Exhaust gas controlling method of engine

摘要

An exhaust gas control method of an engine may include calculating a target mass flux of EGR gas by using air mass entering into a cylinder and target air mass supplied into the engine, calculating a target effective flow area (EFAd) of the EGR valve by using the target mass flux of the EGR gas and front/rear condition of the EGR valve, and calculating a valve opening rate of the EGR valve by using a predetermined curve fitting formula and the target effective flow area (EFAd).

主权项

1. An exhaust gas control system of an engine, the system comprising:
an EGR line that recirculates exhaust gas of an exhaust line to an intake line; an EGR valve that is disposed on the EGR line to control the recirculated exhaust gas; and an ECU that is configured to control the EGR valve according to a driving condition, wherein the ECU performs:
calculating a target mass flux of EGR gas by using air mass entering into a cylinder and air mass supplied into the engine;calculating a target effective flow area (EFAd) of the EGR valve by using a target mass flux of the EGR gas and front/rear condition of the EGR valve; andcalculating a valve opening rate of the EGR valve by using a predetermined curve fitting formula and a target effective flow area (EFAd); wherein the target mass flux of the EGR gas is calculated by the following formula:
{dot over (m)}egrd={dot over (m)}a−MAFd wherein {dot over (m)}egrd is a target mass flux of the EGR gas, MAFd is a target mass flux of the intake air detected, {dot over (m)}a is a mass flux of the air entered into the cylinder; wherein the {dot over (m)}a isηV·ρint·Vd·N120,  ηV a volume efficiency of a cylinder, ρint is a density of intake air, and Vd is a stroke volume of a cylinder, and N is an engine speed; and wherein the curve fitting formula is as follows:
EGR valve lift =P1+P2·EFAd+P3·(EFAd)2+P4·(EFAd)3 wherein the EGR valve lift denotes a target valve opening of the EGR valve, P1, P2, P3, and P4 are constants, and the EFAd is a target effective flow area.