Effect of Secondary Swirl Strength on the External Aerodynamics of a Gas Turbine Fuel Injector

The present work investigates the effect of the secondary swirler geometry on the gas flow field and the shear layer thickness in a counter-rotating gas turbine swirl injector. The counter-rotating swirl injector geometry consists of a primary swirler and a counter-rotating secondary swirler separated by a pre-filming thin surface. Three counter-rotating swirl injectors having different swirl numbers of the secondary swirler have been used for this study. The primary swirler’s swirl number is kept constant and within the strong swirl regime. The gas flow field in the axial and transverse plane is captured using particle image velocimetry (PIV) experiments. The geometry with a high swirl number has the highest axial, radial, and tangential velocities. The secondary swirler’s swirl strength affects the recirculation zone that the primary swirler creates at the injector outlet, and radial expansion in the central toroidal recirculation zone (CTRZ) has also been observed.