Low Order Models of Thermoacoustic Instabilities within Combustors

Abstract

The two-way interaction between the flame and acoustic waves leads to thermoacoustic instabilities within combustors. To understand and quantify the flame response to oncoming acoustic waves, flame transfer functions (FTFs) or flame describing functions (FDFs) have been widely used. The G-equation low order model has been proved as a power tool to reconstruct FTFs or FDFs. This talk will firstly present the application of this low order model to the determination of the nonlinear flame dynamic response of turbulent premixed flames subjected to transverse and longitudinal acoustic disturbances. A Two-way Nonlinear Unforced Flame Speed Modeling approach was proposed. The turbulent effects were accounted for in the flame propagation speed term and the steady flame term in the kinematic equation of the flame front; an expansion method was then used to obtain the FDF. Then, the G-equation model method is applied to obtain the dynamic responses of conical and V-shape flames to dual-frequency inputs. The contributions of the two-frequency inputs and their couplings to the nonlinear flame response are identified. 

Speaker

Prof. Jingxuan Li is currently a Professor at the School of Astronautics, Beihang University, China. He is also the Deputy Secretary-General of Beijing Thermophysics and Energy Engineering Society. In 2012, he received his PhD degree from Ecole Centrale de Paris, France. He did postdoctoral research in the Department of Aeronautics and the Department of Mechanics at Imperial College London from 2013 to 2017, and then joined the Department of Aeronautics, Beihang University. His research interests include combustor thermoacoustic instabilities, laser diagnostics and noise control. He has published more than 40 international academic papers related to thermoacoustic instabilities, and has authorized 15 Chinese invention patents.