Numerical Simulation Study on the Dynamics of Bluff-Body Flames under Oxygen-Lean Conditions

Abstract

As modern aeroengine combustors advance towards high temperatures, afterburners are inevitably affected by diminished oxygen content in incoming flows, thus affecting combustion efficiency, instability, and flammability limits. In this study, the dynamic combustion characteristics of V-shaped bluff body-stabilised diffusion flames were investigated using a large eddy simulation method with an oxygen mass fraction range of 14–23% and temperatures ranging from 900 to 1100 K. The results show the significant effects of oxygen content and inflow temperature on the flame/flow behaviours downstream of the bluff-body flame holder. In a separated shear layer, two distinct modes of flow/flame shedding are observed when varying the oxygen content and inflow temperature. The results show that BVK instability governs the far-field wake flow/flame features, whereas the oxygen concentration and temperature significantly affect their oscillation amplitudes. In addition, variations in the incoming oxygen content and temperature shift the axial position of the transition from KH instability to BVK instability. Finally, a spectral analysis is conducted to investigate the characteristics of pressure and heat release pulsations under different scenarios. This study highlights the importance of oxygen content on the combustion dynamics of bluff body-stabilised diffusion flames at various temperatures, which is essential for optimising combustion efficiency and stability in practical applications.

Exploring Vortex–Flame Interactions and Combustion Dynamics in Bluff Body-Stabilized Diffusion Flames: Effects of Incoming Flow Velocity and Oxygen Content

“…In order to confirm the accuracy of the model, Deng et al [32] conducted model validation under the experimental conditions in reference [43], using the same numerical model used in this study. Figure 4 compares the calculated results and experimental data for different radial positions of reactive and nonreactive flows, and the results are consistent.…”

“…In order to confirm the accuracy of the model, Deng et al [32] conducted model validation under the experimental conditions in reference [43], using the same numerical model used in this study. Figure 4 Comparison between numerical simulation and experimental results [32]. Black dots/black square: experimental data; red line: numerical simulation results.…”

“…Their research also demonstrated that as the temperature ratio changes, the flame transitions between BVK and KH instabilities. Deng et al [32] used numerical simulation to study the effects of incoming temperature and oxygen content on the flame instability of a bluff, and found that the incoming temperature and oxygen content significantly affect the position of the interconversion between the KH instability and the BVK instability.…”

“…Figure 4. Comparison between numerical simulation and experimental results[32]. Black dots/black square: experimental data; red line: numerical simulation results.…”

Impact of Oxygen Content on Flame Dynamics in a Non-Premixed Gas Turbine Model Combustor

“…With the increasing performance requirements of combustion chambers and increasingly stringent emission regulations [1][2][3][4], gas turbine combustion chambers are required to operate at high temperature and high pressure [5][6][7][8][9], which usually leads to the occurrence of combustion instability [10][11][12][13][14][15][16][17]. The combustion instability phenomenon will be accompanied by pressure pulsation and exothermic pulsation in the flow field inside the combustion chamber [18][19][20][21], which leads to vibration of the combustion chamber components and affects the safe operation of the engine [22][23][24]. In order to solve the adverse effects of combustion instability on the combustion chamber, it is necessary to study the combustion instability phenomenon to prevent the combustion instability phenomenon from leading to a decrease in the combustion chamber's stable operation time.…”