Thermal Fluid-Solid Interaction Model and Experimental Validation for Hydrostatic Mechanical Face Seals

Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants.More accurate models on the operating mechanism of the seals are needed to help improve their performance.The thermal fluid–solid interaction（TFSI）mechanism of the hydrostatic seal is investigated in this study.Numerical models of the flow field and seal assembly are developed.Based on the mechanism for the continuity condition of the physical quantities at the fluid–solid interface,an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method.Dynamic mesh technology is adopted to adapt to the changing boundary shape.Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure.The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data.Using the TFSI model,the behavior of the seal is presented,including mechanical and thermal deformation,and the temperature field.The influences of the rotating speed and differential pressure of the sealing device on the temperature field,which occur widely in the actual use of the seal,are studied.This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals,and the model is validated by full-sized experiments.

A NUMERICAL SIMULATION OF 3-D INNER FLOW IN UP-STREAM PUMPING MECHANICAL SEAL

Numerical simulation of 3-D inner flow between Up-stream Pumping Mechanical Face Seals （UPMFS） faces was initially done by CFD software, which made the flow visualization come true. Simulation results directly discover the action of hydrodynamic lubrication, and by comparison with that of Conventional Mechanic Face Seals （CMFS）, the advantage over bigger bearing capability, less friction and much less leakage are explained clearly. Otherwise there are also some different ideas and results from precedent analysis and computational research results： dynamic and static pressure profiles can be obtained respectively instead of the analytic total pressure distribution only, pressure distribution is nonlinear, while always be solved as linear, lower pressure is observed at the area of inner diameter caused by the grooves, but its possible cavitations effects to the performance of UPMFS still need further study.

Friction and wear behavior of different seal materials under water-lubricated conditions

The shaft mechanical face seal in a high-speed turbopump of a liquid rocket engine often operates under extremely harsh conditions.For example,a low-temperature and low-viscosity fluid(such as liquid oxygen or liquid hydrogen)is used as a lubricant.The performance of the seal rings,especially the friction and wear behavior,directly determines whether the seal functions normal.In this study,the friction and wear behavior of several ring materials are tested using a pin-on-disk tribo-tester,and the wear morphology of the ring is investigated.The friction coefficients(COFs)and mass-wear rates under dry-friction and water-lubricated conditions,which are used to simulate low-viscosity conditions,are obtained.The results show that at a pressure-velocity(PV)value of 2.4 MPa-(m/s),the COF between the copper graphite(stator)and copper-chrome alloy disk(rotor)is low(with a value of 0.18)under the dry-friction conditions,and the 5-min wear mass of the copper graphite is approximately 2 mg.Under the water-lubricated conditions,compared with other materials(such as copper-chrome alloy,S07 steel,alumina ceramic coating,and nickel-based calcium fluoride),the S07 steel with a diamond-like carbon film is preferred for use in a high-speed turbopump under extreme conditions.The results of this study can provide theoretical and experimental guidance in the design of mechanical face seals in liquid rocket engines.

Truncated separation method for characterizing and reconstructing bi-Gaussian stratified surfaces

Existing ISO segmented and continuous separation methods for differentiating the two components contained within a bi-Gaussian stratified surface were developed based on the fit of the probability material ratio curve.In the present study,because of the significant effect of the plateau component on tribological behavior such as asperity contact,wear and friction,a truncated separation method is proposed based on the truncation of the upper Gaussian component defined by zero skewness.The three separation methods are applied to real worn surfaces.Surface-separation and surface-reconstruction results show that the truncated method accurately captures the upper component identically to the ISO and continuous ones.The identification of the lower component characteristics requires performing a curve fit procedure on the data left after truncation.However,the truncated method fails in identifying the upper component when the material ratio of the transition is less than 9％.