A Study On Evaporation Characteristics Of Dimethyl Ether Droplets At High Pressure

Dimethyl ether (DME) is one kind of the promising clean alternative fuels. With the help of DME, a practical and feasible approach to solve the two big difficult problems-the crisis of energy and the environmental pollution is pioneered. DME is catching many researchers' attention in recent years, but there are still many rooms for the study of DME evaporation characteristics. Besides, at present the research is conducted at normal pressure. However, most of the fuels are evaporating, while mixing and burning during the diffusion combustion stage. Thus vaporization is at high temperature and pressure then, so the results of vaporization under normal pressure could not be applied here any more. The present study tries to thoroughly explore the vaporization characteristics of DME droplets at high pressure.The thermodynamics equilibrium estimation is an important issue in the high-pressure vaporization model. To precisely calculate it, the concept fugacity is introduced in the study. Under high pressure, the surface of droplets is not a pure liquid fuel, but a mixture of the fuel and ambient gas. And with the increase of ambient pressure, both the critical temperature of the mixture and the critical mole fraction of fuel are reduced.The calculation or prediction methods of thermo-physical properties are formed under high pressure, by means of Soave-Redlich-Kwong state equation with real gas effects and the mixture rule. There will be violent variance in thermo-physical properties of liquid and gas phase as the surface of the droplet gets near the Critical Point. One of the variances is that the heat of phase change is up to zero, and another is the conductivity coefficient rises steeply.Taking into account the gas phase solubility, real gas effects and the circulation inside the liquid droplet, an one-dimension model for high-pressure vaporization of fuel droplets are presented. Besides, a single DME droplet evaporation at high pressure was simulated with the models. The influences of ambient pressure, temperature, velocity and initial droplet size on the DME droplet vaporization at high pressure are discussed.