For laser machining of porous end face mechanical seals for centrifugal pumps, the membrane pressure distribution of the seal face is obtained by solving the Reynolds equation using the finite element method. The force deformation, end leakage, and liquid film stiffness of the dynamic and static seal rings with different restraints and different structures are calculated. The sealing performance parameters such as the Rigidity Ratio and the Rigidity Ratio were analyzed to analyze the effect of deformation on the sealing performance. The results show that the deformation of the end face has a great influence on the sealing performance, which will lead to an increase in leakage and a decrease in the Rigidity Ratio. The constraint of the sealing ring plays an important role in the deformation. Selecting appropriate constraints can reduce the angle of the sealing face and improve the liquid film. Stiffness enhances sealing stability.
1 Theoretical model
Figure 1 LST-MS geometry and open-end geometry
Figure 1 shows the structure and end geometry of the LST-MS, in which the surface of the stationary ring is laser-processed to form spherical micro-holes. The micro-holes are radially distributed and symmetrically distributed at equal intervals in the circumferential direction. Assume that the sealing surface does not directly contact, there is a certain thickness, and the liquid film pressure does not change in the direction of the liquid film thickness. The sealing fluid is Newtonian fluid and the viscosity remains unchanged. Irrespective of the influence of the curvature of the sealing surface, the steady state of the liquid film pressure distribution The control equation, that is, the Reynolds equation is:
2 Calculation Results and Analysis
2.1 Structure/Constraint
Figure 2 Static ring structure and its constraint diagram
Two structures of the stationary ring shown in Fig. 2 were selected to study the deformation of LST-MS and its effect on the sealing performance.
The size and structure of the static ring of the structure 1-3 remain unchanged. Only the position of the restraint and the B-shaped ring is different, so as to study the influence of different restraint modes on the deformation of the seal ring, wherein the position and structure of the B-shaped ring in FIG. 2(a). "Differently, the "/" side in Figure 2(b) is axially constrained, and the 5-6 sides in Figure 2(C) are axially constrained.
The static section of the structure is rectangular (Fig. 2(d)). The back of the stationary ring is axially constrained. It is used to study the effect of the seal ring structure on the deformation of the ring. The O-ring and the anti-rotation pin and drive pin hole are ignored during calculation. Influencing, the spring force is regarded as uniform load, neglecting the influence of gravity and centrifugal force.
2.2 Calculation Results and Analysis
The prescribed compression deformation is positive, and the tensile deformation is negative; when the ring face is clockwise, the rotation angle is negative; when the counterclockwise rotation occurs, the rotation angle is positive; the static ring face rotation is defined as the opposite of the moving ring. The figure shows the deformation of the moving and stationary rings at P0 = 0.5 MPa. The deformation values ​​of the moving and stationary rings at different P0 are shown in Table 1 and Table 2. It can be seen that the LST-MS end faces are no longer deformed. It is a parallel plane, and the pressure generated by the dynamic pressure effect of the micro-holes makes the end surface concave curved surface.From Figure 3, it can also be seen that the moving ring with the same structure and operating parameters, due to the static ring structure and constraints Differently, the size of the deformation is not the same, and under different pressures on the outside diameter, the deformation of the moving ring between the structures is not the same, because the static modulus of the ring is larger than the moving ring, so the static ring The deformation value is smaller than that of the moving ring.From Table 1 and Table 2, it can be seen that in the four structures, the axial deformation value of the ring 3 of the structure 3 is smaller than that of the other structures, but the static ring deformation value is smaller than that of the other structures. The other structures are much larger, because the constrained 5-6 sides of the structure 3 are located at the inner diameter, and the P0 value is high, so that the imbalance between the pressures on both sides of the outer ring at the outer diameter causes a large deformation; at the same time, the pressure P0 The moment formed increases with the increase of P0, so the rotation angle of structure 3 also changes from a negative value to a positive value. It can also be seen from the table that the static rings of structures 2, 3, and 4 are not deformed because the back surface is constrained, and the position of the restraint is not the same, and the size of the deformation is not the same. It can be seen that as the pressure increases, both the deformation and the corner increase.
Fig. 3 Schematic diagram of force deformation of different structures/restricted seal rings (moving ring *1000 times, static ring *10000 times)
Table 1 Dynamic surface deformation
Table 2 Static ring end face deformation
Affected by the deformation of the end face, the performance parameters of the LST-MS have also changed, as shown in Table 3. It can be seen that, considering the deformation of the end face, the leakage amount is significantly increased. Although the liquid film stiffness of the structures 2 and 4 is increased, considering the rigidity-to-loss ratio, considering the deformation, the sealing performance is reduced. In summary, Structure 2 is the smallest leak in the four structures, but the ratio of maximum to minimum leakage is high. Therefore, considering the pressure deformation only, the LST-MS with Structure 2 has the best overall sealing performance. Based on this, it can be seen that optimizing the design of LST-MS by selecting appropriate constraints to improve the working stability of the seal and prolonging the service life of the seal is not only necessary but also feasible.
Table 3 Effect of deformation on sealing performance of LST-MS
3 Conclusion
(1) Force deformation has an important influence on the sealing performance of LST-MS. Deformation leads to an increase in leakage and a decrease in the ratio of rigidity to leakage, thus deteriorating the sealing performance.
(2) The position of the seal ring of the stationary ring and the constrained position on the back side have an impact on the deformation of the moving and static rings; selecting appropriate constraints and positioning the auxiliary sealing ring can control the deformation moment, reduce the rotation angle of the sealing surface, and increase Sealed the ratio of just leaked to improve its stability.
(3) There is no inevitable correspondence between the size of the seal deformation and its working performance. That is, the minimum deformation of the sealing ring does not necessarily correspond to the optimal sealing performance. It should be analyzed and optimized according to the specific operating conditions, structure and material pairing.
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