掺混比例对航空煤油/柴油的着火和碳烟排放影响

Effect of Blending Ratio on Ignition and Soot Emission in Aviation Kerosene/Diesel Blended Fuel

航空煤油/柴油掺混作为一种典型的宽馏程燃料,具有提升着火能力、改善低温冷起动并对柴油机结构可靠性影响较小等潜在性能.基于电加热定容燃烧弹,耦合纹影法、广域低通化学发光法和高频背光消光法等光学诊断方法,研究了不同航空煤油掺混比例对航空煤油RP-3/柴油掺混燃油喷雾、着火和碳烟排放特性的影响.结果表明:在航空煤油中掺烧柴油,有利于提高掺混燃油的着火能力,但同时也会提高碳烟排放,产生明显的红外信号.随着柴油掺混比例的增加,冷态喷雾体积几乎没有变化,但在高温蒸发环境下,喷雾锥角及体积均略微下降.添加25%(体积分数)的柴油可明显缩短着火滞燃期,且碳烟面积和碳烟质量规律与纯煤油相近,随着柴油组分的进一步增加,碳烟面积和碳烟质量都相应明显增加.此外,掺混25%柴油的航空煤油掺混燃油,可大幅提高燃油的着火性能,且碳烟排放维持在较低水平;航空煤油中添加较少比例的柴油适合在航空发动机中使用,从而成为一种比纯航空煤油更有潜力的单一燃料.

As a typical wide-range fuel,aviation kerosene/diesel blended fuel has the potential to improve ignition ability and low-temperature start,and less impact on the structural reliability for diesel engine.Based on an electric heated constant volume combustion vessel,the effects of different aviation kerosene blending ratios on the blend fuel spray,ignition and soot emission were studied using optical diagnosis methods including schlieren,wide-area low-pass luminescence and high-frequency backlight extinction.The results show that blending diesel fuel in aviation kerosene is beneficial to improve the ignition ability,but leads to increase soot emission and produce obvious infrared signals.Specifically,with the increase of the diesel blending ratio,the non-evaporating spray volume hardly changes,but in the high-temperature evaporation environment,both spray cone angle and volume decrease slightly.The addition of 25%(volume fraction)diesel can significantly shorten the ignition delay period,and the soot area and soot mass are similar to those of pure kerosene.With the further increase of diesel components,both soot area and soot mass increase significantly.Furthermore,blending 25%diesel in the aviation kerosene fuel can significantly improve the ignition performance of blending fuel,and maintain a low level of soot emission when the fuel is applied in diesel engines.Blending less ratio of diesel fuel into the aviation kerosene is suitable for use in aero engines,thus becomes a single fuel with more potential than pure aviation kerosene.