Unsteady characteristic in integrated flameholder combustion flow field

Integrated flameholder is widely used in advanced combustors. The unsteady characteristic of integrated flameholder combustion flow fields is critical. In this study, experiments and numerical simulation were carried out for the inspection of methods and analysis of their unsteady characteristic. By comparison of experimental and numerical results in two cases, the relative error is found to be about 10%.The comparative results denote that the large eddy simulation-transported probability density function method has positive performance in the calculation of pressure fluctuation in integrated flameholder combustion fields. After evaluating the numerical methods, the velocity and temperature field were analyzed as the basis of further unsteady analysis. Then, the fast Fourier transform (FFT) and empirical mode decomposition (EMD) were applied to analyze the velocity fluctuation and pressure fluctuation in the combustion flow field. The distribution and tendency of fluctuation frequency and amplitude are related to various factors. The velocity fluctuation frequency is low near the central axis, and the velocity fluctuation amplitude is high on both sides of the central axis; the pressure fluctuation frequency is low on either side of the recirculation zone, and the pressure fluctuation amplitude gradually increases downstream as the flame develops. Besides, the result of unsteady analysis demonstrates that FFT is suitable for the analysis of fluctuation amplitude, and the combination of EMD and FFT can give more information on the fluctuation frequency from complex nonlinear data.