Passive flow control in liquid-propellant rocket engines with cavitating venturi

In a companion liquid rocket engine development project, due to the overall weight constraint of the propulsion system, a cavitating venturi is selected to control the liquid fuel and liquid oxidizer mass flow rates. Two cavitating venturis, one for the fuel and the other for the oxidizer, are designed to deliver the desired mass flow rates for a specified operating inlet pressure, temperature, and inlet cross-sectional area. The converging and diverging angles of the venturis are selected from the literature for minimum pressure losses. An experimental setup is designed to verify that the cavitating venturis can deliver the specified flow rates. Two different techniques are used to pressurize the system: in the first method, pressurized nitrogen gas is used, and in the second method, high pressure combustion gases generated from a solid propellant gas generator are used. Transient mass flow rates could not be measured using standard methods due to the short duration of the water tests; instead, average mass flow rates are calculated. The results verify that the designed cavitating venturis can indeed provide the desired mass flow rates.