Technical Paper
Air/Fuel Ratio Control in Diesel-Dual-Fuel Engine by Varying Throttle, EGR Valve, and Total Fuel
2010-10-25
2010-01-2200
From our experiences in converting diesel engine into diesel-dual-fuel engine with natural gas as primary fuel, accurate air/fuel ratio control is vital to the high engine performance, good vehicle drivability, and low emissions. Two components enter in calculating the air/fuel ratio, namely, the amount of fresh air and the amount of diesel and natural gas. Throttle and EGR valve are two actuators directly affect the amount of air, and the desired total fuel determines how much fuel should be injected at an instance. As opposed to inactive, fully opened throttle in typical diesel engine, the throttle in diesel-dual-fuel engine is regulated to cover wider range of desired air/fuel ratio. As a result, the problem of controlling the amount of air in diesel-dual-fuel engine becomes that of multi variables in which both throttle and EGR valve are involved. We present a novel algorithm that breaks the multi-variable control problem into two single-variable problems.