过渡态燃料变化梯度对旋流火焰燃烧稳定性影响的数值模拟研究OA

[Objective]To investigate the mechanism by which the fuel change gradient during transition states affects combustion instability in swirl flames.[Methods]In this study,a single-stage axial swirl propane diffusion flame model combustor was numerically simulated using Large Eddy Simulation(LES)coupled with the Flamelet Generated Manifolds(FGM)combustion model.Three different fuel change gradients(k=∞,1.54,0.77)were examined to analyze the flow and combustion processes.[Results]Steady-state flow field analysis confirmed that the central recirculation zone and corner recirculation zones are critical for flame stabilization.Transient simulation results demonstrated that the fuel change gradient has a decisive influence on both the transition process and the final state:under the step transition condition(k=∞),the complete transformation of the flame morphology from an elongated to a short,drum-like shape exhibited a delay of approximately 40 ms.In all transition cases,the time-averaged temperature at the final state was higher than that of the steady control group without transition,and the temperature increased with the fuel change gradient.Specifically,under the step transition condition(k=∞),the terminal state temperature at the outlet of the combustion chamber is 100 K higher than that of the steady-state control group without transition.The energy of the dominant Proper Orthogonal Decomposition(POD)mode,which characterizes combustion instability,increased significantly with the fuel change gradient and reached its maximum under the step transition condition(k=∞).[Conclusion]The study confirms that a larger fuel change gradient introduces stronger unsteady disturbances into the combustion system,thereby significantly increasing the risk of triggering combustion instability.