Many of the materials referenced for this project are not available for public release. Please consult the references section of the paper for more details.
This paper serves as the culmination of the literary aspect of AE-2699 (research option), at the Ben T. Zinn Combustion Lab, for the spring term of 2018. This paper is an investigation of fuel types for scramjet combustors, specifically those of conventional fuels, solid fuels, and gelled propellants. The conventional fuels covered are: methane, ethylene, heptane, JP-10, hydrogen. Given the prevalence of these fuels, they will be compared on their ignition time delay. The solid fuel analysis references a combustor composed of poly-methyl-meth-acrylate (PMMA) and will focus on features specific to solid fuel, i.e. fuel regression rate. Gelled propellants will be examined, specifically atomization and related difficulties intrinsic to gelled propellants. As a result of this investigation, it was determined that conventional fuel selection should be the default selection, solid fuels should be selected in cases where the mission parameters are fixed (but additional research is needed in that area), and gelled propellants selection should be held off until atomization efficiency is increased.
The viability of conventional liquid/gaseous fuels has already been cemented. Previous research and testing have proven their application for general use. They are also the easiest to control and present the easiest interchangeability of fuels. Solid fuels have possible viability in specialized cases. Their usage requires that the flight profile and conditions be pre-determined but offer a higher density and simpler control systems (at the cost of a lower specific impulse). However, improvements to their efficiency needs to be made before solid fuel can see viability on the level of current conventional fuels. Gelled propellants seem to be primarily in the stages of testing and without improvements in atomization quality or injection scheme , they are simply too inefficient when compared to conventional or solid fuels.
Special thanks to the many graduate students of the Ben T. Zinn combustion lab for their guidance through some of the more advanced topics I came across while doing research. Additional thanks to Research Engineer, David Wu for additional guidance.