高反压下喷嘴雾化特性的理论探讨

 本文对高反压下正压力指数的喷嘴雾化特性的可能原因进行探讨。试验技术上采用高压封闭容器,引起小液滴回流会造成液雾测量上畸变。从机理上,本文提出两个因素:对空气雾化喷嘴,由强紊流脉动与液滴簇的相互作用可能引起不同尺寸液滴碰撞而凝聚;对压力雾化喷嘴,可能由于高反压下液体微团速度迅速衰减而使决定最终雾化生成的气动作用力比低反压时为小的情况出现,本文详细分析了后者情况,证明通常文献及书中普遍叙述“高反压下促进雾化的气动作用力增大”的论点,并不完全正确。

THEORETICAL EXPLANATION ON THE SPRAY CHARACTERISTICS UNDER HIGH BACK PRESSURES

Theoretical explanations on spray characteristics having positive pressure index were presented. Experimentally using high pressure container for drop size measurement will cause recirculation of small droplets introducing spray measurement error. Theoretically, two factors are of importance. For air blast atomizer the interaction between turbulent fluctuation and droplet cluster causing droplet collision between droplets of different sizes promotes droplet agglomeration. For pressure swirl atomizer, because of the fast decay of the filament velocity after leaving the nozzle exit under high back pressure, it is possible that the aerodynamic forces encounted by the filament under high back pressure, which determine the final formation of spray, may even be less than that under low back pressure. A detailed analysis was provided which showed clearly that a very popular statement in atornization literature that the aerodynamic force for atornization will increase with pressure, is not always true.