Pyrolysis, ignition and combustion of solid fuels for ramjet applications.

摘要

The utilization of the most attractive metal additive, boron powder, in ramjet application still remains in the development stages. This is due mainly to the combustion efficiency problems associated with boron. On the other hand, the very popular metal additive, magnesium, has very good ignitability and high combustion efficiency, but has a low heating value. The scope of this study was concentrated on these two kinds of metal additives and three different types of polymeric binders--HTPB, PTFE, and high energy poly(BAMO/NMMO). Using various combinations of these ingredients, a total of 17 different solid fuels were investigated.; The purpose of the present research was to study the pyrolysis, ignition, and combustion characteristics of the abovementioned fuel samples, using high-powered CO{dollar}sb2{dollar} laser testing system, a windowed strand burning setup, and two cross-flow combustion facilities--a kerosene burner and a blowdown supersonic wind tunnel.; The pyrolyzed species of solid fuels were identified by a GC-MSD. The ignition characteristics of boron/HTPB fuels were determined by the CO{dollar}sb2{dollar} laser ignition system. A hypothesis based on absorptivity, thermal diffusivity, and reactivity was proposed to interpret the observed phenomena. The effects of four additives on ignition delay time of boron/HTPB fuels were measured, and CeF{dollar}sb3{dollar} was found to be the most effective one.; Several combinations of boron and magnesium/PTFE fuels were tested. A sample composed of 20% Mg/30% B/50% PTFE exhibited a highly vigorous reaction, and it appears to be very promising for improving boron combustion efficiency. Mg/PTFE/Viton A fuel only recently has been considered as a possible candidate for ramjet (solid ducted rocket) applications. This fuel exhibited a very unique burning phenomenon--ambient oxygen has an adverse effect on the ignition delay time and also on the burning rate. An explanation for this behavior was postulated and supported by several different measurements. Finally, a sample containing 30% boron and 17.6% Poly(BAMO/NMMO) were tested. Based on the experimental results, it can be concluded that with the help of a highly energetic binder, an efficient combustion of boron can be expected.