Sealing Capability Research Articles

Comparative study of the sealing mechanism and performance between magnetic fluid and magnetorheological fluid seals

Magnetic fluid and magnetorheological fluid are two of the most effective magnetic media seals, yet the sealing effectiveness of both has not been compared systematically. To investigate the differences between magnetic fluid and magnetorheological fluid seals, a comparative experimental device is proposed to study the sealing mechanism and performance of the two sealing media at different temperatures. Numerical simulation is used to study the magnetic field distribution of the comparative experimental device and calculate the theoretical pressure resistance (PR) of the two sealing media, respectively. The correctness of the theoretical PR formula of the magnetic media seals with additional temperature coefficient is verified by the comparative experimental results. The results show that the number of resumptions of the magnetorheological fluid film decreases with increasing temperature, while the magnetic fluid film consistently undergoes only one recovery. In addition, the self-healing capability and PR of magnetorheological fluid seals are better than that of magnetic fluid seals, and it is less affected by temperature and has stronger temperature adaptability.

Assessment of the CO2 Geological Storage Potential of Yanchang Shale Gas Formation (Chang7 Member) Considering the Capillary Sealing Capability of Caprock

Reducing net carbon emissions is of great significance for sustainability. Carbon capture, utilization, and storage (CCUS) technology is regarded as one of the most effective approaches to reducing net carbon emissions. A prerequisite for the implementation of the CO2 geological storage project is the assessment of the storage potential of the storage site. In this study, a calculation method of storage potential was proposed to estimate the CO2 storage potential of the Yanchang shale gas reservoir in the Ordos Basin, China. In this method, the CO2 sealing capability of the caprock is taken into account, which determines the maximum CO2 storage pressure of the reservoir. The overall CO2 storage potential consists of four types of storage states (free-state, adsorption, dissolution, and mineralization). The maximum CO2 storage pressure of the Yanchang shale gas reservoir is 13.4 MPa via breakthrough pressure experiments, and the corresponding theoretical storage potential is 7.59 × 1011 t. The potential for free-state, adsorption, dissolution, and mineralization sequestration are 8.42 × 1010 t, 6.88 × 1010 t, 2.45 × 109 t, and 6.05 × 1011 t, respectively. Due to the difficulty in completing mineralization within the engineering time scale, the mineralization potential should not be taken into account when estimating the available CO2 storage potential. The available CO2 potential (including free-state, adsorption, and dissolution) of the Yanchang shale gas reservoir is 1.54 × 1011 t, which is a considerable amount. The Yanchang shale gas formation will be able to accommodate 41.49% of global annual CO2 emissions (according to the data in 2021) if the available CO2 storage potential of the Yanchang shale gas reservoir is fully exploited.

Experimental investigation on the critical pressure and self-repairing capability of converging magnetic fluid seal with stepped pole pieces

A new design of converging magnetic fluid seal with stepped pole pieces is presented. The new seal has advantages over the traditional magnetic fluid seal, notably simple processing and reduced manufacturing costs. Experimental research is conducted on the new seal's critical pressure and self-repairing capability for different steps, step heights, and radial and axial sealing clearance. Results demonstrate that the theoretical and experimental critical pressure of the new seal is in excellent agreement, the critical pressure and self-repairing capability of the new seal are closely related to the number and height of steps and the sealing clearance. Furthermore, the new seal is found to exhibit superior sealing performance compared with the ordinary magnetic fluid seal.

Experimental study on the critical pressure of divergent stepped magnetic fluid seal with a small clearance and single magnetic source

Herein, a divergent stepped magnetic fluid seal with a single magnetic source is designed to improve the pressure capability of ordinary magnetic fluid seal under small clearance. To explore the effects of injection volume, axial clearance, radial clearance, axial tooth number and radial tooth number on divergent stepped magnetic fluid seal, the pressure capability of magnetic fluid seal with an ordinary structure was comparatively analyzed through experimentation. According to the experimental results, there is no leakage or ejection of magnetic fluid from the sealing device when the critical pressure of divergent stepped magnetic fluid sealing is reached. The divergent stepped magnetic fluid seal structure performs better in pressure resistance the magnetic fluid seal with an ordinary structure. Also, the existence of axial teeth in the stepped magnetic fluid sealing structure leads to an increase in polar teeth, which not only extends the leakage path of the sealing medium but also exacerbates energy loss for the magnetic fluid carried by the sealed medium. This is effective in improving the pressure resistance of the magnetic fluid seal. When the axial tooth number reaches or exceeds the radial tooth number and the axial clearance falls below the radial clearance, the divergent stepped magnetic fluid seal with small clearance has a pressure capability that is 4.1–6 times higher than the critical pressure of ordinary magnetic fluid seal. When the axial clearance exceeds the radial clearance and the axial tooth number falls below the radial tooth number, the divergent stepped magnetic fluid seal has a critical pressure that is 1.9–3.6 times higher than that of conventional magnetic fluid seal.

Finite Element Analysis and Experimental Study on Magnetorheological Fluid Seal of the Hydraulic Cylinder

In order to solve the leakage problem of the engineering mechanical hydraulic cylinder, a magnetorheological fluid (MRF) seal structure with a multistage source is designed. The magnetic field in the gap of the sealing structure is analyzed by ANSYS finite element analysis method, the influence about the number of magnetic sources and the length of pole teeth on the pressure capability of the MRF seal is studied, and the results are analyzed. The results show that the suitable number of magnetic sources is 10; The length of the pole teeth with the best magnetic concentrating effect is 0.7 mm. Then, the influence of the MRF injection volume, reciprocating speed, reciprocating distance and holding pressure time of the hydraulic cylinder on the MRF sealing pressure capability is studied. The experimental results show that the maximum pressure capacity can be achieved when the MRF injection volume is 12 ml. With the increase of reciprocating speed, the pressure capability of the MRF seal decreases obviously. With the increase of reciprocating distance and holding time, the sealing pressure capability has no obvious change. Through the finite element analysis and experimental study of the MRF seal, it is of great significance to develop a device with high sealing performance suitable for the hydraulic cylinders.

Error Analysis in Numerical Simulation of the Static Pressure Capability of Magnetic Fluid Seals

Magnetic fluid is a typical type of functional fluid which can be magnetized and controlled by an external magnetic field. In magnetic fluid seals, magnetic fluid is attracted in sealing gaps by a magnetic field gradient to form non-contact sealing. Compared to traditional sealing methods, they possess unique advantages such as zero leakage, long lifetime, low friction torque, and high reliability. Although the design and performance estimation of magnetic fluid seals rely mostly on numerical simulation, a number of simplifications or even mistakes during the simulation process exist in previous studies. The error caused by simplifications and mistakes has not been studied, leading to a possible problem of simulation results in reliability and consistency with experimental data. Here, we examined the influence of common simplifications and mistakes in numerical simulation of the static pressure capability of magnetic fluid seals, including material properties, geometric modeling, and theoretical formulas. A novel method of structure optimization based on a derivative-free multiparameter algorithm is also presented. A test bench for magnetic fluid seals is established, and the difference between simulation and experimental results is discussed. This research provides a precise, efficient, and standard procedure for numerical simulation of magnetic fluid seals.

Sealing capability of the Eocene–Miocene Horda and Lark formations of the Nini West depleted oil field – implications for safe CO2 storage in the North Sea

The Nini West depleted oil field in the Siri Canyon, Danish North Sea, is considered a potential storage site for safe sequestration of CO2 to fulfill Denmark's ambition to reduce CO2 emissions using carbon capture storage (CCS) technologies. The Paleocene Nini West sandstone reservoir is overlain by several caprocks forming a 900 m thick seal complex composed of the regionally distributed Eocene–Miocene Horda and Lark formations. The integrity and capacity of the seal complex has been evaluated using a multidisciplinary analytical approach integrating organic and inorganic compositional data, physical properties, wireline logs, and mud gas data. The seal complex consists of clay-dominated mudstones with a relatively homogenous lithology constituting a tight seal. Mud gas logs are introduced as a novel proxy for seal integrity in a CCS context, and they show only very limited vertical gas migration has occurred from the reservoir into the basal part of the seal. Average porosities range from ∼15–20% and both measured and modelled average permeabilities range from only 0.11–0.39 μD. The seal mudstones have narrow unimodal pore throat size distributions, and 40% of the samples have extremely small median pore throat radius r50. The seal has high supercritical (sc)CO2 displacement pressures, and it can hold back a vertical column of scCO2 of minimum ∼600 m providing a comfortable seal safety column-overhead. The current findings have relevant application to other depleted oil fields and saline aquifers with similar seals in the larger Central Graben area in the North Sea.

Pressure capability analysis of magnetic powder seals and pole tooth design by multiparameter optimization

Ferrofluid seals have been an increasingly popular sealing technique with unique advantages like zero leakage, long lifetime and low friction torque. But ferrofluid seals are incapable of specific working conditions, due to intolerance of extreme temperatures and limited pressure capability per stage. Recently, a novel sealing method using magnetic powders has been put forward to solve the problems. However, studies on the seal performance and theory of design are still blank. Here for the first time, we give a theoretical analysis of pressure capability of magnetic powder seals. The formula of pressure capability is derived, and a determinant coefficient is put forward. For sealing structure design, four derivative-free optimization algorithms are used to optimize geometric parameters of pole teeth. Finally, a sealing test bench was established, and the experimental data were compared with the simulation results. This research provides a basic theoretical and experimental guidance for magnetic powder seals.

Experimental Study of Converging Ferrofluid Seal With Small Clearance and Double Magnetic Sources

To improve the pressure capability of ferrofluid seals with small clearance, a converging ferrofluid seal with double magnetic sources was designed. The magnetic field distribution in the clearances of the converging ferrofluid seal was studied by employing the finite-element method, and the theoretical pressure capability of the seal is calculated. The effects of ferrofluid injection volume, radial clearance, axial clearance, and the numbers of radial pole teeth and axial pole teeth on the pressure capabilities of converging ferrofluid seal device were investigated by experimental methods and compared with the experimental pressure capability of the stepless ferrofluid seal. The results show that the experimental and theoretical pressure capabilities of the converging ferrofluid seal are in good agreement. The saturated ferrofluid injection volume of the converging ferrofluid seal device is 1 mL. The experimental pressure capability of the converging ferrofluid seal does not decrease with increasing clearance or decreasing number of pole teeth. The pressure capability of the converging ferrofluid seal is related not only to the size of the clearance but also to the number of pole teeth. The pressure capability of the converging ferrofluid seal is better than that of the stepless ferrofluid seal.

Flow and Ingestion in a Turbine Disc Cavity under Rotationally-Dominated Conditions

An investigation of hot gas ingestion driven by the disc pumping effect in a chute seal was conducted at the Oxford Rotor Facility. Measurements of mean pressure, unsteady pressure and gas concentration have been logged and analysed under different operating conditions. The sensitivity of mean cavity pressure coefficient, frequency spectra of the unsteady pressures and sealing effectiveness to changing conditions of purge flow, annulus flow, rotor disc speed and seal clearance have been studied. The steady pressures revealed the development of two vortices in the cavity, induced by the sharp change in geometry of the stator wall. The increased shear at the interface between these two vortices strengthened the unsteady activity at this location. The addition of mainstream flow improved the sealing capability of the chute seal under certain operating conditions. The excitation of further frequencies when an axisymmetric annulus flow was introduced suggests a complex interaction between annulus and purge flows.

Effects of Clearance on the Performance of a Labyrinth Seal Under Wet-Gas Conditions

Abstract The labyrinth seal is one of the most popular noncontact annular seals used in centrifugal compressors to improve machine efficiency by reducing the secondary flow leakage. Reducing the radial clearance Cr can effectively decrease the seal's leakage and therefore increase the machine efficiency. However, reducing Cr can also introduce undesired effects on the machine's vibration behaviors. This paper experimentally studies the impact of reducing Cr on the leakage and rotordynamic coefficients of a 16-tooth see-through labyrinth seal under wet-gas conditions. The test seal's inner diameter is 89.256 mm. Two rotors with different diameters are used to obtain two radial clearances (0.102 mm and 0.178 mm). Tests are carried out at a supply pressure of 62 bars, three speeds from 10 krpm to 20 krpm, three pressure ratios from 0.21 to 0.46, and six inlet liquid volume fractions (LVFs) from zero to 15%. The test fluid is a mixture comprised of air and silicon oil. Test results show that, for all pure-air and mainly air conditions, decreasing Cr decreases (as expected) the test seal's leakage mass flowrate. For all test cases, direct dynamic stiffness KΩ is negative, producing a negative centering force on the associated rotor. For inlet LVF ≤ 8%, the effects of decreasing Cr on KΩ are negligible. When inlet LVF = 12% and 15%, decreasing Cr increases KΩ (decreases the magnitude). In other words, when inlet LVF = 12% and 15%, decreasing Cr reduces the test seal's negative centering force on the rotor, and would increase the critical speeds of the rotor. The value of the effective damping Ceff near 0.5ω represents the seal's capability to suppress the rotor's potential whirling motion at about 0.5ω. For all pure-air and mainly air conditions, decreasing Cr generally increases the Ceff value near 0.5ω; i.e., decreasing Cr improves the test seal's stabilizing capability against the rotor's potential whirling motion at about 0.5ω.

In vivo Study of Sealing Capability of Raw Propolis Extract and Calcium Hydroxide on Dentin Surface.

AimThis research aimed to investigate the differences in the sealing capability of propolis extracts and Ca(OH)2 on dentin surfaces.Materials and MethodsEighteen mandible incisors of Wistar rats were prepared at a depth of 0.5 mm after which they were randomly divided into 3 groups (n=6) including control (C), pulp-capped with Ca(OH)2 group (P1), and indirect pulp-capped with propolis extract group (P2). All the cavities were sealed with glass ionomer restorative cement. Moreover, the sections of the teeth were obtained after six Wistar Rats from each group were sacrificed on the second day after treatment. The rats’ incisors were cleaved transversally to the area where Ca(OH)2 and propolis extract bonded with dentin for the SEM (scanning electron microscope) analysis and examined using microphotographs test with 5000x magnification. All the samples were measured and examined with spectrophotometry test to determine the bonding distance between Ca(OH)2 and dentin, as well as propolis extract and dentin. The result from the two tests was analyzed with SPSS using an independent t-test at p <0.05.ResultsThere were significant differences between the calcium hydroxide and propolis extract groups (p<0.05) based on the results obtained in the form of spectrums chemical functional groups of spectrophotometry examination. No new chemical bonding or compound was also observed to have been formed between propolis extract with dentin as well as calcium hydroxide with dentin.ConclusionThe adaptation or sealing capability of propolis extract was found to be better than calcium hydroxide to the dentin surface.

Numerical Study on Key Parameters of Magnetorheological Fluid Reciprocating Seal with Four Magnetic Sources

In order to improve the pressure capability of Magnetorheological fluid (MRF) reciprocating seal with four magnetic sources, MRF reciprocating seal structure was designed based on the formula of MRF reciprocating seal. The magnetic field distributons in the sealing gap of MRF reciprocating seals were analyzed by using finite element analysis of magnetic field. The influences of structure parameters such as sealing gap, ratio of permanent magnet height to length, ratio of pole tooth length to width, ratio of slot width to pole tooth width and ratio of pole piece height to the shaft radius on the sealing capabilities were studied. The results were analyzed and discussed. The results show that the pressure capability of MRF seal decreases significantly with the increase of sealing gap. The pressure capability of the MRF seal increases firstly and then decreases with the increase in the ratio of permanent magnet height to its length. The pressure capability of the MRF seal increases firstly and then decreases with the increase in the ratio of pole tooth length to its width. The pressure capability of the MRF seal increases firstly and then decreases with the increase in the ratio of slot width to pole teeth width. The pressure capability of MRF seal decreases with the increase in the ratio of pole piece height to shaft radius.

Magnetic Field Finite Element Analysis of a Novel Diverging Stepped Magnetic Fluid Seal

In order to improve the anti pressure capability of magnetic fluid seal under the large gap condition, a novel diverging stepped magnetic fluid seal was designed and set the pole teeth on the stepped shaft. The magnetic field distribution in the gap of diverging stepped magnetic fluid seal were numerical simulations by the finite element method of magnetic field. The effects of axial pole teeth number, radial pole number, radial sealing gap height and axial sealing gap on the anti pressure capability of a novel diverging stepped magnetic fluid seal were studied. The results show that the anti pressure capabilities of magnetic fluid seal increase with the increase of axial pole teeth numbers. The anti pressure capabilities of magnetic fluid seal firstly decrease and then increase with the increase of radial pole teeth numbers. The anti pressure capability of magnetic fluid seal firstly decreases and then increase with the increase of radial sealing gap height. The anti pressure capabilities of magnetic fluid seal decrease with the increase of axial sealing gap width.

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.

Design of Magnetic Circuit and Finite Element Analysis of Stepped Ferrofluid Seal with Small Sealing Gap

For the sake of study the pressure capability of ferrofluid seals with small sealing gap, a diverging stepped ferrofluid structure with small sealing gap was designed according to the theory of stepped ferrofluid and magnetic path design, and the length and cross-sectional area of the permanent magnet (NeFeB) are obtained. On the basis of these parameters, the ferrofluid distribution of seal gap is calculated by using the magnetic ferrofluid element method, and the pressure capability is obtained, then the reliability of the magnetic path design is obtained according to the capability of withstand voltage. There are some findings as following after analysis and comparison. It is the magnetic flux leakage at the junction of the pole boot and NeFeB that cause pressure capability calculated by the magnetic path method is lower than that calculated by the finite element method.

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.

Design, Construction, and Preliminary Investigations of Otta Seal in Iowa

Faced with limited financial resources, pavement engineers constantly seek more durable and economical technologies for road preservations and rehabilitations. Consequently, there have been many efforts to study resurfacing strategies, including various types of sealing for local roads. Among different sealing methodologies, Otta seal is a technique that has not yet been sufficiently studied in the U.S.A. For this investigation, the first Otta seal site in the state of Iowa was constructed using a double-layer Otta seal design over 6.4 km of cracked asphalt pavement. Otta seal design and construction details are documented and discussed, and test sections using various aggregates are compared for performance. The key lesson learned was that proper aggregate selection within gradation limits and aggregate spread rates were critical factors for Otta seal performance. Otta seal capability for holding loose aggregate particles and for dust control were examined, and there were indications that excessive proportion of fine aggregate particles could lead to diminished performance associated with fugitive dust emissions and unbound aggregate particles. Although the Otta seal provided a smooth surface satisfying road user and agency requirements, it did not significantly add structural capacity to the existing asphalt pavement. The findings from this study will benefit road officials and other decision makers who need to consider alternatives for resurfacing distressed low-volume asphalt roads.

Numerical and Experimental Studies of a Novel Converging Stepped Ferrofluid Seal

To improve the pressure capability of ordinary ferrofluid seals with a large gap, a novel type of converging stepped ferrofluid seals was proposed. The leakage positions and the magnetic field distributions in the sealing gaps of the new device are studied computationally by means of the finite-element method. The theoretical pressure capabilities of the seal are calculated based on a new expression introduced for the particular new seal geometry and for different sealing gaps. Computational results for effects of the radial and axial sealing gaps on the pressure capabilities of the seal are compared to the experimental results obtained from measurements employing a prototype of the proposed new seal. A good agreement between theoretical and experimental results is obtained. It is found that the pressure capabilities of the new seal depend on the height of the radial sealing gap and on the width of the axial sealing gap.

Sealing capability and marginal fit of titanium versus zirconia abutments with different connection designs.

PURPOSELimited data is available regarding the differences for possible microleakage problems and fitting accuracy of zirconia versus titanium abutments with various connection designs. The purpose of this in vitro study was to investigate the effect of connection design and abutment material on the sealing capability and fitting accuracy of abutments.MATERIALS AND METHODSA total of 42 abutments with different connection designs [internal conical (IC), internal tri-channel (IT), and external hexagonal (EH)] and abutment materials [titanium (Ti) and zirconia (Zr)] were evaluated. The inner parts of implants were inoculated with 0.7 µL of polymicrobial culture (P. gingivalis, T. forsythia, T. denticola and F. nucleatum) and connected with their respective abutments under sterile conditions. The penetration of bacteria into the surrounding media was assessed by the visual evaluation of turbidity at each time point and the number of colony forming units (CFUs) was counted. The marginal gap at the implant- abutment interface (IAI) was measured by scanning electron microscope. The data sets were statistically analyzed using Kruskal-Wallis followed by Mann-Whitney U tests with the Bonferroni-Holm correction (α=.05).RESULTSStatistically significant difference was found among the groups based on the results of leaked colonies (P<.05). The EH-Ti group characterized by an external hexagonal connection were less resistant to bacterial leakage than the groups EH-Zr, IT-Zr, IT-Ti, IC-Zr, and IC-Ti (P<.05). The marginal misfit (in µm) of the groups were in the range of 2.7–4.0 (IC-Zr), 1.8–5.3 (IC-Ti), 6.5–17.1 (IT-Zr), 5.4–12.0 (IT-Ti), 16.8–22.7 (EH-Zr), and 10.3–15.4 (EH-Ti).CONCLUSIONThe sealing capability and marginal fit of abutments were affected by the type of abutment material and connection design.