ID 145

A study on dynamic characteristic of the liquid swirl injector’s internal flow

 

Abstract:

Liquid rocket engine are divided into three parts: feed system, injector, and combustion chamber. The injector is a device for injecting the propellant; and propellant’s atomization and mixing characteristics could be enhanced with well-designed injector. Also, well-designed injector can make the stable combustion. Studies on injector dynamics has been carried out to find the way of reducing combustion instability by using injector. And injector’s flow characteristics is important in this phenomenon. In this study, the closed type swirl injector’s internal flow were taken to investigate the internal characteristic of swirl injector. The closed type swirl injectors were made of transparent material, and using the continuous light source, the backlight image inside the swirl chamber was taken by using a high speed camera with 7000 framerates. As a result, it was confirmed that the intensity profile of the swirl chamber has the extreme value at the interface of the air and water in the swirl chamber, and the diameter of the air-core was measured from this result. And FFT analysis were conducted with air-core diameter of the 7000 fps images and it was found that the air-core was fluctuated periodically. Also, it was found that the fluctuating frequency was proportional to the mass flow rate. Experiments with varying swirl injector geometry were also carried out. As a result, it was found that the swirl chamber structure is closely related to the amplitude of the air-core diameter fluctuation and the tangential inlet size is related to air-core fluctuation frequency.