预喷油量对甲醇-柴油双燃料发动机燃烧特性影响试验

Impact of pre-Injection quantity on combustion characteristics of methanol-diesel dual fuel engine

【目的】通过一台高压共轨直列四缸柴油发动机改造的甲醇-柴油双燃料发动机进行试验,研究预喷油量对甲醇-柴油发动机燃烧特性的影响。【方法】选取1800r/min,30%和70%负荷,20%~40%掺烧比工况,调节不同预喷油量,采集各个仪器的实时数据,分析缸内平均压力、压力升高率、瞬时放热率、滞燃期和平均温度随预喷油量的变化。【结果】30%负荷,CCR超过30%,预喷量增大,主喷滞燃期延长,主喷燃烧阶段前期受柴油雾场燃烧主导,此负荷下引入预喷能有效改善发动机工作噪声,但预喷量的影响不高;70%负荷,CCR超过30%,预喷量的增大,主喷滞燃期明显缩短,主喷燃烧阶段前期受甲醇-空气均质压燃主导。【结论】30%和70%负荷,大掺烧比的工况尽量不采用预喷或采用较小的预喷柴油量来降低NOx的排放。

【Objective】This study aimed to investigate the impact of pre-injection quantity on the com-bustion characteristics of a methanol-diesel dual fuel engine,which was modified from a high-pressure common-rail four-cylinder diesel engine.【Method】The engine was tested at 1800 r/min with 30%and 70%loads,and varying compression ratios(CCR)ranging from 20%to 40%.The pre-injection quantities were adjusted,and real-time data from each instrument were recorded.The average pressure,pressure rise rate,instantaneous heat release rate,ignition delay period,and average temperature change in the cylinder were analyzed in relation to the pre-injection volume.【Result】The results indicated that when the CCR ex-ceeded 30%,increasing the pre-injection quantity prolonged the delay period of the main injection.During the early stage of main injection combustion,diesel mist field combustion was the dominant factor.Under this load condition,the application of pre-injection effectively improved engine noise,although the influence of pre-injection quantity was not significant.At 70%load and CCR above 30%,increasing the pre-injection quantity significantly shortened the delay period of the main injection,and the main injection combustion stage was dominated by methanol-air homogeneous compression combustion.【Conclusion】For 30%and 70%loads,utilizing little or no pre-injection quantity of diesel fuel can effectively reduce NOx emissions un-der high CCR conditions.