Research On Air Fuel Ratio Control Of A Premixed Gas Engine

With the increasing of air pollution,the government vigorously advocated energy conservation and emission reduction,emission regulations become increasingly strict;The government promotes the use of clean energy to reduce emissions.Natural gas as one of clean fuels,and proven reserves,also widely used in the natural gas engine gradually.Air-fuel ratio as an important parameter in the operation of natural gas engines,its precise control for natural gas engines to reduce emissions,improve the economy and improve the dynamic is of great significance.In this thesis,the air-fuel ratio control system of premixed gas engine is studied.Based on the structure of the premixed gas engine system,analyzed the pre-mixed gas engine intake system.Studied and established the premixed gas engine model,the fuel electronic throttle model and the oxygen sensor model.Due to the engine air-fuel ratio system there is a large delay,the air-fuel ratio closed-loop control strategy can not meet the performance requirements of the air-fuel ratio control system,After analyzing the static feedforward air intake model of the premixed gas engine,the feedforward control strategy is designed.Taking into account the emission performance and economic performance of the system,the air-fuel ratio lean combustion control strategy is designed,and the air-fuel ratio self-learning control strategy is designed to improve the self-adaptability of the system.The fuzzy control strategy is introduced in the control strategy of fuel electronic throttle,designed he fuzzy PID compound controller,the simulation experiment and the bench test show that the fuzzy PID compound control strategy is superior than the conventional PID control strategy in the control effect.In order to verify the control strategy proposed in this thesis,the air-fuel ratio control system is designed,including system hardware,control software and calibration software,also the air-fuel ratio system experiment platform is setted up.The correctness and validity of the air-fuel ratio control system that designed in this thesis are verified by simulation experiment and bench test.