Parameters Influencing the Characteristic Exhaust Velocity of a Nitrous Oxide/Ethene Green Propellant

Abstract

Currently, several green propellants are under investigation to replace the toxic and carcinogenic monopropellant hydrazine (${\mathrm{N}}_2{\mathrm{H}}_4$ ). Beside alternatives as ammonium dinitramide-based propellants, hydroxylammonium nitrate-based mixtures, or high concentrated hydrogen peroxide, mixtures of fuels with nitrous oxide (${\mathrm{N}}_2\mathrm{O}$ ) called HyNOx or NOFBX represent promising green propellants. Compared to classical ${\mathrm{N}}_2{\mathrm{H}}_4$ , ${\mathrm{N}}_2\mathrm{O}/\mathrm{fuel}$ mixtures offer a higher performance ($I_{\mathrm{sp}}$ and $c^{*}$ ), no or low toxicity, and low propellant costs. To investigate the handling and performance of a propellant mixture consisting of ${\mathrm{N}}_2\mathrm{O}$ and ethene, hot gas combustion tests with an experimental combustor were conducted. This paper summarizes the results of 134 combustion tests conducted with the premixed propellant injected in gaseous state. Calculated and measured performances ($c^{*}$ and ${\eta }_{c^{*}}$ ) depending on mixture ratio, characteristic combustion chamber length $L^{*}$ , and chamber pressure are shown and discussed. Furthermore, the residence timescales of the propellant mixture inside the combustion chamber are normalized by the chemical timescale of the combustion process. Thus, combustion efficiencies depending on dimensionless Damköhler numbers are derived.