The unsteady flow field of a transonic axial compressor Rotor 37 was numerically simulated

and the modal information of fluid pressure and velocity were obtained by the dynamic modal decomposition method(DMD). The stability of the compressor under different working conditions was determined

the main characteristic structures of the flow field were captured

and the stall aura of the compressor was found by the modal cloud diagram. The results showed that

the near stall point and the plugging point had unstable modal orders; the maximum error between DMD frequency and pressure spectrum was 063%; with the rise of backpressure

the fluid mass in the two adjacent blades gradually moved to the leading edge of the blade

and its range was expanded; at the near stall point

with the mixing of main flow and reflux

a semi-ellipsoidal vortex was generated in the middle of the blade suction surface and the flow channel was blocked

which was the initial manifestation of a spike stall.