Abstract: The atomizing performance of effervescent atomizers are examined with special emphasis on the influence of gas injector geometry on spray characteristics.A particle dynamic analyzer (2D PDA) is used to measure mean drop size,drop size distribution and velocity distribution.All tests are carried out at normal atmospheric pressure and temperature.Water injection pressures are varied from 0.20 to 0.60 MPa and air/liquid ratios from 0.04 to 0.12 by mass.Three different gas injectors are used,one having 4 holes,each of 2.2 mm diameters and the others 20 holes of 0.7 and 1.0 diameters.They are used in conjunction with three mixing tubes of different lengths.The results obtained show that the changes in the number and size of the gas injection holes have significant influence on atomization qualities of horizontally ejecting effervescent atomizers.Moreover,there is an optimum length of the mixing tube leading to higher atomization quality.However,when swirling the liquid,atomization quality appears to be slightly improved.