The auto-ignition boundary of ethylene/nitrous oxide as a promising monopropellant

C₂H₄/N₂O has recently been proposed as a promising monopropellant for hydrazine replacement. In this work, the auto-ignition capability of argon diluted C₂H₄/N₂O was experimentally investigated firstly in a rapid compression machine by detecting the light emission and the pressure evolution profiles. The auto-ignition boundary temperature which separates the non-ignition and successful ignition cases was then determined and modeled as a function of pressure and mixture composition. Results show that the auto-ignition temperature decreases with the increase of pressure and increases with the argon dilution fraction and fuel oxidizer ratio. In addition, for successful auto-ignition cases, the ignition delay times were measured and used to validate several recently developed kinetic mechanisms. A mechanism was developed and showed good agreement with the measured ignition delay time as well as the auto-ignition boundary temperature at all test conditions. Finally, the auto-ignition boundary temperatures at practical rocket engine conditions (without dilution) were numerically predicted at various pressure and fuel oxidizer ratio conditions. The model is of merit for designing the cooling system and the local flow residence time to reduce the risk of fuel line explosion and the resonance acoustic induced combustion instability in practical rocket engine.