Global Consumption Speed of Jet Fuel/Air Flames and the Impact of Fuel Chemistry

Large hydrocarbon fuels are used for ground and air transportation and will be for the foreseeable future. A key parameter when burning these fuels is the turbulent consumption speed, which is the velocity at which fuel and air are consumed through a turbulent flame front. Such information can be useful as a model input parameter and for validation of modeled results. In this study, turbulent consumption speeds were measured for three jet-like fuels using a premixed turbulent Bunsen burner. The burner was used to independently control turbulence intensity, unburned temperature, and equivalence ratio. Each fuel had similar heat releases (within 2%), laminar flame speeds (within 5-15%), and adiabatic flame temperatures. Despite this similarity, for constant Re-D and turbulence intensity, A2 fuel (i.e. jet-A) has the highest turbulent flame speeds and remains stable (i.e. without tip quenching) at lower phi than the other fuels. In contrast the C1 fuel, which consists of heavily-branched alkanes, contains no aromatics and has a relatively high average molecular weight, has the slowest turbulent flame speeds and is the most prone to tip quenching. The C1 fuel has the highest stretch sensitivity, in general, as indicated by calculated Markstein numbers. This work shows that turbulent flame speeds and tip stability of multi-component large hydrocarbon fuels can be sensitive to the chemical class of its components.

Automated summary

This study reveals that the turbulent flame speeds and tip stability of multi-component large hydrocarbon fuels can vary depending on the chemical composition. The jet fuel A2 (i.e. jet-A) exhibits higher turbulent flame speeds and better stability compared to other fuels, while the C1 fuel, consisting of heavily-branched alkanes, no aromatics, and relatively high average molecular weight, shows the slowest turbulent flame speeds and is most prone to tip quenching.