STUDY OF THE EFFECT OF TURBULENCE PROMOTERS IN CIRCULAR COOLING CHANNELS

摘要

A numerical analysis of a gas turbine first stage bucket with internal cooling (model MS7001E) is presented. The internal cooling system consists of 13 cylindrical channels with turbulent promoters (ribs), which are implemented in order to achieve temperature decrements inside the body blade. Three different geometrics (square, triangular and semi-circular cross-section) are studied. Each configuration is analyzed having full or half ribs. These are placed inside the cooling channels. The effects generated by the aspect ratio variation between rib pitch and rib height (P/e), for a constant aspect ratio given by ribs height and hydraulic diameter (e/D_h) are considered. The numerical simulation was developed using finite volume method, by means of commercial software based on computational fluid dynamics (CFD). Each one of the models generated for each study case was built in a 3D model, including the platform and airfoil of the blade. The models consider the effects generated by the hot combustion gases are flowing around the blade and the coolant flow is flowing inside the cooling channels. The study includes the solution of the conjugate heat transfer. The results show that the cooling channels with squared and triangular full-ribs present better cooling effects inside the body blade, reducing the temperature until 10°C at some point in the blade. However, these configurations produce a pressure drop from 3 to 4 times higher than cooling channels without ribs. The half ribs produce lesser temperature decrement, having smaller pressure drop. On other hand, the aspect ratio (P/e) has only effects on the pressure drop.