超临界环境碳氢燃料液滴蒸发过程研究

Study on Droplet Evaporation Process of Hydrocarbon Fuel in Supercritical Environment

通过分析正十二烷(C_(12)H_(26))在宽温度压力范围条件下的物理特性,建立了C_(12)H_(26)液滴在亚/超临界氮气环境中蒸发的分子动力学模型,分析了液滴寿命、界面厚度、扩散系数等特征参数,探讨了亚临界到超临界环境中的C_(12)H_(26)液滴的蒸发规律。结果表明:C_(12)H_(26)的粘度、密度、比热容等物理特性在临界点处发生剧烈变化,在压力为1.5 MPa温度为640 K时,密度将会随着温度的继续升高下降1.88 mol/L,下降幅度达80%;在超临界环境中,C_(12)H_(26)液滴蒸发不再遵循D2定律,液滴界面厚度出现激增且扩散系数显著增大,相较于亚临界环境,在超临界环境中,液滴界面厚度增加了16A,扩散系数增加了56%,液滴由亚临界状态的表面蒸发转变为超临界状态的扩散。

By analyzing the physical characteristics of n-dodecane(C_(12)H_(26))in a wide temperature and pre-ssure range,the molecular dynamic model of C_(12)H_(26) droplet evaporation in sub/supercritical nitrogen environment was established,the characteristic parameters such as droplet life,interface thickness,diffusion coefficient,etc.were analyzed,and the evaporation rule of C_(12)H_(26) droplet in sub-critical to supercritical environment was discussed.The results show that the physical properties of C_(12)H_(26),such as viscosity,density and specific heat capacity,change sharply at the critical point.When the pressure is 1.5 MPa and the temperature is 640 K,the density will decrease by 1.88 mol/L with the increase of temperature,up to 80%.In supercritical environment,the evaporation of C_(12)H_(26) droplets does not follow D2 law.The interfacial thickness of droplets increases sharply,and the diffusion coefficient increases significantly.In supercritical environment,the interfacial thickness of droplets increases by 16A,the diffusion coefficient increases by 56%,and the droplets change from surface evaporation in subcritical state to diffusion in supercritical state.