Design pre-study of a linear cascade test rig for turbine components

Abstract: In the modern society different gas turbine applications play a major role such as power generation and the jet engine. To achieve higher efficiency for the gas turbine cycle experimental heat-transfer and aerodynamic research is necessary. The division of Heat and Power Technology at KTH has recently invested in a linear cascade test rig for turbine components. To receive reliable results from future experiments it is important that the flow pattern in the cascade correspond to the flow pattern inside a real turbine. The test section is affected by both up- and downstream phenomenon and therefore the design of the inlet and outlet of the test section is of great importance. A Computational Fluid Dynamics (CFD) analysis of the test rig is necessary to find a suitable geometry. The aim over the cascade is to achieve periodicity, for example, when the pressure distribution is repeated over the section of blades used in the cascade.   A model of the inlet to the test section and the test section itself has been created. The domain has been discretized into finite volumes by applying a mesh and then solved with the commercial CFD package, ANSYS CFX14, to predict behavior of the fluid along the test rigs different parts.   Two different geometries of the inlet were analyzed, one with a short transaction and the other with a longer transaction. The present work indicates that a transaction with a longer duct has a more uniform velocity- and pressure profile downstream. The solution for the fluid behavior inside the test section did not converge and the results are not reliable. However the results indicate that; some periodicity is achieved over the section of blades, transonic velocities occur and a high level of vortices further downstream the cascade is located. The reason why the solution did not converge and is unreliable could be numerous, one major impact may be that the underlying mesh isn’t good enough and does not resolve the aerodynamic phenomena that occur correctly.