Session: 04-42 Combustion dynamics - flow instabilities

Paper Number: 128941

128941 - Flame Interaction and Stabilization Mechanisms in a Dual Premix Swirl Combustor With a Pilot Bluff Body 

The centrally staged stratified swirling flame has found widespread application within lean premixed combustors, due to its good flame stability and low pollutant emission. Nevertheless, under specific operational conditions or in the presence of thermoacoustic oscillations, phenomena such as the stratification and merging of pilot flame and main flame have been observed. In this study, we conducted a comprehensive investigation into the mechanisms governing the interaction between the pilot and main flames in an innovative dual-swirl model combustor. By utilizing a 10kHz PIV/OH* synchronized measurement method, we captured the transient merging processes between the pilot flame and the main flame. Then, the morphological characteristics of stratified flames were investigated under different stratification ratios (SR). To elucidate the combustion stabilization mechanism of the pilot diffusion flame, methane and hydrogen were successively introduced into the central bluff body.

Results indicated that SR has a significant effect on the morphology of the staging flames. When maintaining the fuel/air ratio (FAR) of the pilot flame constant and reducing SR, the stratified flames transformed into M-shaped flames. Conversely, keeping the equivalence ratio of main flames constant and increasing SR, the stratified flames were transformed into axially stretched V-shaped flames. When the pilot flame splits from the main flame, maintaining the total equivalence ratio constant and reducing SR could lead to the re-merging of the pilot and main flame. Before flame merging, the stratified flame exhibits a double V-shape, we have observed the periodic generation and blow-off of the primary recirculation zone (PRZ) under the influence of  processing vortex core (PVC). As the FAR of the pilot flame was excessively low, the pilot flame was incapable of stabilizing the main flames. Consequently, the main flame was lifted due to the influence of the airflow, causing the convergence of the inner and outer mixtures, ultimately resulting in flame merging. The introduction of jet diffusion flame at the central bluff body disrupted the structure of the PVC, thereby reinforcing the stability of stratified flames. Furthermore, the hydrogen diffusion flame exhibited a higher axial velocity in comparison to the methane diffusion flame, significantly enhancing the flow within the recirculation zone of the stratified flame. This phenomenon resulted in a reduction of axial dimensions and an expansion of radial dimensions within the stratified flame

Presenting Author: Linye Li Shanghai Jiao Tong University

Presenting Author Biography: Linye Li received a BE degree in Thermal and Power Engineering from Central South University, China. He is currently a PhD student at the School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China. His research interest is combustion instabilities in hydrogen-mixed stratified swirling flame.

Authors:

Linye Li Shanghai Jiao Tong University
Xiaojing Tian State Key Laboratory of Clean and EfficienTurbomachinery Power Equipment
Shengming Yin Shanghai Jiao Tong University
Haodong Zhang Shanghai Jiao Tong University
Yifan Yang Shanghai Jiao Tong University
Guoqing Wang Shanghai Jiao Tong University
Zhenzhen Feng State Key Laboratory of Clean and EfficienTurbomachinery Power Equipment
Liangliang Xu Shanghai Jiao tong University
Xi Xia Shanghai Jiao Tong University
Fei Qi Shanghai Jiao Tong University