Hypergolic Propellant Ignition Phenomenon Associated with Two-Phase Oxidizer Flow Injection

Abstract

During pulse-mode operation of a bipropellant engine that uses mixed oxides of nitrogen and monomethyl hydrazine as a propellant, a titanium alloy injector with an unlike-doublet impinging stream absorbs the heat from the injector face, which is heated to a high temperature during combustion. When the injector’s temperature exceeds the boiling point of the oxidizer under several operating conditions, evaporation will occur at the initial inflow of each pulse. This evaporation phenomenon causes an unsteady two-phase flow that affects ignition and combustion phenomena. In this paper, this abnormal ignition and combustion phenomenon associated with the two-phase flow is investigated through experiments with a single-element injector. Data analysis on the impinging stream instability and the ignition phenomenon reveals that the unsteady oxidizer jet caused by evaporation may act as a trigger for high-frequency instability.