Seal Structure Research Articles

Influence of impeller clearance structure on volume loss of centrifugal pump

In this paper, the three-dimensional full flow field model of double volute structure centrifugal pump is established, and the ring seal, teeth seal and interlocking seal structures are set up. The K-e turbulence model of CFX software is used to simulate and analyse the fluid flow state at the gap of different mouth ring structures of centrifugal pump. The results show that the staggered ring structure can effectively reduce the leakage and improve the volumetric efficiency of centrifugal pump.

Failure analysis on rubber sealing structure of mandrel hanger and improvement in extreme environments

In view of the failure of the sealing structure of mandrel hanger under high pressure and extreme temperature environment, according to the sealing structure characteristics and application requirements of conventional mandrel hanger, based on the principle of the minimum sealing pressure ratio of metal sealing surface and the constitutive model of rubber material, the advantages and disadvantages of three conventional sealing structures are analyzed and compared. Based on the heat conduction theory and the energy conservation equation of thermal coupling, the transient temperature field model of the hanger seal structure is established. The heat transfer analysis and thermo-mechanical coupling calculation of the new metal seal structure are carried out at extreme temperature. The results show that the contact pressure on the double U and single U sealing rings is greater than 140 MPa at extreme temperature, which meets the principle of minimum sealing pressure ratio. The temperature distribution law of the conventional rubber structure under the temperature and pressure load is analyzed, and the reason of early failure of rubber is found. The mandrel hanger of full metal sealing structure is used in the field. The mandrel hanger of full metal have been tested for more than 20 times of gas pressure. The pressure is stable and the sealing effect is good. The test results show that this new structure has the advantages of good seal performance.

Core-scale geophysical and hydromechanical analysis of seabed sediments affected by CO2 venting

Safe offshore Carbon Capture Utilization and Storage (CCUS) includes monitoring of the subseafloor, to identify and assess potential CO2 leaks from the geological reservoir through seal bypass structures. We simulated CO2-leaking through shallow marine sediments of the North Sea, using two gravity core samples from ∼1 and ∼2.1 m below seafloor. Both samples were subjected to brine−CO2 flow-through, with continuous monitoring of their transport, elastic and mechanical properties, using electrical resistivity, permeability, P-wave velocity and attenuation, and axial strains. We used the collected geophysical data to calibrate a resistivity-saturation model based on Archie’s law extended for clay content, and a rock physics for the elastic properties. The P-wave attributes detected the presence of CO2 in the sediment, but failed in providing accurate estimates of the CO2 saturation. Our results estimate porosities of 0.44 and 0.54, a background permeability of ∼10−15 and ∼10-17 m2, and maximum CO2 saturation of 18 % and 10 % (±5 %), for the sandier (shallower) and muddier (deeper) sample, respectively. The finer-grained sample likely suffered some degree of gas-induced fracturing, exhibiting an effective CO2 permeability increase sharper than the coarser-grained sample. Our core-scale multidisciplinary experiment contributes to improve the general interpretation of shallow sub-seafloor gas distribution and migration patterns.

Design and Analysis of 10 MW HTS Double-Stator Flux-Modulation Generator for Wind Turbine

Due to the advantage of stationary seal structure, HTS double-stator flux-modulation direct-drive generators (HTS-DSFMDDGs) have been proposed and researched. In order to investigate HTS-DSFMDDGs for large offshore wind turbines, the design and analysis of the machine have been conducted in this paper. Firstly, the generator structure and the principle are introduced and the parameter optimization procedure is described. Then, the influence of design parameters such as pole number of field coils, pole ratio (ratio of rotor pole-pair number to armature coil pole-pair number) and diameter of air-gap on the performance, in terms of mass and cost of active material, is presented. Finally, the optimal parameter for the 10 MW HTS-DSFMDDG is determined.

Possibility of dopant morphology control in the process of polymer impregnation with pharmaceuticals in a supercritical CO2 medium

In this paper we present the results of polymethylmethacrylate (PMMA) impregnation with carbamazepine (CBZ) in a supercritical carbon dioxide (scCO2) medium at two different temperatures (75 °C and 105 °C) at a constant CO2 density. The obtained impregnated PMMA samples were analyzed by PXRD and Raman spectroscopy techniques. We have found that, irrespective of the impregnation process temperature, CBZ entrapped in the polymer matrix does not crystallize there but a CBZ solution in the PMMA is formed instead. It has been found that the CBZ concentration in the PMMA matrix grows as the impregnation process temperature rises due to the increase in the CBZ equilibrium concentration in the scCO2 phase, at that the conformational state of the CBZ molecules in the PMMA matrix was also found to depend on the impregnation process temperature. Finally, we showed that depending on the impregnation process temperature it is possible to obtain a PMMA matrix with either an opened or a sealed porous structure. In the latter case, not only CBZ, but also CO2 can be entrapped, remaining in the PMMA matrix in the high-density fluid state.

Research on leakage performance and dynamic characteristics of a novel labyrinth seal with staggered helical teeth structure

A novel labyrinth seal with staggered helical teeth (SHT) structure is proposed in this paper. The influence of seal clearance, pressure drop, tooth number and eccentricity on the novel model is studied by numerical simulation. In addition, the differences of static characteristics between the labyrinth seal with SHT structure and labyrinth seal with ordinary helical teeth (OHT) structure are also compared and analyzed. The results show that the numerical model for the labyrinth teeth structure has better accuracy compared with the experimental results. The SHT structure has better leakage performance than OHT structure because the former can induce higher turbulent energy dissipation at the staggered position. Besides, the fluid-induced forces increase with the increase of eccentricity and pressure drop. The novel model and corresponding results can provide meaningful references for the research of ring seal structure.

Simulation and Experimental Investigation of a New Type of Combined Seal Structure

Abstract Based on the study of leakage characteristics of labyrinth seal structure (LSS), a new type of combined seal structure (CSS) consisting of the labyrinth structure and the nozzle structure has been proposed. The sealing characteristics of CSS and LSS are compared by means of numerical simulation and experiments, and the effects of the internal resistance of the device, structural geometric parameters and other factors on the leakage characteristics of CSS are studied. The results illustrate the following conclusions: (a) When the inlet flow is 12 m3/h and the internal resistance of the device is 2000–4000 Pa, the leakage rate of CSS decreases by 30%–40% in comparison with that of LSS, which indicates that the performance of CSS is much better than that of LSS. (b) The leakage rate increases as the internal resistance of the device increases. When the internal resistance of the device increases from 2000 Pa to 8000 Pa, the leakage rate increases from 26% to 72%. (c) When the internal resistance of the device is constant, the larger the inlet flow, the smaller the leakage rate. (d) The choice of nozzle radius in structural geometric parameters is more important for the leakage rate than the tooth height and teeth numbers. When the nozzle radius decreases, ΔPAB (pressure difference between the labyrinth structure and the nozzle structure) and the leakage rate decrease accordingly.

Structural Parameter Analysis of Self-Tightening Metal U-Shaped Seal Ring

The effects of different structural parameters on the sealing performance of self-tightening metal U-shaped seal rings were studied. A two-dimensional axisymmetric model of a self-tightening U-shaped seal ring was established using finite element software. The influence of structural parameters such as side wall thickness, bottom wall thickness and boss radius on the sealing performance of the seal ring was analyzed by the control variable method. The results show that as the thickness of the side wall increases, the stress shows a downward parabolic trend, which is the smallest at 0.55 to 0.65 mm; as the bottom wall thickness increases, the stress first increases steadily, and then decreases slowly after 0.8 to 0.9 mm; When the inclination angle is from 0 to 9 °, the sealing ring can obtain better sealing performance. The results have guiding significance for the design, optimization and application of subsequent seal ring structures.

Application of asphalt rubber cape seal as asphalt pavement surface course for rehabilitated trunk highway in east Gansu

Although been frequently used as a preventative maintenance measure for asphalt pavements, the Cape seal process has not been widely adopted as a possible alternative for rehabilitated pavement. This research evaluated the feasibility of applying asphalt rubber Cape seal structure into the surface course of reconstructed highway in west China. The Cape seal is composed of 11-16 mm chips spread over asphalt rubber membrane sprayed in advance, by which followed a micro surfacing layer with SBR latex modified asphalt emulsion. Based on a test section in the Banxiao highway project, the construction of asphalt rubber Cape seal and micro-surfacing were investigated experimentally. In addition, to guide the engineers, major issues during construction of the Cape seal were discussed and corresponding countermeasures were suggested.

Prisoners’ Voices

Frederic Rzewski composed Coming Together and Attica in response to the 1971 uprising at the Attica Correctional Facility. The texts for the works draw upon testimonies of two men who participated in the riot: Samuel Melville and Richard X. Clark, respectively. Rzewski condemns the government crackdown on the uprising through representations of both prisoners and prison. In these and other works, the prisoner is a figure of suffering. Both Melville and Clark suffer through efforts to raise a voice about the hardships of incarceration only to have that voice break apart into fragments and silence. Prison emerges as a space of increasing confinement, conveyed by rigorous compositional schemes that tightly link individual sections and close them off in a larger sealed structure. The musical evocation of confinement along with the expression of psychological distress in the texts creates scenes of suffering. Through these scenes, Rzewski brings out the infliction of pain that scholars have viewed as a fundamental aspect of incarceration. The interaction between the critiques of incarceration and the compositional schemes in Coming Together and Attica is an example of how artists at the time (Steve Reich and sculptor Melvin Edwards) drew upon abstract idioms and materials in works that comment on contemporary political developments.

Moisture-proof seal optical fiber connector

Aiming at the problem of water mist condensation on the fiber end face in a high-power fiber laser system, the most important factor causing this problem is that the traditional optical fiber connector does not have the mois-ture-proof sealing performance. The connector structure assembly and use process are analyzed in-depth, and the causes of the moisture-proof seal defects are pointed out. Through technological innovation and process improvement, a moisture-proof seal fiber connector is designed and completed. The principle and structure of the moisture-proof seal of the new connector are introduced. The main performances of the new connector are tested comprehensively, including immersion test, constant damp heat test, online application test. The experimental results show that the new connector has a better moisture-proof seal with IL less than 0.2 dB.

Oil film characteristics and flow field analysis of asymmetrical hydrostatic support structure with full hydraulic fixed-length shear servo cylinder

The heavy-duty servo cylinder is the main actuator of the full-hydraulic fixed-length shear. The cylinder requires horizontal articulated mounting for accurate curve forces. The output of the curvilinear force causes the piston rod to be subjected to a dynamic bias load, and the presence of the bias load adversely affects the servo cylinder seal structure. In this paper, an asymmetric hydrostatic support structure is designed in the guide sleeve for the bias load problem of the servo cylinder, and the anti-offset capacity of the structure is theoretically studied. The oil film characteristics and oil film stiffness of the structure are deduced and analyzed. Fluent software is used to simulate, and then analyze the influence of inlet pressure, piston rod speed, eccentricity and partial load on the performance of asymmetric static pressure bearing oil film. Asymmetrical hydrostatic support structure servo hydraulic cylinder test bench is built for anti-bias load performance and friction performance experiments. The research results show that the new asymmetric hydrostatic support structure has a good effect on balancing the dynamic partial load, effectively reducing the friction of the servo cylinder and making the automatic alignment of the piston rod and the guide sleeve, which proves that the technology can be effective, increase the service life of the servo hydraulic cylinder and then improve the overall efficiency of the full hydraulic dividing shear, while broaden the application field of the heavy duty servo cylinder.

Analysis of sealing performance of a kind of profiled rubber gasket used in the radial contact seal structure

Sealing performance of standard rubber gaskets in the radial contact seal structure are observed through the experiment. A kind of profiled rubber gasket is proposed to replace the standard gasket. Leakage experiment and numerical simulation are carried out to study the sealing performance and failure mode of the profiled gasket. Several equations are presented to help analyze the failure reason. Results show that sealing performance of the profiled rubber gasket is more reliable than that of the standard rubber gasket. The failure reason of the profiled rubber gasket is that the friction force between the gasket external face and tube wall cannot balance the tube internal pressure. Dimension precision of the metal compressive ring has a great effect on the failure pressure.

Effect of the protrusion shape on gas ingestion of two sealing structures

The windage loss caused by protrusion in a rotor–stator cavity has been studied in detail, and there are abundant fitting formulas that have been summarized to calculate the moment coefficients. Some other theorists have emphasized its effect on the sealing efficiency, proposing that installation of protrusion could alleviate gas ingestion. However, the protrusion shape which is an influential factor on the sealing efficiency has not been focused in previous research. Using the experimental method of measuring CO2 volume fraction, cavity pressure, and power consumption, we investigated the effects of several typical protrusion shapes on various parameters for two sealing structures, in order to obtain the optimal shape. Results showed that a variation of the protrusion shape had little impact on the static pressure, but the total pressure and the sealing efficiency increased in different degrees. Furthermore, even though the hexagon shape resulted in the highest sealing efficiency, we observed that the drop shape had the best overall performance in all of the eight models, which could result in higher efficiency of the turbine cavity. The combination of a radial seal structure and protrusion could improve sealing efficiency better.

Computational fluid dynamics study of magnetic liquid rotary seal for sealing liquid

When applied in sealing liquid, the instability of the interface between the magnetic liquid and the sealed liquid in the direct-contact magnetic liquid seal structure will occur and increase, eventually leading to the failure of the magnetic liquid seal. In order to understand the destruction process of the interface between the magnetic liquid and the sealed liquid more intuitively, the two-phase flow of the magnetic liquid and the sealed liquid was simulated numerically. Phase distribution and velocity distribution are obtained through the simulation.

Label-free attomolar protein detection using a MEMS optical interferometric surface-stress immunosensor with a freestanding PMMA/parylene-C nanosheet

We demonstrated an optical interferometer-based surface-stress immunosensor using freestanding polymethyl methacrylate (PMMA)/parylene-C nanosheet with high sensitivity for detection of biomolecules. PMMA/parylene-C nanosheets were transferred onto a silicon substrate with microcavities to fabricate freestanding submicron-thick membrane with a sealed cavity structure. The adhesive force between the transferred parylene-C and binder parylene-C layer was measured to be 1.06–2.4 N/10 mm by tape test. Evading Debye shielding, these nanomechanical sensors allow detection of the adsorption on the membrane surface through changes in surface stress transduced by the electric charge. We optimized the density of receptors and mode of immobilization for high sensitivity. To evaluate the selectivity of the sensor, membrane deflections induced by various proteins were measured and the spectral shifts showed high selectivity only for the target antigen. The minimum limit of detection (LOD) of the sensor for human serum albumin antigen was 0.1–1 fg/mL (1.5–15 aM), which was 20,000 times lower than that of the conventional micro-cantilever sensor.

A high-accuracy non-contact online measurement method of the rotor-stator axial gap based on the microwave heterodyne structure

Rotor-stator axial gap is a key design parameter that affects the efficiency and safety of large rotating machines. An optimal axial gap value should be determined so that the rotating machines could work at the highest efficiency. To realize active clearance control (ACC) of rotating machines, high-accuracy non-contact online measurement of the axial gap must be carried out. However, direct current (DC) offset signals in absolute distance measurement, limited working space of sensors, and extremely harsh working environment all pose challenges to the realization of high-accuracy, non-contact, and online performance required by the axial gap measurement. Therefore, no mature measurement method exists at present. In this paper a rotor-stator axial gap measurement method was proposed based on the phase difference ranging principle. The structure of microwave heterodyne could effectively eliminate the errors caused by DC noise during absolute distance measurement. To break through the bottleneck of axial gap measurement accuracy, an axial gap measurement error model was established, and a signal carrier frequency error processing method along with a phase measurement error processing method based on spatial distance scanning were proposed. A platform modeled on the rotating machines’ structure of edge labyrinth gas seal was built in the laboratory to carry out room temperature rotor-stator axial gap measurement. A prototype of the axial gap measurement based on a microstrip type sensor was developed, and the system’s calibration and measurement performance evaluation experiments were carried out. Experimental results verified the effectiveness and accuracy of the proposed method. The measurement accuracy is better than 30 μm (at 0.5–3 mm) and better than 1% (at 3–18.5 mm).

Investigation of Cracks Observed in Underwater Bridge Seal Structures and Crack Control by Means of Material Design

AbstractA large number of cracks were observed in a bridge seal structure during an underwater inspection. The seal is 13.2 m long, 5.9 m wide, and 6.8 m deep and thus is considered mass concret...

Morphological evolution of oxide layer and its effect on glass-to-metal seal

In this work, whisker growth morphology, fine and coarse grain morphologies of oxide layer were performed on metal before sealing to study the surface oxide morphology impact on bonding behavior of seals. The results reveal that these different morphological oxides have the similar chemical composition, namely Mn1.5Cr1.5O4, and a twin structure is evidenced by transmission electron microscopy (TEM) in the whisker. After sealing, these whiskers completely dissolved into the glass due to its relatively high specific surface area and low required dissolution activation energy for atomic dissolution from grain boundary. Further, crack analysis presents that the complete dissolution of whisker promotes the interface integrity and increases the bonding strength of oxide/glass interface. It is a stark contrast to the seals to fine and coarse grain oxide layers. This study may offer guidance for designing interface structure of seals, especially for preparing the superficial materials of metal parts.

Multifunctional Fused Deposition Modeled Acrylonitrile Butadiene Styrene-Based Structures With Embedded Conductive Channels

Abstract The applicability of additive manufacturing (AM) continues to expand because of research and development efforts in industrial, academic, and governmental institutions. The lure of additive manufacturing lies in the quick time-to-market and ability to produce parts and components with high degrees of topographical complexity empowered by the layer-by-layer production approach. One challenge that is attracting a significant amount of attention is improving the multi-functionality of additively manufactured parts, as enabling multi-functionality will result in transitioning AM to a broader application domain. The objective of this paper is to report novel developments that improve the functionality of polymer-based parts by adding electrical conductivity and fluid management to the existing load-bearing capabilities. A space structure was 3D-printed using acrylonitrile butadiene styrene (ABS) with embedded internal channels throughout the entire structure and then sealed using an acetone-diluted epoxy. The inner surfaces of the embedded channels of the sealed structure were then metallized using an electroless silver-coating process; these processes were found to be robust and independent of the inner diameter and length of the structure. The electromechanical performance of the structure was verified by applying mechanical loading while monitoring the change in electrical resistivity. The latter was found to remain nearly constant up to the point of ultimate mechanical failure. Finite element modeling was used to identify the areas of structural weaknesses and assist in elucidating the failure modes. The results were found to be in good agreement with the experimental data.