Gas turbine engine combustors widely employ injection of liquid fuel in cross flow air as a fuel atomization process. Fuel atomization has a major impact on the efficiency, exit profile and emissions of the combustors. Since the quality of spray directly affects the performance of the combustors, it is important to understand a complex phenomenon of spray formation involving trajectory evolution, surface breakup, column fracture and dispersion of secondary droplets. There are several ways of analyzing spray formation which include experimental measurements, numerical analysis using Direct Numerical Simulation (DNS), a combination of output from Volume of Fluid (VOF) and empirical correlations or a hybrid Eulerian-Lagrangian multiscale method. In any of the numerical methods used for the analysis of the sprays, the mesh topology and resolution have a great impact on the accuracy of the predictions.
In the present work, evaluation of mesh topology particularly hexahedral and polyhedral meshes, is carried out to understand their effect on the accuracy of the spray prediction and explore the possibility of employing the polyhedral mesh for such a complex phenomenon. The mesh generation for polyhedral meshes is comparatively easier than hexahedral meshes and it has better control on the growth of the element size, resulting in lesser mesh count. A hybrid Eulerian-Lagrangian multiscale method developed earlier is used along with scale resolving turbulence model (Large Eddy Simulation) in this work. The test case considered for the analysis is taken from the experimental analysis done by Gopala et al. [2]. Momentum flux ratio of 10 and weber number of 1500 are selected for the present analysis. Simulation results from both the mesh topologies are compared with the experimental results for quantities like jet penetration length, Sauter mean diameter and droplet velocity profiles at different z/d locations. It is observed that both the mesh topologies considered, perform equally well and therefore, polyhedral mesh topology can be employed successfully for hybrid spray modeling.
