Ramjet Technology. Chapter 16. Solid Fuel Ramjets

Abstract

The ramjet powerplant for aircraft propulsion, conceived nearly 40 years ago [22,23], has been available in useful form for less than a decade. Its deve_opers focused their efforts largely on liquid fuels, particularly hydrocarbons of the gasoline or kerosene type. Nevertheless, during the period of resurgent interest occasioned by World War II, there was early recognition that solid fuels might offer certain design and performance advantages.Although the Germans were chiefly interested in coal and even wood, Sanger and Bredt [36] did suggest the use of metal dispersions to obtain higher flame temperatures and, Hence, thrust coefficients. Lippisch [20] and Schwabl [37] were first attracted to solids because of the inherent simplicity of the fuel system in short-duration missiles and artillery or mortar shells. They carried out numerous burner tests with briquetted carbon and natural coal charges, later extending the scope of their work to designs suitable for piloted aircraft.At Great Britain's National Gas Turbine Establishment, Roberson [33] prepared a theoretical performance survey covering a very large number of solid fuels. Actual experimental work appears to have been confined to aluminum and was conducted Some attention was also given to aluminum hydrocarbon slurries by Mazurkiewicz [25].In this country, at the Applied Physics Laboratory of The Johns Hopkins University, Berl [8] developed techniques for improving the output of a lean propylene oxide burner through the addition of aluminum and magnesium powders. At the Jet Propulsion Laboratory of the California Institute of Technology, Bartel and Kannie [7] used carbon tubes in flow combustion tests and Alperin [1] considered the problem from a theoretical viewpoint. Damon and his associates at the Bureau of Mines [11] initially investigated coal for ramjet use, but later began to incorporate the light metals in their formulations. Smith [39] extended to ramjet flow conditions the earlier fundamental investigations of Hottel and his Massachusetts Institute of Technology co-workers [44,12,29] into the mechanism of burning carbon spheres. The experimental phases of the program were continued under the direction of Hottel and Williams [3,4]. Collins and Squiers of the Continental Aviation and Engineering Corporation intensively examined the application of magnesium to booster [24,40] and gun-launched [42] ramjets. To a lesser extent they also employed aluminum, boron, and napthaiene in their experimental program. Wolf and others from Experiment Incorporated [46] assisted in the early magnes-.um fuel and burner development.Two types of propellant charges resulted from this joint program. Either of these ^ives satisfactory performance under the internal flow conditions obtained in supersonic ramjets and meet to a large extent all other requirements for operational feasibility. Later, the effect of a solid or liquid dispersed phase, such as magnesium oxide, on the aerothermodynamic relations employed in ramjet design calculations was examined [47]. [50,53]...