Multi-coupled numerical simulations of the DLR Generic Single Sector Combustor

ABSTRACT

This paper presents a set of numerical analyses carried out on a model combustor equipped with a prefilming airblast injection system using a multi-coupled approach that includes the solution of the liquid film over the prefilming surface. The main objective of this study is to perform a systematic investigation of all the relevant aspects involved in the liquid fuel preparation of airblast atomizers, ranging from the interaction between the gas phase and the liquid film to the effect of velocity fluctuations on the dispersion of droplets downstream of the injector exit. Measurements at high pressure and reacting conditions are available for the case considered here, therefore, allowing to perform such investigation at engine-relevant conditions. The solution of the liquid film evolution over the prefilming surface suggests that the interaction between the gas phase and the liquid film is an important aspect to be considered for a reliable simulation of prefilming airblast systems since it has a strong impact on both velocity and fuel temperature at the atomizing edge. The role of primary breakup has been investigated by performing a sensitivity analysis to different theoretical and correlation-based models. Results obtained from this analysis, performed using Reynolds averaged Navier–Stokes simulations, show that the various formulations predict a quite different diameter, affecting the mixing field in the downstream region and therefore pointing out the necessity of more advanced and robust formulations. A comparison between experimental measurements and a scale-adaptive simulation of the combustor, performed using the spray setup determined in the sensitivity analysis, demonstrates the necessity of including in the simulation time-resolved velocity fluctuations to improve the prediction of the dispersion of droplets and therefore give a reliable prediction of fuel location and mixing.

KEYWORDS:

• CFD
• Multi-coupled simulation
• Film modelling
• Primary breakup modelling
• Scale-Adaptive Simulation

Acknowledgments

The authors would to express their gratitude to Dr.-Ing. Christoph Hassa from DLR for providing geometry and experimental data of the investigated test case.