Investigations of the optimum form of the outer meridional contour in the region of the final stage of the L.P. cylinder of a steam turbine of great output were carried out on a three-stage multishaft steam turbine, with actual steam parameters. The final stage was provided with a separate shaft having a hydraulic brake. The output of the final stage was measured and, besides, detailed investigations of the flow in control cross-sections of the stage as well as on the outer contour under investigation were carried out.

The flow pattern observed has shown the sources of losses taking place in a flow around an outer contour of complicated form.

The investigations made it possible to select the optimum form of the meridional contour ensuring the highest efficiency of the final stage.