Combustion properties of fuels and methods to improve them

High-energy-density liquid fuels have been synthesized and used because they can provide more volumetric propulsion energy than conventional petroleum-derived aviation turbine fuels, thereby potentially increasing the maximum flight range and airspeed of aircraft. However, cyclic hydrocarbons in high-energy-density fuels have lower hydrogen contents than those in conventional normal paraffin fuels, resulting in a long ignition delay and a low combustion completion level, especially when the aerocraft is operating at low air pressure, high altitude, and low oxygen/fuel ratio conditions for hypersonic flights. An effective technology to improve the fuel ignition property is to use a catalyst to accelerate the fuel's combustion reaction at a relative low temperature. In this chapter, we summarize typical techniques to analyze the combustion process, combustion characters of fuels, and the methods to enhance ignition and combustion.