Experimental Study on Starting Process and Idle Speed Closed-Loop Control of Natural Gas Engine
|School||Beijing University of Technology|
|Course||Thermal Power Engineering|
|Keywords||Natural gas engine Cold starting Idle speed Closed-loop control|
As world energy crisis is more and more serious and environmental protection is widely concerned, recently natural gas as a new alternative fuel has been attentive and supported.In this paper a simulating device producing engine signals is developed independently. It can simulate engine sensor signals. The value of Signals can be shown in the nixietube. There are some advantages such as friendly man-machine interface,simple operation and so on. All kinds of engine sensor signals used for ECU debugging can be provided by a simulating device. Internal relationship of sensors during different engine conditions can be reflected. A good sensor simulation conditions is provided for dynamic software debugging of ECU. The results show that all kinds of combined analog signals can be produced flexibly by the simulating device. The simulating device can play an excellent auxiliary role in ECU software logical debugging and fault test.In this paper a set of engine speed acquisition system developed independently is introduced. Engine speed signal can be real-time acquired accurately. Engine speed data can be saved in the Excel file in order to analyse them conveniently. The engine speed acquisition system can play an excellent auxiliary role in engine experiments. And it is a set of simple and convenient testing tool in engine bench test.In addition, in this paper multi-chip ECU control system developed independently for vehicle-used natural gas engine is applied. Control strategy is designed independently. Program is developed by C language. Refitting JL465Q5 engine is applied as the test bench. A lot of experiment study has been done. For example, cold starting experiment, idle speed closed-loop control experiment, cylinder disconnection experiment and transient condition experiment and so on.When cold starting experiment is done, some parameters can be controlled through experimental monitoring system in order to do some comparative experimental study with different values, for example injection pulse width of natural gas, ignition advance angle, and bypass air valve opening and so on. Some influencing factors to starting process of natural gas engine are discussed, for example, residual gas in cylinder, cold water temperature, ignition energy multi-time ignition and so on.When idle speed closed-control experiment is done, two control strategies are applied, they are idle speed control with single closed loop and idle speed control with double closed loop. Single closed loop is to control idle speed through bypass air intake quantity with PID algorithm. And injection pulse width of natural gas and ignition advance angle keep invariant. In the experiment goal speed is set as follow, 1600rpm, 1200rpm and 850rpm. From the experiment results the author analyses different parameters to idle condition influence of natural gas engine. The parameters are as follow, Air_Kp, Air_Ki, injection pulse width of natural gas and ignition advance angle. Double closed loop is derived from single closed loop. In addition to control bypass air intake quantity with PID algorithm, ECU also control injection pulse width of natural gas with PID algorithm at the same time. They are independent each other and have PID parameters respectively. Comparative experimental study between single closed loop and double closed loop is done when the goal speed is respectively set as follow, 1200rpm, 850rpm and 800rpm. A series of test conclusions are acquired. In addition, lower idle speed experiment is done, such as 750rpm and 700rpm.The goal of the cylinder disconnection experiment is to verify the effect of idle speed closed-loop control. Fault condition of spark plug is simulated in order to study the reliability of idle speed closed-loop control through disconnecting the high voltage wire connecting the spark plug in idle condition.The goal of the transient condition experiment is to study the ride comfort from one speed to another speed. The goal idle speed is greatly related with cold water temperature of natural gas engine. The goal idle speed should be fallen gradually as cold water temperature is higher. Therefore, the transient condition experiment must be done in order to obtain stability at different speed transition.