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In the present study a modified pressure swirl atomizer is designed and manufactured to be suitable for a wide range of operating conditions. The spray performance of the modified pressure swirl atomizer is experimentally investigated under different internal atomizer geometry. The studied parameters are injection pressures which changed from 0.5 to 10 bar, the orifice length to orifice diameter ratio (L/D) which taken as 0.22, 0.25, 0.27and 0.29 (L is taken constant at 1 mm), spin chamber diameter(Ds) which taken as 8, 10 and12 mm, swirling passage size (width x depth) which varied as 1x1, 1.5x1.5, 2x2 and 2.5x2.5 mm and nozzle constant K, these parameters are studied at constant spin chamber angle (Ø) of 90°. The spray performance such as spray shape, spray cone angle, radial spray concentrations, spray momentum and breakup length are studied under different operating and geometrical conditions using water as atomized liquid. The spray shape is photographed using digital camera to determine the spray cone angle and breakup length while the radial spray concentrations are measured by using the tubes patternator technique and the spray momentum is calculated from the spray concentration. An experimental test rig consists of fuel line, gear pump, valves and pressure gauges is used to study the spray performance at the above different operating conditions. An empirical formula for breakup length is developed in this work. A breakup length is measured experimentally to valid the results obtained of breakup length from digital photos. A comparison is carried out between the measured SCA with empirical equation for calculation SCA. The results indicated that by decreasing the size of swirl passage by about 60% the spray cone angle increased by about 50 %. It is also noticed that the breakup length decreased by about 51% when spin chamber diameter increased by about 33%.
