Numerical Study On The Supercritical Evaporation Of The Multi-component Fuel Droplet

With the development of modern engine towards high pressure and large power,both the temperature and the pressure are more and more higher in the cylinder, theatomization and evaporation process of liquid fuel are finished in the hightemperature and high pressure environment. Because of the problem of energy andenvironment, the mixed alternate fuel is gradually replacing traditional petroleumfuels. The DME/LPG mixed alternate fuel which can meet the engine requirementsand reduce the emission has been widely studied, its evaporation process is verydifferent from the traditional petroleum fuels, so it is necessary to have theoreticalresearch of the evaporation process of the DME/LPG mixed alternate fuel, getting theevaporation characteristics.Based on the theory of the sub critical evaporation of multi-component fueldroplets and the supercritical evaporation of single component fuel droplets, themathematical model for the supercritical evaporation of multi-component droplets isestablished. Use the theory of high-pressure vapor-liquid equilibrium for calculatingthe mole fraction of each component, getting the relationship between the molefraction of each component and the temperature and pressure of the environment. Theresults from the Raoult’s law and VLE equation are compared and find the differencesof them.Considering the variation of mixed fluid property parameters under the hightemperature and high pressure environment, select the appropriate calculation modelto calculate the thermo physical parameters and the transportation parameters, such asthe density, specific heat of air, and partial molar heat of phase transition, thetransport diffusion coefficients, viscosity, and the thermal conductivity. Use the bestmixing rule to establish the model and then analyze the result.The program is established by using the Fortran language to solve themathematical model for the supercritical evaporation of multi-component dropletsand get the variation of the droplet diameter and the droplet temperature. Theinfluence of the temperature of the environment、the pressure of the environment、theinitial diameter of the droplet and the temperature of the droplet for the variation ofthe droplet diameter and the droplet temperature have been discussed. The Contrast between the sub critical evaporation of multi-component droplets、the supercriticalevaporation of single component droplets and the supercritical evaporation ofmulti-component droplets, and get the difference of them.