Study Of The Flow Structure On The Rotor-stator Interactions In A Transonic Compressor

The interaction between the moving blades of the compressor has an important influence on the performance of the compressor.The flow state of the vortex structure in the compressor flow field is very complicated,which requires an effective solution.In this paper,NASA Stage35 is used as a numerical calculation model,and LES is used to calculate the single-stage compressor.First,the structure of the main flow field is analyzed in detail.It is found that there is a detached shock wave on the leading edge of the rotor from the results of the mach number,pressure coefficient and the vorticity coefficient of the three components in S1 flow surface.The use of axial pressure gradient reveals that there are three wave sources in the flow field,which are at the trailing edge of the rotor,the leading edge and the trailing edge of the stator respectively.These wave sources cause the oscillation of the flow field in the whole passage.In this paper,Dynamic mode decomposition(DMD)and Fourier mode decomposition(FMD),two dynamic methods are used to decompose flow field parameter of S1 surface.Spectrum characteristics reveal the variation of the flow field corresponding to each mode,and the mode reflects the relationship between the structure frequency and the spatial position.The results show that there are three dominant frequencies in the modal diagrams obtained by the two decomposition methods.The first order corresponds to the Blade Passing Frequency(BPF)of the rotor blade,which is the dominant frequency of the vortex in the passage.The second and third order frequencies are denoted as high frequency harmonics,which appear as small-scale disturbances in space.Then,the three-dimensional flow field of the stator passage is analyzed,and the three-dimensional Q criterion is used to analyze the main vortex structure in the stator passage.The upstream wake periodic shedding from trailing edge of the rotor and cut by the leading edge of the stator.There exists in energy loss due to part of the root and the horseshoe vortex interaction.Horseshoe vortices also exist on the top of the stator passage.The tip of the blade is not only affected by horseshoe vortex,but also induced by small-scale induced vortices generated by the interaction between the upstream rotor tip clearance leakage flow and the endwall boundary layer.The unsteady vortex structure is used to establish the structural characteristics of dominant vortices in the stator passage.Finally,the three-dimensional flow field of the stator passage was treated by Dynamic mode decomposition(DMD)and Fourier mode decomposition(FMD).The dominant frequency in the modal diagram was consistent with the S1 flow surface.It shows that S1 surface can reflect the main field structure.The first-order modalities show that the rotor wake periodically enters the stator passages and is mainly stretched during the flow.The second and third orders represent small-scale vortex shedding from the leading edge of the stator and the top of the blade.To sum up,this article has two innovations.First,the three vibration wave sources were found using pressure gradient,at the trailing edge,the leading edge and the trailing edge of the passage respectively.Secondly,the three-dimensional flow field is decomposed by Dynamic modal decomposition(DMD)and Fourier modal decomposition(FMD)to study the spectral characteristics of the flow field and the flow structure correspond with the modes.It provides a new idea for the research of internal flow.