To improve hydrodynamic stability in combustor, an unsteady flow analysis method is needed, the proper-orthogonal-decomposition (POD) method based on a large eddy simulation (LES) unsteady flow field and experimental verification were used to analyse and evaluate the influence of the precession vortex core (PVC) motion law on the pulsation downstream of different swirler configurations. The pulsation results of the unsteady simulation are in good agreement with the experimental results, and both show that the pulsation quantity of Case 1 is maximum. The analysis results by POD show that the pulsation energy is mainly concentrated in the first two modes. The results of motion state, regularity of the time coefficient and frequency characteristics also show that the characteristics of PVC in the combustor are consistent with those in modes 1 and 2. There is an optimum value of swirl number, which is 0.72, for which the influence on the flow field's stability is minimum. In addition, the stability of the airfoil vane is higher than that of the straight vane. The mean flow field and the coherent flow field in the pulsation flow field of Case 3 are most favourable to combustion stability, and the unstable factors of the transition flow field and the turbulent flow field are the smallest in shape and energy. The experimental results prove that there is no typical frequency of pulsation within 5000 Hz in Case 3.

Large eddy simulation was employed to simulate the effects of different vane angles of the primary and pilot stages on the ignition process of a combustor under normal temperature and pressure conditions. The simulation results of different vane angles of the pilot stage were then verified experimentally. Kernel initiation and flame propagation in the cases of ignition success and failure were analysed. It was found that in the ignition failure case, the flame kernels are confined to the downstream zones of the venturi and cannot propagate radially, and almost no negative displacement exists in the axial direction. However, in the ignition success case, sub-fire kernels are always present outside the radial boundary of the primary stage. Five ignition modes were finally proposed: (I1) typical ignition, (I2) relatively high-speed ignition, (I3) single-kernel alternating dominant, (I4) main kernel dominant, and (I5) dual-kernel dominant modes. Using high-speed photography, the flame shape changes and ignition characteristics in the cases of successful and failed ignition with different pilot-stage vane angles were investigated.