Analysis Of Self-Cleaning For Diffuser Self-Pumping Hydrodynamic And Hydrostatic Mechanical Seal

Non contact mechanical seals,due to their advantages such as long service life and stable sealing performance,have been undertaking important shaft end sealing tasks in rotating equipment under complex operating conditions such as high temperature,high pressure,and high speed.Traditional fluid wedge mechanical seals,represented by dry gas seals and upstream pumping mechanical seals,contain impurities and particles in the sealing medium that enter the sealing end face with the pumping effect of the end face groove during actual operation,resulting in a decrease in pumping volume and unstable end face temperature.At the same time,it increases the possibility of particles crossing the sealing dam and damaging the sealing end face.Therefore,this study focuses on the dynamic and static pressure type mechanical seal with self pumping fluid,establishes a fluid solid simulation calculation model for the fluid domain of the sealing end face,and uses FLUENT numerical simulation software to simulate and analyze the end face flow field.By changing particle parameters,end face structural parameters,and operating conditions,the influence of discrete relative sealing performance and the variation pattern of end face chip removal performance are studied,and the significant influencing factors of different parameters on chip removal performance are explored.Study the relationship between the flow characteristics of the end face flow field and particle discharge,and reveal that the expansion type self pumping fluid dynamic and static pressure mechanical seal with drainage holes and collecting ring grooves in the static ring has self-cleaning characteristics under solid conditions.By analyzing the trend of chip removal rate and particle motion trajectory,the friction and wear effects of impurity particles on the dynamic and static ring end faces are studied.Provide theoretical support for the design of noncontact mechanical seals with wide applicability and sealing stability.The main research content and conclusions are as follows:1.A geometric calculation model for the fluid domain of the sealing end face was established based on the research object of the self pumping fluid dynamic and static mechanical seal with expansion.The model was unstructured meshed using ICEM,and the end face flow field was simulated using the Laminal model and DPM model in FLUENT.The ratio of escaped particles to released particles per unit time was defined as the end face chip removal rate,And use this indicator to characterize the self-cleaning characteristics of the dynamic and static pressure mechanical seal with self pumping fluid of the expansion type;2.Based on the DPM model,the influence of different particle inlet volume fraction,particle diameter,rotational speed,and pressure difference on the discrete relative sealing performance was studied.The research shows that the movement state of solid particles is mainly affected by the continuous phase flow field.Compared with the clean water condition,the area of the end highpressure cloud under the solid containing condition decreases,changing the pressure gradient distribution of the end flow field.The impurity particles between the sealing end faces can increase the opening force of the liquid film on the end face to a certain extent,but it will lead to a significant increase in leakage.The increasing trend of leakage is related to the rotational speed and medium pressure difference.As the rotational speed increases,the dynamic pressure effect increases and the leakage decreases.The increase in medium pressure difference directly leads to a synchronous increase in pressure on both sides of the sealing dam,and the leakage rate also increases rapidly.3.The influence of changes in discrete phase parameters,operating conditions,and structural parameters on the end face particle discharge performance was studied.The results show that the dynamic and static end face structures of the self pumping fluid dynamic and static mechanical seal with expansion type have self-cleaning characteristics,which can achieve the discharge of particle impurities from the end face.Under low particle volume fraction,the change in chip removal rate at the end face is relatively stable.As the particle volume fraction increases,the chip removal rate first increases and then rapidly decreases;The particle diameter affects the force state of particles in the spiral groove,and as the particle diameter increases,the flow resistance of particles increases;Under high rotational speed and low medium pressure,the chip removal performance of the end face reaches the optimal level,with a chip removal rate of up to 92.3%.As the medium pressure increases,the static pressure of the end face increases,and the chip removal rate gradually decreases.Under the same operating conditions and discrete phase parameters,the structural parameters of the end face mainly change the pressure distribution of the end face flow field,while the motion behavior of particles is mainly related to the changes in the flow field.4.Based on the Finnie wear model,the friction and wear effects of impurities on the sealing end face were analyzed,and the changes in the degree of end face wear caused by different particle diameters,particle mass flow rates,particle shapes,and rotational speeds were quantitatively analyzed,The results show that the forms of abrasive wear in the end face flow field of the self pumped fluid dynamic and static mechanical seal mainly include erosion wear caused by particles impacting the wall surface at a certain angle and speed,and wear caused by the pressure gradient force on solid particles in the spiral groove,friction,cutting,and compression on the wall surface they pass through.Due to sudden changes in the velocity and angle of fluid movement on the inner diameter side of the expansion ring groove,the maximum range of wall wear corresponding to the expansion ring groove occurs.The wear of the root area of the spiral groove is mainly due to the change in particle movement angle when particles enter the spiral groove from the collector ring groove under differential pressure,resulting in erosion wear phenomenon in the root area of the groove.The wear of the static ring end face corresponding to the spiral groove flow channel is caused by the continuous impact of particles on the side of the spiral groove,which continuously erodes the static ring end face under the lifting force in the flow field,forming erosion wear.This thesis studied the self-cleaning characteristics of the self pumping fluid dynamic and static mechanical seal with expansion,and analyzes the factors that affect the self-cleaning characteristics of the seal face from the perspectives of flow field changes and performance changes.At the same time,it provides a basis for the structural selection,applicable working conditions,and end face wear and friction reduction of the self pumping mechanical seal with expansion under solid working conditions.