Experimental investigations on the self-pulsation dynamics in a gas-centered swirl coaxial atomizer are conducted using water and air. Experiments are performed in the pulsation regime by precisely varying the momentum flux ratio for different values of swirl number, recess length, and lip thickness. High-speed imaging is used to understand the underlying mechanism of the onset of pulsation. While the transition to the pulsation regime takes a route of intermittency in a nonrecessed injector, the transition in a recessed injector is seen to be spontaneous. The spray width fluctuates significantly in the pulsation regime, and hence the temporal variation in the spray width is used to characterize the pulsation frequencies. Three factors, the constrained shear layer instability between the liquid and the gas streams inside the recess region, the spread rate of the gas jet, and its interaction location with the liquid stream, are shown to dictate the presence of dominant pulsation frequencies and even their higher harmonics in many recessed configurations. It is further shown that the nondimensional pulsation frequency depends only on the lip thickness and is independent of the flow and other geometrical parameters of the injector considered in the present paper.

使用水和空气进行了以气体为中心的旋流同轴雾化器中自脉冲动力学的实验研究。通过针对不同的旋流数，凹槽长度和唇部厚度值精确地改变动量通量比，从而在脉动状态下进行实验。高速成像用于了解脉动发作的潜在机制。虽然在非凹陷式进样器中向脉动状态的过渡采用了间歇性途径，但在凹陷式进样器中的过渡是自发的。喷雾宽度在脉动状态下显着波动，因此，喷雾宽度的时间变化用于表征脉动频率。凹入区域内的液体和气流之间受约束的剪切层不稳定性是三个因素，气体射流的扩散速率及其与液流的相互作用位置表明，在许多凹陷的结构中，存在着主导的脉动频率，甚至它们的高次谐波。进一步表明，无量纲的脉动频率仅取决于唇的厚度，并且与本文中考虑的喷射器的流量和其他几何参数无关。