Internal and External Flow Characteristics on Variation of Swirl Strength for a Fuel Flexible Injector for Micro Gas Turbine Engines

Abstract The internal and external aerodynamics of fuel flexible lean burn gas turbine injector is numerically investigated to obtain a detailed understanding of the recirculation zone and shear layer characteristics. The injector geometry consists of a main and pilot swirlers that are organized in clockwise and anticlockwise orientations, with several fuel tubes interspersed. Two axial swirlers are positioned in the pilot in a clockwise and anticlockwise direction, while one axial and two radial swirlers are arranged in the main in a clockwise and anticlockwise manner. The area mass flow split ratio is used to construct the injector. There is a 30:70 mass flow split between the main geometry and the pilot geometry. The central toroidal recirculation zone (CTRZ) characteristics are captured for different swirl numbers, for pilot, main and the full injector. Individual recirculation zones are formed at the pilot and main mixers and they combine to form the required single CTRZ at full injector exit. The swirl number of swirlers of main and pilot was varied keeping other parameters constant and it is observed that a slight change in swirl number can impact changes in flow characteristics and CTRZ formation of both mixers of injector.