Effect of the physical properties of liquid and alr on the spray characteristics of a pre-filming airblast nozzle

The atomization and combustion characteristics of fuels injected in aviation gas turbine engines are very important in the research and development of gas turbine combustors and have a significant impact on engine efficiency and pollutant emissions. In this study, spray atomization characteristics of pre-filming airblast nozzles developed for use in aviation gas turbine combustors were experimentally investigated for different air to liquid ratios (ALR) and air pressure differences (ΔP (%)). Pure water and Jet A-1, which have different viscosities and surface tensions that greatly affect the atomization characteristics, were used as the working fluid. Spray atomization characteristics were investigated by simultaneous measurement of droplet sizes and velocities using PDA (phase Doppler anemometry) and spray visualization using a CCD camera coupled with a Nd:YAG laser as a light source. The atomization characteristics of water and Jet A-1 showed significant differences in spray angle, velocity distribution and mean droplet size. Jet A-1 spray with lower surface tension showed a smaller mean drop size (WMSMD) than water spray did. As the ALR increased, the mean droplet size of the two liquids decreased. From the analysis of the spray flow characteristics, the surface tension associated with aerodynamic instability was the dominant variable in the atomization process with liquid sheet disintegration. The experimental constants included in the previously proposed empirical formulas for predicting the mean droplet size of the pre-filming airblast nozzle spray were presented for the two liquids used in the experiment.