The influence of quantity and distribution of cooling channels of turbine elements on level of stresses in the protective layer TBC and the efficiency of cooling

摘要

The modern turbine engines are designed to operate in the temperatures of combustion gases, of order 1800-2000 K, which considerably exceed admissible values for applied metals. Therefore turbine elements should be protected against raw thermal environment to keep the acceptable lifetime and standards of safety. There are two ways of protection: (1) different cooling systems of the turbine elements and (2) thermal barrier coatings (TBC). As an example of the turbine element a nozzle guide vane was analysed. It was protected by TBC layer of 0.1 mm thickness and several systems of cylindrical cooling channels. Different numbers of the cooling channels, their distribution as well as diameters were considered. The aim of the work was estimation of: the efficiency of cooling vanes, the level of Mises stresses in the vane and the influence of the protective layer TBC on the thermal response of the turbine element. All considered variants were compared. In the simulation real boundary conditions were applied, i.e. the temperature of combustion gases was 1600 K and inlet velocity of cooling gas 1.23 m/s. For delimitation of temperature fields the Computational Fluid Dynamics (CFD) analysis was applied, using the programme ANSYS Fluent. The turbulence model of flow k- was applied in numerical calculations and the temperature distributions were established. Computational Structural Mechanics (CSM) analysis was done with ABAQUS, taking into account temperature fields. It lead to calculation of the stress distributions in the blade and in the protective layer TBC. The most important stress concentrations took place near cooling holes, which had significant influence on endurance of the turbine elements.