Flow in an Annular Axial-Radial Diffuser

The subject-matter of interest is an annular, axial-radial diffuser with a small relative length. The diffuser is intended for the outlet of flow from the last turbine stage. Investigated are possibilities of a theoretical solution to the flow in a diffuser, based on a potential flow in the stream core and on the viscous flow in the boundary layer. Compared are two methods of solution to the potential flow in the given diffuser: a numerical calculation and a method of electrical analogy. By the method of calculation investigated are the influence of compressibility of the flowing medium upon the potential flow, and the influence of viscosity within the boundary layer. Given are the main data about a wind tunnel necessary for the research into the diffusers and the exhaust chambers, and experimental information gained in measurements taken on the diffuser. Comparison is made about the results of experiments and calculations. Pointed out is the influence of the exhaust chamber upon the diffuser. In an operating turbine, the flow in a diffuser is significantly influenced by the regime of flow in the last stage. Given are the results of the experimental research into the velocity field at the inlet into the diffuser depending on the aerodynamic loading of the last stage, and described are flow conditions within the diffuser with the turbine running idle when the last stage is in windage operation.