Atomization and Sprays

HOLOGRAPHIC INVESTIGATION OF THE EFFECT OF ELEVATED AMBIENT TEMPERATURE ON THE ATOMIZATION CHARACTERISTICS OF IMPINGING JET SPRAYS

RÉSUMÉ

A study of impinging jet sprays formed by a pair of 0.8-mm jets impinging at an angle of 90 ° at ambient temperatures from 25 to 250 °C has been conducted using a double-pulse, two-reference-beam holographic technique. The working fluids utilized were water, a 59 wt% aqueous glycerol solution, and ethanol. Velocity measurements and drop size distributions were obtained for various regions of the spray, and the universal root-normal distribution was used as a representation of the cumulative volume distributions. Generally, the qualitative nature of the spray pattern remained the same as temperature increased, but the size of the resulting droplets decreased as a result of evaporation and increased instabilities. Furthermore, the wave structure, which is characteristic of a fully developed impinging jet spray, became less distinct as temperature increased. The average velocity of the particles within a 20 ° envelope of the spray centerline in the dense region was approximately equal to the mean jet velocity. At downstream locations, the average droplet velocity decreased to approximately 65% of the mean jet velocity. In addition to the data obtained, the advantages of using double-pulse holography are highlighted. Namely, spatial and temporal aspects of the entire spray can be obtained simultaneously. This is a powerful feature, especially in light of the ability of holography to be used to analyze dense regions of a spray.