Lean premixed prevaporized combustion (LPP) is a promising approach for the reduction of emissions in gas turbine combustion. Typically, modern gas turbines operate at high pressure and high temperature flow conditions, giving rise to very short self ignition times. Consequently, the residence time of the mixture in the premix duct has to be minimized. Complete fuel vaporization and mixing can only be achieved by an improvement of the atomization process towards a fine droplet size spectrum over the whole range of operating conditions. In this paper an air assisted pressure swirl atomizer is introduced and analyzed. The special design of the nozzle under investigation enhances the interaction between the liquid sheet of the atomizer and the co-flowing air around the nozzle. The visualization of the atomization process gives detailed insight into the fundamental atomization phenomena of the atomizer. In addition, extensive measurements of droplet size distributions describe the dependence of the atomization process on liquid flow rate and air velocity, respectively. All phenomena occurring are explained in detail by means of a theoretical analysis of the flow pattern. With the help of this kinematic model, it can be shown why co-rotating swirls of atomization air and liquid cone lead to better atomization than counter rotating swirls.

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