Thermal characteristics and cooling effect for SCO2 dry gas seal with multiple dynamic groove types

The aim of this research is to investigate the impact of the dynamic groove type and coolant mass flow ratio (CMFR) on sealing performances and cooling effects of a supercritical carbon dioxide (SCO2) dry gas seal (DGS) with the newly designed external direct flush cooling structure. SCO2 DGSs are considered one of the most suitable dynamic seal options in SCO2 turbomachines due to their superior sealing performance. To address the thermal issues faced by SCO2 DGSs and the wasted shaft space in conventional cooling methods, a direct flush cooling method is proposed. Based on previous literature that mainly focused on the film region, the chamber-seal film flow field is modeled to obtain the comprehensive aerothermal characteristics of the SCO2 DGS in the current paper. The real gas properties of SCO2 are obtained by a table look-up program based on the database of the National Institute of Standards and Technology (NIST). By solving the 3D Reynolds average equations, the effects of CMFR on the cooling performance are discussed in detail for DGSs with 4 dynamic groove types. Numerical calculations are conducted with three CMFRs of 0.3, 0.6 and 0.9, applied to four dynamic groove DGSs. The obtained results indicate that, for the baseline cases, the temperature in the fluid film groove region of the Spiral groove DGS and ST groove DGS is 6.1% lower than that of the other 2 DGSs. As for the direct cooling cases, the direct flush cooling structure exhibits a good cooling effect, leading to a maximum of 42.3% temperature reduction in the film region compared to the baseline case. Under the same CMFR, ST groove and DS groove DGS exhibit better thermal characteristics in the chamber region, with the temperature coefficient 15.4% lower than that of the Spiral groove and T groove DGS. While the Spiral groove and ST groove have a better cooling effect in the film region, with the temperature being 5% lower than the other 2 DGSs.