angle occurs later when the temperature is lower. 
     
     
         14 . The spark ignition gasoline engine of  claim 12 , wherein the second crank angle occurs earlier when the temperature is lower. 
     
     
         15 . The spark ignition gasoline engine of  claim 12 , wherein the first crank angle occurs later and the second crank angle occurs earlier when the temperature is lower. 
     
     
         16 . The spark ignition gasoline engine of  claim 12 , wherein information about the first and second crank angles is used in a lookup table for controlling injection timing. 
     
     
         17 . The spark ignition gasoline engine of  claim 12 , wherein information about the first and second crank angles is used in a lookup table for controlling injection timing;
 and wherein the crank angle limits are determined by laboratory measurements of engine parameters.   
     
     
         18 . The spark ignition gasoline engine of  claim 12 , wherein during cold operation, the first crank angle is at least 10 degrees later than it would otherwise be. 
     
     
         19 . The spark ignition gasoline engine of  claim 12 , wherein during cold operation, the first crank angle is at least 20 degrees later than it would otherwise be. 
     
     
         20 . The spark ignition gasoline engine of  claim 12 , wherein during cold operation, the second crank angle is at least 10 degrees earlier than it would otherwise be. 
     
     
         21 . The spark ignition gasoline engine of  claim 12 , wherein the start of direct injection is adjusted so as to begin after the selected first crank angle and before the selected second crank angle. 
     
     
         22 . A spark ignition gasoline engine that is fueled with gasoline and uses direct injection;
 and wherein reduction of particulate emission is obtained by increasing a fraction of directly injected fuel that is introduced between a selected first crank angle degree that occurs on the intake stroke and a selected second crank angle degree that occurs on the compression stroke;
 and wherein the fraction of directly injected fuel that is introduced between the first selected crank angle degree and a second crank angle degree on the compression stroke increases with increasing fuel delivery rate. 
   
     
     
         23 . The spark ignition gasoline engine of  claim 22 , wherein the fuel delivery rate is adjusted so as to increase the fraction of directly injected fuel that is introduced between the first and second crank angle degrees. 
     
     
         24 . The spark ignition gasoline engine of  claim 22 , wherein a higher fuel injection pressure is used for at a least some time during a cold start period of the first 100 seconds of engine operation. 
     
     
         25 . The spark ignition engine of  claim 22 , wherein when the engine temperature is lower, the selected first crank angle occurs later than it otherwise would. 
     
     
         26 . The spark ignition engine of  claim 25 , wherein port fuel injection is also employed and is used so as to reduce particulate emissions. 
     
     
         27 . The spark ignition engine of  claim 22 , wherein the selected first and/or second crank angles are determined by inputs from a look up table. 
     
     
         28 . The spark ignition engine of  claim 22 , wherein increased fuel injection pressure is employed so as to increase the fraction of fuel that is directly injected between the selected first and second crank angles. 
     
     
         29 . The spark ignition engine of  claim 22 , wherein increased fuel injection pressure is employed so as to increase the fraction of fuel that is directly injected between the selected first and second crank angles and wherein an increase in fuel injection pressure of 50% can increase the onset BMEP for particulate emissions by at least 15% relative to the onset BMEP for particulate emissions where a 50% higher fuel injection pressure is not employed. 
     
     
         30 . The spark ignition engine of  claim 22 , wherein a temporary fuel injection pressure increase is employed during high power engine operation. 
     
     
         31 . The spark ignition engine of  claim 22 , wherein an electric fuel pump is employed to temporarily increase fuel injector pressure. 
     
     
         32 . The spark ignition engine of  claim 22 , wherein the first and second selected crank angles are varied based upon use of EGR. 
     
     
         33 . The spark ignition engine of  claim 22 , wherein air preheating is used to reduce particulate emissions.