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Abstract The present work investigates the swirl velocity field and atomization processes of a lean burn gas turbine swirl injector. The injector includes a complex configuration of a pilot mixer and a main mixer with a mass flow split ratio of 31:69. The pilot and main mixer include a set of counter-rotating axial and radial swirlers of different swirl numbers. Incoming airflow from the pilot’s axial and radial swirler is separated by a prefilmer venturi. Jet in swirl cross-flow scheme is employed for injecting fuel into both pilot and main mixer. Particle image velocimetry (PIV) techniques are employed to investigate the air swirl flow field and atomization processes at the exit of the injector. Axial plane and transverse plane particle image velocimetry (PIV) experiments are conducted to obtain the three-component velocity of the gas phase at selected planes. Experiments are carried out at various air-to-liquid ratios ranging from 7.30 to 30.45, keeping the liquid flow rate constant, with three injector configurations: pilot, main, and pilot plus main mixer. Individual recirculating flow structures are observed in the case of both pilot and main mixer, and they merge to form a central toroidal recirculation zone in the case of the full injector assembly. The air momentum dominates the overall spray topology and droplet dispersion at higher air-to-liquid ratio conditions for all three configurations. Spray PIV measurements highlighted significant radial drifting of pilot spray droplets under the influence of main mixer swirl streams. Overall, swirl sense is controlled by the main mixer, and significant slip velocities are observed at the shear layer regions.
Sahu et al. (Mon,) studied this question.