Seal Structure Research Articles

Cooling behaviors of a novel flow channel in mechanical seals of extreme high-speed rotation for cryogenic rockets

Mechanical seals usually require a special cooling system to control the high temperature generated by friction heating of rotating rings under the condition of extreme high-speed rotation. The working fluid is often in direct contact with the friction surface, and there is a risk of leakage. In the present paper, a novel cooling scheme driven by centrifugal force is proposed to cool the mating face in mechanical seals of turbopump in cryogenic rockets, which could achieve the absolute zero leakage of cooling fluid. To verify the flow feasibility and cooling effect of the new cooling structure, a three-dimensional numerical model is developed to predict the high-speed rotational flow and fluid–solid coupled heat transfer for liquid oxygen. The results show that the novel cooling scheme to cool the rotating ring II in the mechanical seal of cryogenic engines is reasonable and feasible, which could run itself relying on the radial centrifugal force, and could effectively control the temperature of the rotating ring II within the allowable range of the materials. This paper provides a new idea for cooling structure of mechanical seals in cryogenic rockets and numerical experience for ultra-high speed rotating flow and heat transfer with phase change.

Preparation and optimization of fisetin loaded glycerol based soft nanovesicles by Box-Behnken design.

The present study focused on the development and optimization of glycerosomes for dermal delivery of fisetin. The fisetin loaded glycerosomes formulation was optimized by Box-Behnken design. The independent variables were the lipoid S 100, glycerol, and sonication time, whereas the dependent variables were the vesicles size, entrapment efficiency, and flux. The mechanism of skin penetration of fisetin loaded glycerosomes formulation was determined by the DSC and FTIR studies. Confocal scanning microscopy was used to detect the penetration ability of glycerosomes. The optimized fisetin loaded glycerosomes formulation was converted into a Carbopol® gel matrix, and the latter was analyzed for various parameters. The optimized formulation of glycerosomes presented vesicles size, entrapment efficiency and flux of 138.8±4.09nm, 86.41±2.95% and 5.04±0.17µg/cm2/h, respectively. The transmission electron microscopy of optimized fisetin loaded formulation revealed the spherical and sealed structure of glycerosomes vesicles. The confocal study confirmed that the Rhodamine B incorporated glycerosomes penetrated up to deeper layers of skin. The DSC and FTIR studies revealed that the hydration of skin layers and skin lipid fluidization could be the penetration mechanism of fisetin glycerosomes formulation. The optimized fisetin loaded glycerosomes gel formulation presented a flux of 4.24±0.14μg/cm2/h, and exhibited zero-order release kinetics. The texture analysis of fisetin glycerosomes gel displayed a sufficient hardness, consistency, cohesiveness, and index of viscosity. It was concluded that the prepared fisetin loaded glycerosomes gel was suitable for the dermal application.

Effects of Double-Side Labyrinth Seals on Aerodynamic Performance in a Transonic Shrouded Turbine Stage

Labyrinth seals on both rotor casing and blade tip as an effective method to control the leakage flowrate of the shroud and improve aerodynamic performances in a transonic turbine stage are investigated in this study. Compared to the case without the labyrinth seal structure, the cases with three different types of sealing teeth have been shown to reduce significantly the tip leakage flow by computational simulations. The double-side sealing teeth case reduces the leakage flowrate from 3.4% to 1.3% and increases the efficiency by 1.4%, which is the maximum efficiency improvement of all cases. The sealing structures increase the loss inside the shroud while reducing the momentum mixing between shroud leakage flow and mainstream. Therefore, the circumferential distribution of leakage velocity is changed, as well as the distribution of high-loss zones at turbine outlet. Furthermore, the leakage-vortex loss, which is associated with the blockage effect of sealing structure to the tip leakage flow, gains more improvement than the passage-vortex at the rotor outlet section in double-side seal case. In addition, it has also been found that with a larger gap at tip, the double-side seal has better effects of reducing the leakage flow and improving the aerodynamic performance in the transonic turbine stage.

Design and experimental study of the porous foam metal magnetorheological fluid damper based on built-in multi-pole magnetic core

The porous foam metal magnetorheological fluid damper has a broad application prospect in the field of vibration isolation of precision instruments with small damping force because it does not need complex dynamic seal structure. The traditional single-ring magnetic pole porous foam metal magnetorheological fluid damper has a small effective area for the magnetic core that affects the damper output range due to the geometric constraints of the coil and the low magnetic field utilization. Therefore, in order to increase the effective area ratio of the magnetic core, this article introduces the built-in multi-pole magnetic core into the porous metal magnetorheological fluid damper and integrates four axial wound fan-shaped magnetic poles on the magnetic core to improve the output performance of the damper. The magnetic circuit is analyzed based on Ohm’s law of magnetic circuit, and the mathematical model of damping force is established. Based on this, the important geometric parameters of the damper are determined. The finite element method is used to simulate the magnetic field of the damper, and the output performance of the damper is numerically simulated. The dynamic performance test system of the damper is set up to test the designed damper, and the test data and numerical simulation results are verified with each other. The results show that the damping force peak and dynamic regulation range of the damper designed in this article are higher than those of the traditional porous foam metal magnetorheological fluid damper with magnetic core, which effectively improves the mechanical properties of the magnetorheological fluid damper with porous foam metal.

Circumferential Sealing Structure of a Subsea Oil and Gas Pipeline Repair Clamp

A subsea oil and gas pipeline repair clamp and circumferential sealing structure are designed. Based on the principle of equal contact pressure on the contact surface and the thick-walled cylinder calculation, a formula for the contact pressure between the sealing ring and the outer wall of the pipeline is derived. An axisymmetric finite element model is constructed for circumferential sealing with an ABAQUS software suite. The model is used to calculate the contact pressure necessary for the sealing structure, which requires different sealing pressures, and to determine the respective bolt preload for a ∅219-mm clamp. The model also defines a maximum effective contact pressure and average effective contact pressure between the sealing ring and the outer wall of the pipeline. The prediction of the contact force caused by the deformation of a sealing ring due to the geometry restriction was experimentally verified. The finite element and experimental results confirm the validity of grounding in theory and derived formula. The calculations can provide the guidelines for the design of the seal structure of a clamp and the overall structure, as well as future engineering applications.

Research on Calibration Method of Temperature Field for Large Sealed High Temperature Equipment

Large sealed high temperature equipment usually refers to heat treatment equipment with a volume of more than 0.15m3, sealed structure and internal heating and constant temperature function. It is widely used in the fields of biochemistry, chemical pharmacy, medical and health, agricultural research, automobile and military industry. It`s a very important processing equipment. The accuracy of temperature field and vacuum sealing directly affect the quality of products. Taking the hot-pressing tank as an example, the furnace temperature tracker and wireless pressure module are used to calibrate it on the spot. According to the calibration results of temperature field distribution and temperature field performance, whether it meets the process requirements is analyzed.

Optimal Design of the Sealing Structure of a Hydraulic Cylinder on the Basis of a Surrogate Model

In this study, a finite‐element simulation model was established for a two‐dimensional hydraulic cylinder seal structure with highly nonlinear materials and contacts for achieving the optimal sealing effect with the structure. The effects of gaps as well as single and double O‐rings on the sealing effect were examined. On the basis of this examination, a parametric model was developed for double‐O‐rings without gaps, which are suitable for hydraulic cylinder sealing. Suitable design variables, objective functions, and constraint conditions were determined for the parametric model. Then, a surrogate model was fitted and optimised through a constrained Latin hypercube method, an interpolating recmultiquadric radial basis function method, and the genetic algorithm. The results indicate that the seal and seal groove structures obtained through optimisation with the surrogate model provide a superior sealing effect to unoptimised structures. Therefore, the combination of the developed surrogate model and finite‐element method can provide a theoretical reference for the design of the sealing structure of hydraulic cylinders.

Design of Magnetic Circuit and Simulation of Magnetic Fluid Sealing with Three Magnetic Sources

In order to obtain the maximum magnetic energy product in the sealing gap of the magnetic fluid sealing structure to improve the pressure capability of the magnetic fluid sealing, based on the magnetic circuit design theory and the magnetic fluid sealing theory, a parallel connection with three magnetic sources is provided. The magnetic fluid seal structure is designed for the magnetic circuit. The magnetic field in the magnetic fluid seal structure is calculated by the finite element method, and the pressure capability of the magnetic fluid seal is calculated. The results are analyzed and discussed. The results show that the magnetic flux leakage at the junction of the pole piece and the permanent magnet and the axial length of the intermediate pole pieces are short, which results in a nonlinear relationship between the magnetic induction strength difference between the two pole pieces and the sealing gap between the two pole pieces. The magnetic circuit method is lower than the magnetic fluid seal pressure capability calculated by the finite element method of the magnetic field.

Numerical analysis for the influence of saturation on the base course of permeable pavement with a novel polyurethane binder

Permeable pavements represent an effective approach to optimize the conventional sealed pavement infrastructure. Compared to sealed pavement structures, the porous pavement structure allows fluids to pass through it freely, reducing and controlling runoff in the surrounding area. The stress state of this pavement system under different saturation conditions is one of the most important challenges for the pavement design. This study aims to develop a modulus-reduction method for the pavement material under different saturation conditions by considering hydro-mechanical interaction. To achieve this, a full-scale permeable test track was constructed in this study. A falling weight deflectometer (FWD) was used to measure the deflection of the test track at different saturation states. Using the back-calculated elastic parameters, tire-pavement interaction models were created to conduct finite element method (FEM) simulations of the stress state of the test track subjected to the loads from Accelerated Pavement Testing (APT). The results show that the hydro-mechanical properties of the test track are significantly affected by the water content. As a result, the current design algorithm of fully permeable pavements should consider the effects of saturation to allow for improved designs of fully permeable pavements.

Study on the Rotordynamic Performance of a Novel Anti-stagnation Labyrinth Seal

A novel structure of anti-stagnation labyrinth seal was proposed in this paper. An opposed jet suppressing the circumferential flow was generated in seal cavities with pressure-driven micro-nozzles on adjacent seal teeth. The theoretical identification approach for rotordynamic coefficients based on the infinitesimal theory was applied to predict rotordynamic coefficients of annular gas seals. The effects of the layout of anti-stagnation nozzles, inlet pressure and rotational speed on rotordynamic characteristics were investigated using a computational fluid dynamics (CFD) method. Compared with that of the traditional labyrinth seal, the new seal possesses better stability with a 200% increase in the effective damping coefficients at high whirling frequency. Compared with those in the middle and downstream position, nozzles installed in the upstream of the seal can effectively improve the dynamic stability of the system. The anti-stagnation labyrinth seal shows better stability performance for higher inlet pressure and rotational speed. The leakage flow rate of the anti-stagnation labyrinth seal is slightly higher (an increase of less than 4%) than that of the original labyrinth seal.

Numerical investigation of high pressure turbine blade tip-shaping effects on the aerothermal and dynamic performance

Purpose In order to improve the engine reliability and efficiency, an effective way is to reform the turbine blade tip conformation. The paper aims to discuss this issue. Design/methodology/approach The present research provides several novel tip-shaping structures, which are considered to control the blade tip loss. Four different tip geometries have been studied: flat tip, squealer tip, flat tip with streamwise ribs and squealer tip with streamwise ribs. The tip heat transfer and leakage flow are both analyzed in detail, for example the tip heat transfer coefficient, tip flow and local pressure distributions. Findings The results show that the squealer seal and streamwise rib can reduce the tip heat transfer and leakage loss, especially for the squealer tip with streamwise ribs. The tip and near-tip flow patterns at the different locations of axial chord reflect that both the squealer seal and streamwise rib structure can control the tip leakage flow loss. In addition, the analysis of the aerodynamic parameters (the static pressure and turbine efficiency) also indicates that the squealer tip with streamwise ribs obtains the highest adiabatic efficiency with an increase of 2.34 percent, compared with that of the flat tip case. Originality/value The analysis of aerothermal and dynamic performance can provide a reference for the blade tip design and treatment.

Basal Sodium-Dependent Vitamin C Transporter 2 polarization in choroid plexus explant cells in normal or scorbutic conditions

Vitamin C is incorporated into the cerebrospinal fluid (CSF) through choroid plexus cells. While the transfer of vitamin C from the blood to the brain has been studied functionally, the vitamin C transporter, SVCT2, has not been detected in the basolateral membrane of choroid plexus cells. Furthermore, it is unknown how its expression is induced in the developing brain and modulated in scurvy conditions. We concluded that SVCT2 is intensely expressed in the second half of embryonic brain development and postnatal stages. In postnatal and adult brain, SVCT2 is highly expressed in all choroidal plexus epithelial cells, shown by colocalization with GLUT1 in the basolateral membranes and without MCT1 colocalization, which is expressed in the apical membrane. We confirmed that choroid plexus explant cells (in vitro) form a sealed epithelial structure, which polarized basolaterally, endogenous or overexpressed SVCT2. These results are reproduced in vivo by injecting hSVCT2wt-EYFP lentivirus into the CSF. Overexpressed SVCT2 incorporates AA (intraperitoneally injected) from the blood to the CSF. Finally, we observed in Guinea pig brain under scorbutic condition, that normal distribution of SVCT2 in choroid plexus may be regulated by peripheral concentrations of vitamin C. Additionally, we observed that SVCT2 polarization also depends on the metabolic stage of the choroid plexus cells.

Optimized Sealing Process and Real-Time Monitoring of Glass-to-Metal Seal Structures.

Residual stress is an essential factor to keeping the hermeticity and robustness of a glass-to-metal seal structure. The purpose of this report is to demonstrate a novel protocol to characterize and measure residual stress in a glass-to-metal seal structure without destroying the insulation and hermeticity of sealing materials. In this research, a femto-laser inscribed fiber Bragg grating sensor is used. The glass-to-metal seal structure that is measured consists of a metal shell, sealing glass, and Kovar conductor. To make the measurements worthwhile, the specific heat treatment of metal-to-glass seal (MTGS) structure is explored to obtain the model with best hermeticity. Then, the FBG sensor is embedded into the path of sealing glass and becomes well-fused with the glass as the temperature cools to RT. The Bragg wavelength of FBG shifts with the residual stress generated in sealing the glass. To calculate the residual stress, the relationship between Bragg wavelength shift and strain is applied, and the finite element method is also used to make the results reliable. The online monitoring experiments of residual stress in sealing glass are carried out at different loads, such as high temperature and high pressure, to broaden functions of this protocol in harsh environments.

Optimized Sealing Process and Real-Time Monitoring of Glass-to-Metal Seal Structures

Optimized Sealing Process and Real-Time Monitoring of Glass-to-Metal Seal Structures

Numerical analysis of hub cavity leakage

Purpose This paper aims to predict the effect of the hub cavity leakage on the overall performance with numerical simulations in the fan/booster of a high bypass ratio turbofan engine. Design/methodology/approach Simulations are conducted for leakage at the fan, the outlet of guide vane and the three-stage booster, as well as hub leakage (contain cavities and sealing). The results obtained are compared to the corresponding simulations without hub leakage. Findings The rotor/stator interaction locations are evaluated to discover a better location. The results show that the seal tooth structure produces secondary flow and turbulence in the root of blade suction surface, which increases the aerodynamic loss. The sealing clearance should be controlled to shrink the turbulent region and decrease the leakage. Practical implications This work can provide a theoretical guidance and technical support for the compressor design, which avoid many repeated manufactures and reduce waste of resources. Originality/value This work improves the understanding of the impact mechanism of hub cavity leakage on the performance when the clearance size of seal is variable.

Experimental investigation of sealing ability of lost circulation materials using the test apparatus with long fracture slot

Lost circulation in fractured formations is a major challenge. The addition of conventional lost circulation materials (LCMs) to drilling fluids is the main method to control loss. The seal integrity is affected by different properties of LCMs. Plugging apparatus with slot is extensively used to evaluate sealing performance of the selected LCMs. In general, the fracture in the formation has depths, and the drilling fluids loss far into the formation. A LCM test apparatus with long fracture slot was introduced in this paper. The main objective of this work is to study the effect of LCM type, concentration and particle size distribution on the seal integrity with long fracture slot. The breaking pressure, fluid loss values, position and thickness of plugging zone are the parameters for evaluating LCM performance. Optical microscopy and scanning electron microscopy were used to observe the arrangement and microstructure of the seal. We can better understand the sealing mechanisms in long fracture by analyzing the cell pressure and fluid loss vs. time plot and the seal structure. Results showed that increasing the LCMs stiffness resulted in higher breaking pressure. There is a critical maximum concentration at which LCM will bridging and filling set at the fracture entrance and no tight seal barrier inside the fracture. Loss effect was beneficial to form thicker plugging zone inside the fracture. Suitable wide particle size distribution of LCM formed thick plugging zone inside the fracture. Multi-layer seal barrier can withstand the external load together, resulted in high seal integrities. The addition of fibrous materials in particles resulted in higher breaking pressure and lower fluid loss.

Analysis and structure optimization on buckling destabilization and wrinkling of an automobile weather-strip seal in assemblage

Buckling destabilization and wrinkling of an ethylene-propylene-diene monomer automobile weather-strip seal in assemblage and its structural optimization were studied in this paper. First, an innovative approach that traces buckling bifurcation paths was developed based on an arc-length method, and algorithmic parameters of the method were defined. A finite element analysis model of the automobile weather-strip seal in assemblage was then developed and analyzed using the arc-length method. The maximum buckling load, the deformation of the seal, and the thickness decrease of the lower tube wall in the critical region where it was prone to wrinkle were obtained by this finite element analysis method. Finally, an optimization seal structure was proposed and analyzed, and the deformations and the thickness decrease of the original and optimal structures in the critical regions were compared. The analysis conclusion implies that the optimal structure is more stable. The proposed analysis and optimization method can shorten the product design cycle, improve the structural stability, and decrease the design and trial-product cost considerably.

Study on the water seal formation process in advanced PWR pressurizer using CFD method

Pressurizer is one of the most important equipment in pressurized water reactor (PWR) nuclear power plant. Its function is to maintain the pressure and water quantity of the primary circuit. In the early design, a U-tube was installed in front of the pressurizer safety valve and filled with water to reduce the leakage of non-condensable gas through the valve. This U-tube is called a water seal structure. However, when the safety valve is opened, the water in the U-shaped pipe passes through the safety valve, which generates a large number of thermal and hydraulic loads on the safety valve and downstream pipeline, which is not conducive to the safety of the system. In order to reduce the thermal and hydraulic loads in the safety valve, a new type of water seal structure was designed. The new water seal structure consists of a shovel-shaped structure placed in front of the safety valve pipeline in the dome of the pressurizer. In this paper, the thermo-hydraulic characteristics of the new type of water seal structure are simulated, and the process of steam condensation and water seal formation is studied. The key parameters of water seal formation under different pressure and heat dissipation conditions were studied. The species transport model is used to describe the effect of non-condensable gas on condensation process. The three-dimensional distributions of velocity, pressure and temperature are obtained. The time required for water seal formation was calculated by using condensation rate and water tank volume. The calculation results show that the water seal in the pressurizer can still be formed within the required time under the condition of the influence of non-condensable gas. The temperature difference between inside and outside of water seal is less than 20 K. The new water seal structure satisfies the requirement of the actual start-up process of the reactor.

An anisotropic porous media model for leakage analysis of finger seal

Finger seal is a new type of compliant seal configuration, which is an important part of an aero-engine and its accessory systems. It has superior sealing performance compared with conventional labyrinth seals and a lower manufacturing cost than brush seals. However, numerical simulation of the leakage characteristics of an entitative finger seal structure are very difficult to implement, because the finger laminates are in close contact with one another and the radial deformation of the fingers caused by interference between seal and rotor as well as the centrifugal and thermal expansion of the rotor can change the geometric structure of seal. The published leakage analysis models of finger seal ignore the leakage throughout the interstices between fingers or finger laminates. In view of this, the authors propose an anisotropic porous media model for leakage analysis of finger seal. The model considers the effects of the seal structure parameters, upstream and downstream axial pressure differences and the fit status between seal and rotor. First, the equations of the model and their parameters were obtained by theoretical derivations, while the correction factors were determined based on experiment leakage data in the literature. Second, the accuracy of the model was validated by calculating the leakage of a known seal structure in the literature and comparing these results with the experimental data. At last, a comparison between the anisotropic and isotropic porous media model is carried out. The results of the validation examples show that the model can simulate the leakage of finger seal very well with the errors between numerical results and experimental data are less than 10% for two-thirds of the data points.

Analysis and simulation of straight-through labyrinth seal in hydrostatic support system

PurposeThe purpose of this paper is to improve the bearing capacity and mechanical properties of the oil pocket.Design/methodology/approachIn this paper, a straight-through labyrinth seal is installed in an oil sealing belt. The main structure of hydrostatic support system (HSS) is introduced, and the factors affecting the leakage loss are analyzed. The governing equations involving the momentum equation and the continuity equation for the land section and groove section are established separately based on the three-control-volume theory. To explain the flow capability of the straight-through labyrinth seal, the labyrinth seal with different clearance widths, groove numbers, groove depths and pressure difference is calculated. The results of the simulation are compared and analyzed.FindingsThe groove dimensions and groove numbers have important impact on the leakage and flow pattern of the seal.Research limitations/implicationsThe fluid flow was simulated by commercial tools executed in the ANSYS Fluent, the computational fluid dynamics (CFD) solver and a steady state scheme with the realizable k-ε turbulence model was applied. The cavity structure of the straight-through labyrinth seal, forming turbulence eddy flows in the groove, which is a valid approach to convert turbulence kinetic energy into thermal energy, reduce leakage mass flow.Practical implicationsThis research can provide the theoretical basis and technical support which is conducive to the practical application of the straight-through labyrinth seal in HSS.Social implicationsA new design structure is proposed to improve the bearing capacity and economic benefit of HSSs.Originality/valueA straight-through labyrinth seal is applied to the oil sealing belt and the three-control-volume governing equation is established.