Control device for improving swirl flame stabilization.

Abstract

Aiming to improve the stabilization of unstable swirling turbulent premixed flames, an actively controlled swirler and electrical hardware and control software are developed, implemented, and tested in the present study. Stereoscopic particle image velocimetry is performed to calculate the swirl number and study the flame stabilization. A mixture of methane and air with a mean bulk flow velocity of 5.0m/s and a fuel-air equivalence ratio of 0.6 is examined. This test condition, along with an original swirler vane angle of 30°, led to the initial anchoring of an unstable premixed flame at the burner exhaust. The developed actuation mechanism allows for changing the swirler vane angle from 30° to 60° and back to 30°. Increasing the vane angle from 30° to 60° increases the swirl number to relatively large values, which leads to the formation of a recirculation zone, a downward velocity along the burner centerline, and, as a result, the stabilization of an M-shaped flame. After the vane angle is reduced to 30°, the swirl number decreases but remains relatively large compared to its original value. As a result, the recirculation zone is present at the end of the actuation process and a V-shaped flame is stabilized. Improving the stabilization of the swirl flames is made possible because of the control apparatus and the method developed in the present study. The apparatus and technique designed and tested in this study facilitate the development of robust tools for improving the stabilization of swirling premixed flames in gas turbine combustors.