Fluid Seal Research Articles

The Effect of an Acetabular Labral Tear, Repair, Resection, and Reconstruction on the Hip Fluid Seal

The Effect of an Acetabular Labral Tear, Repair, Resection, and Reconstruction on the Hip Fluid Seal

Numerical and experimental study of magnetic fluid seal with large sealing gap and multiple magnetic sources

To improve the pressure capability of magnetic fluid seal with more than a 0.25 mm single edge gap, a magnetic fluid sealing structure with multiple magnetic sources which has five permanent magnets was designed. Magnetic field distributions under the pole pieces of the magnetic fluid seal with single and multiple magnetic sources were simulated by finite element method and its sealing pressure difference could be calculated according to the theoretical formula of the magnetic fluid seal. The effects of sealing gap height and magnetic source amount on the sealing capability were investigated experimentally. The theoretical and experimental results were compared, analyzed and discussed. The results demonstrated that the magnetic fluid seal with multiple magnetic sources was an effective method to improve the sealing capability for the rotary shaft with large gaps. The theoretical results agreed well with the experimental results when the height of the single edge gap was equal to 0.4 mm. However, it was found that when the height of the single edge gap was larger than 0.4 mm, the difference between the theoretical values and experimental values increased with the gap height because part of magnetic source had less or even no effect on magnetic fluid sealing capability.

New Structure of Crossing Magnetic Poles on Magnetic Fluid Seals

In order to improve the ability of magnetic fluid seals, the new structure of crossing magnetic poles on magnetic seals can be designed. The reluctivity of gap with the crossing magnetic pole is less than the reluctivity of gap without the crossing magnetic pole. The magnetic intensity in the gap can be bigger because of the crossing magnetic poles. According to the pressure formula of magnetic fluid seals, the pressure on the one side of magnetic fluid seals can be increased. The sealing capacity with the crossing magnetic pole is more than the sealing capacity without the crossing magnetic pole. The sealing capacity can be improved by 10%-15%.

Assessment of performance properties of wetsuits

Wetsuits are an integral part of surfing especially in the southern regions of Australia. There is currently little information about mechanical, comfort and thermal properties of wetsuits. There is a demand from wetsuit manufacturers to better understand the neoprene properties and wetsuit performance. The performance characteristics of eight top-selling wetsuits, from both high end and low end of the market, were examined. These characteristics include thickness, elasticity, bursting strength, hydrophobicity, thermal conductivity and seal strength. Tensile assessment revealed that neoprene foam was strong and its stretch recovery was well beyond 1.6 times of the original length. Neoprene was found to be hydrophobic with very low surface energy. High-end wetsuits with higher thickness showed slightly higher thermal resistance than low-end wetsuits, indicating that both thickness and bulk density of neoprene influenced thermal properties. High-end wetsuits with fluid seal were stronger than low-end wetsuits with stitched seal.

Experimental and numerical determination of the static critical pressure in ferrofluid seals

Ferrofluids have various engineering applications; one of them are magnetic fluid seals for rotating shafts. There are various constructions of this type of seals, but the main difference is the number of sealing stages. The development of this construction is a complex process which requires knowledge of ferrofluid physical and rheological properties and the magnetic field distribution inside the sealing gap. One of the most important parameters of ferrofluid seals is the critical (burst) pressure. It is the pressure value at which a leak will occur. This study presents results of numerical simulation of magnetic field distribution inside the seal gap and calculations of the critical pressure value. The obtained pressure values were verified by experiments.

FEM analysis of magnetorheological fluid seal of circular cooler and its experimental research

Magnetorheological fluid (MRF) exhibits drastic changes in rheological properties adjustable and controllable yield stress under external magnetic field. Based on its specialty, the MRF seal technique is proposed to deal with the air leakage of circular cooler to improve the energy efficiency for the steel industry. MRF is regarded as Bingham fluid with its magnetization vector and magnetic force expressed by mathematical functions. The FEM analysis results show that, under magnetic field, MRF which presents good pressure resistance as a result of its yield stress is in a dynamic equilibrium state in non-magnetic seal groove even with pressure difference, and due to the volume force, it presents unsteady swirl flow obviously at the right- angle edges of the two permanent magnets nearby non-magnetic separator, whereas, due to pressure difference, it shows an obvious flow without magnetic field. In the meantime, according to the experiment, it indicates that the air leakage of circular cooler is solvable effectively with the MRF seal method, and it is also proved that MRF shows controllable yield stress under magnetic field.

An In Vitro Study to Assess Determinant Features Associated With Fluid Sealing in the Design of Endotracheal Tube Cuffs and Exerted Tracheal Pressures*

To assess the structural characteristics involved in the design of high-volume low-pressure endotracheal tube cuffs that are associated with fluid sealing effectiveness and to determine the extent of transmitted tracheal pressures upon cuff inflation. In vitro study. Pneumology laboratories. Eight high-volume low-pressure cuffs of cylindrical or tapered shape, made of polyvinylchloride or polyurethane, were studied. Cuffs were tested within a tracheal model, oriented 30° above horizontal to assess 1 hr leakage of oropharyngeal secretions simulant at cuff internal pressures of 15-30 cm H2O. The four best performing cuffs were evaluated for 24 hrs using an internal pressure of 30 cm H2O. The extent of transmitted tracheal wall pressure throughout the cuff-trachea contact area was determined using an internal pressure sensor within a tracheal model upon cuff inflation up to 30 cm H2O. Outer diameter, length, and compliance of each cuff were assessed. Multivariate regression analysis was performed to identify the main determinants of simulant leakage rate. The cuff-trachea contact area and the percentage of tracheal wall pressure measurements greater than 50 cm H2O were computed. Cuff design characteristics significantly differ among tubes. The cuffs made of polyurethane showed the best short- and long-term sealing efficacy. Nevertheless, in the multivariate analysis, the cuff outer diameter (n: 288, p = 0.003) and length (n: 288, p < 0.001), along with the internal pressure (n: 288, p < 0.001), were the only predictors of simulant leakage rate. The tapered cuffs showed the lowest tracheal wall contact area (n: 96, p < 0.001). The tracheal wall pressure distribution pattern was heterogeneous, and the percentage of high tracheal wall pressure significantly differs among the cuffs (n: 96, p < 0.001). The high-volume low-pressure cuffs' outer diameter, length, material, and internal pressure are the main determinants of sealing efficacy. Despite internal pressure within the safe range, transmitted tracheal pressure is extremely heterogeneous and differs among cuffs, occasionally reaching localized, very high, unsafe levels.

A magnetic fluid seal for rotary blood pumps: Behaviors of magnetic fluids in a magnetic fluid seal

A magnetic fluid (MF) seal has excellent durability. The performance of an MF seal, however, has been reported to decrease in liquids (several days). We have developed an MF seal that has a shield mechanism. The seal was perfect for 275 days in water. To investigate the effect of a shield, behaviors of MFs in a seal in water were studied both experimentally and computationally. (a) Two kinds of MF seals, one with a shield and one without a shield, were installed in a centrifugal pump. Behaviors of MFs in the seals in water were observed with a video camera and high-speed microscope. In the seal without a shield, the surface of the water in the seal waved and the turbulent flow affected behaviors of the MFs. In contrast, MFs rotated stably in the seal with a shield in water even at high rotational speeds. (b) Computational fluid dynamics analysis revealed that a stationary secondary flow pattern in the seal and small velocity difference between magnetic fluid and water at the interface. These MF behaviors prolonged the life of an MF seal in water.

Numerical Simulation of the Flow Field in Circumferential Grooved Liquid Seals

Circumferential grooved liquid seals are utilized inside turbomachinery to provide noncontacting control of internal incompressible fluid leakage. Accurate prediction of the flow field is fundamental in producing robust and efficient designs. To validate the capabilities of the computational fluid dynamics FLUENT for incompressible fluid seal flow, comparisons of velocity parameters are made to the published experimental results and other CFD code for a circumferential grooved liquid seal. This work employs a pressure-based CFD code FLUENT to calculate the flow field in the seal, using four different turbulence models respectively. The velocity contours are compared with experimental values. It shows good overall agreement of the axial, radial, and azimuthal velocities in the through-flow jet, shear layer, and recirculation zone. Quantitative comparisons of velocity profiles at the center of the groove are made to experiment. This study verifies the prediction accuracy of three turbulence models. Various structures were considered to obtain a better understanding of the circumferential grooved liquid flow characteristics. The best groove structure to control leakage was also found within the limited designed seal. This study will provide a useful reference for designing the circumferential grooved liquid seal.

A magnetic fluid seal for rotary blood pumps: behaviors of magnetic fluids in a magnetic fluid seal with a shield

A magnetic fluid seal for rotary blood pumps: behaviors of magnetic fluids in a magnetic fluid seal with a shield

Multi-stage magnetic-fluid seals for operating in water – life test procedure, test stand and research results

ABSTRACTThe edge criteria for magnetic-fluid seals durability research are critical for the seal’stechnological usefulness. The magnetic fluid seal technology in water is much moredifficult technological problem in comparison to gas or vacuum environment. There isalways problem with immediate contact between magnetic fluid and the environmentaluninspected liquids. In the paper are presented ways of experiments definitions carried outwith multi-stage rotating magnetic fluid seal operating in permanent contact with utilitywater. The special test procedures have been elaborated and practically used, with theaim to define main characteristics of magnetic fluid seals. These characteristics were: critical pressure,critical motion velocity and working life of the seal. Some grades of commercial, silicon based magneticfluids of hydrophobic properties were tested in sealing system. The test stand and its features as well asresults of tests are presented in the form of tables, cross section draws and diagrams. In conclusion onecan see that multi-stage magnetic-fluid seals could be efficiently used in water for rotating shaft seals ina limited range of motion velocity and work lasting.

A finite element method for a noncoercive elliptic problem with Neumann boundary conditions

AbstractWe consider a noncoercive convection‐diffusion problem with Neumann boundary conditions appearing in modeling of magnetic fluid seals. The associated operator has a non‐trivial one‐dimensional kernel spanned by a positive function. A discretization is proposed preserving these properties. Optimal error estimates in the H1‐norm are based on a discrete stability result. Numerical results confirm the theoretical predictions. (© 2012 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Application study of magnetic fluid seal in hydraulic turbine

The waterpower resources of our country are abundant, and the hydroelectric power is developed, but at present the main shaft sealing device of hydraulic turbine is easy to wear and tear and the leakage is great. The magnetic fluid seal has the advantages of no contact, no wear, self-healing, long life and so on. In this paper, the magnetic fluid seal would be used in the main shaft of hydraulic turbine, the sealing structure was built the model, meshed the geometry, applied loads and solved by using MULTIPHYSICS in ANSYS software, the influence of the various sealing structural parameters such as tooth width, height, slot width, sealing gap on the sealing property were analyzed, the magnetic fluid sealing device suitable for large-diameter shaft and sealing water was designed, the sealing problem of the hydraulic turbine main shaft was solved effectively which will bring huge economic benefits.

3D Numerical Simulation of Magnetorheological Fluid Seal of Circular Cooler and Its Experimental Validation

3D Numerical Simulation of Magnetorheological Fluid Seal of Circular Cooler and Its Experimental Validation

Investigation of the Preservation of the Fluid Seal Effect in the Repaired, Partially Resected, and Reconstructed Acetabular Labrum in a Cadaveric Hip Model

Background: Debate exists on whether hip labral tears should be surgically repaired, partially resected, or reconstructed. Furthermore, limited data exist regarding the fluid seal properties of hip labrum repair and/or reconstruction with iliotibial band autograft when compared with the labrum-intact condition. Hypothesis/Purpose: The purpose of this study was to investigate the fluid seal properties of hip labral repair and reconstruction techniques. We hypothesized that hip labral repair preserves the acetabular labral fluid seal greater than labral tear, partial-resection, and reconstruction conditions. Study Design: Controlled laboratory study. Methods: Six human cadaveric hemipelvises were dissected of all soft tissue, leaving the hip capsule intact. Fluid efflux was measured under 5 conditions using a custom fluid infusion device: (1) hip labrum intact, (2) labral tear, (3) labral repair with suture anchors, (4) partial labral resection, and (5) labral reconstruction using ipsilateral iliotibial band autograft. Joint fluid expression was measured as flow rate under 3 different pressure settings (2, 3, and 4 psi). Statistical differences between conditions were assessed using 2-way, repeated-measures analysis of variance. The Student-Newman-Keuls (SNK) multiple comparison test was used to determine differences between levels. Results: There was a significant increase in fluid efflux with a simulated labral tear (0.54 ± 0.3 mL/sec) when compared with the intact hip labrum condition (0.006 ± 0.008 mL/sec, P < .05). The labrum-repaired condition (0.21 ± 0.2 mL/sec) demonstrated significantly less fluid efflux when compared with the labral-tear condition. Hip labral repair significantly prevented greater fluid efflux when compared with partial labral resection (0.60 ± 0.4 mL/sec) and reconstruction with iliotibial band autograft (0.54 ± 0.3 mL/sec; P < .05). Labral repair did not preserve fluid efflux as effectively as in the labrum-intact condition (0.21 ± 0.2 > 0.006 ± 0.008 mL/sec; P < .05). There was no difference observed in fluid efflux between the labral reconstruction, tear, or resection conditions (P > .05). Conclusion: In this human cadaveric model, hip labral repair outperforms partial labral resection and reconstruction in preserving the joint fluid seal; however labral repair does not restore fluid seal characteristics as effectively as in the labrum-intact condition. Clinical Relevance: Further prospective studies are needed to determine whether hip labral repair outperforms partial labral resection and/or reconstruction in clinical practice.

Coaxial twin-shaft magnetic fluid seals applied in vacuum wafer-handling robot

Compared with traditional mechanical seals, magnetic fluid seals have unique characters of high airtightness, minimal friction torque requirements, pollution-free and long life-span, widely used in vacuum robots. With the rapid development of Integrate Circuit (IC), there is a stringent requirement for sealing wafer-handling robots when working in a vacuum environment. The parameters of magnetic fluid seals structure is very important in the vacuum robot design. This paper gives a magnetic fluid seal device for the robot. Firstly, the seal differential pressure formulas of magnetic fluid seal are deduced according to the theory of ferrohydrodynamics, which indicate that the magnetic field gradient in the sealing gap determines the seal capacity of magnetic fluid seal. Secondly, the magnetic analysis model of twin-shaft magnetic fluid seals structure is established. By analyzing the magnetic field distribution of dual magnetic fluid seal, the optimal value ranges of important parameters, including parameters of the permanent magnetic ring, the magnetic pole tooth, the outer shaft, the outer shaft sleeve and the axial relative position of two permanent magnetic rings, which affect the seal differential pressure, are obtained. A wafer-handling robot equipped with coaxial twin-shaft magnetic fluid rotary seals and bellows seal is devised and an optimized twin-shaft magnetic fluid seals experimental platform is built. Test result shows that when the speed of the two rotational shafts ranges from 0–500 r/min, the maximum burst pressure is about 0.24 MPa. Magnetic fluid rotary seals can provide satisfactory performance in the application of wafer-handling robot. The proposed coaxial twin-shaft magnetic fluid rotary seal provides the instruction to design high-speed vacuum robot.

Study on Magnetic Fluid Static Seal of Large Gap

Researchers have been studying the magnetic fluid seal of small gap in the past. In order to meet the static seal requirements of large gap in aviation, aerospace, metallurgy, and so on. We set up the experimental rig of magnetic fluid static seal and designed the static seal of magnetic fluid. In the experimental rig, we studied the static seal of magnetic fluid and obtained the relationships among the burst pressure and the amount of injection of magnetic fluid, seal gap, temperature and magnetization in the experimental rig. In theory, we calculated the distribution of magnetic field under the seal gap and reasoned sustained pressure and temperature and calculated the burst pressure in different gaps and different saturation magnetization. We analyzed the experimental and theoretical results in detail. The theoretical analysis and tests indicated that magnetic fluid seal of large gap and large diameter can sustain a definite pressure and meet the requirements of practical problems.

Research on Sealing Technology of Magnetic Fluid in Medicinal High-Speed Grinder Gearbox

Seal leakage in medicinal high-speed grinder is one of the problems probe and research by equipment designer and user. In this paper, a new structure of seal is designed with a combination of micro-nano magnetic fluid seal and mechanical lubricating ring. Sealing structure has been optimized through tests on the reliability. Experimental results show that the method can better solve the seal leakage in Medicinal high-speed grinder.

Investigating the Fluid Seal of Supraglottic Airway Devices in Humans Using Indicator Dye via the Drainage Tube: A Potential Roadmap for Future Studies

Background: The fluid seal of supraglottic airway devices (SGA) protects the airway from fluid contamination. We evaluated the suitability of indicator dye placement in the upper digestive tract of anesthetized patients combined with fiberoptical tracing to investigate the fluid seal of SGA. Methods: Patients swallowed a capsule of indigo carmine green (ICG) prior to induction of anaesthesia. After induction of anesthesia, one of two different SGA (either an i-GelTM or an LMA-SupremeTM (LMA-S)) was inserted after randomization. Methylene blue stained normal saline was injected through the proximal opening of drainage tube during mechanical ventilation as well as spontaneous breathing. We monitored regurgitation of ICG with a flexible fiberscope (FO) inserted through the drainage tube and checked for the appearance of methylene blue in the mask bowl with the FO inserted through the airway tube. Results: In thirty-six patients with an i-GelTM and 37 with a LMA-S no regurgitation of ICG was observed at the level of the upper oesophageal sphincter (UES). Methylene blue stained saline was not visible in any patient during pressure-controlled ventilation, but was detected in two of the 36 patients with the i-GelTM during spontaneous breathing. Conclusion: Instilling dye through the drainage tube of SGA models with a built-in drainage tube represents a useful method to examine and to compare the fluid seal of different SGA. Our protocol presented in this study proved to be an easy and reproducible approach for future studies. Furthermore, the clinical results gained during this evaluation highlight the necessity for further investigations regarding the fluid seal competencies of SGAs in humans under clinical conditions.

Influence of the meridional flow and thermomagnetic convection on characteristics of magnetic fluid seal

For the low-speed magnetic fluid seals, the influence of the meridional flow, induced by the shaft rotation, on the distribution of magnetic particles concentration, is studied. Influence of the thermomagnetic convection on the structure of this flow and on the temperature distribution in high-speed magnetic fluid seals is investigated also. The problems were examined by numerical methods. It is discovered that even very slow rotation of the shaft homogenises distribution of the magnetic particles concentration in the seal and thereby enlarges its operation life. For high-speed seals thermomagnetic convection provides the penetration of the fluid flow in the region of the narrow gap and levels off the temperature distribution decreasing its maximum value and thereby enlarges its operation life too. It is found also that the influence of thermomagnetic convection grows with the viscosity increasing.