二甲醚/液化石油气双燃料液滴蒸发特性的数值研究

Numerical Study on Evaporation Characteristics of DME/LPG Dual Fuel Droplet

以单一组分液滴在静止环境中的蒸发模型为基础,建立多组分液滴蒸发的折算数学模型,并以二甲醚(DME)/液化石油气(LPG)双燃料液滴作为研究对象,对其亚临界蒸发过程进行了详细的模拟研究。获得了各组分在不同环境温度和环境压力下液滴蒸发的湿球温度,以及组分摩尔分数变化时双组分液滴湿球温度的变化情况。考察了液滴中组分的初始摩尔分数、液滴初始温度、环境温度和压力及混合规则对蒸发过程的影响,结果表明:相同环境条件下,混合物的湿球温度随DME摩尔分数的增大而升高;液滴初始质量相同时,DME初始摩尔分数越大,蒸发的时间越长;初始质量及组分初始浓度一样的多组分液滴,初始温度越接近湿球温度,蒸发时间越短;环境压力越高,液滴湿球温度越高,气体混合物扩散系数越小,液滴生存期内加热期所占的比例明显增加,蒸发时间较长;使用混合规则二,蒸发时间较长。

Based on simple-component droplet evaporation model, a conversion model for multi- component droplet evaporation was established and used to simulate subcritical evaporation process of dimethyl ether （DMg）/liquefied petroleum gas （LPG） mixture droplet, wet bulb temperature of each component under different ambient temperatures and pressures, and bi-component droplet wet bulb temperature variation with each component mole fraction were obtained. The effects of initial mole fraction and initial temperature of each component in droplet, environment temperature and pressure, and mixing-rules on the multi-component droplet evaporation were examined. The results show that in same environment conditions,the mixture wet bulb temperature increases with DME mole fraction increasing,and for droplet of same initial quality, the larger the DME mole fraction, the longer the evaporation time. For the multi- component droplet with same initial quality and component concentration, the closer to wet bulb temperature the initial temperature is,the shorter the evaporation time; the higher the environment pressure and the wet bulb temperature, the smaller the mixture diffusion coefficient, the heated time proportion during droplet survival period increases obviously and the evaporation time gets longer; when using the No. 2 Mixing Rule the evaporation time becomes longer.