Performance Simulation Of DME High Pressure Common Rail Fuel System

With the development of the society and economy, great quantities of natural resources are consumed and the environment is polluted seriously. Energy and crisis environmental crisis emerged which greatly restricted the development of the social and human life quality.The Automobile Industry is an important aspect in the consumption of energy and a major producer of waste gas. In order to conquer the energy and environmental crisis, the automobile engineers is developing a lot in new engine technologies.DME has good advantage as an alternative fuel. The CETANE of DME is high, and exhaust in low in both NOx and soot which gives a good way to solve the Trade-Off of traditional CI engine. Also, the economy performance is good for DME is easy to vaporize. The common-rail fuel system has high injection pressure and independent, precise timing, the control is flexible which makes it the possibility to be most optimized in any conditions.The Internal Combustion Engine Institute, SHANGHAI JIAOTONG UNIVERSITY is doing a lot of research on DME common-rail fuel system. During the research, we found some differences of DME injection and common rail response characteristic with diesel for the properties of DME is quite different from diesel.In order to analyze the changes of differences of DME injection and common rail response characteristic with diesel, the simulation software AMEsim is used to simulate the system to find out the reasons of these problems. The major work and results includes:(1) The analysis of the structure and principle of common rail fuel system and the modeling of the system.Some hypothesis is made to after the analysis of the structure and principle of common rail fuel system. The major part of the common rail fuel system including the injectors, the pump, the rail and the signal which is to represent the function of ECU are built. The Compare between the simulation results and the experimental results shows that the model is reasonable and correct which means it can be used as a tool to study to DME fuel system characteristics.(2)The study of DME characteristicsThe study shows some characteristics of DME injection:â‘ The timing of DME injection is delayed comparing to diesel, the maximum injection rate and the injection volume is greater than diesel;â‘¡The rail pressure response of DME is slower and the adjusting process is smoother than diesel;â‘¢The pressure fluctuation of the rail becomes more serious if the orifice diameter is enlarged;â‘£The leakage of DME is remarkable and should be limited, the ways to reduce the leakage includes: increase the viscosity of DME, decrease the clearance, increase the contact length, decrease the injection pressure and so on.(3)'cavitation effect'on DME injection characteristicsThe results show that the'cavitation'effects DME injection characteristics a lot.â‘ 'cavitation'lead to the results that the duration of the needle lift is reduced which means that the injection duration is also reduced, then, the injection volume becomes less;â‘¡several ways can be applied to minimize the effect including: increase the diameter of outlet orifice of the injector, decrease the diameter of inlet orifice of the injector and less pre-load force of needle spring.