Non-contacting Seals Research Articles

Analysis and structural optimization of tree-type dynamic pressure groove mechanical seal performance

Abstract This study investigates the influence of the order and groove ratio of a tree-shaped groove on the sealing performance of a mechanical seal system using numerical simulations. A three-dimensional geometric model of the tree-shaped groove is established using SOLIDWORKS, and the mesh is divided in ANSYS Meshing before being imported into Fluent software for analysis. The single-factor experimental method is employed to evaluate the impact of different parameters on the opening force and leakage rate by varying one parameter while keeping others constant. The simulation results reveal that in the low-speed range, the tree-shaped groove with a groove ratio of 3:4:5 exhibits a larger opening force. Conversely, in the high-speed range, the three-stage tree-shaped groove with a groove ratio of 1:1:1 demonstrates a lower leakage rate and a larger opening force. The findings highlight the significant impact of the order and groove ratio of the tree-shaped groove on the sealing performance of the non-contact mechanical seal. The three-stage tree-shaped groove outperforms the second and fourth stages in terms of mechanical sealing performance, particularly in regard to the opening force. This study provides valuable insights into optimizing the design of tree-shaped grooves in mechanical seal systems to enhance their overall performance and efficiency.

Noncontact Seals for an Oil Pump

Noncontact Seals for an Oil Pump

Studies on Improving Seals for Enhancing the Vibration and Environmental Safety of Rotary Machines

There is a constant demand for higher equipment parameters, such as the pressure of a sealing medium and shaft rotation speed. However, as the parameters increase, it becomes more difficult to ensure hermetization efficiency. The rotor of a multi-stage machine rotates in non-contact seals. Seals’ parameters have a great influence on vibration characteristics. Non-contact seals are considered to be hydrostatodynamic supports that can effectively dampen rotor oscillations. The force coefficients of gap seals are determined by geometric and operational parameters. A purposeful choice of these parameters can influence the vibration state of the rotor. It is shown for the first time that the initially dynamically flexible rotor, in combination with properly designed seals, can become dynamically rigid. Analytical dependencies for the computation of the dynamic characteristics are obtained. The resulting equations make it possible to calculate the radial-angular vibrations of the rotor of a centrifugal machine in the seals and construct the amplitude–frequency characteristics. By purposefully changing the parameters of non-contact seals, an initially flexible rotor can be made rigid, and its vibration resistance increases. Due to this, the environmental safety of critical pumping equipment increases.

ЭЖЕКТОРНОЕ УПЛОТНЕНИЕ ВАЛА РОТОРНОЙ МАШИНЫ

The analysis of designs and the principle of operation of contactless ejector shaft seals of rotary machines, fans, aerodynamic heating furnaces, blowers, turbochargers of gas pumping units and other injection machines is considered. A new type of non-contact ejector seal is shown, which in-creases its efficiency when changing the direction of rotation of the shaft and eliminates friction and sparking between sealing surfaces during operation of a rotary machine

Study on the Friction Behavior and Abnormal Conditions of Non-contact Mechanical Seal Based on Acoustic Emission

Study on the Friction Behavior and Abnormal Conditions of Non-contact Mechanical Seal Based on Acoustic Emission

Research of the working body of an oil pumping device

Non-contact seals of a positive displacement pump for pumping of fluid are considered. Experimental studies confirmed the validity of application of non-contact seals in the form of a stepped comb. Empirical dependences of changes in fluid flow during forward and reverse movement of the piston are proposed. Keywords:non-contact seal, fluid flow, pressure, seal, positive displacement pump nga112001@list.ru

Design and Experiment Verification to Combined Dynamic Seal of Wide-Speed Hydraulic Motor Pump

To reduce the wear of lip seal of wide-speed hydraulic motor pump and prolong the service life, the lip compression is reduced and the non-contacting labyrinth seal is used as the front stage, forming a series combined dynamic seal (CDS). The reliability of CDS in the wide-speed range is verified by model experiment. Initially, the structure form and dimension of labyrinth seal with relatively small leakage and heat production were determined by model experiment. Then, by establishing the model of lip seal and simulating the static structure, the relationship between the compression and maximum contact pressure of the lip was obtained. Finally, using the CDS which is formed by combining the different lip seals with the selected labyrinth seal to carry out experiments, the leakage, temperature distribution and lip wear were obtained. The results show that trapezoidal tooth labyrinth seal (TTLS) has better sealing effect and less heat production. When the sealing clearance is 0.1 mm and 0.3 mm, it accounts for 0.11% and 0.32% of the rotor diameter, respectively. Under the same conditions, the smaller the proportion, the better the sealing effect, but the higher the heat production. With the increase of compression, the maximum sealing pressure first increases and then decreases. When the compression of the lip exceeds 0.1 mm, the CDS will not leak significantly in a wide-speed range, but the greater is the compression, the faster is the temperature rise in the closed cavity. Lip wear is positively correlated with pv and the wear decreases with the decrease of compression.

One-way thermomagnetic simulation of magnetic coupling in natural gas pressure energy utilization

ABSTRACT Magnetic coupling is an approach employed to prevent gas leakage by transforming the dynamic seal into a non-contact static seal for the recovery of natural gas pressure energy. The impact of thermal demagnetization necessitates the consideration of the heat dissipation characteristics resulting from eddy current losses in the rotating magnetic field. We performed a numerical study of thermal-magnetic coupling in a magnetic transmission validated by experimental results. The Maxwell software was utilized to simulate the distribution characteristics of induced current, while the Fluent software was employed to analyze the dissipation of heat caused by eddy currents. The obtained simulation results reveal a proportional increase in induced current and eddy current losses with the rotation speed. Also, the eddy current losses increase together with the thickness of the isolation cover, since more volume of the conducting media is affected by the eddy currents. Furthermore, reducing the electrical conductivities of the isolation cover and enhancing the internal flow rates can effectively decrease the temperature of the magnetic coupling and mitigate thermal demagnetization. These research findings offer valuable insights for the design and optimization of non-contact transmission methods, ultimately enhancing the safety of natural gas top-pressure energy recovery equipment.

Experimental investigation on large clearance shaft seal for gas-liquid mixtures

In order to find a solution for the oil leakage problem of a large clearance shaft seal on a marine diesel engine, a series of improvement measures were proposed based on the mechanisms of centrifugal separation, reverse pumping, oil groove and staggered labyrinth. A shaft seal test system that can simulate the gas-liquid environment was built, and verification tests were conducted. Test results showed that the oil leakage didn’t decrease after adding radial or inclined ribs on the oil slinger but increased significantly instead. Adding an oil groove on the oil baffle also didn’t reduce any oil leakage. Fortunately, the addition of the staggered labyrinth effectively reduced the oil leakage. By combining with CFD simulation, the test results were explained, and the sealing functions of different structural features were studied. For structural design work of the non-contact shaft seal, the following design suggestions were proposed. First, the centrifugal effect on the liquid medium can be enhanced by adding ribs on the oil slinger, but the obstruction of oil return should be avoided at the same time. Second, the rotational speed should be fully considered when using the reverse pumping effect. Third, the oil guide groove should be adapted to the airflow and rotation state at its location. Finally, the staggered labyrinth has a stronger throttling effect compared with the straight-through labyrinth, which can reduce the outward transportation of oil by airflow.

Experimental Study on Non-contact Labyrinth Seal under Negative Pressure Intervention

The non-contact labyrinth seal structure of a high-speed gearbox was taken as the research object, a non-contact labyrinth seal structure under negative pressure intervention was designed, and its rationality was verified by simulation analysis. An airfoil-shaped acquisition device for collecting negative pressure was designed, and its rationality was analyzed by simulation. According to the design, a test platform for non-contact labyrinth seal under negative pressure intervention was built to measure the pressure data of each sealing chamber of the non-contact labyrinth seal under different working conditions. The results showed that it was effective to balance the internal and external pressure of the non-contact labyrinth seal by using the negative pressure collected by the airfoil-shaped device in the complex flow field of the high-speed gearbox. It also showed that the non-contact labyrinth seal structure under negative pressure intervention designed in this paper is an effective way to solve the leakage problem of the non-contact labyrinth seal used in high-speed gearbox.

Numerical study of erosion on labyrinth seals of Francis turbine

Sediment erosion is one of the most challenging problems in hydropower plants in Nepal. The sediments like quartz erode the turbine components like runner blades, labyrinth seals and others. This study has focused on the erosion effects in different labyrinth seals of the Francis turbine. Labyrinth seals are non-contact seals used for minimizing unwanted leaks between stationary and rotating parts. The labyrinth consists of two parts: a static seal connected to the turbine covers and a rotating part connected to the runner. The labyrinth gap is small for a new turbine and so the leakage is low. The leakage grows as the gap widens due to erosion in the seals. This causes a reduction in the efficiency of the turbine. Thus, numerical analysis performed on 2-dimensional straight-through (unilateral and bilateral), stepped, and full-length labyrinth seals of Francis turbine have been covered in this research paper. The numerical models were constructed with a structured grid using ICEM. CFD simulation in OpenFOAM was carried out to understand the flow with sediment particles in different labyrinth seals. The volume eroded was evaluated using the Finnie erosion model. The pressure, velocity profile and volume eroded in labyrinth seals were investigated. The study showed stepped labyrinth seal had a maximum volume eroded on both the stator wall and rotor wall compared to other seals. Similarly, the study revealed that the rotating part of the labyrinth seal is more affected by sediment erosion than the stationary part of the seal. This is due to the high accumulation of sediment particles in the rotor wall of the labyrinth seal.

Analysis of the operating conditions of contactless seals during reciprocating motion of plunger pairs of drives of construction machines

Hydraulic drive of construction machines and mechanisms used in technological construction processes is increasingly being used in the construction industry. This is due to the small weight and small overall dimensions per unit of drive power, insignificant inertia of moving parts, good dynamic characteristics, ease of reversing, smooth running, durability of mechanisms due to self-lubricity, simplicity and reliability of operation. The reliability of the hydraulic drive of construction machines is largely determined by the effectiveness of the lubrication system of contactless seals of movable joints. The stability of characteristics, efficiency and safety of operation of mechanisms and hydraulic drive, in particular, depends on the quality of lubrication of sliding surfaces. In order to improve the quality and durability of the hydraulic drive for a certain range of plunger diameters and pressure drops in hydraulic units, the most rational means of combating dry friction forces is a slit non-contact seal.

Design of spinning disk atomization equipment for synthesis of drug-loaded microparticles.

The synthesis of drug-loaded microparticles with precise control over size distribution and shape is crucial for achieving desired drug distribution in microparticles and tuning drug release profiles. Common large-scale production techniques produce microparticles with a broad particle size distribution and require challenging operating conditions. Recent methods employing microfluidics have enabled the production of microparticles with a uniform size distribution. Still, these methods are limited to low and moderate production rates and can handle fluids with a limited range of physicochemical properties. In this study, we couple the spinning disk atomization (SDA) technique for microdroplet production with a precipitation method to generate drug-loaded polymeric microparticles with a narrow size distribution. The design criteria and fabrication of equipment with a non-contact seal system that integrates spinning disk atomization and precipitation methods for conducting laboratory experiments involving volatile hydrocarbons while ensuring operational and personnel safety are discussed. The production of itraconazole drug-loaded microparticles using the SDA setup that considers the system's operation, maintenance, and safety aspects are discussed, and the system's efficiency is evaluated through material balance. This laboratory equipment is capable of producing drug-loaded microparticles with a narrow size distribution under moderate operating conditions and can be scaled up suitably to meet high production requirements. The applications of this equipment can be explored in various fields, such as the production of drug particles, conversion of waste polymers into microparticles, and microencapsulation of food ingredients.

Optimized Design of a Multistage Centrifugal Pump Based on Volumetric Loss Reduction by Auxiliary Blades

Throat ring leakage is a major factor deteriorating the performance of multistage centrifugal pumps. This paper focuses on the optimization of multistage centrifugal pumps by incorporating the principle of the Tesla valve and adding an auxiliary set of blades to the impeller body. By changing the direction and magnitude of the leaking fluid’s flow, the leakage volume of the impeller throat ring is reduced. The study results demonstrate that the experimental error in head calculation with numerical simulation at the optimal working condition was 0.65%, verifying the accuracy of the numerical simulation method. The leakage volume of the throat ring decreased by up to approximately 28.99% compared to the original structure, which significantly increased the pump’s head and overall efficiency. Near the optimal operating point, the pump’s head and overall efficiency increased by approximately 8.1% and 8.7%, respectively. The larger the flow rate, the greater the improvement in the pump’s head and total efficiency. Near high-flow operating conditions, the pump’s head and overall efficiency increased by approximately 116.45% and 110.84%, respectively. The auxiliary blade structure introduces a non-contact seal which, compared to traditional seal structures, improves seal life and reduces seal costs. Additionally, the auxiliary blades can shift the optimal operating point of the multistage centrifugal pump towards a higher flow rate, improving the pump’s delivery capability.

Numerical analysis of a double interlocking padded finger seal performance based on thermo-fluid-structure coupling method

Non-contacting finger seals represent an advanced non-contacting and compliant seal in gas turbine sealing technology. This paper proposes a new structure of non-contacting finger seals with double interlocking pads. The numerical analysis model based on the thermo-fluid-structure coupling method for the new type finger seal was established. The influence of working conditions on leakage of the seal was studied and compared with the single padded non-contacting finger seal. The results show that the interface between the bottom of the finger pad and rotor surface is the main leakage path that forms the gas film with obvious variations of pressure and flow velocity. Under high temperature and high pressure operating conditions, the hydrodynamic effect of the gas film is enhanced, and lifting force is significantly improved. The deformation of fingers is composed of elastic deformation and thermal deformation. At room temperature, the deformation of fingers is mainly elastic deformation and points to the center of the rotor, which reduces the gas film clearance. The deformation of fingers at high temperature and high pressure creates a circumferentially convergent gap between the bottom of the pad and the rotor, which is beneficial to improve the loading capacity and to reduce leakage of the seal. Compared with the typical single padded non-contacting finger seal, the double interlocking padded finger seal proposed in this paper reduces the leakage factor by about 37%, which provides an advanced seal concept with the potential to improve sealing performance under high temperature and high pressure working conditions.

Design and Simulation of a New Near Zero-Wear Non-Contact Self-Impact Seal Based on the Tesla Valve Structure

This study proposes a new near zero-wear non-contact self-impact seal based on the passive fluid blocking principle and the Tesla valve structure, which is characterised by near zero-wear, a long lifetime, a simple structure and high stability. Research shows that the impact-blocking effect of a three-dimensional leakage channel can realise the stepwise throttling effect of the sealing medium. Furthermore, the pressure, number of seal stages and seal spacing significantly affect leakage. Leakage can be effectively controlled by increasing seal series and reducing seal spacing. The proposed near zero-wear impact seal is more suitable for the gas medium. Compared with the conventional sealing form, the new seal is simplified significantly. Large spacing and fixed design can significantly improve the ability to seal pairs to resist vibration and impact during operation, and the sealing performance is not restricted by the rotation speed. The form of the proposed seal will enable a new non-contact mechanical seal technology and a new structure to be developed, thereby advancing the existing seal field.

Design and Performance Analysis of a New Non-contact Self-impact Seal

Design and Performance Analysis of a New Non-contact Self-impact Seal

Nonuniform Clearance Effects on Pressure Distribution and Leakage Flow in the Straight-through Labyrinth Seals

Straight-through labyrinth seal is a simple and reliable noncontact seal structure widely used in aeroengines. During the actual operation of aeroengines, the labyrinth seal clearance might experience a nonuniform variation in the flow direction due to asymmetric structure and uneven temperature. In order to characterize the degree of nonuniformity, the nonuniformity coefficient is defined in current paper. The effect of nonuniform causes (rotor deformation or stator deformation), nonuniform type (convergent clearance or divergent clearance), and nonuniformity coefficient (nonuniformity degree) is carefully studied by numerical simulation. Comparative analysis has shown that there is no obvious difference in flow coefficient (less than 0.8% in current studies) between two nonuniform causes. As for nonuniform type, the nonuniformity impact of divergent type on the flow coefficient is more significant than that of convergent type, as a result of stronger axial inertia. Pressure distributions of teeth cavities indicate that the total pressure drop of the divergent type is more obvious than that of the convergent type when the pressure ratio is the same. With the same dimensionless minimum tip clearance, clearance nonuniformity would result in the increase of leakage flow of the straight-through labyrinth, particularly for the condition with small pressure ratio, large circumferential Mach number, and small dimensionless minimum tip clearance. When the nonuniformity coefficient is within the range of -0.1 to 0.1, the variation curves of nonuniformity impact factor versus the nonuniformity coefficient almost coincide (the maximum deviation is no more than 1.2%) under different operation conditions (Reynolds number, pressure ratio, circumferential Mach number, and dimensionless minimum tip clearance). Current work proves it that the effect of seal clearance nonuniformity on the leakage flow requires special attention for the refined design of aeroengines.

Effects of both cavitation and non-Newtonian behavior on the performance of oscillatory anisotropic poroelastic squeeze film

PurposeThe purpose of this study is to present a theoretical investigation of the effects of cavitation and couple stress on the squeeze film behavior between an anisotropic poroelastic rigid disc and a sinusoidally oscillating rigid disc.Design/methodology/approachBased on the microcontinuum theory of Vijay Kumar Stokes and the Elrod–Adam algorithm, the non-Newtonian Reynolds equation coupled with modified Darcy's law for lubricant flow through the porous disc is derived. This numerical study includes the continuity of tangential velocity at the porous–fluid interface and the effects of percolation of the polar additives into the anisotropic porous disc.FindingsThe effects of couple stress, oscillating amplitude, percolation additives, permeability and anisotropic permeability on the squeeze film characteristics are discussed. It is found that both the percolation effect of the lubricant additives and the anisotropic structure of the porous surface reduce the flow in the porous disc, resulting in a decrease in pressure. It is also observed that cavitation effects are more pronounced for Newtonian fluids than couple stress fluids.Originality/valueThe results of this study can be used to design a variety of engineering applications such as bearings, wet clutches and non-contact mechanical seals.

Methodology of Designing Sealing Systems for Highly Loaded Rotary Machines

Higher parameters of centrifugal machines are constantly required, such as the pressure of the medium to be sealed and the speed of rotation of the shaft. However, as the parameters increase, it becomes more and more difficult to ensure the effectiveness of sealing. In addition, sealing systems affect the overall safety of equipment operation, especially vibration. In order to harmonize the sealing functions and increase the dynamic rigidity of the rotors of centrifugal machines, a method for modeling complex sealing systems has been developed. Non-contact seals are considered as hydrostatic–dynamic bearings that can effectively dampen rotor oscillations. A general approach to the analysis of non-contact seals as automatic control systems and an algorithm for constructing their dynamic characteristics at the design stage were proposed for the first time. Models of “rotor-gap seal”, impulse seal and “rotor–hydraulic face” systems, and seal-supports of a shaftless pump have been studied to assess the effect of these seal systems on the oscillatory characteristics of the rotor. Analytical dependencies are obtained for calculating the dynamic characteristics and stability limits of seals as hydromechanical systems. The directions for improving the safety of operation of critical pumping equipment due to a targeted increase in the rigidity of non-contact seals are determined, which leads to an increase in the vibration resistance of the rotor and the environ-mental safety of centrifugal machines. The paper proposes a method for designing sealing systems based on the configuration of sealing components in order to achieve harmonization between sealing and vibration reliability, taking into account oscillatory processes due to hydrodynamic sealing characteristics.