Forced excitation of swirl injectors using a hydro-mechanical pulsator

Benjamin Ahn, Purdue University

Abstract

Experimental study on a liquid swirl injector under varying pressure pulsations was investigated using a hydro-mechanical pulsator. The pulsator and swirl injector were designed, built and cold flow tested at Two Phase Flow Laboratory, at Purdue University. The swirl injector was subjected to periodic pressure pulsation in high frequency range, up to 700 Hz, by the hydro-mechanical pulsator. The air core diameter inside the transparent swirl injector vortex chamber and the nozzle orifice were measured by the high speed camera. In addition, the spray cone developed near the nozzle exit was measured. Periodic pressure oscillation across the injector changed the air core diameter as much as 15% and the spray cone angle as much as 6% downstream from the nozzle exit plane. The frequency at which the air core diameter and the spray cone angle vary matched the pulsation frequency created by the pulsator. In addition, the images of the pulsating spray discharging into the ambient environment and a high-frequency, high amplitude propagating wave inside the injector generated due to cavitation were also captured and described qualitatively. This study leads to the conclusion that the flow behavior inside the swirl injector varies as pressure drop oscillates across the injector. The pressure oscillation is responsible for amplifying and de-amplifying the air core diameter and the spray cone angle. Of importance is also the expanding and contracting spray cone angle discharging into an ambient environment during the unsteady state. It is also concluded that the hydro-mechanical pulsator is an effective way to generate smooth periodic pressure oscillation.

Degree

M.S.A.A.

Advisors

Heister, Purdue University.

Subject Area

Aerospace engineering

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