Catalyst bed behavior of hydrogen peroxide/kerosene bipropellant thruster in monopropellant and bipropellant modes with cavitating venturi valve

For typical hydrogen peroxide/kerosene bipropellant thruster applications, hydrogen peroxide is injected into a catalyst bed prior to an injection of kerosene. During this period, the bipropellant thruster operates in a monopropellant mode. For ignition, kerosene is injected into hot oxygen gas and water vapor, which are the decomposition products of hydrogen peroxide. After ignition, the bipropellant thruster operates in a bipropellant mode. During this ignition sequence, the catalyst bed switches from the monopropellant mode to the bipropellant mode. The pressure drop in the catalyst bed differs between these modes. It is necessary to understand why this difference exists. In this study, I examined the cause of the difference in the pressure drop of the catalyst bed by catalyst bed modeling. The catalyst bed model was tuned according to the results of experiments conducted using a 40 N monopropellant thruster. Subsequently, the model prediction and experimental results of a 330 N bipropellant thruster were compared. Using the model prediction, the cause of the difference in the catalyst bed pressure drop was examined. A possible cause of the pressure drop difference between the two modes is the difference in gas density owing to the injection pressure difference of hydrogen peroxide.