撞壁距离对柴油喷雾特性的影响

Impact of Impinging Distance on Diesel Spray Characteristics

利用复合激光诱导荧光(PLIEF)技术,通过高温高压定容燃烧弹研究了撞壁距离对柴油喷雾撞击平板后的燃油分布影响.试验中,撞壁距离从12.5 mm变化到32.5 mm.结果表明:撞壁距离对燃油分布有重要影响,随着撞壁距离的增加,液相燃油质量分数增加,过浓区间(φ>2)的气相燃油质量分数减小,较浓区间(1<φ≤2)的气相燃油质量分数增加到一定数量并保持变化不大,稀混合气区间(0<φ≤1)的气相燃油质量分数逐渐增加;瞬态最大当量比(φmax)降低;瞬态最低温度(Tmin)发展趋势与φmax相反;气/液相喷雾壁面射流半径和高度大幅减小,甚至不与壁面相撞.

The planar laser induced exciplex fluorescence(PLIEF)technique was used to quantitatively study the fuel distribution of diesel spray flat wall impingements in a constant volume combustion vessel. In the experiment,the impinging distance was changed from 12.5 mm to 32.5 mm. It is found that the impinging distance have an important impact on the fuel distribution. With an increase in impinging distance,the mass fraction of liquid phase fuel increases,while the mass fraction of vapor phase fuel decreases in the excessively rich mixture area of φ>2.In the richer mixture area of 1<φ≤2,the mass fraction of vapor phase fuel still increases with the increase of impinging distance until to a certain value and then keep unchanged. In the lean mixture area of 0<φ≤1,it still gradually increase with the increases of the impinging distance. In addition,the transient maximum equivalent ratio(φmax)decreases and the transient minimum temperature(Tmin)increases. The wall jet radius and height of the vapor-liquid phase spray decreases,or even does not impinge on the wall.