Seal Structure Research Articles

Castelo Velho: um projeto comum de arquitectura e paisagem?

Os restos vegetais carbonizados (carvões e sementes) recuperados durante as campanhas de escavação realisadas em Castelo Velho foram analisados com o objetivo d’obter informações sobre o contexto ambiental e económico no seio do qual o projeto arquitectónico tomou forma. Os resultados obtidos parecem sugerir uma possivel gestão voluntária da paisagem vegetal de forma a assegurar a visibilidade do recinto murado. A descoberta de uma estrutura repleta de sementes (cevada de grão vestido, trigo de grão nu e papoila d’ópio), associadas a cêramica, é particularmente marcante num sitio onde os restos de sementes/frutos são muito raros. Trata-se possivelmente de um depósito simbólico.

Experimental investigation of wind-induced internal pressures in nominally sealed building structures

The action of internal pressure cannot be neglected in wind-resistant design of large-span structures, high-rise buildings, and low-rise residential buildings. In this study, the internal pressure characteristics were first measured in still air in a completely closed building structure without any leakage. Then a series of wind tunnel tests were conducted to study the probability density distribution characteristics of the internal pressure responses in a nominally sealed building with background leakage. The mean and peak internal pressure responses associated with different background leakage distributions and wind directions were further investigated, and the experimental results were compared with those suggested by the Chinese wind load code GB50009-2012. The results indicated that the internal pressure in the completely closed building was non-stationary, and varied significantly when collected at different time points. Furthermore, a period of about 24 h was observed from the measured time history of internal pressure over 9 d. The internal pressure in a nominally sealed building structure nearly fitted a normal Gaussian distribution. When background leakage was uniformly arranged on the surface of the building, the mean internal pressure coefficient remained unchanged with increasing background leakage, varying within the range from −0.15 to −0.14, indicating lower magnitudes than the value of −0.2 suggested by the Chinese wind load code. The minimum negative peak internal pressure coefficient was −0.255 when the peak factor was 3.5, indicating a lower magnitude than the value of −0.326 calculated in the Chinese wind load code.

Numerical and Experimental Investigation of the Sealing Effect of a Specific Labyrinth Seal Structure

A numerical simulation and experimental study were performed to investigate the sealing effect of the labyrinth seal used in a wheel-side reducer. A three-dimensional computational fluid dynamics model was established based on the labyrinth structure. The effects of the temperature and viscosity of lubricant, rotor speed, pressure ratio, clearance, and cavity size of the sealing structure on the sealing were analyzed, and the leakage amount under the corresponding values of different factors was also analyzed. The results indicated that increase in the lubricating oil temperature, viscosity, pressure ratio, and seal clearance lead to decrease in the sealing effect and increases in the leakage. And the effect of rotational speed on the seal is low. To verify numerical simulation, the results of numerical analysis, a test bench was set up to simulate the work of the reducer, and the sealing effect of the sealing structure was examined. The simulation result was compared with the actual results. Both the numerical simulation and experiment indicate that the labyrinth seal achieves the desired sealing effect.

Investigation of two-phase change flow in mechanical seal with complex solid surfaces

Phase change flows between seal faces play an important role in the performance of mechanical seals. Cavitation and boiling phenomena are observed to occur between mechanical seal faces. Most studies on phase change flows in mechanical seals focus on only one phenomenon. However, in different mechanical seal structures, for example, sector-groove seals, cavitation and boiling may appear simultaneously when the temperature and speed are changed. This study contributes to ongoing investigations in the field by proposing a phase change flow model considering both cavitation and boiling in mechanical seals. First, the governing equations and main features of the proposed model are discussed based on the mass conservation law, which is particularly useful in cases where both cavitation and boiling occur. Then, numerical schemes were constructed by employing the liquid volume fraction and analyzed by considering two different forms of fluid flux equations. Case studies of two models, namely, the wavy face seal and hydrostatic seal, were conducted and separately analyzed, and the numerical results demonstrated the feasibility of the proposed model. Then, numerical simulation and experiment of a sector-groove seal were conducted to demonstrate the advantage of the proposed model. The proposed model is especially effective for analyzing the two-phase flow field bounded by complex solid surfaces.

Parametric study on the aeroelastic stability of rotor seals

Labyrinth seals are widely used in rotating machinery and can be prone to aeroelastic instabilities. The rapid development of computational fluid dynamics now provides a high-fidelity approach for predicting the aeroelastic behavior of labyrinth seals in three dimension and exhibits great potential within industrial application, especially during the detailed design stages. In the current publication a time-marching unsteady Reynolds-averaged Navier-Stokes solver was employed to study the various historically identified parameters that have essential influence on the stability of labyrinth seals. The findings from the numerical approach agree well with analytical criteria in determining the overall stability of the seal structure while being able to capture the acoustic behavior of the upstream or downstream large cavities and its influence on the inter-fin cavities. The high-fidelity approach provides additional insights on the effects of nodal diameter, travelling wave direction, pressure ratio, and the linearity of the phenomenon for relatively large vibration amplitudes, all of which can aid during the design space exploration.

Improved bioavailability of raloxifene hydrochloride using limonene containing transdermal nano-sized vesicles

The present investigation was carried out with the aim of optimization of raloxifene hydrochloride-entrapped, limonene containing transfersomes for transdermal delivery. Several formulations were prepared by varying independent variables such as Phospholipid, sodium cholate and limonene while vesicles size, entrapment efficiency and polydispersity index were the dependent variables for Box-Behnken Design. Further, bioavailability assessment of raloxifene in Wistar rats was evaluated after transdermal application and compared with its oral formulation. It was observed that the optimized raloxifene loaded transfersomes formulation showed vesicle size of 107.8 nm, polydispersity index of 0.252 and entrapment efficiency of 90.2% which is close to the predicted values of 114.45 nm, 0.251 and 82.82% respectively generated by the Design Expert software. The TEM image shows the outline and the core of the well identified sealed spherical structure. Confocal laser microscopy study demonstrated that the prepared transfersomes formulation was capable to increase the permeation of probe dye into deeper layer of rat's skin in comparison to the control dye solution. The transdermal flux presented by the transfersomes gel formulation was found to be 13.20 μg/cm2/h whereas the control gel showed the transdermal flux of 2.35 μg/cm2/h across rat skin. Further the in vivo pharmacokinetic study revealed that the relative bioavailability following application of transfersomes gel in Wistar rats was found be increased by 2.71 times as compared to the oral suspension of raloxifene. It was concluded that the prepared transfersomes formulation was found to be a potentially useful drug carrier for the enhancement of raloxifene bioavailability in rats.

Study On Axial Clearance and Seal of Scroll Compressor

In order to reduce the leakage of the axial clearance, the sealing strip is mounted at the top of the scroll tooth. For achieving the axial displacement compensation seal, it is put forward to open a hole that it is in one side of the high pressure chamber at the bottom of sealing groove. The high pressure chamber gas is introduced into the bottom of the seal. It can form a pressure difference. The article begins with the design of sealing groove structure. The stress analysis was carried out on the sealing strip, and sealing strip was established displacement calculation model of change. Secondly, through the simulation experiment, the friction and wear properties of several kinds of seal materials are compared and analysed. To select PEEK as sealing strip material is the most appropriate. Finally, taking typical parameters of involute scroll compressor as an example, the compressive performance of scroll teeth with sealed structure and non-sealed structure is simulated. The results show that the sealing displacement and axial clearance are basically the same under the two schemes. The sealing scheme is proved to be feasible. This lays the foundation for the further study of the axial seal of the variable section scroll compressor.

Compact fiber-optic ultrasonic sensor using an encapsulated micro-cantilever interferometer.

A compact optical fiber Fabry-Perot interferometer is proposed and demonstrated for ultrasound wave (UW) measurement. The sensor consists of a suspended cantilever in a sealed hollow-core fiber, while the end-face of the leading-in fiber together with the end-face of the suspended fiber act as two reflection mirrors and form an air cavity. A short section of graded index fiber is also employed as a micro-lens to improve the fringe contrast of the interference spectral pattern. Due to the suspended fiber structure, the sensor presents high sensitivity to UW loading, which allows the freely suspended fiber to be stretched and compressed easily. By spectral side-band filtering technology, a simple intensity interrogation technology is used for UW demonstration. Moreover, the sealed sensor structure avoids disturbance from other environment parameters, thus presenting good stability for UW detection.

Harmonisation of Coolant Flow Pattern with Wake of Stator Vane to Improve Sealing Effectiveness Using a Wave-Shaped Rim Seal

The rim seal of the gas turbine is intended to protect the material of the turbine disk from hot combustion gases. The study of the rim seal structure is important to minimise the coolant flow and maximise the sealing effect. In this paper, a wave-shaped rim seal for stator disks is proposed and its effect is confirmed by numerical analysis. To characterise the flow phenomena near the wave-shaped rim seal, a simplified model of the wave-shaped rim seal (Type 1 model), which excludes the rotor blade and stator vane, is analysed and compared with the conventional rim seal. Then, through analysis of the wave-shaped rim seal geometry (Type 2 model), which includes the rotor blade and stator vane, a reduction in egress and ingress flow was observed owing to the wave-shaped rim seal, and the sealing effectiveness on the stator disk of turbine was increased by up to 3.8%. Implementation of the wave-shape geometry in the radial seal is a novel choice for turbine designers to consider in future for better-performing and more-efficient turbines.

Rotationally-induced unstable flow characteristics and structural optimization of rim seals

In view of rotationally-induced unsteady rim sealing flow issues in the absence of mainflow nonuniform pressure fields, the large eddy simulation method validated by the enclosed rotating cavity flow measurement was adopted to investigate the instability of the flow in the enclosed rim seal cavity. On this basis, the unsteady Reynolds-averaged numerical calculation was carried out for three structures: typical axial and radial rim seals as well as the chute seal that is visible in actual engines. The unsteady sealing flow characteristics for typical rim seal structures are investigated. The dynamic characteristics of the large-scale vortex structures in the rim seal region are revealed by fast Fourier transform and cross-correlation analysis methods. Finally, the rotationally-induced sealing characteristics for different rim seal structures and the enlightenment of the seal structure optimization are given. The results show that the rotationally-induced rim sealing flow has inherent instability characteristics; a series of large-scale vortex structures are generated in the rim clearance region, which propagate in the circumferential direction at a speed lower than the rotor, and the vortex frequency, number of revolutions and number of vortices depend on the rim seal type; overall, the chute rim seal has the highest rotationally-induced sealing effectiveness.

An optimization study on the seal structure of fully-rotary valve energy recovery device by CFD

Leakage in isobaric energy recovery devices (ERDs) is inevitable. Three seal structures are introduced and studied for a fully-rotary valve energy recovery device (FRV-ERD) to reduce leakage. Effects of pressure difference and geometrical parameters of seal structure on leakage are investigated and compared for different seal structures. Results show that, as the key component of this ERD, the fully-rotary valve (FRV) achieves its best seal performance with the bilateral seal. For the FRV-ERD of design parameters, both the efficiency and required clearance are improved by using the bilateral seal to replace the original seal. The calculated efficiency is improved from 89.48% to 92.05% at the clearance of 30 μm under operating pressure and the required clearance increases from 18.1 μm to 20.4 μm. Based on the results of the optimized bilateral seal, an approximate leakage rate equation is proposed and can be used for design calculation. The performance of FRV-ERD with the optimized bilateral seal is improved greatly. Compared with FRV-ERD with the original seal, the efficiency of FRV-ERD with the optimized bilateral seal is improved from 89.48% to 96.33% at the clearance of 30 μm under operating pressure, and the required clearance increases from 18.1 μm to 29.5 μm, easing machining difficulty greatly.

Ringed seal demography in a changing climate.

Climate change is affecting species' distributions and abundances worldwide. Baseline population estimates, against which future observations may be compared, are necessary if we are to detect ecological change. Arctic sea ice ecosystems are changing rapidly and we lack baseline population estimates for many ice-associated species. Provided we can detect them, changes in Arctic marine ecosystems may be signaled by changes in indicator species such as ringed seals (Pusa hispida). Ringed seal monitoring has provided estimates of survival and fertility rates, but these have not been used for population-level inference. Using matrix population models, we synthesized existing demographic parameters to obtain estimates of historical ringed seal population growth and structure in Amundsen Gulf and Prince Albert Sound, Canada. We then formalized existing hypotheses about the effects of emerging environmental stressors (i.e., earlier spring ice breakup and reduced snow depth) on ringed seal pup survival. Coupling the demographic model to ice and snow forecasts available from the Coupled Model Intercomparison Project resulted in projections of ringed seal population size and structure up to the year 2100. These projections showed median declines in population size ranging from 50% to 99%. Corresponding to these projected declines were substantial changes in population structure, with increasing proportions of ringed seal pups and adults and declining proportions of juveniles. We explored if currently collected, harvest-based data could be used to detect the projected changes in population stage structure. Our model suggests that at a present sample size of 100 seals per year, the projected changes in stage structure would only be reliably detected by mid-century, even for the most extreme climate models. This modeling process revealed inconsistencies in existing estimates of ringed seal demographic rates. Mathematical population models such as these can contribute both to understanding past population trends as well as predicting future ones, both of which are necessary if we are to detect and interpret future observations.

Versatile triboelectric nanogenerator with a hermetic structure by air supporting for multiple energy collection

Triboelectric nanogenerator (TENG) exhibits considerable application prospects in many fields, which highlights the importance of the structure of TENGs. Various types of TENGs have been proposed and developed, nevertheless, the TENGs still face defects in structural stability, flexibility and environmental adaptability. In this work, we reported a novel air supported-TENG (A-TENG) with a hermetic structure for harvesting multiple kinds of energies. The output performance of the A-TENG under various internal air pressures were systematically studied, which proves that A-TENG can yield a maximum output when the internal pressure is 0.5 kPa. Besides, the internal air can balance the distribution of the applied force, homogenizing the forward and reverse signals of output performance. Furthermore, the influences of different factors on the output performance were compared and analyzed. As the size of external balloon grows, the optimum internal pressure corresponding to maximum output signals shows a slight diminishing trend. By controlling the internal air pressure, applied force, frequency, air relative humidity, temperature, and external resistance at 0.5 kPa, 50 N, 5 Hz, 20%, 10 ℃, and 5 MΩ respectively, the A-TENG can generate an optimum instantaneous power density of 6.74 W/m2. Typically, constituted with fully sealed structure, the A-TENG can effectively deal with the humidity or wet environment and accommodate diverse forms of mechanical energies including mechanical pressure, wind blowing, and air vibration, etc. This work proposes a visible solution for the structural optimization of TENGs, endowed with conspicuous advantages of being simple, lightweight, flexible, and cost effective, broadening the application areas of TENGs.

Sealing properties and structure optimization of packer rubber under high pressure and high temperature

During hydraulic fracturing operations of low-permeability reservoirs, packers are the key component to ensure the success of multistage fracturing. Packers enable sections of the wellbore to be sealed off and separately fractured by hydraulic pressure, one at a time, while the remainder of the wellbore is not affected. However, reliable sealing properties of the packer rubber are required to meet the high-pressure and high-temperature (HPHT) conditions of reservoirs (such as 70 MPa and 170 °C). In this study, the structures of the packer rubber with two different materials are optimized numerically by ABAQUS and validated by experiments. The optimization process starts from the packer rubber with a conventional structure, and then, the weakest spots are identified by ABAQUS and improved by slightly varying its structure. This process is iterative, and the final optimized structure of a single rubber barrel with expanding back-up rings is achieved. For the structure of three rubber barrels with metallic protective covers, both HNBR and AFLAS fail under HPHT conditions. For the final optimized structure, the packer rubber made of AFLAS can work better under HPHT than that made of HNBR which ruptures after setting. The results show that the optimized structure of a single rubber barrel with expanding back-up rings and the material AFLAS are a good combination for the packer rubber playing an excellent sealing performance in multistage fracturing in horizontal wells.

Study on Welding Techniques of 316L Lined Bimetallic Pipe

It is well known that welding technique was often a knotty problem for bimetallic lined steel pipes to use widely. A number of failures in secession of weld cracking and weld corrosion had been observed in oil fields in recent years, which seriously disrupted the order of oil and gas production. To solve welding problems of 316L bimetallic lined pipes, works outcome about failure analysis and welding process research were presented in this paper. Failure analysis results confirmed that Welding defects, high hardness regions was the main reasons about failure problems of weld crack while structure design defects of seal weld and bad back-protection effects of flux-cored wire resulted in weld corrosion. Welding defects in the regions of seal weld became the failure source while the high hardness both in the region of seal weld and weld joint formed the crack propagation channel, and therefore both initially contributed to weld cracking. Additionally owing to the structure design of seal weld, liner layer would be heated over and over again during the period of seal weld and then it was not enough to protect CRA layers from being damaged during the period of girth weld. As a result the corrosion resistance in the welding area was reduced to become a weak area. On the basis of failure analysis, further research work was carried out to improve welding performance. Seal weld structure and girth weld process was improved. The difference of welding wires and welding process was analyzed, and their defects were described separately. Results showed that the welding performance welding by ERNiCrMo-3 and supporting technology was more reliable than ATS-F309L and supporting technology, whether seal weld or butt welding. The distribution and value of the hardness could be effectively controlled; Moreover, corrosion resistance performance was also better. Therefore, the seal weld and girth weld conducted by ERNiCrMo-3 and supporting technology was feasible.

About the Inexpediency of Widely Using Honeycomb Seals in Steam Turbine Flow Paths

The article presents the results from an incisive analysis of using end and internal honeycomb seals (HS) in two T-60/73-7.8/0.04 steam turbines produced by the Kaluga Turbine Works (in Russian, KTZ) intended for being used at the Ufa TETs-5 combined heat and power plant. The honeycomb seals were installed in the flow path of these turbines on the customer’s request and have been applied at KTZ for the first time. Expectedly, the use of HSs could decrease parasitic steam leaks, thereby resulting in improvement of the turbine efficiency. According to assessments made by the ARMS research and production enterprise and expectations of KTZ specialists, the replacement of conventionally designed labyrinth seals by seals with honeycomb inserts would make it possible to increase the turbine efficiency by approximately 1% due to essentially narrower radial gaps in the end, diaphragm, and shroud seals. Experimental investigations of HSs during their operation under model test bench conditions have shown that parasitic leaks of working fluid may indeed be reduced using these seals. However, this is only possible for a narrow range of optimal ratios between the physical design parameters of the seal honeycomb structure and the gap between the stator and rotor elements. The ideas of applying HSs in steam turbines were borrowed from the experience gained from operation of gas turbine engines. In steam turbines whose supports are made with plain bearings, the rotor rotates over an intricate trajectory with respect to the steam turbine casing longitudinal axis. With vibration that takes place under steam turbine real operating conditions, the use of HSs is not expedient, at least in turbines with a flexible shaft. It is shown, taking a particular example, that the narrow gaps (0.15–0.30 mm) between the steam turbine stator and rotor elements as recommended by the HS manufacturers, with which the useful effect from application of HSs manifests itself, cannot be implemented under field conditions. Such statement stems from the results of acceptance tests of two T‑60/73-7.8/0.04 steam turbines produced by KTZ that were carried out at the factory’s test bench. It has been found after opening the turbine and examining its parts after the thermal tests on the bench that all HSs made with narrow radial gaps were destructed. The commissioning team involving the customer’s representatives has recognized that further operation of the steam turbines with such seals is impossible. A decision was made at KTZ to fit the steam turbines with new seals with increased radial gaps. Had the turbines not been opened at the factory, the destructions of their HSs would have been revealed in the course of steam turbine overhaul after 6 years of their operation.

Magnetic Circuit Design and Finite Element Analysis of Ferrofluid Seal of Engineering Machinery Hydraulic Cylinder

In order to solve the problem that the construction machinery hydraulic cylinder seal has a short life and cannot achieve zero leakage, This paper creatively applies ferrofluid sealing technology to engineering machinery hydraulic cylinders. In order to obtain the maximum magnetic energy product in the sealing gap of the ferrofluid sealing structure of the engineering machinery hydraulic cylinder, the pressure resistance performance and life expectancy of the ferrofluid seal of the engineering machinery hydraulic cylinder are improved. Based on the theory of magnetic circuit and the theory of ferrofluid seal, the magnetic circuit design of a ferrofluid seal structure with a uniform pole piece with eight magnetic sources is designed. The finite element analysis method was used to verify the pressure resistance of the ferrofluid seal of engineering machinery hydraulic cylinder, and the calculation results were analyzed and discussed. The results show:The design method of the magnetic circuit structure is reasonable and feasible, and has important reference significance for the design of the ferrofluid seal of the engineering machinery hydraulic cylinders.

Tightly Sealed 3D Lipid Structure Monolithically Generated on Transparent SU-8 Microwell Arrays for Biosensor Applications

Artificial lipid membranes are excellent candidates for new biosensing platforms because their structures are similar to cell membranes and it is relatively easy to modify the composition of the membrane. The freestanding structure is preferable for this purpose because of the more manageable reconstitution of the membrane protein. Therefore, most of the lipid membranes for biosensing are based on two-dimensional structures that are fixed on a solid substrate (unlike floating liposomes) even though they have some disadvantages, such as low stability, small surface area, and potential retention of solvent in the membrane. In this paper, three-dimensional freestanding lipid bilayer (3D FLB) arrays were fabricated uniformly on SU-8 microwells without any toxic solvent. The 3D FLBs have better stability and larger surface area due to their cell-like structure. In order to improve the sealing characteristics of the 3D FLBs, the applied frequency of the ac field was controlled during the electroformation. The 3D FLBs were observed through transparent SU-8 microwell arrays using confocal microscopy and demonstrated perfect sealing until 5.5 days after the electroformation at more than 1 kHz. Also, the details of the sealing of a fixed 3D freestanding lipid structure were discussed for the first time. The unilamellarity and biofunctionality of the 3D FLBs were verified by a transport protein (α-hemolysin) assay.

Seal Design and Test Verification of Lunar Sample Container

One of the key tasks of China’s lunar exploration phase three project is to collect lunar sample and return to earth under the condition of unmanned state, and to maintain the original state of the lunar sample, and to ensure the accuracy of the ground data analysis. Reliable sealing of lunar samples is key. This paper designs sealing scheme of lunar sample container, through the iteration test comparison and data analysis, seal structure is optimized, applicable sealing materials are determined. The test verification results show that the leakage rate of lunar sample container is better than that of 5 × 10-9 pa.m3.s-1, and the sealing performance meet index requirements, which can realize high purity seal of lunar sample and prevent contamination of lunar sample.

The significance of vapor pressure in quality preservation of stored commodities under gastight conditions

While investigating the preservation of the aroma of various spices we compared the effects of hermetic conditions, vacuum and carbon dioxide versus aerated storage. The quality of the tested spices stored under hermetic conditions was comparable to those stored in vacuum after 120 d of storage. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure. Throughout the investigation on specialty coffee, the volatility was evaluated as particularly important because coffee taste and aroma are influenced by compounds that are volatile. We hypothesize that hermetic storage reduces the rate of the volatiles to spread to the atmosphere. Dry food commodities can be stored for extended periods, provided there is no insect infestation and their water activity is low enough to prevent microbial growth. However, in aerated storages quantitative and qualitative losses still occur. If the moisture content is maintained sufficiently low, insects and quality loss remain the main concern for the quality preservation of durable agricultural commodities. Although in hermetic storage, the major emphasis is placed on the control of insect pests, for quality preservation just maintaining the vapor pressure in the sealed structure is sufficient. Quality preservation under hermetic conditions remains an aspect that deserves more attention. This characteristic of hermetic storage is the tendency to maintain within the hermetic structure the substances that have the ability to vaporize.