Flexible Seal Research Articles

A novel flexible seal technology and its application in heat transfer of rotary air preheater

The leakage of rotary air preheater (RAPH) greatly affects its heat transfer efficiency in energy conversion. Non-contact rigid seal usually produce large leakage. Contact flexible seal can reduce the leakage of RAPH. However, the friction due to the contact is lack of attentions. In this paper, the heat transfer efficiency of RAPH with flexible seals are studied. Firstly, a herringbone contact flexible seal (HCFS) is provided to reduce the leakage. Then the friction force of HCFS was calculated according to finite element method (FEM). Next, the friction powers on the axial, radial and bypass directions for different interference are examined by theoretical analysis. In the end, the friction power of RAPH with HCFSs is compared with that from the experimental data and shows a good consistency. The results implied that the whole heat transfer efficiency of RAPH increased after installing appropriate HCFSs. The HCFS technology is beneficial to reduce leakages, improve heat transfer efficiency and optimize RAPH.

The importance of Southern Ocean frontal systems for the improvement of body condition in southern elephant seals

Abstract As top predators, it has been suggested that southern elephant seals serve as sentinels of ecosystem status to inform management and conservation. This is because southern elephant seals annually undertake two large‐scale foraging migrations for 2–3 and 7–8 months to replenish resources after fasting during breeding and moulting and often rely on dynamic macroscale latitudinal fronts to provide favourable foraging through aggregating prey. Yet it is largely unknown whether southern elephant seals respond to changes in frontal systems over the years, whether their foraging success is associated with specific frontal systems shifts, and how flexible southern elephant seals populations are in behaviourally adapting to changes in frontal systems. This study examines the relationship between frontal systems and the resource acquisition of 64 southern elephant seals during four post‐moult and three post‐breeding migrations between 2005 and 2010. Satellite‐relay‐data‐loggers provided in situ measurements concurrent with >27,500 dive profiles to define fronts and interfrontal zones between the Subtropical Frontal Zone and the Southern Boundary of the Antarctic Circumpolar Current. For >430,000 in situ measurements water mass properties could be identified. Generally, southern elephant seals associate more frequently with more southerly, higher‐latitude fronts/zones. Body condition improvements related to a given frontal system or water mass vary strongly according to year, season, month and sex. The variability in body condition improvements is higher in some frontal systems than in others, probably owing to shifts in the Subantarctic and Polar Front. During a migration, some individuals stay within ≤3 frontal systems, whilst others change between several frontal systems and primarily improve their body condition in upper ocean waters. Southern elephant seals do not trace particular water masses across frontal systems, and both surface and deep foraging strategies are used. This suggests that southern elephant seals do not target particular water masses but adjust foraging and movement strategies to exploit boundary areas at which mixing and prey aggregation is high. The large behavioural plasticity towards the spatio‐temporal variability in the different oceanographic regions they encounter could indicate resilience against environmental changes.

Validation of a commercial fluid-structure interaction solver with applications to air cushion vehicle flexible seals

Air cushion vehicle (ACV) flexible seals operate in a complex and chaotic environment dominated by fluid-structure interaction. An efficient means to explore relationships between interdependent governing parameters that affect performance is through high fidelity numerical simulation. As previous numerical efforts have employed separate iterative partitioned solvers, or have implemented simplified physics, the approaches have been complex, computationally expensive, or of limited utility. This research effort performs numerical simulations to verify and validate the commercial multi-physics tool STAR-CCM+ as a stand-alone partitioned approach for fluid-structure interaction problems upon a free surface. An implicit, incompressible finite volume fluid solver is fully-coupled to an implicit, nonlinear finite element structural solver to successfully replicate Turek-Hron benchmark results for an elastic beam in unsteady laminar flow. To validate the implementation as an ACV seal parameter exploratory tool, a planer bow seal model is developed and results are obtained for various cushion pressures and inflow speeds. Previous numerical and experimental results for deflection and resistance are compared, showing good agreement. A dimensional analysis is conducted to identify potential non-dimensional forms of parameters related to seal resistance. This work is a stepping stone for future researchers having interests in ACV seal design and other large deformation, fluid-structure interaction problems. By modeling all necessary physics within a single verified and validated computational desktop, a designer's ability to comprehensively investigate seal geometries and interactions has never been more promising.

Suture-Less Circumcision by Glutaraldehyde Albumin Glue Enhanced Laser Tissue Welding—A Comparative Study

Background: Suture-less circumcision by Feracrylate glue creates a weak and non waterproob bond. Hence, there is wound dehiscence and delayed healing which favor infection in many patients. I am describing a new technique for suture-less circumcision which is free from above limitations. Methods: In my center in the time span of 2 years, I did 51 cases of circumcision with Laser tissue welding technique (group A). Age range was 5 months to 21 years. During the same time span, in 56 patients circumcision was done by Feracrylate glue (group B). The age range was 3 months to 22 years. This group was kept as a control. Patients in both groups were randomly distributed. The technique of circumcision by Laser tissue welding is as follows. Patient is under short GA, the prepuce above the artery forceps is chopped off by scissors and bleeders are coagulated by bipolar cautery. Now, 0.9 ml 40% human albumin is taken in 1 ml syringe and mixed with 0.1 ml of 10% glutaraldehyde solution. The syringe is shaken vigorously to mix both the components. The skin and mucosa of penis are held by tooth forceps and a thin layer of this mixture is layered over it all around. Infrared Laser of 5 watts power and 850 nm illuminated over this bond for 60 seconds to polymerize it. Results: In group A, 2 (3.9%) patients developed partial wound gape, no patient had complete wound gape. 3 (5.88%) patients had grade 2 infections which settled with conservative treatment of oral antibiotics. In group B, 6 (10.71%) patients had partial wound gape and 8 (14.28%) patients had complete wound gapping. 11 (19.64%) patients developed grade 2 and 8 (14.28%) patients grade 3 wound infection. All these 19 patients’ post-operative antibiotics were started and given for 7 - 10 days. The Glutaraldehyde albumin mixture bond is already described in medical literature (Bioglue) for its use to seal coronary anastomosis after CABG operation, to seal sutures of cardiac surgery and for aortic dissection, etc. It is a surgical adhesive composed of purified bovine serum albumin (BSA) and glutaraldehyde and is already American FDA approved. It creates a flexible mechanical seal independently of the body’s clotting mechanism. In my technique, 0.9 ml of 40% human albumin is mixed with 0.1 ml 10% glutaraldehyde solution which costs only 50 cents which is a massive 1000 times cost reduction. Laser application polymerizes the glue and forms a waterproob bond in less than a minute. In my technique, percentage of glutaraldehyde used is only 10% compared to 50% in bioglue, hence it is non-toxic to the tissues. Conclusion: Suture-less circumcision by glutaraldehyde albumin glue enhanced Laser tissue welding is a safe, cheap and effective technique of performing circumcision. It is an important advance in circumcision surgery after a long time. The technique becomes a foundation for its vast application in other areas of surgery.

Numerical results of the influence of thermal effects on the turbo machine rotordynamics induced by light-rubs against a brush seal

Brush seals are an efficient alternative for labyrinth seals in turbomachinery. Brush seals show on the one hand a better leakage reduction in relation to their axial length and hence allow a shorter design of the machinery. On the other hand, the particularly small gap between bristles and the engine shaft increases the risk of rotor-stator-contact. The flexible brush seals induces basically light-rubs that in some cases might lead to spiral vibrations and thermal mechanical instabilities.Spiral vibrations are caused by a thermal deflection of the rotor induced by a heat flow into the shaft. To predict areas of instabilites during the design process a tool was developed at the Berlin Institute of Technology. The model combines a rotor dynamic model and a thermal model. The thermal system is reduced using a stationary solution, so that the final system, on which the stability analysis is performed, is comparable to the established Kellenberger model.The paper presents the numerical model for the predictions of unstable regions depending on rotational speed. This is illustrated by means of an example of an axial compressor manufactured by MAN Diesel & Turbo.

Application of Golay Coded Pulse Compression in Air-coupled Ultrasonic Testing of Flexible Package Seal Defect

Air-coupled ultrasonic testing is a possible implementation method for online seal defect detection of flexible package. However, large acoustic impedance difference between air and solid material leads to difficulties in coupling ultrasonic energy into solid materials and results in a poor signal to noise ratio (SNR). To solve this problem, pulse compression technique based on Golay codes has been applied in air-coupled ultrasonic testing of flexible package seal defect. The effects of different Golay codes (4, 8 and 16 bits) and Golay codes with different bit length (1, 2, and 3 circles) are investigated to obtain a reasonable parameter selection. The results demonstrate that the Golay coded pulse compression technique can improve the SNR ratio of the received signal remarkably, and suppressed the side lobe of the compressed pulse effectively. An improvement in SNR of the seal region image up to 9.4 dB is achieved, compared with the non-modulated excitation method.

Impact dynamic analysis of C/C composite finger seal

With the development of science and technology, the performance of an aero-engine has been given more rigorous requirements. Seal device is an important component part of an aero-engine, and the improvement in its performance may be an efficient way to further improve the performance of an aero-engine. Finger seal is a flexible seal and has higher performance price ratio, therefore it gets more attention and research recently. The phenomenon of noncontact state converting to contact state will occur in every working cycle of finger seal that inevitably lead to the finger seal bearing the impact effect of rotor. But so far, the influence of impact on the finger seal performance has not been discussed and researched. To overcome this shortcoming, the stress–strain curves of C/C composite under different impact velocities are obtained by the Gleeble3500 thermo-simulator system in the paper, and then the elastic modulus of C/C composite in three directions is calculated by experimental data. The effects of impact velocity and impact damping on the impact force are analyzed by means of the impact theory. The new structural stiffness of finger seal and the impact displacement excitation of the rotor are built through impact effect analysis. On this basis, the equivalent dynamic model of C/C composite finger seal with distributed mass is established to evaluate the impact effect. By the model, the difference of calculated results is analyzed under whether considering the impact effect or not. And the effect of impact velocity and coefficient of restitution on the dynamic performance of the finger seal is also analyzed under considering the impact effect, respectively. The above results show that the impact effect has significant influence on the leakage and wear of finger seal, therefore when the performance of the finger seal was analyzed, it is necessary to consider the impact effect.

Climate loads in insulating glass units: comparison of theory and experimental results

The verification of insulating glass units in ultimate limit state often gives rise to the question of how to take into account the edge seal in the design of the glass panes. Usually the edge seal is calculated as immovable, as this is a more conservative assumption. A flexible edge seal, as to be expected under realistic conditions, leads to a lower climate load and therefore to lower stresses in the glass. In order to determine the influence of a flexible support on the verification of the ultimate limit state under the applicable standards in Germany, various setups of insulating glass units were subjected to cyclically recurring temperatures of $$-$$ 18 to $$+53\,^{\circ }\hbox {C}$$ in a climate chamber. In this procedure, the atmospheric pressure was measured as well as the pressure in the cavity, as were the deformations of the edge seal orthogonally to the glass panes. Based on these, a comparison of analytical calculations of the climate load and the experimentally determined climate load is conducted. By means of the experimentally determined pressure difference in the cavity and the measured deformations of the edge seal, an effective spring stiffness in tension of the edge seal under the climatic test conditions was calculated using a finite element (FE) model. On the basis of an effective spring stiffness in tension assumed in a FE simulation, the influence of a flexible edge seal on the design of the glass panes is determined and discussed.

A comparative analysis of innovative microchannel heat sinks for electronic cooling

In this work, a comparative analysis of innovative microchannel heat sinks such as two-layered and multi-layered microchannel heat sinks (MCHS), or thin films within flexible complex seals and cooling augmentation using microchannels with rotatable separating plates, is presented. A compilation of the numbers of layers, main characteristics, setups, advantages and disadvantages, thermal resistance, pumping power in double-layer (DL-MCHS) and multi-layer MCHS (ML-MCHS) is presented. In addition, the thermal resistance is analyzed in order to present a comparison between the single-layer MCHS (SL-MCHS) and multi-layer microchannels. The results of comparison indicates that double-layer and multi-layer MCHS have lower thermal resistance and require smaller pumping power and they resolve the high streamwise temperature rise problem of SL-MCHS.

Development of flexible ceramic-glass seals for intermediate temperature planar solid oxide fuel cell

The ceramic-glass was employed as the most commonly used seal materials in planar solid oxide fuel cell (SOFC). In this study, a novel glass with relative low glass soft temperature was added into Al2O3 powders to form ceramic-glass composite seals by tape casting technique. Based on the tested result of gas tightness and compressibility, it was found that the seals with 40 wt% glass exhibited excellent seal performance at the leakage rates of only 0.01 sccm.cm−1 under gas pressure of 10.2 kPa, and compressive load of 0.17 MPa at 750 °C. The seals showed the desired thermal cycle stability at low leakage rates within 10 thermal cycles. It can be observed that the deformability of seals sharply increase when the glass contents was higher than 30 wt%. Microstructural analysis of the seals also exhibited very good interfaces bondage and chemical compatibility which was in good agreement with gas tightness prediction for the flexible ceramic-glass seals model. The seals have been applied in large size cell test to confirm its applicability in SOFC.

Development and application of a packer-type drilling-free liner hanger

In liner cementing, the upper cement plug and inner components of a common hanger needs to be drilled out after cementing, which will result in a poor cementing quality or even gas leakage at the flare opening. Therefore, a new packer-type drilling-free liner hanger has been developed, and a hydraulic setting-control packer, a flexible drilling-free seal box, and an auxiliary bearing back-off mechanism that go with the line hanger have been designed at the same time. Specific operation procedures include: (1) run in the liner string to the designed depth, then fully circulate the drilling fluid, finally drop the ball. When the tripping ball gets into the seat, the pressure will go up to cut off the hanging control pin and set the hanger; (2) continue to hold the pressure and cut off the ball seat pin to form circulation; (3) trip in the drill pipe to exert pressure on the hanger, back off to release the hanger from the running tool; (4) lower the drill pipe plug upon the completion of cement injection, cut off the releasing control pin of hollow casing plug, and run down further to bump with the bumping assembly; (5) remove the cementing head and connect the kelly driver, hold pressure again, then slowly pull up the drill tools, exert hydraulic pressure on the setting hydraulic cylinder of the packer assembly to cut off the setting control pin and set the packer; and (6) pull up the tools to the flare opening and wash out excessive cement slurry by circulating to realize free drilling of the whole hole. The successful application of the liner hanger in 127 mm diameter liner in Well BQ203-H1 indicates that the packer-type liner hanger has such advantages as easy hanging and back-off, accurate bumping, simple setting, and sound sealing performance.

Analytical and Numerical Analyses of Partially Submerged Membranes

AbstractThe presented work investigates the deformed shape and tensile state of inflated membranes partially submerged in fluid. The understanding of membrane behavior is of primary concern in marine-related problems, as well as other fields. This analysis is motivated by the flexible seals of surface effect ships and inflatable pontoons. A new exact solution for the governing differential equations and a new finite-element approach are developed. The stiffness influence coefficient method is used to derive the stiffness of the curved elements in which the end nodal displacements define the degrees of freedom. The methods of analysis are shown to provide two-dimensional results that are in excellent agreement in terms of both deformed geometry and membrane tension.

Numerical simulation for the loop seal in the circulating fluidized bed and experimental validation

The controllable and flexible loop seal of CFBs is essential for steady and high-efficient circular running. Based on the energy-minimization multi-scale (EMMS) model, a revised drag force coefficient expression was coupled with the two-fluid model (TFM) and the kinetic theory of granular method (KTGF) to investigate the hydrodynamic characteristics of the loop seal and standpipe in a CFB. 2D simulations for the standpipe and loop seal were implemented to test the validity of the physical and mathematical models, and excellent numerical performances and encouraging results were observed. The flow character and solids' streamline in the standpipe and loop seal, solids inventory, aeration position and the fluctuation of riser's total pressure drop were analyzed in detail. Some suggestions on the design of the experimental apparatus were proposed to ensure the experimental system's stability and controllability. Under the working conditions in this paper, the simulation results are in agreement with the laboratory ones, which reveals these models in this work is competent for the simulation of the standpipe and loop seal of CFBs.

Investigation of the mechanical behavior of a flexible solid metal seal for a cryogenic butterfly valve

Seat tightness at the fully shut position should be a consideration in the development of a butterfly valve for use in a liquefied natural gas (LNG) vessel. A flexible solid metal seal offers sufficient tightness of the butterfly valve and meets the specifications for cryogenic temperature. In the present study, characteristics for a cryogenic butterfly valve, such as the flow coefficient and the pressure loss coefficient, were estimated by numerical fluid analysis carried out to simulate 3-D flow and to study performance as it was affected by the opening angles of the valve disc. A design criterion to ensure the seat tightness of the butterfly valve at the fully shut position was proposed, in which the contact pressure between the metal seal and the valve disc would be compared with the fluid pressure. Numerical structural analysis showed that the contact pressure can be calculated by simulation of the frictional contact behavior on the surface of the metal seal and the valve disc. As a result, an adequate flexibility of the metal seal and the valve disc was required in order to accomplish a contact pressure that would be high enough to satisfy the seat tightness requirement. Under cryogenic temperature, thermal shrinkage caused the metal seal to adhere closely to the valve disc periphery at both sides and raised the contact pressure to a relatively high value, though there was no contact across a small area at the center position, which is susceptible to leakage. An additional displacement of the metal seal and the valve disc appeared at an operating fluid pressure of 6.9 bar and produced sufficient contact pressure at the no-contact area. This was verified by experimental leakage tests performed at room and cryogenic temperatures.

Gas-tight coke-oven doors

The gas-tightness of coke-oven doors may be improved by means of a flexible membrane seal in which the edge of the membrane is pressed against the perimeter by a spring; gas-exhaust channels; and separation of the door’s welded housing from the lining module using a sealing frame. This follows from many years of operational experience at two coke batteries equipped exclusively with such doors. A direct-action gate is proposed. The use of such gas-tight doors at coke plants within the Commonwealth of Independent States is recommended.

초저온 버터플라이 밸브용 탄성 메탈실의 누설방지에 관한 연구

LNG 선박에 사용되는 초저온용 버터플라이 밸브의 개발에 있어, 누설검증은 가장 중요한 설계공정 중 하나이다. 초저온에서 누설방지가 가능한 실로서 인코넬 스프링과 같은 탄성지지체가 포함된 O-링 형태의 메탈실이 널리 사용되고 있으나, 제작비가 고가인 단점을 갖고 있다. 이에 대한 대안으로 부가적인 탄성지지체 없이도 누설조건을 만족시키며, 제작비가 저렴한 탄성 메탈실의 개발이 요구되고 있다. 본 연구에서는 탄성 메탈실의 누설방지를 위한 설계조건을 정립하여, 초저온 및 고압환경에서 누설방지가 가능한 탄성 메탈실의 형상을 수치해석을 통해 고찰하였다. 아울러 이를 기반으로 시제품을 개발하고, 상온 및 초저온 상태에서 BS6755 및 BS6364 에 준하는 누설시험을 실시하여 누설여부를 확인하였다.

Modeling of air cushion vehicle's flexible seals under steady state conditions

The purpose of this paper is to demonstrate the efficacy of modeling a surface effect ship's air-cushion flexible seal utilizing a two-dimensional beam under steady state conditions. This effort is the initial phase of developing a more complex three-dimensional model of the air-seal-water fluid-structure interaction. The beam model incorporates the seal flexural rigidity and mass with large deformations while assuming linear elastic material response. The hydrodynamic pressure is derived utilizing the OpenFOAM computational fluid dynamic (CFD) solver for a given set of steady-state flow condition. The pressure distribution derived by the CFD solver is compared with the pressure required to deform the seal beam model. The air pressure, flow conditions and seal geometry are obtained from experimental analysis. The experimental data was derived from large-scale experimental tests utilizing a test apparatus of a canonical surface effect ship's flexible seal in a towing tank over a variety of test conditions.

Coal-Dust Motion Law and Control Technology of the Feeder

The aim of this paper is mainly to study the main coal-dust pollution sources in the coal preparation plants of Ping Shuo Branch of China National Coal Group. Through the combination of many measurement data with numerical simulation of gas-solid two-phase flow, dust precipitation mechanisms have been gained for the feeder in Ping Shuo Coal Preparation Plant. Dust pollution of the feeder is caused by the positive pressure of the induced feeding wind-flow and the bad seal itself. Firstly, the durable flexible seal material is used to seal up the feeder. Secondly, the seal guide-chute with the dust collector is installed on the belt. Finally, the air volume and the pressure of the dust collector are determined by means of numerical simulation, and the reasonability of the plan is explained from the angle of the dust control mechanism. The main technical parameters of the dust control plan, such as the seal guide-chute length, and the air volume and the pressure of the dust collector, are determined through the numerical simulation. The simulation result and the actual result verify the above dust control plans. The study methods and results provide a guide for the dust control in a certain similar business.

킥모터 플렉시블 씰 개발을 위한 고무의 성능 평가

A Kick Motor, KSLV-I second stage propulsion system, utilizes a flexible seal for pitch and yaw axis controls during combustion. A flexible seal consists of the alternate laminate of rubber and composite reinforcement between forward and aft rings. A Kick Motor nozzle is rotated by the shear deformation of rubber layers. Consequently, the development of rubber, which is appropriate to the usage condition of flexible seal, is very important. A tensile test, QLS test (shear modulus and failure shear stress), and aging test have been carried out to confirm the performance of rubber developed. Test results show that the shear modulus of rubber are 0.4310 ~ 0.4997MPa and the failure shear stress is more than 2.5MPa.

Acoustic Dampening Pipe Shoe

Pipe shoe can include pipe retained by clamp attached to top plate. Acoustic isolation block is disposed for compression between top plate and bottom plate. Top plate is retained to bottom plate by stud(s) and nut(s). Flexible peripheral seal is disposed around acoustic isolation block between top and bottom plates. Pipe shoe can include thermal insulation and/or protective covering over any portion of pipe shoe and/or hot pipe.