Research On Rail Pressure Fluctuation Characteristics And Control Strategy Of Diesel High Pressure Common Rail System

With the proposal of China Ⅵ emission regulations,diesel engine pollution and emission requirements are becoming increasingly stringent,and it is urgent to upgrade common rail and fuel injection control technology.The high pressure response speed of the high-pressure common rail system can achieve efficient,precise and multi-stage injection,improve atomization effect and combustion efficiency,and reduce harmful gas emissions.Compared with foreign countries,China’s high-pressure common rail system has problems such as unstable pressure under full-load working conditions and poor control effect under unsteady working conditions.In this paper,AMEsim software is used to construct the physical model of diesel engine high-pressure common rail system,and then verification tests are carried out on relevant experimental platforms,and rail pressure fluctuations and control strategy analysis are carried out.The main work includes:Firstly,the working principle of key components such as common rail pipe,fuel injector,and high-pressure oil pump of Bosch’s second-generation common rail system was deeply studied,and a one-dimensional physical model was established based on AMEsim.Using the experimental vehicles of Weibo Technology,a high-pressure oil pump output efficiency test platform was built,and the output efficiency of the highpressure oil pump was obtained through experiments and simulations.The results show that the error between the experimental and simulation results is less than 5%,which verifies the accuracy of the model.Secondly,according to the physical model,the analysis of camshaft speed,fuel injection pulse width,fuel injection amount,fuel injection duration,and common rail pipe structure on the pressure fluctuation of common rail pipe under different working conditions is deeply studied.The results show that the cam speed has a greater influence on the amplitude and frequency of pressure fluctuation,and the plunger diameter and pump oil delay angle have little influence on pressure fluctuation.With the increase of fuel injection,the pressure fluctuation increases,and the maximum value of pressure fluctuation also shows a linear growth trend,and with the increase of fuel injection volume,the degree of fluctuation amplitude attenuation shows an upward trend.When the fuel injection pulse width is constant,and the maximum value of its pressure fluctuation shows an increasing trend,the degree of pressure fluctuation attenuation shows a decreasing trend.Finally,according to the existing conditions,a control scheme with current to voltage as the control medium is formulated,and the outer loop control model is appropriately simplified under the condition of analyzing the mechanism of the entire common rail control system.In terms of control,the control scheme based on linear rail voltage feedback is studied,and a composite control strategy of ADRC is proposed.Compared with traditional PID controllers,ADRC controllers have good anti-interference and fast response capabilities in the presence of interference or when changing the amount of fuel injection.