Numerical Simulations of the Combustion Process in a Research Thruster operating with N2O/C2H4 and Comparison to Experimental Data

Since decades, the highly toxic hydrazine is used as propellant for in-space propulsion. During the last years, several non-toxic alternatives – so-called green propellants – were developed. One promising replacement for hydrazine are mono- and bipropellants consisting of nitrous oxide and one or more fuels. Here, the German Aerospace Center (DLR) investigates a propellant consisting of nitrous oxide and ethane in premixed monopropellant configuration. In parallel to experimental work performed at DLR’s test site in Lampoldshausen, reaction mechanisms for the combustion of N2O/C2H4 and N2O/C2H6 were developed by DLR’s Institute of Combustion Technology. To gain insight in the combustion processes, the reaction mechanisms were used to simulate the combustion inside a research thruster. For modelling, the commercial CFD solver Ansys Fluent was used. In sum two different basic configurations were simulated: 1) The reaction of premixed N2O/C2H4 by employing the N2O/C2H4 mechanisms and 2) the reaction of premixed N2O/C2H4 by using the N2O/C2H6 mechanisms. As for all cases a large experimental database is available, the results of the simulations were directly compared to the experimental results regarding chamber pressure, thrust and wall heat flux. To match the experimental data, different reaction and turbu- lence models were used and evaluated. Depending on the specific model selection, a very good agreement of the simulation data with the experimental results was achieved

Hydrogen Production and Carbon Capture by Gas‐Phase Methane Pyrolysis: A Feasibility Study

Using natural gas and sustainable biogas as feed, high-temperature pyrolysis represents a potential technology for large-scale hydrogen production and simultaneous carbon capture. Further utilization of solid carbon accruing during the process (i. e., in battery industry or for metallurgy) increases the process\u27s economic chances. This study demonstrated the feasibility of gas-phase methane pyrolysis for hydrogen production and carbon capture in an electrically heated high-temperature reactor operated between 1200 and 1600 °C under industrially relevant conditions. While hydrogen addition controlled methane conversion and suppressed the formation of undesired byproducts, an increasing residence time decreased the amount of byproducts and benefited high hydrogen yields. A temperature of 1400 °C ensured almost full methane conversion, moderate byproduct formation, and high hydrogen yield. A reaction flow analysis of the gas-phase kinetics revealed acetylene, ethylene, and benzene as the main intermediate products and precursors of carbon formation

Nitrous Oxide Fuels Blends: Research on premixed Monopropellants at the German Aerospace Center (DLR) since 2014

In 2014 DLR started research activities focused on premixed monopropellants consisting of nitrous oxide and hydrocarbons. Those propellants offer promising characteristics as they are non-toxic, deliver a high Isp consist of components with low cost and could simplify a propulsion system due to self-pressurized operation. Initially DLR chose a mixture of nitrous oxide (N2O) and ethene (C2H4). In the course of the project, a mixture of nitrous oxide and ethane (C2H6) was included to the research activities. The activities are part of DLRs Future Fuels project and divided into five main parts: 1) investigations of the combustion behavior of the propellant in a rocket combustor, 2) testing and developing of flame arresters, 3) development and reduction of reaction mechanisms, 4) numerical simulations of the combustion process and 5) basic miscibility investigations. The emphasis within the project is on the first three tasks, while the last two tasks are used to widen the knowledge about the propellants physical and combustion properties. The following paper will give a short summary of the activities carried out within the projects and focus on selected results regarding premixed propellants