Steady-State Combustion Characteristics of a Pentad Impinging-Jet Injector Using Green Hypergolic Propellant

This study examines the steady-state combustion characteristics of a green hypergolic ignition propellant. The propellant, with an ignition delay time of approximately 7.5 ms as determined by drop tests, utilized a 95% concentration hydrogen peroxide solution as the oxidizer and a solution comprising 95% tetraethylene glycol dimethyl ether and 5% NaBH₄ as the fuel. A pentad impinging-jet injector was employed for the experiments. A total of 28 combustion tests were conducted, with combustion pressures of approximately 30 and 70 bar and an oxidize-to-fuel ratio (ROF) ranging from approximately 2.5–5.5. The results indicate that an increase in both combustion pressure and ROF leads to enhanced characteristic velocity efficiency, which is likely linked to the mixing characteristics of the hypergolic propellant. The study suggests that for impinging-type injectors utilizing hypergolic propellants, designing a higher propellant momentum ratio compared to injectors for non-hypergolic propellants could be beneficial.