Numerical simulation of supercritical carbon dioxide turbine thermal stress based on multiphysics coupling method

Abstract

Abstract Supercritical carbon dioxide Brayton cycle has significant advantages such as high efficiency, low cost and small size. Turbine is a key turbomachinery in the supercritical carbon dioxide Brayton cycle system. It works in the harsh environment of high pressure, high speed and high temperature gradient. The huge thermal stress is an important cause of the turbine structure failure. In this paper, the thermal stress analysis is conducted for a supercritical carbon dioxide turbine with an output of 200 kW and a rotational speed of 40,000 rpm. In order to consider the coupling relationship between the temperature field and the structural stress field, the flow-thermal-solid coupling analysis method is applied to calculate the thermal stress of the supercritical carbon dioxide turbine impeller. The results of thermal deformation and thermal stress analysis of the turbine impeller are obtained by the numerical simulation. The high stress region not only appears in the geometrical structure, but also in the region with large temperature gradient. The analysis results show that the maximum equivalent stress appears at the fillet between the turbine impeller and the seal with a value of 324 MPa. This value is less than the yield limit of the material at 500 °C. The turbine impeller structure meets the strength design requirements.