Research The Characteristics Of The Large Motor Sliding Bearing Labyrinth Seal Resisting Negative Pressure

Labyrinth seal is a kind of non-contact seal which can effectively avoid the contact and friction between rotor and stator,which also has stable sealing performance and long service life. It has been widely used in rotating machinery such as large motor, compressor and blower. With the development of national economy and the implementation of energy policy,the equipment of cement, mining, steel and electric power industries become increasingly larger. Thus, the demand of large motor also gradually increase. However, due to the large motor internal cooling fan, local large negative pressure area is formed on the end surface in the sliding bearing, which can lead to lubricating oil leakage. Owing to the effect of the negative pressure, lubrication oil in the bearing chamber climb along the axial direction of the motor after long-term operation, the lubricating oil is adsorbed on the motor stator coil,leading to the damage of coil insulating layer. The safe running of the motor can not be guaranteed, To ensure the reliability of the motor system, a higher request that sliding bearing sealing bear negative pressure is put forward. At present, leakage of lubricating oil often occurs to sliding bearing because of negative pressure, so the ability to bear negative pressure of sealing structure needs to be further studied.The main works of this thesis are as following:(1) This thesis briefly review typical labyrinth sealing leakage formula, and proposes a new iterative calculation method for labyrinth sealing in which introduces positive pressure air flow.(2) Analysis the flow field analysis method of labyrinth seals, and according to the motor sliding bearing shaft end of the labyrinth seal. A three dimensional model was built by finite element method. The flow field, pressure field in the labyrinth chamber and leakage characteristic were studied by using CFD fluid calculation software Fluent. Through the control of a single variable method, the labyrinth seal was analyzed multiple sets of simulation data, then to come to a conclusion, the effects of the external negative pressure,speed and labyrinth geometry size and other factors on the influence of the sealing chamber pressure and the labyrinth leakage. On the basis of the simulation of straight-though labyrinth,further optimization of sealing structure to anti negative pressure had been designed, this come to conclusion of the effects on the seal leakage of the introduction of positive pressure airflow, it will provide basis theoretical calculation on the motor of straight-through labyrinth seal structure design.(3) Redesigned sliding bearing structure for motor sliding bearing oil phenomenon because of the negative pressure, analyzing the reasons for its leakage, combined with different sealing structure principle and influence factors of the sealing performance. Build a test bench which can simulate different negative pressure, different speed, positive pressure conditions work. Through the experiments, to explore the seal structure of negative pressure resistance performance and the optimization test of the labyrinth sealing anti negative pressure, this had verified the rationality of straight-through labyrinth seal introduction positive pressure optimization design.