基于超声雾化的碳氢燃料多液滴流制备系统

基于超声雾化和载气输运技术,设计了速度、全局当量比可独立控制的碳氢燃料多液滴流制备系统。所生成的多液滴流能够更加真实地模拟内燃机喷雾外围液滴群的流动与混合状态。采用高亮度LED光源,并从90°角度拍摄多液滴流散射光,获得了不同空气流量(10、20、30、40L/min)和正庚烷供给速度(150、200、250、300mL/h)下的多液滴流高速摄影图片。发现多液滴流离开喷嘴管出口后可保持一段时间的单向稳定流动。空气卷吸和液滴挥发的共同作用导致稳定段长度随出口速度升高而先增大后减小。当喷嘴管出口液滴流速度低于5.2m/s时,在稳定段之后将出现明显的空气卷吸漩涡,而且出口速度越低,漩涡越多且形状更加规则。离喷嘴管出口较远时,液滴扩散范围增大和燃料挥发可能导致采用散射光法已逐渐无法观测到多液滴流。

Multi-droplet stream creating system of hydrocarbon fuel based on ultrasonic atomization technology

A multi-droplet stream creating experimental system was developed based on ultrasonic atomization and air-transporting technologies. The speed and grand equivalence ratio of the stream could be adjusted easily to simulate the flow and mixing conditions of the droplet group at the spray fringes. The streams were highlighted by a bright LED and shot at 90°angle by high-speed camera when the air flux were 10, 20, 30, 40 L/min and the n-heptane supply flux were 150, 200, 250, 300 mL/h. The pictures showed that there was a stable flow near the nozzle exit and its length firstly increased and then decreased with air flux increasing. When the stream speed was lower than 5.2m/s, the air entrainment eddies emerged. The eddy became more distinct and its number increased with the air flux reduction. The stream could not be shot by its scattering at 90°angle when it was far away from the nozzle exit probably because of the droplet diffusing and volatilization.