One Dimensional Hydrocarbon Fueled Scramjet Model with Droplet Evaporation and Finite Rate Chemistry

Abstract

*† The quasi-one-dimensional equations of fluid motion are coupled with the equations for finite-rate chemistry to model high speed (supersonic) combustor flow fields. A numerical calculation method has been incorporated to predict the evaporation percentage of the transversely injected fuel spray with downstream distance x from the injector(s) by tracking a single droplet from each injector. The effects of the droplet heat up period and forced convection on the evaporation process have been taken into account. This helps the proposed model to free itself from the huge responsibility of assuming appropriate values for the mixing length of the fuel droplet, which is usually the case. The variation in the evaporation percentage with the downstream distance for varying air velocities, pressures, temperatures etc have been taken care of. The model also incorporates the effects of area change, friction, mass injection, heat transfer through the walls of the combustor on the combustor performance. The model is clearly oversimplified compared to the complex three dimensional turbulent mixing and induced shock train processes known to exist in supersonic combustors. Nevertheless, it includes sufficient physics to provide a rapid interpretation of the global features of the supersonic combustors. Accordingly, it may be useful in the early conceptual design studies of the supersonic combustor. The simulations done, as a part of this work, are for Jet-A fuel, C12H23, assuming it to be a single component fuel.