微乳化乙醇柴油热物性计算与分析

车用清洁型微乳化油是内燃机的理想代用燃料之一．微乳化油热物性参数难以计算，从而影响在内燃机上对它的定量计算研究．以微乳化乙醇柴油为例，用经验公式计算其蒸发焓、生成焓、液体比热容、导热率和微乳化油蒸气的扩散系数，分析了温度和压力以及不同溶醇量对热物性参数的影响规律，为微乳化油热物性参数的计算提供一种工程方法．结果表明：随着温度的增加，微乳化乙醇柴油蒸发焓、导热率降低，定压比热容和微乳化油蒸气扩散系数增加；随着压力增加，微乳化油蒸气扩散系数降低；随着混合燃料中乙醇含量的增加，定压比热容和混合气扩散系数均增大，蒸发焓减小；乙醇含量对混合燃料导热率的影响与燃料温度有关，在一定温度下乙醇含量效应发生逆转；微乳化乙醇柴油中乙醇含量增加有利于燃料蒸发．

Calculation and analysis of the thermophysical parameters of microemulsified ethanol-diesel blended fuel

The micro-emulsified fuel is an ideal alternative oxygenous fuel for diesel engines due to its excellent combustion characteristics. Fueled with the micro emulsified fuel， a diesel engine can give off remarkably lower harmful emissions， especially particulate. It is necessary to take into account instantaneous variations of the thermophysical parameters of blended fuels with temperature and pressure. For these reasons， we took the micro emulsified ethanol-diesel fuel for example， using the empirical formulas to calculate thermophysical parameters of this blended fuel， including the specific heat capacity， viscosity， thermal conductivity and diffusion coefficient. And the effects of the temperature， pressure and ethanol content on the initial blended fuels condition were investigated. Results indicate that the enthalpy of vaporization and liquid thermal conductivity of the micro-emulsified ethanol-diesel fuel decrease，and liquid specific heat capacity and diffusion coefficient increase with the temperature rising. The diffusion coefficient decreases with the pressure rising. And the liquid specific heat capacity and diffusion coefficient increase with ethanol content rising at the initial blended fuel. The effects of ethanol content on liquid thermal conductivity are significantly dependent on the liquid temperature. The effect of ethanol content changes backward at certain liquid temperature. The increase of ethanol content can contribute to the evaporation of the micro-emulsified ethanol-diesel blended fuel．