Experimental study on ignition behaviors of green hypergolic propellants depending on fuel properties: NaBH4-promoted fuels/H2O2 oxidizer

Abstract

This study investigated the ignition behavior of NaBH₄-promoted hypergolic propellants influenced by the physical properties of fuels through two different experimental methods: drop and impinging jet tests. The results showed that, for the fuel with a high viscosity and low vapor pressure (SPLP01), almost no flammable vapor was observed during ignition. By contrast, for the fuel with a low viscosity and high vapor pressure (SPLP02), substantial amounts of flammable vapor clouds were generated during ignition. Notably, for SPLP02, an increase in the jet momentum did not significantly reduce the ignition delay time under the fuel-lead conditions. This was attributed to the rapid formation of gas-phase intermediates at the impingement point, which hindered the physical mixing of the fuel and oxidizer. Furthermore, the concentration of hydrogen peroxide had a greater impact on the ignition behavior than the physical properties of the fuels.