STEAM TURBINE AXIAL EXHAUST DIFFUSER INVESTIGATION USING A TEST RIG AND ITS NUMERICAL MODEL

Exhaust casings are one of the most important steam turbine components. The main purpose of the exhaust casing is to increase the last stage enthalpy drop, which results in an increase of the whole turbine output. It plays a significant role especially in turbines with lower outputs and in turbines whose condenser is cooled by air. In such cases, the exhaust casings with an axial diffuser is usually used. This paper deals with the investigation of the axial diffuser outlet part based on experimental measurements performed on a test rig installed in a wind tunnel in the Doosan Skoda Power laboratories and numerical simulations. The first part of the paper is about the general issues appearing the exhaust diffusers. Then, the design of the experimental test rig which aim is to simulate the flow conditions in real turbines is described. The last part of the paper is about experimental measurement as well as numerical results. The main observed phenomenon which is the effect of the circumferential angle on the inlet of the diffuser is described on different designs which were tested from the static pressure recovery factor point of view. For measuring flow parameters, a static wall pressure measurement was used together with multi-hole pneumatic probes. For numerical simulations, the commercial code ANSYS CFX 18.2 was used.