Experimentelle Untersuchung der Druckverluste von Injektorelementen- und Flammenrückschlagsicherungen für ein (N2O/C2H4) Premixed Green Propellant Triebwerk Experimental investigation of the pressure drop occurring in injector- and flashback-arrestor elements used for a N2O/C2H4 green propellant combustion demonstrator

Kurzfassung

Nowadays in many attitude and orbital control systems a propellants based on hydrazine are used. Due to the high toxicity and the associated high costs for storage and transport, the German Aerospace Centre (DLR) in Lampoldshausen is conducting in new and less toxics fuels. The so called “Green Propellants” should offer a lower toxicity and a better performance than hydrazine . A promising variant represents a so called premixed propellant consisting of nitrous oxide and ethylene. In this case, the oxidizer and the fuel are premixed and liquefied stored in a tank. Due to the premixed condition of the propellant flashback into the tank during the engine operation is possible. Preventing flashback is the essential safety factor for an engine working with a premixed propellant. Porous materials such as sintered metals could be suitable to prevent flashback. The pressure drop of the flashback arrestor is similar to injectors a crucial element for the later mass flow, design and performance of the engine. The pressure drop of various porous sintered metals is investigated experimentally in this thesis. Following the experiments, the measurement data will be compared to the results of the classical pressure drop formulas for porous media from Forchheimer and Ergun. The test engine for nitrous oxide/ ethylene mixtures (HyNOx) of DLR is recently operating with gaseous propellant. Thus the investigation of the pressure drop across porous media is analysed by using several gases. Due to the compressibility and the high speeds of a gaseous flow differences between the theoretical predictions and the actual pressure drop measurement occur. Furthermore in this thesis the introduction of a design tool for porous materials will be made. With this design tool accurate prediction of the pressure drop will be possible . Finally, a check is made whether a flashback arrester of sintered metals can be generally used with the selected propellant combination to prevent flashback.