Hydrostatic and hydrodynamic jet flows and liquid film formation-leakage control characteristics in mechanical seals

To address problems of excessive temperature rise, severe vaporization and cavitation, and unacceptable leakage in mechanical seals under ultra-high-speed and cryogenic conditions of rocket turbopumps, a novel mechanical seal (JDSC) integrating upstream pumping spiral grooves, feed holes, equalizing pressure grooves, and centrifugal spiral channels is proposed. By coupling Lee boiling model, ZGB cavitation model, and SST k-ω turbulence model, a three-dimensional flow and heat transfer numerical model capable of accurately capturing vaporization and cavitation phase change is established, and experimental and numerical verification is performed from four aspects: feed hole jet flow, face hydrodynamic flow, global heat generation and transfer, and phase change phenomena. Research shows that externally pressurized hydrostatic fluid generates hydrostatic jet flow and ordered blockage vortices in feed holes and equalizing pressure grooves; centrifugal spiral channels and upstream pumping spiral grooves induce hydrodynamic centrifugal and pumping effect, dividing face fluid into hydrodynamic centrifugal and pumping jets. These jet flows carry face-generated viscous heat rapidly into seal chamber and alter classical Taylor vortex pattern in seal chamber, promoting thorough mixing of cold and hot fluids and significantly enhancing heat transfer. Hydrostatic jet flow, hydrodynamic centrifugal and pumping jets form a mechanism of full-path cooling, hybrid hydrostatic-hydrodynamic pressure buildup, and phase suppression. Compared with classic upstream and downstream pumping seals, phase change area ratio can be reduced by over 77% and 66% in the novel seal, respectively. Meanwhile, hydrodynamic centrifugal and pumping jets constitute a new leakage control path, and the leakage otherwise caused by the externally pressurized fluid is suppressed, resulting in an 18% reduction in leakage rate compared with the JSC seal.