喷注压降对液液同轴离心式喷嘴喷雾锥角的影响研究

Effects of Injection Pressure on Spray Angle of Liquid-Liquid Swirl Coaxial Injector

为了研究不同喷注压降下液液同轴离心式喷嘴喷雾锥角的变化规律,采用高速摄像机观测喷雾形态。试验结果表明:内、外喷嘴单独工作时,喷雾锥角随着喷注压降的增加而增加。内、外喷嘴同时工作时,喷雾锥角随内喷嘴喷注压降的增加而减小,随着外喷嘴喷注压降的增加而增加。通过与内、外液膜同向旋转时喷雾锥角的变化规律对比,发现内、外液膜的旋转方向对外混式液液同轴离心式喷嘴喷雾锥角的影响不大,因为离心式喷嘴产生的锥形液膜的切向速度会很快转化为径向速度。由于液膜切向速度迅速转化为径向速度使得内、外液膜反向的动量转变为同向动量,从而造成利用角动量守恒来预测喷雾锥角的理论模型用于计算反向旋转的外混式喷嘴时存在较大误差。对于内、外液膜反向旋转的外混式喷嘴,由于液膜旋转方向对喷雾锥角的影响不大,可以按照同向旋转的公式进行计算。

To investigate the spray angle variations of liquid-liquid swirl coaxial injector under different injection pressure,spray regimes were observed by a high speed camera in the experiment. The experiment results indicate that spray angle increases with the increase of injection pressure,when inner or outer injector is operated alone. However,when inner and outer injector are operated together,spray angle decreases with increase of inner injection pressure and increases with increase of outer injection pressure. Moreover,the conclusion that rotating direction of cone liquid sheet has a little effect on spray angle for outer mixing injector is obtained,by comparing with the varying regularity of spray angle of injector with co-rotating liquid sheets. The opposite momentum of inner and outer liquid sheets transforms into the homodromous momentum as tangential velocity of cone liquid sheet transforms into radial velocity fast,which causes a big error when the model of predicting spray angle according to the law of conservation of momentum is applied to calculate spray angle of outer mixing injector with counter-rotating liquid sheets. For outer mixing injector,spray cone angle can be calculated by the theoretical formula suitable for co-rotating liquid sheets,because rotating direction hardly affects cone liquid sheet in this condition.