Session: 04-37: Combustion dynamics - experiments II

Paper Number: 123297

123297 - Experimental and Numerical Study of Thermoacoustic Instability Characteristics and Mechanisms of Swirling Flame With Outer Flame 

Previous research has identified that a stable outer flame structure exists in swirling flame can enhance the flameout characteristics of swirl combustion. However, it may exhibit thermoacoustic instability under low equivalent ratio conditions. In this study, the combustion instability characteristics of swirling flame with outer flame under different operating conditions were investigated. The sound signal was captured by microphone, and the chemiluminescence at 10 kHz was used to measure OH distribution simultaneously. The results indicate that combustion instability occurs at low equivalent ratios, with peak frequencies ranging from 560 Hz to 720 Hz. When maintaining a constant airflow, unstable behavior undergoes a process of formation, development, weakening and disappearance starting from higher equivalent ratios until flameout. However, the sound frequency during the unstable state remains relatively unchanged. Conversely, the instability frequency increases linearly with increasing airflow rate. Subsequently, Reynolds stress model (RSM) and Flamelet Generated Manifold (FGM) model were employed to conduct unsteady RANS simulations for typical unstable conditions. The flame pattern captured by simulation is generally consistent with OH-PLIF observations. By examining the flow field structure, it was observed that the air did not merge but separated when it left the inner and outer circulation channels - a phenomenon not previously reported in other studies - suggesting its potential as a novel approach for studying swirling combustion dynamics. Furthermore, pressure spectrum characteristics obtained from simulation results exhibit similarities to experimental findings. The physical field of single pressure pulsation periods was investigated. The results reveal that there are periodic disturbances from both double helix vortex in the inner swirl nozzle and periodic expansion and contraction in the downstream region of the inner recirculation zone. These pulsation features are highly consistent with the SPOD modes derived from the chemiluminescence data.

Presenting Author: Yuanhong Qi Institute of Engineering Thermophysics, Chinese Academy of Sciences; National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine, Chinese Academy of Sciences; School of Aeronautics and Astronautics, University of Chinese Academy of Sciences;

Presenting Author Biography: The author, Qi Yuanhong, is a doctoral student at the Institute of Engineering Thermophysics, Chinese Academy of Sciences. He received his bachelor's degree in engineering from Sichuan University in June 2018 and was admitted to the Institute of Engineering Thermophysics of the Chinese Academy of Sciences in September 2019. The main research direction of the author is the combustion instability characteristics and mechanism of aeroengine combustion chamber.

Authors:

Yuanhong Qi Institute of Engineering Thermophysics, Chinese Academy of Sciences; National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine, Chinese Academy of Sciences; School of Aeronautics and Astronautics, University of Chinese Academy of Sciences;
Bin Hu Institute of Engineering Thermophysics, Chinese Academy of Sciences; National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine, Chinese Academy of Sciences; School of Aeronautics and Astronautics, University of Chinese Academy of Sciences;
Qiang Shi Institute of Engineering Thermophysics, Chinese Academy of Sciences; National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine, Chinese Academy of Sciences
Sanqun Ren Institute of Engineering Thermophysics, Chinese Academy of Sciences; National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine, Chinese Academy of Sciences;
Wei Zhao Institute of Engineering Thermophysics, Chinese Academy of Sciences; National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine, Chinese Academy of Sciences; School of Aeronautics and Astronautics, University of Chinese Academy of Sciences
Qingjun Zhao Institute of Engineering Thermophysics, Chinese Academy of Sciences; National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine, Chinese Academy of Sciences; School of Aeronautics and Astronautics, University of Chinese Academy of Sciences; Beijing Key Laboratory of Distributed Combined Cooling Heating and Power System