二甲醚和柴油高压喷射喷雾与燃烧可视化对比研究

A Comparative Study of Visual Spray and Combustion Characteristics of Dimethyl Ether and Diesel under High Pressure

为明晰高压喷射条件二甲醚闪急沸腾状态下的喷雾形态、自着火和火焰发展特性,通过高温高压定容燃烧弹,利用高速相机基于纹影法对比研究了柴油和二甲醚的喷雾和燃烧特性。实验中将喷射压力设置为60、100MPa,环境背压设置为4MPa,在喷雾、燃烧条件下环境温度分别设置为400、800K。研究结果表明:同工况下二甲醚的喷雾贯穿距和喷雾面积均小于柴油,但其喷雾锥角大于柴油,雾化时间短于柴油,雾化效果优于柴油。随着喷射压力的提高,二甲醚与柴油的贯穿距和喷雾面积都增大,100MPa喷射压力下二甲醚喷雾面积较60MPa增大18.18%,而同工况下柴油增大23.5%。相比于柴油,二甲醚燃烧滞燃期和火焰浮起长度较短,燃烧持续期与柴油相当,但二甲醚燃烧火焰亮度、火焰面积和碳烟生成量明显低于柴油。随着喷射压力的提高,柴油与二甲醚的碳烟生成量均降低,但二甲醚的碳烟生成量降低效果更加显著,该文碳烟生成量用体积分数KL因子总和来表示,发现100MPa喷射压力下的二甲醚KL总和较60MPa减小33.3%,而同工况下柴油减小19.32%。

To clarify the spray,auto-ignition and flame development characteristics of dimethyl ether under flash boiling condition of high pressure injection,the spray and combustion characteristics of diesel and dimethyl ether were studied comparatively by using a constant volume vessel and the[JP2]schlieren method.During the experiment,the injection pressure was 60 MPa and 100 MPa,the ambient pressure[JP]was 4 MPa,and the ambient temperature was 400 K and 800 K under spray and combustion conditions respectively.The results showed that the penetration distance and spray area of dimethyl ether were smaller than those of diesel,but the spray angle was larger than that of diesel,the atomization time was shorter than that of diesel,and the atomization was better than that of diesel.With the increase of injection pressure,the penetration distance and spray area of both dimethyl ether and diesel increased.The spray area of dimethyl ether under 100 MPa injection pressure increased by 18.18%compared with 60 MPa,while that of diesel under the same condition increased by 23.5%.Compared with diesel,the ignition delay and flame lift-off length of dimethyl ether were shorter,and the combustion duration was similar,but the flame brightness,flame area,and soot of dimethyl ether were lower significantly.With the increase of injection pressure,the soot of diesel and dimethyl ether decreased,but the soot of dimethyl ether decreased much more significantly.For example,the KL sum of dimethyl ether under 100 MPa injection pressure decreased by 33.3%compared with 60 MPa,while that of diesel under the same working condition decreased by 19.32%.