Auslegung, Konstruktion und Heißgastests von Injektoren zur Anwendung in einem Demonstratortriebwerk für einen Green Propellant aus Lachgas (N2O) und Ethen (C2H4) Design, Construction and Testing of Injectors used in a demonstrator unit for a Nitrous Oxide (N2O)/Ethene (C2H4) Green Propellant

Kurzfassung

For decades, hydrazine has been one of the most important and widely used monopropellants for spacecraft applications. The handling of the propellant is complicated by its high toxicity and the related safety issues. In addition, there are political efforts to restrict the usage of hydrazine. Therefore, low-toxic and ecologically friendly “green” monopropellants are currently being investigated internationally. The so-called nitrous oxide fuel blends, mixtures of nitrous oxide and hydrocarbons, are a promising group of propellants with a high specific impulse Isp. At the German Aerospace Center’s (DLR) Institute of Space Propulsion in Lampoldshausen, a mixture of nitrous oxide (N2O) and ethene (C2H4) is being investigated experimentally using a demonstrator unit. In the future, nitrous oxide and ethene are to be stored together in a single tank and in a liquefied state. At the current state of the test bench both components are stored separately and mixed in gaseous state in the feeding line. For the characterization of the propellant mixture and the combustion processes, new injectors are needed which allow a variation of the massflow and ensure safe test runs. As oxidizer and fuel are already mixed in the feeding line, prevention of a possible flashback is a main concern. Within the scope of this work, various new injectors are designed and tested. Former tests, the new injection systems, and hotgas tests carried out with those systems will be presented. By using porous sintered metals, flashbacks could be prevented. In exchange, a high pressure loss has to be accepted at this point. A first series of tests has been carried out to characterize the performance of the propellant combination and the combustion chamber could be ignited using a spark plug for the first time. However, during the course of this work, many failed tests indicated that the premixed state of the propellant and the related problem of flashbacks into the feeding line has to remain in the center of attention and requires further investigation.