柴油机燃用柴油/甲醇混合燃料时的燃烧特性研究(英文)

Study on Combustion Characteristics of a DI Diesel Engine Operating on Diesel/Methanol Blends

通过添加助溶剂形成一种稳定的柴油/甲醇混合燃料,并开展了柴油机燃用此混合燃料的燃烧特性研究。研究结果表明:随着混合燃料中甲醇含量的增加,预混燃烧阶段的放热率增加,扩散燃烧时间缩短。滞燃期随甲醇含量的增加而增加,此现象在低负荷和高转速下更为明显。甲醇含量对快燃期长短影响较小,总燃烧期随甲醇含量的增加而缩短。低转速下放热率曲线中心随甲醇含量的增加而移近上止点,最大压力升高率和最高放热率随甲醇含量的增加而增加。高转速高负荷下放热率曲线中心随甲醇含量的增加而移近上止点,高转速低负荷下放热率曲线中心随甲醇含量的增加偏离上止点;高转速下最大压力升高率和最高放热率随甲醇含量的增加而增加,而进一步增加甲醇含量反而使最大压力升高率和最高放热率降低。当混合燃料中含氧量小于6%时,缸内最高压力随甲醇含量的增加而增加;进一步增加含氧量时缸内最高压力保持不变或略有降低。缸内最高平均气体温度基本上不随甲醇含量而变化。

A stabilized diesel/methanol blend was realized and the combustion characteristics and heat release analysis of the diesel/methanol blend was carried out in a DI diesel engine. The study showed that the increase of methanol mass fraction of diesel/methanol blends will result in the increase of heat release rate in premixed burning phase and shorten the combustion duration of diffusive burning phase. Ignition delay increases with the increase of methanol mass fraction and the behavior is more obviously at low engine load and high engine speed. Rapid burn duration varies less with methanol mass fraction and the total combustion duration decreases with the increase of methanol mass fraction. At a low engine speed, the centre of heat release curve tends to be close to the topdeadcentre with the increase of methanol mass fraction at all engine loads and fuel delivery advance angles, and the maximum rate of pressure rise and the maximum rate of heat release increase with the increase of methanol mass fraction. At a high engine speed, the centre of heat release curve closes to the topdeadcentre with the increase of methanol mass fraction at high engine load and will depart from the topdeadcentre at low engine load, and the maximum rate of pressure rise and the maximum rate of heat release gives an increasing trend with the increase of the methanol mass fraction and a slight decreasing trend with further increasing of methanol mass fraction. Maximum cylinder gas pressure increases with the increase of methanol mass fraction when oxygen mass fraction is less than 6%, and then it remains a constant value or drops slightly with a further increase of oxygen mass fraction. Maximum mean gas temperature remains almost unchangeable versus methanol mass fraction.