Research And Development Of Air-Fuel Ratio Control System For Natural Gas Engine

The research and development of air-fuel ratio control system for natural gas engine can improve the fuel utilization rate and engine emission level, which at the same time guarantee the engine effective power and with important scientific research value and practical application value. Due to the natural gas engine with complicated nonlinearity and time-varying, there is more strictly requirement for control system of air-fuel ratio.This chapter firstly researches and analyses the structure of natural gas engine and theory of air-fuel ratio control system. And based on this, the air-fuel ratio control plan of natural gas engine is made. According to throttle angle and engine transient speed signal, theoretical air-fuel ratio for the system is determined. Also regarding to engine behavior, effective difference control is done by the connection between open-loop control and closed-loop control in order to make sure the control speed and precision of natural gas engine air-fuel ratio. Then as for the concerning controller, sensor and actuator for air-fuel ratio control plan are selected. And the control hardware is designed including signal conditioning circuit, system power circuit, clock and reset circuit, EPR valve control-driven circuit, alarm circuit and display circuit, which lays a foundation for the further development of air-fuel ratio control system of natural gas engine.At last, according to control system hardware of natural gas engine air-fuel ratio, the design includes main program module, steady condition control module, transient condition control module, fault diagnosis control module and software of air-fuel ratio control system. During the design of software, the design method of structuralization and modularization are adopted on the basis of control features of natural gas engine air-fuel ratio and its functions. And anti-interference measures for software is put up. The on-line commissioning of control system software was tested after the design, achieving a good control result for air-fuel ratio and the expected control objective.