In order to reveal the relationship between the melting of pulse separation device (PSD) and the pressure oscillation

several melting moments were selected for research. Large eddy simulation (LES) was carried out for the numerical simulation of II pulse flow field

and the pressure-time curve and fast Fourier transformation (FFT) results were obtained successfully.The analysis results show that the additional disturbance in the flow field generated by opening PSD when the Ⅱ pulse is working

and the acceleration of interstage narrow channel

are the main factors to obstacle vortex shedding caused by boundary layer separation. In the early ignition

the double pulse motor (DPM)is prone to slight pressure oscillation. With the PSD melting

the whole flow field becomes more and more stabilized.