Numerical Simulation And Experimental Research Of Fuel Injection Process In A DME Engine

DME(dimethyl ether) becomes a potential alternative fuel for it's clean and efficient combustion performance, but there are still many problems that be applied to diesel engine because of it's specific characteristics. The design of DME injection system is the most important aspects in all of the problems. Based on the extensive literatures reading, this paper summarizes the characteristics of DME and the main problems and requests in DME injection system. The aims of numerical simulation and development of the correlative technology of the fuel injection system in the world are analyzed. A mathematic model of pump-pipe-nozzle fuel injection system that common used by DME is created according to the reasonable assumption. The mathematic model is based on the dynamic principle of the pressure wave spread in high pressure pipe including equations of the conservation of mass, the dynamics equations of moving parts of pump and nozzle's boundary conditions. The jointed equations are solved by characteristic lines method and finite difference method, and the simulation procedure is developed with FORTRAN language. Some specific circumstantialities that DME have during injection in pump-pipe-nozzle system are considered, and after comparison with test data the procedure is proved to simulate the process of DME fuel injection. As a result, the press change curve in the pump side , high pressure fuel pipe and the nozzle side and the lift curve of needle etc. can be obtained. A visual debugging interface is developed with VB. Operator can adjust the input parameters by dialog box on the interface and then observe the results'variety through plotting function in post-process module. The debugging interface make it very convenient to change the input parameters and process the results. It combines the visual function of VB with the FORTRAN source procedure and make the results very intuitively by plotting curves. Eventually, a fluid-solid coupling FEA model is used to investigate the fuel fluid velocity distribution in the clearance between plunger and plunger sleeve in the form of static and transient analysis by FEA software named ANSYS and make some suggestions to improve fuel clearance leakage of DME engine. It's helpful to solve fuel clearance leakage between plunger and plunger sleeve of DME engine.