An experimental program has been proposed to validate a hypothesis proposed to describe the combustion instability behavior of liquid propellant rocket engines that use like-doublet injectors. This research will conduct fundamental cold flow spray experiments to determine the effect of the ratio between the average liquid jet breakup length and the impingement distance (I_j/I_i) has on the sensitivity of the spray to transverse acoustic oscillations. Single jet tests with and without acoustic excitation will determine the jet breakup lengths for five injection velocities between 5 and 25 m/s. Using the single jet results, like-doublet tests with and without acoustic excitation will be conducted for several I_j/I_i, ratios: I_j/I_i ＞ 1, I_j/I_i, ～ 1, and I_j/I_i ＜ 1. The I_j/I_i ratio will be varied by changing the impingement angle and orifice spacing for each injection condition. Several acoustic frequencies will excite the spray above, below and at the natural breakup frequencies observed with the non-acoustic baseline experiments. Preliminary qualitative test results demonstrated fully-developed spray patterns. Impact waves were seen to distort and cause the liquid sheet to disintegrate into waves of ligaments and droplets.
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