Session: 04-06 Combustion Dynamics - Modeling II

Submission Number: 176379

Dynamics of Tilted Conical Flames in Transverse Flows 

Many modern combustion systems use a secondary injection strategy also called axial staging, for downstream burning that results in lower emissions. However, such flames are prone to combustion dynamics due to ambient velocity and equivalence ratio perturbations. In this study, we focus on a phenomenological model for the flame dynamics of a tilted conical flame in a uniform transverse flow. We model the flame dynamics using the thin flame sheet approximation (the G-equation) in a linearized framework. The dynamics are characterized by using the unsteady global heat release rate oscillations which are conventionally represented using the Flame Transfer Function or FTF. Prior literature focused on FTF modeling assuming axisymmetric or weakly asymmetric flame configuration in two dimensions. However, in real engines, axially staged flames result in three-dimensional shape stabilized in a combination of two flow directions (axial injection direction and transverse main flow), resulting in a time-averaged tilted conical shape.  While axisymmetric flames show no global response to transverse fluctuations, tilted conical flames result in a non-zero global response depending on tilt angle. We consider the velocity and equivalence ratio coupled mechanisms as source disturbances. The effect of flame tilting and flame height on the FTF gain and phase is studied for response to either or both coupling mechanisms.

Presenting Author: Eishun Takeo Research & Innovation Center

Presenting Author Biography: Dr. Takeo is currently a Research Engineer at the Research & Innovation Center of Mitsubishi Heavy Industries, Ltd. One of his research interests focuses on Reduced-Order Modeling of thermoacoustic instabilities in, mainly, heavy duty gas turbines.

Authors:

Eishun Takeo Research & Innovation Center
Vishal Acharya Ben Zinn Aerospace Combustion Lab., Georgia Institute of Technology