| Various vortices may emerge during gas flow through compressor cascade.And the characteristics of whole flow field are under the domination of the formation,evolution and development of the secondary flow vortices.As the load of the compressor improved,the internal flow presents significant three-dimensional characteristics,as the percentage of secondary flow loss goes higher.In order to uncover the mechanism of the internal flow in a highly loaded compressor cascade,the vortices as well as the interactive relationships of them were analyzed and discussed in this paper.Firstly,numerical simulations have been conducted by different turbulence models in NUMECA software.For the sake of reliability of the simulation,the numerical results were compared with experimental data.Secondly,the results of numerical were analyzed with the method of topological analysis,then the three-dimensional vortex structure inside passage of cascade is presented.Besides,in order to explore the mechanism of unsteady flow in a highly loaded compressor cascade with large positive incidence,the separation vortices evolution law and the effect of the vortices on flow field parameters were analyzed with CFX software and the method of topological analysis.The analysis suggest that k-ε(EWF) is the most accurate turbulence model at the simulation conditions of this paper.Among the nine vortices discovered,passage vortex has the most powerful organization effect.Finally,the flow structure presents a profile of coexistence of passage vortex with concentrated shed vortex.Two dimensional unsteady numerical investigation show that,there are two kinds of vortices at large positive incidence,including suction surface separation vortex and trailing edge shedding vortex.The vortex-shedding frequence of the suction surface separation vortex and trailing edge shedding vortex is 104.7Hz and 156.0Hz,respectively.The separation vortex may restrain and merge puny vortices,and makes the aerodynamic loading of blade rise partially. |
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