间歇式空气辅助喷雾的时变特性研究

Experimental study of time-resolved microscopic spray characteristics of an intermittent air-assisted injection system was carried out using a high-speed camera and a phase-Doppler particle analyzer(PDPA). The droplet size-velocity joint probability density function(JPDF)，mean droplet diameter and velocity were compared and analyzed for different injection control parameters and spatial sampling positions. The local gas velocity and interphase slip velocity in the spray were calculated. The results show that when the fuel/air injection duration ratio is larger than 8，the projected area of the spray keeps increasing with the injection time. The droplet size-velocity JPDF under various operating conditions shows a single-peak distribution. The droplet diameter is mainly distributed in the range of 0—40 µm and the droplet velocity is within the range of 0—150 m/s. The increase of the fuel injection duration significantly increases the spray droplet diameter and decreases the droplet velocity. The air/fuel injection duration ratio larger than 0.25 causes the droplet to be further accelerated at the later stage of spray development. The interphase slip velocity under different fuel/air injection duration ratio will not be affected by the sampling time while the interphase slip velocity under various air/fuel injection duration ratio is affected by both the air injection duration and the sampling time.