二甲基醚(DME)碰壁喷雾特性和燃烧特性试验研究

Experimental Investigation on the Spray and Combustion Characteristics of Dimethyl Ether (DME) Spray Impinging on a Wall

用阴影法和火焰直接成像法对二甲基醚 (DME)碰壁喷雾特性和燃烧特性进行了试验研究。研究结果表明 ,二甲基醚碰壁后沿壁面发展特性与柴油极为相似 ,即沿壁面径向扩散 ,形成油雾的爬壁现象 ,二甲基醚沿壁面发展速度比柴油慢 ,但碰壁后的反弹量比柴油多 ;加热条件下二甲基醚碰壁试验研究表明 ,热碰壁沿壁面的发展速度比冷碰壁快 ,反弹量比冷碰壁多。在平板上方有一个明显的浓度梯度变化区域 ,碰壁后期在平板与燃烧室壁面存在一个二甲基醚浓度高的三角区域。二甲基醚碰壁对燃烧滞燃期影响不大 ,但着火位置靠近壁面 ,大部分的二甲基醚都是着壁之后燃烧 ,并且燃烧火焰在高浓度的三角区域持续较长时间 ,因而碰壁燃烧持续期略有延长 ,与柴油相比 ,二甲基醚燃烧火焰几乎经过整个壁面上部燃烧室的区域 ,火焰经过的面积大。

In this paper,the spray characteristics of DME spray impinging on a wall have been investigated by use of the shadow photographic method.The test results show that the general appearance of the DME impingement spray is similar to that of diesel spray,but the wall spread of DME spray is slower than that of diesel spray,the amount of DME rebounded from the wall is larger than that of diesel spray.At a high environmental temperature,the wall spread of DME is faster than that under cold condition,and the amount of DME rebounded from the wall becomes larger.The high speed photography shows that there is a high concentration zone of DME between the wall and the bomb wall.The wall combustion processes have been investigated also,the results show that the wall combustion has no effect on ignition delay ,the ignition position is near the wall,but the combustion duration prolongs a little.The combustion duration of the DEM rich zone between the wall and the bomb wall lasts a long time.Compared to diesel fuel,the surface of DME flame is larger after impingement.At the end of combustion,it can also be found that there is a weak light near the nozzle,which indicates the nozzle has leakage at high temperature environment.