| The reliability of shaft end seal plays an important role in assuring the safety and service life of the rotating machinery, and achieving the maximization of economic benefit.In recent years,with the rapid development of sealing technology, a new kind of hydrodynamic mechanical seal,named self-pumping mechanical seal,was put forward based on the principle of centrifugal pump.Compared with the existing hydrodynamic mechanical seal, the self-pumping seal has the advantages of good sealing performance, strong anti-interference ability, simple structure and little installing space. Besides, it has no require for buffer fluid supply auxiliary system.In this thesis, the research object was self-pumping mechanical seal which dynamic pressure grooves were distributed on the rotating ring and liquid inlet groove was arranged on stationary ring, and its sealing face flow field was investigated by numerical simulation based on Fluent, the influence of groove’s structural parameters and working parameters on seal performances were discussed and the structural parameters were optimized. Finally, the characteristics of the leakage were studied through experiments.The main research work and conclusions are as follows:(1)The whole structure, seal face structure, working principle, main performance parameters of the self-pumping mechanical seal were introduced, and the force condition of rotating ring was analyzed.The analysis result showed that the self-pumping mechanical seal had self regulating ability at work, when it was disturbed, the seal can quickly restore to the balance position.(2)The sealing face flow field was numerically simulated by Fluent and the influence of groove’s structural parameters and working parameters on the seal performance, including helix angle α, groove number Ng, the spiral groove depth Hg, annular groove depth H, annular groove width L, the ratio of groove length and dam length γ, the ratio of groove width and ridge width d,the pressure p and the rotate speed n, were discussed. The influence degree of groove’s structural parameters and working parameters were also analyzed based on a large number of orthogonal test data. The results showed that Ng, γ, d, p have a significant effect on the opening force FO and the leakage rate Q. L have effects on FO and Q. However, α, Hg, H have relatively little effect on FOand Q. Besides, n have a significant effect on Q, but it has the opposite effect on FO.(3)According to the optimum design theory, a mathematical model for the optimization design of self-pumping mechanical seal face structure was established. The methods of using partial orthogonal polynomial regression design and programming solver were applied to solve the model under a special working condition.The optimal combination of the groove structure parameters was obtained when p=0.5MPa, n=4000rpm and the corresponding values of the structural parameters were α=22°, Ng=8, γ=0.48, d=0.7, H=0.5mm, Hg=50μm, L=2mm. And its sealing performance was the best.(4) The leakage characteristics experiment of the self-pumping mechanical seal was conducted based on the mechanical seal performance test device. Comparing the leakage rate from experiments with that of numerical simulation, the results showed that, the experimental results are in agreement with the numerical simulation results in a certain error range.It meanedthe liquid film calculation model of self pumping mechanical seal was validated correctly, and had certain reference value. |
