A Joint Experimental and Large Eddy Simulation Characterization of the Liquid Fuel Spray in a Swirl Injector

Abstract

The quality of liquid fuel spray injection determines to a large extent the performance of aero-engine combustors. This investigation focuses on the detailed characterization of the liquid fuel spray in a test rig targeted at aero-engine applications. The liquid fuel is injected as a hollow cone by a simplex atomizer and the injector comprises a radial swirler. Two features of the droplet distribution are less commonly found. First, the distributions of droplet diameters exhibit nonaxisymmetric patterns, which are investigated for three types of swirlers. Second, it is found that the size-conditioned velocity distributions feature a single wide peak for small droplets and become bimodal for the largest droplets, with a first peak at low velocities, and a second one at higher velocities. Experiments are complemented with large eddy simulations and Lagrangian particle tracking. The spray interacts with the lateral injector surface and requires a droplet–wall interaction model for the liquid film. Simulations do not retrieve the lack of rotational symmetry that is found experimentally indicating that this feature is not linked to the nature of the flow. This is also consistent with further experiments with a different atomizer confirming that this is due to imperfections in the atomizer geometry. Another result is that certain swirler designs are more robust to atomizer imperfections. Simulations accounting for the liquid film yield a bimodal distribution for the droplets' axial velocity distribution which is not obtained without this model, indicating that it is important to represent the droplet–wall interaction.