高反压环境中空气雾化喷嘴的雾化性能

ATOMIZATION OF AN AIR-BLAST NOZZLE AT HIGH AMBIENT PRESSURES

关键词:  燃料喷嘴  喷雾  气体雾化  液滴  压力效应  反压力

Key words:  Fuel injector  Spraying  Gas atomization  Drop  Pressure effect  Back pressure

摘要:

使用美国Ｐｕｒｄｕｅ大学＂热力科学及推进研究中心＂的高反压喷嘴试验设备，试验研究了空气雾化喷嘴在高反压环境中的雾化性能。试验中对一种典型空气雾化喷嘴，使用粘度分别为０．００１，０．０５０和０．１００Ｐａ·ｓ的三种液体，在０．１～１．８ＭＰａ反压范围内，用Ｍａｌｖｅｒｎ粒度分析仪，测量了喷雾的液滴平均直径及液滴尺寸分布。试验结果表明，在试验的环境压力和液体粘度范围内，提高喷嘴的气液比总是起着改善雾化的作用。随着液体粘性的增高，其作用明显加强。试验还发现，对于高粘性的液体，随着环境压力的提高，喷雾中的液滴尺寸趋于更加均匀。即液滴尺寸分布参数增大。在较宽的粘度范围内得到的试验数据发现了以往使用的半经验公式中的错误，进一步改善了该公式并拓宽了其使用范围。从而加深了对雾化机理的认识。

Abstract:

An experimental study on atomization of an air-blast nozzle at high ambient pressures was carried out at High Pressure Lab. of Thermal Science and Propulsion Center, Purdue University, U. S. A. The mean drop diameters and the drop size distributions of the sprays for three liquids with viscosities of 0. 001,0. 050 and 0. 10 Pa·s at ambient pressure of 0. 1￣1. 8MPa were measured with Malvern Particle Size Analysiser.The experimental results show that for all liquids and all ambient pressures,the mean drop size always diminishes with increase in air/liquid ratio, This effect is enhanced for liquids of higher viscosity. It is also found in this study that the drop size distribution parameter increases with increase in ambient pressure,thus indicating a more uniform drop size in the spray.This study proves whether the mean drop size goes up or down with increase in air pressure depends on the liquid viscosity. For liquids of low viscosity, such as water, an increase in pressure causes the mean drop size to decrease. For liquids of high viscosity, the mean drop size is increased by an increase in air pressure.The experimental data obtained in the present investigation demonstrate that the semi-empirical equation for mean drop size is improved by using liquid density inthe expression for Reynolds number instead of air density.