Combustion behavior of XM46 liquid propellant

A specially designed liquid propellant strand burner was utilized to study intrinsic burning behavior of XM46 by feeding it into the flame zone. Unlike other monopropellants studied, numerous unusual phenomena were encountered while using XM46 in this system which prevented the stabilization of flame at a fixed location. The flame regressed down into the feeding system regardless of the rate at which the propellant was fed upward. The mechanism for this behavior is theorized as being liquid-phase reactions caused by the transport of radicals beneath the reaction surface due to agitation within the liquid. Another phenomenon observed was the presence of a black, conical region immediately above the regressing surface which appeared to grow with increasing feed rate and was not present at all in static tube tests (with no feeding motion). The black cone temperature was measured to be about 300 degrees C. Tube tests were also conducted in specially constructed thin-wall straws made from combustible wax paper. Use of these straws results in an unconfined flame and minimizes heat loss to the tube walls thereby allowing the LP to burn at its intrinsic burning rate. Pyrolysis tests of XM46 were conducted in a specially designed pyrolyzer used in conjunction with a gas chromatograph/mass spectrometer to determine the decomposition species concentrations as a function of temperature to better understand the combustion process of this unique liquid propellant. These tests have shown the major pyrolysis products to be NO, N2O, N-2, CO2, CO, H2O, HCN, and C2H4 when pyrolyzed at temperatures between 130 and 540 degrees C. The number of moles of these species evolved from a fixed amount of XM46 have also been shown to vary with pyrolysis temperature.