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

A study of impinging jet sprays formed by a pair of 0.8-mm jets imping ing at an angle of 90 degrees at ambient temperatures from 25 to 250 d egrees C has been conducted using a double-pulse, two-reference-beam h olographic technique. The working fluids utilized were water, a 59 wt% aqueous glycerol solution, and ethanol. Velocity measurements and dro p size distributions were obtained for various regions of the spray, a nd the universal root-normal distribution was used as a representation of the cumulative volume distributions. Generally, the qualitative na ture of the spray pattern remained the same as temperature increased, but the size of the resulting droplets decreased as a result of evapor ation and increased instabilities. Furthermore, the leave structure, w hich is characteristic of a fully developed impinging jet spray, becam e less distinct as temperature increased. The average velocity of the particles within a 20 degrees envelope of the spray centerline in the dense region was approximately equal to the mean jet velocity. At down stream locations, the average droplet velocity decreased to approximat ely 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 simul taneously. This is a powerful feature, especially ill light of the abi lity of holography to he used to analyze dense regions of a spray.