Ramjets Fuels

In the past years, many fuels were tested for ramjet applications [1, 2] Most important features in the selection of fuels for ramjet applications are: 1. specific impulse (the amount of propellant required to accelerate the missile). 2. fast fuel/air kinetics to allow high combustion efficiency and short combustors. 3. density 4. storability 5. cost 6. storage safety. In fact, higher specific impulse allows higher thrust per unit weight of fuel, this saving the onboard propellant. When a long range is required, the higher Isp, the smaller fuel mass and consequently the lighter overall mass of the missile is required, yielding a greater acceleration for a given thrust. In air-to-air (small) missiles, the specific impulse per unit volume is critical for the shape design and lodging. Storable liquid fuels, e.g., liquid hydrocarbon (LHC), are attractive for their high density. In order to avoid instable and inefficient combustion, injectors may be able to allow vaporization and mixing of the liquid fuel with air in a very short time. The fast kinetics speed up the combustion improving its efficiency, i.e., increasing the amount of burned fuel that contributes to the thrust. The rate of reaction depends on the combustor inlet temperature and pressure.