Compressible Modeling of the Internal Flow in a Gas-Centered Swirl-Coaxial Fuel Injector

• Published in: Journal of propulsion and power 2012-07, Vol.28 (4), p.685-693
• Main Authors: Trask, Nathaniel, Schmidt, David P, Lightfoot, Malissa, Danczyk, Stephen
• Format: Article
• Language: English
• Subjects: Atomization; Atomizing; Closures; Flux; Fuels; Injectors; Liquids; Mathematical models; Turbulence
• ISSN: 0748-4658; 1533-3876
• DOI: 10.2514/1.B34102

Predicting the liquid film dynamics inside the injector cup of gas-centered swirl-coaxial fuel injectors requires a general two-phase approach that is appropriate for all liquid-volume fractions, high Mach and Weber numbers, and complex geometries. A Eulerian two-phase model is implemented to represent the liquid and gas interactions in the injector as well as the atomization processes occurring at the rough interface. Previous work using an incompressible formulation encountered difficulty in matching film profiles at large mass flow rates. The current work is an enhanced approach that includes compressibility effects. The improvement gained by implementing a compressible formulation is attributed to a sudden expansion occurring following the injector lip. Two-dimensional results are compared to high-speed photographs of the liquid film within the injector cup. Applications of closures for the turbulent liquid flux commonly used in the literature are presented and are shown to substantially overpredict the atomization rate. By limiting the rate at which entrainment occurs via the Schmidt number, the film profile is accurately predicted over a wide range of momentum flux ratios, highlighting the stabilizing effect the swirl has upon the atomization process. The applicability of this modeling approach and an assessment of the necessity for investigating Reynolds stress closures in future work are assessed.