压力振荡对气液同轴离心式喷嘴自激振荡的影响

Influence of pressure oscillation on self-pulsation of gas-liquid swirl coaxial injector

为了研究供应系统振荡对气液同轴离心式喷嘴自激振荡的影响,采用水和空气作为模拟介质,开展了室压条件下冷态喷雾试验。通过试验分析了供应系统有/无振荡两种情况下离心式喷嘴的喷雾形态,以及供应系统有/无振荡两种情况下气液同轴离心式喷嘴自激振荡的喷雾形态。发现当离心式喷嘴供应系统振荡时,离心式喷嘴产生的锥形液膜也周期性地振荡,同时出现Klystron效应。液膜周期性振荡以及Klystron效应出现的频率与供应系统振荡频率一致。Klystron效应的出现使得喷雾锥角突然减小,锥形液膜发生折叠。供应系统振荡对自激振荡喷雾形态也有显著影响。供应系统振荡引起的Klystron效应使得液膜锥角减小,从而造成"圣诞树"型自激振荡喷雾上的"树枝"增多,同时自激振荡频率增加。这是因为当速度大的液膜追上速度小的液膜时,就会产生Klystron效应并使液膜速度增加。而液膜运动速度越大自激振荡频率也就越大。虽然在供应系统中施加激励没有发生"锁频"现象,但是自激振荡的强度在一定程度上减弱,并且伴随着自激振荡的"分频"现象,即自激振荡频率从一个主频向两侧分化为两个主频。

To understand the influence of pressure oscillation on the self-pulsation characteristics of the gas-liquid swirl coaxial injector,non-reactive spray experiments are conducted with water and air at atmospheric pressure.The spray morphology of the pressure swirl injector with and without pressure oscillation is investigated,and that of the gas-liquid swirl coaxial injector with and without the pressure oscillation when self-pulsation occurs is also investigated.The results indicate that the conical liquid film produced by the pressure swirl injector oscillates periodically with the pressure oscillation in the supply system,and the Klystron effect occurs simultaneously.The frequency of the conical liquid film oscillation and the Klystron effect occurrence is consistent with that of pressure oscillation in the supply system.The Klystron effect decreases the spray cone angle,and wrinkles the conical liquid film.The self-pulsated spray morphology of the gas-liquid swirl coaxial injector is also significantly influenced by the pressure oscillation in the supply system.The decrease of the spray cone angle caused by the Klystron effect increases the branches of the Christmas tree and the frequency of self-pulsation.This is because the Klystron effect occurs when the faster liquid film overtake the slower liquid film,which increases the velocity of the liquid film.And the larger the liquid film velocity,the larger the self-pulsation frequency.Although frequency locking does not occur with pressure oscillation,the strength of self-pulsation is decreased to some extent,and one dominant self-pulsation frequency evolves into two domain frequencies.