Study On The Performance Of Liquid Film Sealing Applicable To Power-Law Fluid Spiral Structure

Liquid film seal with spiral structure which contains spiral groove upstream pumping liquid mechanical seal and helical seal are widely used in rotating machines for the petrochemical industry because of its advantages of performance.Considering that most of the liquid media show the characteristics of non-newtonian fluid in petrochemical industry.In order to get more in line with the performance parameters of the liquid film seal with spiral structure in the actual working conditions while sealing power-law fluid,so as to provide a theoretical basis for design and application of the seal.In this paper the performance of spiral groove upstream pumping liquid mechanical seal and helical seal were analyzed respectively while sealing power-law fluid,where the theoretical analysis and numerical simulation were adopted.1.For the spiral groove upstream pumping liquid mechanical seal:(1)The end effect which means pressure loss at the inlet where the liquid is pumped into the spiral groove was considered,resulting in the pressure at the spiral groove root being modified in the equation of the liquid film of pressure distribution which was derived by narrow theory.Then the modified approximate analytical method has been obtained.Compared with the results by the uncorrected analytical method,and the rationality of approximate analytical method has been verified.Furthermore,the influence of the end effect on the performance of spiral groove upstream pumping liquid mechanical seal with different geometric parameters and operating parameters has been analyzed.The results showed that the influence of the end effect on the performance of the seal can be neglected while the land-to-groove ratio>0.8,the spiral groove depth ? 25?m,the shaft speed<7000r/min,and the spiral angle,the value of(Rg-Ri)/(Ro-Ri),the seal pressure difference,the balance film thickness in any case.(2)Taken sealing model with weak end effect as the research object,the Reynolds equation and the two dimensional steady flow flowing equation of newtonian fluid had been respectively replaced by the Reynolds equation and the flowing equation of power-law fluid based on Muijderman's pressure governing equation for newtonian liquid lubricated bearing.Then the approximate analytic analysis on the performance of the spiral groove liquid film mechanical seal being applied to seal power-law fluid has been obtained.Compared with the results by the uncorrected analytical method,and the rationality of approximate analytical method has been verified.Furthermore,the influence of the seal with different physical property parameters,operating parameters and geometric parameters has been analyzed.The results showed that the flow behavior index,the consistency coefficient,the seal pressure difference,the shaft speed,the balance film thickness,the spiral groove depth,the spiral angle,the land-to-groove ratio and the value of(Rg-Ri)/(Ro-Ri)both have significant effects on the opening force and the leakage.2.For the helical seal:Taken helical-shaft type helical seal as the research object,the velocity distribution equation of the two dimensional steady flow of newtonian fluid had been replaced by the velocity distribution equation of the two dimensional steady flow of power-law fluid based on Crease's sealing capability equation for newtonian liquid lubricated helical seal.Then the approximate analytic analysis on the performance of the helical seal being applied to seal power-law fluid has been obtained.Compared with the results by the uncorrected analytical method,and the rationality of approximate analytical method has been verified.Furthermore,the influence of the seal with different physical property parameters,operating parameters and geometric parameters has been analyzed.The results showed that the flow behavior index,the consistency coefficient,the seal pressure difference,the shaft speed,the balance film thickness,the spiral groove depth,the helical angle,the relative groove width and the relative groove depth both have significant effects on sealing capability.