Study and development of a method for reducing blade tip clearance losses in axial carbon dioxide turbines

Relevance. The need to reduce emissions into the atmosphere and increase the efficiency of the equipment of thermal power plants, due to the possible introduction of oxygen-fuel energy complexes, the working medium of which is carbon dioxide at supercritical parameters. Aim. Evaluation of the effect of modification of the profile geometry of the blades of carbon dioxide turbines on the end losses in the inter-blade channels. Object. Nozzle unit of the first stage of a carbon dioxide turbine operating on the Alam cycle. Methods. To research and modeling the heat flow in the interblade channels of a high-temperature carbon dioxide turbine, the thermodynamic cycle parameters of Alamah and geometric characteristics of the first stage were preliminarily calculated and obtained from previous works. Numerical simulation of the flow in the interblade channels was carried out in the software package ANSYS. The grid was built in the ANSYS Meshing grid generator. Simulation was carried out in the ANSYS Fluent module. Carbon dioxide was used as a working fluid from the Fluent library with a change in the thermodynamic properties of the environment in accordance with the considered parameters. Results. The authors have determined that when using ribbing in the interblade channel due to the formation of overflows, the intensity of vortex formation is reduced. This reduces as well the energy dissipation on the surface of the walls. It was established that at modification the ribs should be made with a variable decreasing cross section, since the use of such a profile will eliminate the influence of the edge trace from the use of the rib in the channel. The use of a rib with a decreasing height (about 1 mm) and a length equal to half of the channel allowed to reduce the share of end losses in the interblade channels of a carbon dioxide high-temperature turbine by an average of 37.5%.