Experimental investigations on flow-flame-acoustic dynamic characteristics of a central staged burner
JIN Ming1, LU Yudi1, LI Yuansen1, LIU Weijie2, GE Bing1, ZANG Shusheng1
1. School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; 2. Aero-Engine Academy of China, Aero Engine Corporation of China, Beijing 101304, China
Abstract：[Objective] To reveal the influence of interaction between pilot and main flames on flow and thermoacoustic instability characteristics, the flow and thermoacoustic dynamic characteristics of the pilot stage, main stage, and centrally staged flames in the combustion chamber of the central staged model combustor are studied in detail through experiments.[Methods] High-speed measurement methods such as high-frequency particle image velocimetry, high-speed camera, pressure sensors, and photomultiplier tube are used to study the flow-flame-acoustic dynamic characteristics of the central staged burner. During the experiments, the unsteady flow field, flame CH* signal distribution, global heat-release rate, and pressure pulsation characteristics are measured under different testing conditions.[Results] The results showed that the pilot swirling jet had a significant influence on the flow-flame-acoustic dynamic characteristics of the stratified burner. Furthermore, when the pilot stage used a swirling flame, the main recirculation zone was formed downstream of the nozzle outlet and the high-temperature burned gas was rolled back to improve the combustion stability of the swirl flame. The peak value of pressure was 683 Pa, and the main peak values of dynamic pressure and heat release were both visible at a frequency of 120 Hz. However, the dominant frequency of the flow field proper orthogonal decomposition (POD) time coefficient spectrum showed that the dominant frequencies of large-scale shedding vortex in the flow field were 68 and 109 Hz, indicating that the interaction between pilot and main flames caused the thermoacoustic instability frequency to be inconsistent with large-scale vortex shedding frequency. Moreover, the dominant frequency of pressure and heat release were slightly shifted when the pilot stage was operated with a swirling air jet, and it was reduced by 5 Hz and got to 115 Hz. However, the main recirculation zone disappeared, resulting in a strengthening of the thermoacoustic instability and an increase in the peak pressure to 2 947 Pa. The dominant frequency of the flow field POD time coefficient spectrum showed that the frequency of the shedding vortex generated by the swirling flow shear layer of the main stage was 115 Hz, which was well locked with the frequency of the thermoacoustic instability mode under this condition. The results, in this case, showed that acoustic-velocity-flame instabilities were mutually coupled under the single-swirling flame self-excited oscillation condition. However, for the flame interaction case, the flow instability frequency induced by flame and pressure oscillations changed significantly, and the coupling between acoustic-velocity-flame instabilities was also destroyed.[Conclusions] When the main stage is operated with swirling air, whether the pilot stage is operated with swirling air or swirling flame, the stable main recirculation zone can always be observed at the burner exit plane. However, when the main stage is operated with a swirling flame, the swirling air from the pilot stage destroys the main recirculation zone, which is detrimental to the main-stage swirling flame's combustion stability. The main recirculation zone reappears when the pilot stage is converted into a swirling flame. The increased heat load also causes the accelerated expansion of the gas, which induces a stronger vortex in the swirling flow shear layer. However, the interaction between the pilot flame and the main flame accelerates the dissipation of the vortex.
金明, 陆羽笛, 李原森, 柳伟杰, 葛冰, 臧述升. 中心分级燃烧器流-热-声动态特性实验研究[J]. 清华大学学报（自然科学版）, 2024, 64(1): 99-108.
JIN Ming, LU Yudi, LI Yuansen, LIU Weijie, GE Bing, ZANG Shusheng. Experimental investigations on flow-flame-acoustic dynamic characteristics of a central staged burner. Journal of Tsinghua University(Science and Technology), 2024, 64(1): 99-108.
[1] HAN X, LAERA D, YANG D, et al. Flame interactions in a stratified swirl burner:Flame stabilization, combustion instabilities, and beating oscillations[J]. Combustion and Flame, 2020, 212:500-509. [2] MONGIA H C, HELD T J, HSIAO G C, et al. Challenges and progress in controlling dynamics in gas turbine combustors[J]. Journal of Propulsion and Power, 2003, 19(5):822-829. [3] MENON S. Acoustic-vortex-flame interactions in gas turbines[M]//LIEUWEN T C, YANG V. Combustion instabilities in gas turbine engines:Operational experience, fundamental mechanisms, and modeling. Reston:American Institute of Aeronautics and Astronautics, Inc., 2005:277-314. [4] BALACHANDRAN R, AYOOLA B O, KAMINSKI C F, et al. Experimental investigation of the nonlinear response of turbulent premixed flames to imposed inlet velocity oscillations[J]. Combustion and Flame, 2005, 143(1-2):37-55. [5] BELLOWS B D, BOBBA M K, FORTE A, et al. Flame transfer function saturation mechanisms in a swirl-stabilized combustor[J]. Proceedings of the Combustion Institute, 2007, 31(2):3181-3188. [6] SHREEKRISHNA N, HEMCHANDRA S, LIEUWEN T. Premixed flame response to equivalence ratio perturbations[J]. Combustion Theory and Modelling, 2010, 14(5):681-714. [7] BELLOWS B D, BOBBA M K, SEITZMAN J M, et al. Nonlinear flame transfer function characteristics in a swirl-stabilized combustor[J]. Journal of Engineering for Gas Turbines and Power, 2007, 129(4):954-961. [8] THUMULURU S K, LIEUWEN T. Characterization of acoustically forced swirl flame dynamics[J]. Proceedings of the Combustion Institute, 2009, 32(2):2893-2900. [9] SCHIMEK S, MOECK J P, PASCHEREIT C O. An experimental investigation of the nonlinear response of an atmospheric swirl-stabilized premixed flame[J]. Journal of Engineering for Gas Turbines and Power, 2011, 133(10):101502. [10] SCHIMEK S, AĆG OSI AĆG B, MOECK J P, et al. Amplitude-dependent flow field and flame response to axial and tangential velocity fluctuations[J]. Journal of Engineering for Gas Turbines and Power, 2015, 137(8):081501. [11] TERHAAR S, AĆG OSI AĆG B, PASCHEREIT C O, et al. Impact of shear flow instabilities on the magnitude and saturation of the flame response[J]. Journal of Engineering for Gas Turbines and Power, 2014, 136(7):071502. [12] OBERLEITHNER K, SCHIMEK S, PASCHEREIT C O. Shear flow instabilities in swirl-stabilized combustors and their impact on the amplitude dependent flame response:A linear stability analysis[J]. Combustion and Flame, 2015, 162(1):86-99. [13] PALIES P, DUROX D, SCHULLER T, et al. Experimental study on the effect of swirler geometry and swirl number on flame describing functions[J]. Combustion Science and Technology, 2011, 183(7):704-717. [14] PALIES P, DUROX D, SCHULLER T, et al. The combined dynamics of swirler and turbulent premixed swirling flames[J]. Combustion and Flame, 2010, 157(9):1698-1717. [15] TERHAAR S, AĆG OSI AĆG B, PASCHEREIT C O, et al. Suppression and excitation of the precessing vortex core by acoustic velocity fluctuations:An experimental and analytical study[J]. Combustion and Flame, 2016, 172:234-251. [16] CHONG C T, LAM S S, HOCHGREB S. Effect of mixture flow stratification on premixed flame structure and emissions under counter-rotating swirl burner configuration[J]. Applied Thermal Engineering, 2016, 105:905-912. [17] KIM K T, HOCHGREB S. The nonlinear heat release response of stratified lean-premixed flames to acoustic velocity oscillations[J]. Combustion and Flame, 2011, 158(12):2482-2499. [18] HAN X, LAERA D, MORGANS A S, et al. Flame macrostructures and thermoacoustic instabilities in stratified swirling flames[J]. Proceedings of the Combustion Institute, 2019, 37(4):5377-5384. [19] SIROVICH L. Turbulence and the dynamics of coherent structures. I. Coherent structures[J]. Quarterly of Applied Mathematics, 1987, 45(3):561-571. [20] CULLER W, CHEN X L, SAMARASINGHE J, et al. The effect of variable fuel staging transients on self-excited instabilities in a multiple-nozzle combustor[J]. Combustion and Flame, 2018, 194:472-484. [21] RICHARDS G A, JANUS M C. Characterization of oscillations during premix gas turbine combustion[J]. Journal of Engineering for Gas Turbines and Power, 1998, 120(2):294-302.
2024, Vol. 64 
