Liquid-Fuel Injection into Supersonic Cross Flow

Abstract

ABSTRACT An experimental observation of kerosene injected into supersonic flow is presented. A reflected shock tunnel is used to produce high-temperature Mach 2 airflow. A flat plate injector model with a 0.5 mm orifice is installed at the tunnel nozzle exit. The liquid injection velocity is controlled from 47 m/s to 61 m/s. A high-speed schlieren system is used to observe the jet breakup and mixing phenomena. Schlieren observations show that the bow shock/boundary separation shock interactions have a significant effect on the spray dissipation. The interactions induce a strong spray whipping motion, causing droplet dispersion from the concentrated spray cone and quick vaporization into the airflow. The dispersed droplets also interact with the large eddy structures on the spray cone surface; a series of schlieren images shows the development of eddy structures, and their dissipation distances are closely related to the jet-to-freestream momentum ratio, J. Increasing J enhances the instability of the spray cone and decreases its dissipation distance. A Mie scattering system is also used to characterize the spray. Side-view and top-view Mie scattering images of the spray are captured by an intensified-CCD camera. The top view Mie scattering images of the spray at different heights from the wall also show the formation of vortices and the whipping motion of the spray caused by shock/shock interaction. To characterize the droplet dissipation distance, 100 schlieren images were averaged. The image was pseudo-colored to indicate the spray boundary, and this was used to identify the penetration height and spray dissipation distance. The local vertical peak of the schlieren intensity was identified. Based on the distribution of the peaks, the layers of droplet evaporation and gas-phase mixing zones could be recognized, and the penetration heights and dissipation distance of the spray identified. The trajectory relation of momentum flux ratio and penetration height is also presented in this paper, meeting the need for experimental data on penetration height of liquid jets in high-temperature supersonic flows. The penetration height results in this study are lower than those of Lin, perhaps due to differences in free stream temperature and measuring technique.