Ignition of hypergolic propellants
Abstract
A two-part study was undertaken to investigate ignition of hypergolic propellants. The first part focused upon development and implementation of fundamental and phenomenological sub-models to describe system-level processes that lead to ignition. Propellant injection, jet formation, atomization, vaporization, and chemical reaction were considered. Sub-models were completed to handle the propellant feed system hydraulics, the vaporization of the injected droplets, and predicting ignition. The second part involved the development of an experiment to isolate and study the effect of liquid-liquid contact on hypergolic ignition under a controlled environment. The hypergolic ignition of droplets of monomethyl hydrazine, 2-Azido-N,N-dimethylethanamine, N,N,N’,N’-Tetramethylethylene-1,2-diamine, a blend of 2-Azido-N,N-dimethylethanamine and N,N,N’,N’-Tetramethylethylene-1,2-diamine, 1-Butyl-3-methyl-imidazolium dicyanamide, and a solution of sodium borohydride and triglyme with approximately 600 µL of red fuming nitric acid that formed a convex meniscus in a quartz tube were investigated using a controlled descent under a nitrogen environment. Ignition was only observed for monomethyl hydrazine and the solution of sodium borohydride and triglyme. Thin filament pyrometry with an infrared camera was employed as a novel technique to measure the temperature of the near flame field of monomethyl hydrazine and red fuming nitric acid combustion with maximum temperatures recorded around 1600K. Using an unrestrained, approximately 100 µL pool of red fuming nitric acid, the influence of monomethyl hydrazine fuel droplet size and fuel droplet impact velocity on explosion delay time, ignition delay time, and radiation energy released prior to ignition was explored. For the parameters explored (fuel droplet diameters on the order of 2 to 5 mm, impact velocities on the order of 10 to 300 m/s, and Weber numbers on the order of 0.01 to 10), impact velocity and Weber number were statistically significant predictors of explosion and ignition delays. The radiation energy released from an explosion prior to ignition was determined to be independent of fuel droplet size and impact velocity. Although many more tests need to be run to better determine trends of the highly stochastic droplet impact and hypergolic ignition events, it is obvious that liquid-liquid reactions play an important role in hypergolic ignition.
Degree
Ph.D.
Advisors
Pourpoint, Purdue University.
Subject Area
Aerospace engineering
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