Low toxic nitromethane based monopropellant for gas generator cycle air turbo ramjet engine

Ryojiro Minato ^*

Department of Engineering, Muroran Institute of Technology, Muroran, Hokkaido, 050-8585, Japan

Abstract: The present study proposes ethanol-nitromethane mixture as a safe, storable, and low toxic monopropellant for a gas generator cycle air turbo ramjet engine and evaluates its propulsion performance. The present study proposes that nitromethane is mixed with ethanol to adjust gas generator combustion temperature. The author developed the computational code for the present analysis and verified its accuracy. The specific thrust of ethanol-nitromethane is nearly identical to that of ethanol-liquified oxygen and is higher than methanol-hydroxylammonium nitrate aqueous solution and hydrazine. Hydrazine has the highest Isp among the propellants in the present analysis. However, Isp of ethanol-nitromethane is nearly equal to that of ethanol-liquified oxygen and higher than those of methanol-hydroxylammonium nitrate aqueous solution, and hydroxyl terminated polybutadiene-ammonium perchlorate. With the propellant-to-air ratio range in the present study, ethanol-nitromethane has the stoichiometric condition at the ram combustor around the propellant-to-air ratio range from 0.2 to 0.25 and can obtain high ram combustion temperature. This result is favorable for ethanol-nitromethane because it improves the specific thrust and the specific impulse. Therefore, ethanol-nitromethane can be a promising low-toxic liquid monopropellant for the air turbo ramjet engine.

Keywords: Air turbo ramjet; Monopropellant; Nitromethane; Low toxicity; Ethanol

https://doi.org/10.1016/j.jppr.2022.08.001