Measurements and Modeling of the Dynamic Response of a Pilot Stabilized Premixed Flame Under Dual-Input Perturbation

Abstract

Pilot flames have been widely used for flame stabilization in low-emission gas turbine combustors. Effects of pilot flame on dynamic instabilities, however, are not well understood. In this work, the dynamic interactions between main and pilot flames are studied by perturbing both flames simultaneously, i.e., with a dual-input forcing. A burner is used to generate a premixed axisymmetric V-shaped methane flame stabilized by a central pilot flame. Servo valve and sirens are used to produce forcing in the pilot and main flames, respectively. A diagnostic system is applied to measure the flame structure and heat release rate. The effects of forcing frequency, forcing amplitude, phase difference between the two forcing signals as well as the Reynolds number are studied. Both the flame transfer function (FTF) and the flame dynamic position are measured and analyzed. It is found that the total flame response can be modified by the perturbation in the pilot flame. The mechanism can be attributed to the effect of pilot flame on the velocity field of the burnt side. Vortex is found to be able to amplify the pilot–main dynamic interactions under certain conditions. An analytical model is developed based on the linearized G-equation, to further understand the flame interactions through the velocity perturbations in the burnt side. Good agreements were found between the prediction and the experiment results.