Detailed and Simplified Chemical Kinetics of Aviation Fuels and Surrogates

摘要

Current fuel quality regulations for aviation kerosene provide significant scope for large regional and source differences. The chemistry of high-performance fuels aimed at specific applications and devices show less variation but their chemistries remain complex. There is now arguably a well- established need to incorporate accurate chemical mechanisms into calculation procedures. Flow timescales associated with high performance propulsion devices also increasingly lead to difficulties associated with the burning characteristics of the current generation of propulsion fuels. In particular, chemical time-scale restrictions pose a particular challenge in terms of combustion initiation and/or flame stability. The current development of alternative combustor designs based premixed or partially premixed lean burn technologies further emphasises the need to consider finite rate chemistry effects. Critical steps in the derivation of realistic chemical mechanisms include the definition of a surrogate (or model) fuel and validation of the performance of the surrogate against practical fuel samples. The required practical parameter space typically leads to a need to determine heat release characteristics, burning velocities, effects of strain, ignition delay times, the dynamics of the fuel breakdown process and quantification of key intermediate species. The latter is often essential in understanding the propensity of a device to form pollutants, such as soot, that may affect signatures and combustor life. Furthermore, current indications suggest that fuel sources will become significantly more diverse in the future and may, for example, encompass Fischer-Tropsch and/or bio-derived components. The current proposal outlines a route towards surrogate fuel mechanisms of sufficient accuracy and generality to support the development of practical devices.