Spray dispersion in a counter-swirling double-annular air flow at gas turbine conditions

The dispersion of a kerosene fuel spray generated by plain-jet-in-crosflow injection into the inner annulus of a counter-swirling double-annular airflow was investigated experimentally. Tests were conducted at 6 bar and 12 bar static air pressure and 750 K air temperature and at the corresponding cold test conditions in terms of air density, with an additional excursion to higher air density (9.3 bar at 290 K). The airflow, was characterized by laser Doppler anemometry (LDA) and the spray dispersion was investigated by phase Doppler anemometry, (PDA). It was found that the very small droplets generated at high pressure have such a great ability to follow the streamlines of the air flow that they remain trapped in the inner annulus, preventing the formation of a uniform fuel-air mixture in the annular flow. For an in-depth discussion of the results, the appropriate versions of the Stokes number are introduced and evaluated.