Mixing and Evaporation of Multiple Size Group JP-7 Fuel Droplets Injected into a Supersonic Air Stream - Efficiency of Cylindrical versus Rectangular Combustion Chamber

摘要

This report deals with the formulation, implementation, and testing of three numerical techniques based on (i) a full multiphase approach, (ii) a MUlti-SIze Group (MUSIG) approach, and (iii) a Heterogeneous MUSIG (H-MUSIG) approach for the prediction of mixing and evaporation of liquid droplets injected into a stream of air flowing inside a combustion chamber. The numerical procedures are formulated following a Eulerian approach, within a pressure-based fully conservative Finite Volume method equally applicable in the subsonic, transonic, and supersonic regimes, for the discrete and continuous phases. The k-sigma two-equation turbulence model is used to account for the droplet and gas turbulence with modifications to account for compressibility at high speeds. For the purpose of comparing the performance of the various methods, three configurations involving stream-wise and cross- stream spraying in rectangular and cylindrical domains are investigated and solutions for evaporation and mixing in the subsonic and supersonic regimes for droplets sprayed in turbulent flow streams are generated. Results, displayed in the form of droplet velocity vectors, contour plots, and axial profiles indicate that solutions obtained by the various techniques exhibit similar behavior. Differences in values are relatively small with the largest being associated with droplet volume fractions and vapor mass fraction in the gas phase. This is attributed to the fact that with MUSIG and H-MUSIG no droplet diameter equation is solved and the diameter of the various droplet phases are held constant, as opposed to the full multiphase approach.