A Novel Control Method of Air Fuel Ratio for Natural Gas Engine

In order to meet the increasingly strict emission requirements, the control of the engine's air-fuel ratio (AFR) has been the research focus of major manufacturers and universities. However, due to the long delay time of AFR measurement, the inaccurate estimation of the intake air mass into the cylinder, and the errors in the amount of the injected fuel, precise AFR control for engines is still a challenging issue, especially during the transition condition. Aiming at the problem of AFR control in natural gas engine, this paper redefines the objective of AFR control and establishes a new error system of the AFR, a feedforward plus feedback strategy is then proposed to regulate the error to approach zero, trying to reduce or even eliminate the overshoot of air-fuel ratio caused by feedforward, which may lead to unstable combustion of the engine. Moreover, the proposed strategy is verified by co-simulations on the platform of Matlab/Simulink with GT-POWER.