Penetration and drop size distributions of liquid jets in high subsonic crossflows

Liquid jets in subsonic crossflows find varied applications in propulsion systems which include gas turbine combustors, aircraft afterburners and liquid fuelled ramjets. In the wake of environmental concerns and rising fuel costs, there is a renewed interest in the detailed study of sprays and its characterization as applicable to propulsion systems. An optimal fuel concentration is desirable for propulsion systems to achieve stable ignition, high efficiency and lower emissions. In a gas turbine afterburner, fuel is injected transversely into the air stream through a plain orifice injector from fuel manifolds, distributed across the combustor cross section. In a conventional ramjet, air is captured and decelerated to a subsonic velocity by an inlet diffuser, before fuel is added to the air stream. Therefore the liquid jet break-up processes leading to the development of the spray plume along with its ensuing droplet distribution downstream must be reasonably well understood. Although there have been many studies on the break-up and penetration of jets in subsonic crossflows, the literature pertaining to conditions relevant to ramjets and afterburners which is characterized by significant cross stream velocities (Mach 0.25-0.5) is very scarce. Among the investigations reported almost all of them have concentrated on the macroscale penetration aspects and detailed information about the spray characteristics such as drop size distribution in the near and far field is lacking. In this work the structure of spray plumes from water jets injected into high subsonic crossflows of Mach numbers between 0.3-0.6 were experimentally investigated using high speed imaging and laser diffraction techniques to measure the penetration and drop size distribution