Pump Working Environment And To Improve Mechanical Seal

Mechanical seals are widely used in various fields because of their excellent performance. But the operation of mechanical seals are influenced by the working environment, such as fluids containing solid particles will have a abrasive wear on the mechanical faces, and the poor fluid circulation in seal chamber will lead to poor heat dissipation so that the mechanical seal will be overheated and premature failure. As to this background, the CFD (Computational Fluid Dynamics) technology is used to simulate the operating environment condition of common mechanical seals in this paper. The influence factors on the normal operation of mechanical seals have been investigated. The methods improving the operating environment have been discussed.The fluid fields and temperature fields have been simulated as to different seal chambers, including common mechanical seal without or with flush, and the cone-shaped seal chamber. The factors impacting on the mechanical seal have been considered, such as speed, gap, flushing flows and so on.The main conclusions are as follows:(1) Through the flow fields simulation, the axial velocity close to sealing the bottom is very small in seal chamber, this will be detrimental to heat dissipation of static seal ring and the bottom region, also may result in the accumulation of solids, and axial velocity is larger at R=24mm and R=29mm as to the researched mechanical seal. The flow field is symmetrical at R=26.5mm. The entire flow field is surrounded by a large vortex, following a helical path toward the gland in the region close to the seal chamber and returning in a region close to the seal surface. The circumferential speed, because of rotating seal, in a very short distance (less than 2mm) dropps to a lower level. Heat dissipation is not good in common seal chamber according to the simulation results of the temperature field.(2) Rotating speed and the gap of seal chamber have great influence on the flow field. The operating environment of the mechanical seal is not good in the great speed. The axial velocity and radial velocity will be increased when the gap is larged, which will improve the operating environment of mechanical seals. (3) According to the simulation results of the temperature field, the temperature gradient of rotating seal is relatively small, only the region of sealing surface has large temperature gradient. The static ring has relatively large temperature gradient. The maximum temperature is at the sealing surface of the air side and the air side temperature is higher than that at the fluid-side. The maximum temperature is about 327 K(54℃) in common chamber, and about 313 K(40℃) with flush, less about 14 K(14℃). In the conical cavity, the maximum temperature is about 322 K(49℃). The heat transfer environment has been improved in the chamber with flush and tapered chamber.(4) According to the case of solid-liquid two-phase flow field simulation, as to different diameters of solid particles, the distribution of small diameter particles is centralized on the surface of mechanical seal. The distribution of large diameter particles is centralized on the surface of seal chamber, because large diameter solid particles have large centrifugal force. The maximum volume contents reach 52.7% for the diameter of 0.5mm particles in ordinary chamber, suggesting that this particle is relatively centralized serious. The maximum volume content with flush is about 45% and 36.4% in conical chamber. It is favorable for eliminating solid particles in the chamber with flush and conical chamber.For different volume contents of solid particles, the higher the volume percentage, the serious particles centralized. For the different densities of solid particles, close to the region of mechanical seal, the percentage is higher as the density decreasing. And in the region close to the chamber wall, the percentage of solid particles is higher as the density increasing for the effects of centrifugal force.(5)The chamber with flush has a better operating environment. It can be showed by the simulation results that the axial velocity increases for the effects of flush. It is beneficial for the heat dissipation and the excluding of solid particles. But the flush equipment is complicated, and the cost increases.(6) Conical chamber itself has the function of self-flushing. It is beneficial for heat dissipation and the excluding of solid particles. It is good for the operation of mechanical seals and the environment has been improved in the conical chamber.