| With the continuous development of modern industry,the shaft seal of rotating machinery constantly breaks through the design condition and gradually develops to the multi-phase medium conditions.As we all known,it is necessary to seal in gasliquid two-phase or gas-liquid-solid three-phase environment in many fields,such as petroleum,chemical industry,shipbuilding,marine engineering and so on.The characteristics of multiphase fluid are not merely the simple addition of the characteristics of various fluids,and the interaction mechanism is very complex.Under this special working condition,the traditional single-phase seal operation performance law is no longer applicable.In recent years,a new type of cylindrical seal has attracted much attention in the field of aero-engine seal because of its unique structure.Compared with the traditional seal,the cylindrical seal has smaller clearance and the characteristic of automatic centering.The cylinder seal is gradually used to replace the carbon ring seal at the shaft end in the aero-engine,which can effectively reduce the leakage and the probability of dynamic and static rubbing.Therefore,based on the study of cylinder gas film and combined with two-phase flow lubrication technology,this paper explored the lubrication mechanism and sealing characteristics of cylinder hydrodynamic pressure seal in the state of gas-liquid two-phase medium.Firstly,the whole model of cylindrical spiral groove was established by Solid Works.Then the mesh was divided,and finally introduced into the Fluent software.Under the condition of pure gas phase and gas-liquid two-phase medium,the effects of rotational speed,pressure difference,number of grooves,groove depth and spiral angle on the hydrodynamic seal performance of cylindrical spiral grooves were compared and verified by flow field examples with the classical literature of two-phase flow.The results showed that the dynamic pressure effect of cylindrical spiral groove seal in the gas-liquid two-phase medium was better than that in the pure gas-phase medium.The increase of rotational speed,pressure difference and liquid-gas ratio were beneficial to the improvement of buoyancy force of spirally grooved cylindrical seal.The buoyancy force decreased with the increase of spiral angle and groove depth,increased with increase of the number of grooves and then changed gradually and smoothly.The leakage rate increased with the increase of pressure difference and speed,increased with increase of the spiral angle and then changed gradually and smoothly,increased gradually with the increase of groove depth,and gradually decreased with the increase of the number of grooves.Secondly,according to the difference of liquid-gas ratios,DPM two-phase flow model was selected under low liquid-gas ratio to analyze and compare the effects of rotating speed,pressure difference,liquid-gas ratio and oil droplet diameter on seal leakage rate,buoyancy force and opening-leakage ratio of spiral groove,one-word groove and T-shaped groove.The results showed that at low liquid-gas ratio,the increase of speed,pressure difference and liquid-gas ratio of the three types of grooves is beneficial to the increase of fluid film buoyancy force and opening-leakage ratio.The leakage rate of the three types of grooves gradually decreased with the increase of the rotating speed and the liquid-gas ratio,while increased with the increase of the pressure difference.However,the effect of oil droplet diameter on buoyancy force,leakage rate and opening-leakage ratio was negligible.Finally,the Mixture two-phase flow model was selected under high liquid-gas ratio to analyze and compare the effects of spiral groove,one-word groove and Tshaped groove on seal leakage rate,buoyancy force and open-leakage ratio at rotational speed,pressure difference,liquid-gas ratio and oil droplet diameter.The results showed that under the same working parameters,the buoyancy force and open-leakage ratio of the three grooves with high liquid-gas ratio were greater than those with low liquidgas ratio,and the buoyancy force and opening-leakage ratio under the two kinds of liquid-gas ratio had the same trend with the increase of rotational speed and pressure difference.The leakage rate under high liquid-gas ratio was lower than that under low liquid-gas ratio,and the leakage rate of three groove types under two liquid-gas ratios had the same trend with the increase of rotating speed,liquid-gas ratio and pressure difference.However,the influence of oil droplet diameter on sealing performance was negligible.In this paper,the sealing characteristics of cylindrical seal in gas-liquid two-phase medium were studied systematically,which provided a theoretical basis for the flow law and application of cylindrical seal in gas-liquid two-phase medium. |
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