An approximate method of calculating three-dimensional, compressible flow in axial turbomachines

摘要

The two principal existing methods of calculating axially-symmetric compressible flow in turbomachines are: (1) a simplified one-dimensional analysis, and (2) numerical methods using the complete or linearized flow equations. The first is not satisfactory for multi-stage turbines with appreciable wall divergence; the second is very tedious and time consuming. The purpose of this investigation is to extend the approximate methods, successfully used in calculating incompressible flow in compressors with constant blade height, to the analysis of compressible flow in turbomachines with variable blade height. Assuming that the blades can be completely defined by the exit flow angle, and neglecting the influence of downstream blades, the analysis is made considering the flow between successive blade rows only. With these restrictions, subsonic and isentropic supersonic flow patterns can be determined for arbitrary boundary shapes as long as separation does not occur. Average losses can be accounted for by the use of a polytropic law, and the effect of radial variations in stagnation temperature can be included without difficulty. Examples illustrating the flexibility and practical value of the iteration method, and the rapid convergence of successive solutions are given.