Geometrical Effects on the Fluid Dynamics of an Open-End Swirl Injector

This work seeks to determine the effect of injector geometrical parameters on the internal flow and dynamic characteristics of an open-end swirl injector used in a liquid rocket engine. The electric conductance method was used to measure liquid film thickness in both the steady state and the pulsation state. The measured steady parameters were compared with empirical equations, inviscid theory, and a viscid correction theory. In the pulsation state, quantification of the variation of the mass flow rate via injection pressure fluctuation was the primary subject of analysis. The transient volume flow in the injector was obtained by multiplying the axial velocity of flows and the flow area in the swirl chamber. The axial velocity was calculated through steady volume flow, and the flow area was obtained by measuring the annular liquid film thickness in the swirl chamber. A series of experiments were performed with variable geometry injectors. The experimental results show that liquid film thickness in the open-end swirl injector increases as the geometric characteristic constant A increases. When keeping other parameters constant, the phase contrast of the pressure and flow pulsation increases as the pulsation frequency increases for all the model injectors, and phase contrast increases as the geometric characteristic constant A increases. For a given open-end swirl injector and pulsation frequency, the phase contrast decreases as the pressure drop increases.