Experimental Investigation of the Flame Propagation and Flashback Behavior of a Green Propellant Consisting of N2O and C2H4

Abstract

Regarding the research on alternatives for monopropellant hydrazine, several so called green propellants are currently under investigation or qualification. Aside others, the DLR Institute of Space Propulsion investigates a N 2 O/C 2 H 4 premixed green propellant. During the research activities, flashback from the rocket combustion chamber into the feeding system has been identified as a major challenge when using the propellant mixture. This paper shows the results of ignition experiments conducted in a cylindrical, optical accessible ignition chamber. During the ignition and flame propagation process, pressure, temperature and high-speed video data were collected. The high speed video data were used to analyze the flame propagation speed. The obtained propagation speed was about 20 m/s at ignition, while during further propagation of the flame speeds of up to 120 m/s were measured. Additionally, two different porous materials as flame arresting elements were tested: Porous stainless steel and porous bronze material. For both materials Peclet numbers for flashback were derived. The critical Peclet number for the sintered bronze material was around 20, while for the sintered stainless steel the critical Peclet number seems to be larger than 40. Due to the test results, sintered porous materials seem to be suitable as flashback arresters.

Ethene/Nitrous Oxide Mixtures as Green Propellant to Substitute Hydrazine: Reaction Mechanism Validation

“…Nevertheless, green propellants for European space activities are an accepted challenge for research and for technology development. Similar to research programmes in the U.S. initiated by DARPA (see Tiliakos et al (2001) or ADMG (2012)), DLR investigates the combustion properties of propellants like ethene/nitrous oxide mixtures that have the potential to substitute hydrazine or hydranzine/dinitrogen tetroxide in chemical propulsion systems (Werling et al (2015), Werling et al (2016), Werling et al (2017)). Data from model combustors operated at DLR's rocket propulsion test site at Lampoldshausen (Germany) in combination with investigations of fundamental combustion properties provide valuable test cases to be analysed by CFD computations, thus gaining better insights to the specific design requirements of new rocket engines powered by green propellants.…”

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

“…These instabilities increase the surface of the flame front and thus accelerate the flame. Therefore with increasing pressure prior to ignition the average flame propagation speed rises [40,41].…”

Centrifugal Casting of Paraffin and Beeswax for Hybrid Rockets

“…The two most investigated green propellant substitutes have been AF-M315E and LMP103S, which are hydroxylammonium nitrate (HAN, [NH3OH]NO3) and ammonium dinitramide (ADN, [NH4][N(NO2)2]) based on liquid monopropellants, respectively [23][24][25][26][27]. Bi-liquid green propulsion systems have also been considered as alternatives to hydrazine and NTO, including a nitrous oxide/ethylene combination as well as energetic ionic liquids [28][29][30].…”