Mechanism Study On Contacting Friction Of Dry Gas Seal

The sealing faces of the non-contacting mechanical face seal are separated by undivided fluid films, which could reduce the friction losses and wear. The feature of the non-contacting mechanical face seal is that sealing faces do not contact each other. But for a non-contacting mechanical face seal the contact still exists. The contact between rotor and stator was attracted more and more attention. The study of non-contacting mechanical seal face contact is very important to enhance the behavior and prolong the life of seals.A new experimental structure of dry gas seal was designed in order to detecting the dry gas seal contacting between rotor and stator. The oscillation of the dry gas seal was detected by a piezoelectric sensor. After compared the latitude of typical frequency, a judgment could be made if the seal face contact existed. Some modifications of test rig were taken in order to isolate other source of the oscillation, such as the contact of contacting mechanical seal and hydraulic pressure fluctuation. The result of test showed that for seal under condition there was rubbing contact between rotor and stator. The analysis of the structure of dry gas seal suggested that contact was possible due to the relative misalignment between rotor and stator and the magnitude of the relative misalignment between rotor and stator could be a fixed value when the dry gas seal was working. The relative misalignment between rotor and stator was produced by seal manufacture, seal assemble and other factors. The Reynolds equation was solved and the gas film pressure distribution between the seal faces was obtained. The influence of the misalignment on the seal steady-state behavior and gas film dynamic behavior was analyzed. The result showed the gas film pressure on dry gas seal face was sharply increased at a small region which influenced the steady of seal face pressure. Then some measures were presented to eliminate the dry gas seal face contact. The feasibility of the measures was studied. The result showed that the modification of coning angle and adjusting operating parameter (such as shaft speed and differential pressure) could eliminate the faces contact.