A pressure-swirl fuel nozzle generating a hollow-cone spray with nominal cone angle of 30 degrees is used in a swirl-stabilized combustor. The combustor is circular in cross section with swirl plate and fuel nozzle axes aligned and coinciding with the axis of the chamber. Kerosene is injected upward inside the chamber from the fuel nozzle. Separate swirl and dilution air flows are uniformly distributed into the chamber that pass through the honey comb flow straighteners and screens. Calculated swirl number of 1.5 is generated with the design swirl plate exit air velocity of 30 degrees with respect to the chamber axis. Effects of swirl and dilution air flow rates on the shape and stability of the flame are investigated. Stable and classical liquid fuel sheet disintegration zone exists close to the nozzle with no visible light followed by a luminous blue region and a mixed blue/yellow region that subsequently turns into yellow for most of the part in the flame. A Phase Doppler Particle Analyzer (PDPA) is used to measure drop size, mean and rms axial velocity for two cases of with and without combustion at six different axial locations from the nozzle. For the no-combustion case all air and fuel flow rates were kept at the same values as the combusting spray condition. Results for mean axial drop velocity profiles indicate widening of the spray due to combustion while the magnitudes of the peak velocities are slightly increased. No measurements inside the hollow-cone spray are possible due to burning of fuel droplets. Drop turbulence decreases due to combination of increase in gas kinematic viscosity and elimination of small drops at high temperatures. Sauter Mean Diameter (SMD) radial profiles at all axial locations increase with combustion due to preferential burning of small drops.
Spray Drop Size and Velocity Measurements in a Swirl-Stabilized Combustor
