High Speed Image Analysis of Liquid Sheet Atomization created by a Doublet Impinging Jet Injector

In this study we experimentally determined a variety of spray and atomization characteristics of a doublet impinging jet injector using high speed imaging. Impinging jet injectors are of interest as they are commonly used in rocket engines to atomize the propellants before ignition and have complex flow interactions that are difficult to study both experimentally and numerically. The injector, in this study, used water as a propellant simulant and was tested under a variety of Reynolds and Weber numbers. The spray was illuminated by a backlight which created a shadowgraph of the atomization process and was captured at a rate of 20,000 fps by using a high-speed camera. The mechanism of the atomization process is known to be the wave instabilities, generated by the impact of the streams, that then cause the breakup of the spray into ligaments and ultimately droplets. Post-processing of the shadowgraph images was used to capture and characterize the major elements of the atomization process from the liquid sheet wave instabilities to the ligaments to the droplets. Additionally, techniques were developed for the tracking of both the ligaments and droplets which allowed for greater insight into the dynamic process of atomization.