Research On Rail Pressure Control Strategy And Performance Of High Pressure Common Rail Diesel Engine

The increasingly stringent emission regulations improved the development of electronic control technology of diesel engine. The high pressure common rail technology is one of the key technologies,which make diesel engine to meet the latest emission regulations. Therefore,the research on high pressure common rail is hot spot in the research of diesel engine. In the high pressure common rail system, the control of injection pressure and injection process is independent of each other. The injection pressure and injection process can be controlled respectively and flexible to obtain good engine performance. The injection pressure is determined by Rail pressure. So the performance of pressure control seriously affect the engine performance. A reasonable rail pressure control strategy is very necessary for rail pressure control and the performance of the engine.Firstly,the development status and trends of high-pressure common rail system in domestic and abroad are introduced in this paper. By combining with the emission regulations,the market status of high pressure common rail in domestic and the developing status of the independent high pressure common rail, the necessity of the research of rail pressure control strategy is pointed out. Then,the working principle of common rail system and the working process of the key components are analyzed. What’s more,the features and uses of different rail pressure control methods are described and the influence of rail pressure to engine performance are researched. Finally.the demand of rail pressure control is analyzed.Based on the principles,methods and requirements of rail pressure control, a flexible and controllable control strategy of high pressure common rail is designed. Then the modules’functions and algorithms in rail pressure control strategy are introduced in detail. The module includes:rail pressure correction calculation module, the rail pressure limit calculation module, target rail pressure calculation module, the flow calculation module, goal driven current calculation module and oil metering unit drive parameter calculation module. The parameters in rail pressure control strategy are classified in detail, which helps to adjust the control parameters when the engine calibration test is conducted. The steady-state performance index and dynamic performance index,which be used to evaluation the rail pressure control performance, are put forward.The rail pressure control strategy is compiled by using ASCET software,and then combined with the control strategies of other parts for system integration. On the self-developed ECU, the rail pressure control strategy is realized and the verification tests are conducted. Finally, the influence of rail pressure to engine performance is researched. On this basic, the control parameters in rail pressure control strategy are calibrated.Test results show that:1) The open and closed loop control of rail pressure can be automatically switched in the process of starting and idling. In the starting process, the rail pressure can be quickly established. In the process of idle-speed,the rail pressure can be controlled stably. The control of rail pressure can adjust the rail pressure to make it quickly respond to the change of the operating conditions of diesel engine. Rail pressure affects the calculation of the fuel injection parameters, which influences the injection process.2) Different rail pressure values have great influence on engine combustion, power performance, economic performance and emission performance. Rail pressure values different under engine performance.