Numerical Study on Rotor Cooling of Turbine in Supercritical Carbon Dioxide Cycle

The supercritical carbon dioxide cycle is a Brayton cycle with great application prospects. As a key equipment in this cycle, the turbine machinery usually adopts a dry gas seal as the sealing method between the cylinder and sliding bearing to reduce the leakage of carbon dioxide. In this paper, the numerical model of supercritical carbon dioxide turbine rotor cooling is established, and the grid independence is verified. The effects of inlet temperature and flow rate of dry gas seal and leakage flow rate from cylinder to dry gas seal at the high-temperature inlet side of a turbine upon rotor cooling are studied. The effects of inlet temperature T _in and flow rate Q _v of sealing gas in a dry gas seal and leakage mass flow rate Q _m from a cylinder to dry gas seal on pressure loss, outlet flow distribution, exhaust temperature, and rotor temperature distribution are analyzed. As a result, it can be found that with the increase of the inlet flow rate of dry gas seal gas and the leakage flow rate from cylinder to dry gas seal, the pressure difference between the inlet and outlet of each seal gas increases. When the inlet flow rate of dry gas seal gas ranges from 300 N m³/h to 900 N m³/h, with the leakage flow from cylinder to dry gas seal increasing from 1.3 kg/s to 2.08 kg/s, the pressure difference between inlet and outlet of each seal gas increases by 7.9% to 13.4%. The pressure difference between the inlet and outlet of each seal gas decreases with the increase of the inlet temperature of dry gas seal gas. When the inlet flow rate of the seal gas of the dry gas seal is 300 N m³/h and the leakage flow rate from cylinder to dry gas seal is 2.08 kg/s, the inlet temperature of seal gas increases from 100 to 150 °C, and the flow distribution at the outlet is basically unchanged. The research provides theoretical reference for rotor cooling design of a supercritical carbon dioxide turbine.