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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。
Based on the technology of ultrasonic atomization and carrier gas transportation, a multi-droplet hydrocarbon-fuel preparation system was designed which can independently control the speed and the global equivalence ratio. The generated multi-droplet flow can more accurately simulate the flow and the mixing state of the droplet groups in the periphery of the spray of the internal combustion engine. High-brightness LED light source was used and multi-droplet scattered light was taken from 90 ° angle. Different air flow rate (10,20,30,40L / min) and n-heptane supply rate (150,200,250,300mL / h) Under the multi-drop stream high-speed photography pictures. It was found that the multi-droplet flow left the nozzle tube exit for a period of one-way steady flow. The combined effect of air entrainment and droplet volatilization results in the length of the stabilizing section increasing first and then decreasing as the outlet velocity increases. When the droplet flow velocity at the exit of the nozzle tube is lower than 5.2 m / s, a significant air entrainment vortex will appear after the stabilization section, and the lower the exit velocity, the more whirlpool and the more regular the shape. Spread further away from the nozzle tube, the increased droplet diffusion range and the volatilization of the fuel can lead to the gradual inability to detect multiple droplet streams using the scattered light method.