Influence of the wakes of rotating spokes on the performance of a turbine exhaust diffuser

The design of turbine exhaust diffusers is still commonly based upon conservative design charts which do not consider the influence of the components installed upstream such as the last turbine stage. Based on investigations with different spoke wheels which approximate the blade wakes of the last turbine stage, the influence of a rotating bladed disc on the flow in a exhaust diffuser is presented. The pressure recovery for an annual diffuser with 15 half cone angle and the 5 mm spoke wheel used in the model test is very high and nearly independent on the rotational speed and the corresponding Strouhal number. For a 20 degrees annual diffuser, the pressure recovery increases with Strouhal number