微乳化燃油的粘温特性及燃烧过程

VISCOSITY-TEMPERATURE CHARACTERISTIC AND COMBUSTION PROCESS OF MICRO-EMULSIFIED OIL

为对比分析柴油机燃用微乳化燃油的燃烧特性,采用旋转粘度计测量燃油在各种温度下的粘度以及利用发动机台架和燃烧分析仪,测录燃烧压力随曲轴转角的变化关系,研究微乳化燃油的粘温特性和燃烧过程。结果表明:燃油微乳化后粘度增大;但随着温度的升高,微乳燃油的粘度显著减小,50℃时减至柴油水平。微乳化柴油中掺水或表面活性剂质量分数越高,粘度越大。燃料特性对柴油机缸内压力的影响与转速明显相关,含水质量分数为5.6%微乳化柴油M5.6D、生物柴油和含水质量分数为10%的微乳化生物柴油M10B的最大爆发压力均略高于柴油;在相同工况时,柴油和M5.6D、生物柴油和M10B的放热规律形态差异主要在燃烧前期。燃油微乳化后,预混合燃烧期略微增延长,预混合燃烧占整个燃烧放热比例显著增大,扩散燃烧期明显缩短。与燃用柴油相比,柴油机燃用M5.6D、生物柴油和M10B时,燃烧重心向上止点靠近。

In order to analysis the combustion characteristics of micro-emulsified oil, viscosity was measured at different temperatures in a variety of reagents with a rotating viscometer for studying the viscosity-temperature properties of microemulsified oil, and the curves of the cylinder pressure vs the crank angle were measured on a engine test bed by a combustion analyzer for investigating combustion process. Results indicated that the viscosity of diesel and biodiesel with micro-emulsion technique increases. With the increase of temperature, the viscosity of micro-emulsified oil gradually decreased, and it could reach level of diesel at 50 ℃. Adding water/surfactant mass fraction could lead to increasing the viscosity of mirco-emulsified oil. The effects of fuel characteristics on the cylinder pressure are significantly dependent on the engine speed. The peak cylinder pressures in-cylinder of M5.6D （micro-emulsion diesel with quality percent of 5.6% water）, biodiesel and M10B （micro-emulsion biodiesel with quality percent of 10% water） are a little higher than those of diesel fuel. Under the same conditions, the difference of heat release rate between fuel and mirco-emulsified oil mainly shows in the prophase of combustion process. The premixed combustion is prolonged, the duration of the diffusive combustion is shortened, and heat release accounts of the premixed combustion stage have a larger proportion when diesel engine fueled with mirco-emulsified oil. Compared with the engine fuelled diesel, the gravity of combustion process of M5.6D, biodiesel and M10B is closer to the top dead centre.