Experimental and Numerical Analysis of the Heat Flux occurring in a Nitrous Oxide/Ethene Green Propellant Combustion Demonstrator

摘要

Since the early days of space flight hydrazine is used as a monopropellant to power rockets, satellites or planetary probes. Due to the growing commercial pressure on users and suppliers as well as the need for non-toxic alternatives, several so called "Green Pro-pellants" are under investigation for replacing hydrazine. The most prospective candidates seem to be ionic liquids e.g. HAN-based (AFM-315E) or ADN-based (LMP-103S/FLP-106), hydrogen peroxide or nitrous oxide fuel blends (e.g. NOFBX™). Aside with ADN-based monopropellants the German Aerospace Center's Institute of Space Propulsion in Lampoldshausen is carrying out research on a nitrous oxide/ethene (N_2O/C_2H_4) premixed monopropellant. The benefits of this propellant (Isp about 300s and low toxicity) are facing several challenges, for example the need for a proper flashback-arrestor and the high combustion temperature (up to 3300K). To investigate the combustion, injection and ignition behavior a combustion chamber was manufactured and a test bench was built up. The combustion chamber consists of capacitively cooled segments. The heat flux inside the chamber walls during hot runs was evaluated by comparing the temperature development with the results of several CFD simulations. The simulations were carried out using Ansys CFX. By using the results of the simulations and the evaluated heat flux, water-cooled combustion chamber segment were designed and manufactured. To perform experiments with the chamber segments operation points for the coolant mass flow were derived. For comparing the real flow condition to the behavior of the simulated flow inside the cooling channel, a measuring section was set up. The mass flow, the temperature and the pressure drop of the cooling water was measured and compared with the results of the simulations. Taking the inlet zone and the sensor position into account, the simulated values for pressure drop agree well with the measured data. In this paper the results of the first combustion tests, the estimated heat flux and the numerical and experimental results of the flow behavior inside the cooling channels are presented.