Transonic axial compressor active boundary layer control concept and its evaluation

The article presents a concept of boundary layer control in transonic axial compressors. Two methods for obtaining boundary layer control are presented. It is proposed that by combining those two methods, an efficient way of preventing turbulent boundary layer separation in transonic compressor passages can be obtained without the loss of the compressor flux. The concept, is based on the idea of removing boundary layer flows at one stage, and using this removed flux as a blowing type boundary layer control, at previous stage where lower pressures occur. This creates a loop of secondary flow between those stages preventing the boundary layer separation (especially the shock induced separation) on both stages. Two dimensional numerical analyses are performed to assess the possible passage performance (especially the diffusion factor). On the basis of two dimensional analyses, the possible performance of such compressor stage is estimated. The aerodynamic possibility of greatly increasing the axial compressing stage loadings and pressure ratios without increasing blade velocities and passage flow Mach numbers is shown. This possibility has a growing importance as the overall pressure ratio of turbojet engines and tends to rise with every next engine generation. Main conclusions are drawn, showing the possibilities for further research in the scope of this concept.

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