Swirler Design Parameter Impact On Lean Blowout, Pressure Loss, and Flame Liftoff

Swirl stabilized combustion is a common technique used in gas turbine engine combustors and is accomplished by introducing swirl into the inlet flow, which enhances mixing and stabilizes the combustion event. Coaxial swirlers introduce the fuel and air axially through concentric inlets and use vanes to impart a tangential component to either the fuel, air, or both flows. The present study conducted a parametric analysis of coaxial swirler design by manufacturing an array of 14 coaxial swirlers scaled for use in low flow, small engine operations which incorporated the same base design but varied the swirl number, Sn, by changing the vane angle between 0° and 63°, vane count between four and ten, and vane shape between traditional and helical. Each design was experimentally evaluated using air and propane at different flow conditions to correlate swirler design with lean blowout limits, pressure loss, and flame liftoff. Lean blowout was primarily influenced by swirl number, while vane count and shape had significant impact at Sn = 0.8 but little impact at Sn = 1.5. Pressure loss was unchanged below a Sn of 0.6, and unlike lean blowout, Sn had little impact at 0.8 but significant impact at 1.5. Finally, flame liftoff was mainly driven by swirl number, with vane count and shape the next significant design parameters.