Seal Structure Research Articles

Experimental and numerical simulation study on the influence of structural factors on the leakage characteristics of clearance seals

The leakage characteristics of clearance seals are affected by operating conditions, such as operating parameters and physical properties of the medium, and structural factors such as the clearance and surface structure of the seal. The reasonable design of the seal structure under different operating conditions is very important to ensure the excellent leakage resistance characteristics of the seal. Based on the self-developed plate test platform of the clearance seal, the leakage rate and outlet pressure under different seal clearance and static surface structure conditions have been obtained. The influence of structural factors such as the seal clearance values and its shape and the structure of the static surface on the leakage characteristics of the clearance seal is investigated. The influence mechanism of the structural factors on leakage characteristics of the seal is analyzed by the simulation of the three-dimensional flow field and the turbulent energy dissipation rate of the clearance seal. The results show that the leakage characteristics of the clearance seal are significantly affected by the seal clearance values and its shape, and the sealing surface structure on static and rotor. Under the same value of average seal clearance and compared to the parallel clearance seal, the seal with an axially inclined sealing clearance has better leakage control ability. However, the circumferentially inclined sealing clearance has little influence on leakage characteristics. The best choice of sealing surface structure under different seal clearance conditions is different. Among them, the smooth surface seal, the clearance seal with single-sided opening, and the clearance seal with double-sided holed are the optimal structures when the seal clearance is small (0.05–0.1 mm), moderate (0.3–0.4 mm), and large (0.8–1.0 mm) respectively. This phenomenon is the result of the combined effect of the direct air permeability effect in the sealing clearance, the vortex dissipation effect in the cavity, and the surface friction effect under different conditions.

Towards characterizing full-scale furniture fires in a two-storey house: Gaseous species concentrations during a ventilation-limited fire

This work examines the time evolution and spatial distribution of five combustion gases during a large-scale ventilation-limited furniture fire experiment. Past research has largely focused on measurement of major gases collected in an exhaust hood or at limited locations during gas or liquid fuel fires in a single room or single-storey layout. As such, there is a dearth of temporally resolved gas species data, measured in-situ at various locations in a two-storey structure. The aim of this study is to provide a comprehensive set of gas concentration data collected throughout a two-storey, multi-compartment, completely sealed structure during a furniture fire. Higher concentrations of CO, NOx, HCN and VOCs were measured in areas close to the fire and in the smoke layer, while a uniform distribution of gases was recorded further away from the fire, namely on the upper floor. The results are critical to our understanding of gaseous species evolution during ventilation-limited fires and provides additional insights for tenability and other fire safety measures within a residential context.

Research on Dynamic Sealing Performance of Combined Sealing Structure under Extreme Working Conditions

This study investigates the sealing performance of a combined sealing structure under extremely high and low temperature conditions, considering potential issues like high-temperature aging and low-temperature brittle fracture, which can lead to sealing failure. EPDM rubber underwent uniaxial compression tests at high, low, and normal temperatures, then the sealing performance under extreme working conditions was compared with that under normal temperature conditions. Additionally, the influences of gasket parameters and gas pressure on the sealing performance were analyzed. The result shows that compared with the normal temperature conditions, the maximum von Mises stress is reduced by 65% and the effective sealing length and the maximum contact pressure is reduced by 40% under the high temperature conditions, while the maximum von Mises stress is increased by 7 times and the maximum contact pressure is increased by a remarkable 7 times under the low temperature conditions. In the range of 10–100 MPa, the increase in gas pressure aggravates the O-ring stress concentration and improves the sealing performance relatively. When the thickness of gasket is 0.85–1.05 mm, the stress concentration of the O-ring is lighter and the sealing performance is better.

High-temperature wear mechanism of roller cone bit spiral seal

When drilling, the spiral seal of the roller cone bit and the journal are prone to collision and wear, and the friction heat and downhole high temperature will affect the wear process. The friction and wear experiments of the spiral seal material (20CrNiMo–40Cr) at different temperatures were carried out to study the wear mechanism of the spiral seal and journal of roller cone bit at high temperatures to determine the wear amount, friction coefficient and main wear forms. The wear model of friction pairs is established based on the Archard wear model and experimental results; The wear results at different temperatures are obtained by establishing the spiral seal structure model and simulation research of the roller cone bit. The results show that:(1) Through the friction and wear experiment of friction pair materials, the higher the temperature is the greater the wear amount and friction coefficient are. When the temperature exceeds 100 °C, the wear amount and friction coefficient begin to decline with the increase in temperature. By observing the wear surface morphology, abrasive and adhesive wears occur simultaneously, and the main wear form is adhesive wear under high-temperature conditions.(2) The maximum temperature rise caused by friction and the relationship between wear volume and time at different temperatures are obtained through the simulation of the spiral seal structure. Taking the groove depth value as the index to evaluate the sealing effect, the roller cone bit works in the temperature range (25 °C-400 °C), and high-temperature wear does not affect its sealing performance.

Numerical analysis and formula correction of mechanical seal ring wear of slurry pump based on thermal deformation

In view of the excessive wear of the mechanical seal of the slurry pump in the project and the inconsistency between the theoretical wear and the actual wear, this article studies the wear of the mechanical seal of the slurry pump. In this article, a numerical model of mechanical seal wear based on thermal deformation is established. The hardness, wear coefficient and dry friction coefficient of the sealing ring were obtained through experiments, and the wear morphology was collected by the ultra-depth microscope. In this article, the precise calculation of mechanical seal wear is realized, and the seal ring wear depth under single and multiple field conditions is obtained. The wear formula of the mechanical seal is optimized by adding a correction index, and the end face structure of the mechanical seal is improved. The results show that: the seal ring forms a converging surface due to thermal deformation resulting in more severe wear of the inner diameter relative to the outer diameter; the revised wear equation can more accurately predict the life of the nickel-based tungsten carbide alloy mechanical seal, with a 3.2 times increase in expected life after comprehensive end face improvement.

Folding of sealed origami-inspired capsule with rigid panels and hyperelastic hinges

Origami structures have great potential for space applications owing to the advantages of high packaging ratio, diversified design and predetermined deployment. Inspired from a rigid origami pattern, a novel architecture for large-scale expandable capsules that incorporates a hybrid origami combining rigid panels and flexible hinges is proposed in this paper. The rigid panels ensure the structure with good loading capacity and reliable performance. The flexible hinges with hyperelastic behavior address the geometric mismatch and incompatibility when folding a 3D sealed structure. This paper focuses on the mechanical behavior of the expandable space capsule inspired from origami. Based on our previous work about kinematic analysis, two deformation modes of hyperelastic hinges are determined. Theoretical models to characterize the hyperelastic hinges are described using the hyperelastic constitutive model. Specific experimental devices are designed for the hinges with different deformation modes individually. The accuracies of theorical models are compared to finite element simulations and experiments, and the applicable ranges are evaluated respectively. Furthermore, the mechanical properties of a representative capsule unit are studied with the energy method. Using the theoretical model, a self-energizing deployment of the structure is discovered and then validated through simulation analysis and quasi-static folding tests. The results demonstrate that this proposed concept provides a novel approach to designing origami-inspired deployable structures for on-orbit construction in future space missions.

Wearable bead-based triboelectric nanogenerator with dual-mode operation for monitoring abnormal behavior in dementia patients

A bead-based TENG (BB-TENG) that operates in dual-mode, contact-separation (CS) and free-standing (FS), is demonstrated as a two-in-one device. It serves both as an energy harvester and a sensor. This BB-TENG was designed to collect kinetic energy from two prevalent human movements: pressing related to the CS mode and walking linked to the FS mode. This functionality enables it to detect two typical behaviors of dementia patients while simultaneously harvesting energy: accidental falls corresponding to pressure and aimless wandering associated with walking, thereby enhancing its potential applications. The output characteristics from the BB-TENG was evaluated in terms of open-circuit voltage, short-circuit current and total transferred charge. The flexibility of the BB-TENG, which can be easily attached to a part of the body, gives it superior adaptability compared to other conventional TENGs. Furthermore, its sealed structure provides improved robustness against environmental factors such as humidity, making it suitable for outdoor use. A two-in-one module to enclose a wearable sensor and a flexible energy harvester can immediately alert the caregivers when a dementia patient wanders aimlessly and falls accidentally.

Optimized Design of a Multistage Centrifugal Pump Based on Volumetric Loss Reduction by Auxiliary Blades

Throat ring leakage is a major factor deteriorating the performance of multistage centrifugal pumps. This paper focuses on the optimization of multistage centrifugal pumps by incorporating the principle of the Tesla valve and adding an auxiliary set of blades to the impeller body. By changing the direction and magnitude of the leaking fluid’s flow, the leakage volume of the impeller throat ring is reduced. The study results demonstrate that the experimental error in head calculation with numerical simulation at the optimal working condition was 0.65%, verifying the accuracy of the numerical simulation method. The leakage volume of the throat ring decreased by up to approximately 28.99% compared to the original structure, which significantly increased the pump’s head and overall efficiency. Near the optimal operating point, the pump’s head and overall efficiency increased by approximately 8.1% and 8.7%, respectively. The larger the flow rate, the greater the improvement in the pump’s head and total efficiency. Near high-flow operating conditions, the pump’s head and overall efficiency increased by approximately 116.45% and 110.84%, respectively. The auxiliary blade structure introduces a non-contact seal which, compared to traditional seal structures, improves seal life and reduces seal costs. Additionally, the auxiliary blades can shift the optimal operating point of the multistage centrifugal pump towards a higher flow rate, improving the pump’s delivery capability.

METHODOLOGY FOR DETERMINING THE EXPECTED PRESSURE IN NON-EXPANDING ACCUMULATING STRUCTURES

Shrinkage has a great influence on the operation of the heat accumulator design, therefore, when developing structures with heat storage materials, it becomes necessary to determine the pressure in a non-expanding (closed) storage structure from the compressibility coefficient of the material, which can be considered an operational characteristic of the material. The article presents data on shrinkage (and expansion) of the investigated heat-storage materials and a method for estimating the pressure that can develop in sealed battery structures completely filled with heat-storage materials in a crystalline state. It has been determined that, for the normal operation of structures with heat storage material, it is necessary either to create conditions in it that allow avoiding an increase in pressure, or when filling the structures of the accumulator of heat storage material, take into account the shrinkage of the material, or use heat storage material with melting temperatures lower than is required when working at atmospheric pressure. pressure.

Optimization of cooling water jacket structure of high-speed electric spindle based on response surface method

In high-precision machining machine tools, the high-speed electric spindle is the fundamental transmission component. Nonetheless, the electric spindle's small and tightly sealed internal structure may result in insufficient heat dissipation, resulting in significant heat accumulation during continuous operation. This might induce thermal displacement of the spindle and reduce machine tool machining precision. A response surface was established by a 2-factor 3-level interaction experiment utilizing Design-expert software to reduce the heat displacement of the electric spindle. The electric spindle cooling water jacket was optimized and front and rear bearing cooling water channels were added based on the response surface results. The thermal-solid coupling simulation was carried out using ANSYS, and the optimized data for the front and rear bearing temperature, as well as spindle thermal displacement, were obtained through simulation analysis. Comparing the simulation with the experimental data, it was found that the front and rear bearing temperature decreased by 4.34 °C and 8.97 °C, respectively, and the spindle thermal displacement was reduced by 16.57 μm, resulting in improved machining accuracy. The service life of the bearings was further prolonged by the decreased thermal stress between the inner and outer rings and the balls of the front and rear bearings.

Modeling and analysis of oil frictional loss in wet-type permanent magnet synchronous motor for aerospace electro-hydrostatic actuator

To improve the power density and simplify the seal structure, the Wet-Type Permanent Magnet Synchronous Motor (WTPMSM) technique has been applied to aerospace Electro-Hydrostatic Actuators (EHA). In a WTPMSM, the stator and the rotor are both immersed in the aviation hydraulic oil. Although the heat dissipation performance of the WTPMSM can be enhanced, the aviation hydraulic oil will cost an extra oil frictional loss in the narrow airgap of the WTPMSM. This paper proposes an accurate oil frictional loss model for the WTPMSM, in which the wide speed range (0–20 kr/min) and the narrowness of the airgap (0.5–1.5 mm) are its features. Firstly, the mechanism of the oil frictional loss in the airgap of the WTPMSM is revealed. Then an accurate oil frictional loss model is proposed considering the nonlinear influence caused by the Taylor vortex. Furthermore, the influence of motor dimensions on oil frictional loss is analyzed. Finally, the proposed oil frictional loss model is verified by experiments, which provides a guideline for engineers to follow in the WTPMSM design.

Numerical analysis of a double interlocking padded finger seal performance based on thermo-fluid-structure coupling method

Non-contacting finger seals represent an advanced non-contacting and compliant seal in gas turbine sealing technology. This paper proposes a new structure of non-contacting finger seals with double interlocking pads. The numerical analysis model based on the thermo-fluid-structure coupling method for the new type finger seal was established. The influence of working conditions on leakage of the seal was studied and compared with the single padded non-contacting finger seal. The results show that the interface between the bottom of the finger pad and rotor surface is the main leakage path that forms the gas film with obvious variations of pressure and flow velocity. Under high temperature and high pressure operating conditions, the hydrodynamic effect of the gas film is enhanced, and lifting force is significantly improved. The deformation of fingers is composed of elastic deformation and thermal deformation. At room temperature, the deformation of fingers is mainly elastic deformation and points to the center of the rotor, which reduces the gas film clearance. The deformation of fingers at high temperature and high pressure creates a circumferentially convergent gap between the bottom of the pad and the rotor, which is beneficial to improve the loading capacity and to reduce leakage of the seal. Compared with the typical single padded non-contacting finger seal, the double interlocking padded finger seal proposed in this paper reduces the leakage factor by about 37%, which provides an advanced seal concept with the potential to improve sealing performance under high temperature and high pressure working conditions.

High pressure sealing characteristics of combined structure based on flexible graphite rings

Seal components made of flexible graphite have excellent resistance to temperature, while sealing of high pressure fluids is unsatisfactory. The sealing behavior of flexible graphite rings is characterized by the ratio of the contact pressure to the axial pressure. The FEA results show that the lateral pressure decreases roughly linearly along the direction of the sealing path, and the lateral pressure coefficient increases with increasing axial pressure. We design a combined seal structure based on flexible graphite rings, and extract the contact pressure along two sealing paths. The results imply that the self-sealing effect is more favorable when the pressure of the sealing fluid is increased. The effect of the friction coefficient on the contact pressure is not significant, except at the beginning of the sealing path. Sealing effects are tested under the coupling condition of 350°C and 50 MPa, which verify the sealing performance under high temperature and high pressure. The comparison of the test results of “ kf” (the product of lateral pressure coefficient and friction coefficient) with those of the FEA validates the rationality of the analytical approach. The comprehensive coefficient “ kf” can be easily obtained by testing, and can be used as a key parameter for seal design.

Performance Analysis of the C/C Composite Cylindrical Reverse Inter-Shaft Gas Film Seal

The reverse inter-shaft gas film seal is a gas path seal used in the intermediate bearing cavity of an aero-engine, which is challenging to implement due to its special installation and usage conditions. This paper proposes a C/C (Carbon/Carbon) composite cylindrical reverse inter-shaft seal structure and carries out a performance simulation analysis based on bidirectional fluid–solid coupling technology. The results show that the cylindrical reverse inter-shaft gas film seal with double-layer C/C composite sealing rings with different material mesoscopic parameters can balance seal leakage and friction power consumption and is beneficial to improving the comprehensive performance of the seal. As the mesoscopic parameters of the inner sealing ring material increase in warp and weft density, the sealing leakage rate decreases, and the gas film force and gas friction power consumption all increase. As the pressure difference increases, the sealing leakage rate and gas film force increase. As the rotation speed of the inner and outer rotors increases, the seal leakage rate increases, and the gas film force decreases. A C/C composite sealing ring cylindrical reverse inter-shaft gas film seal has a lower leakage rate and larger gas film force than a graphite sealing ring cylindrical reverse inter-shaft seal, which confers certain performance advantages. The work in this paper can provide a reference for the design of reverse inter-shaft seals.

Design of O-ring with skeleton seal of cutter changing robot storage tank gate for large diameter shield machine

Faced with high pressure and high humidity environment, the seal of the storage cabin gate is the key to ensure the reliable frequent cutter replacing operation for shield machine. In this paper, the design criteria of the gate side seals was proposed. And the numerical analysis model of O-ring seal with skeleton was established. The influence of key structural parameters on the sealing performance was studied. The combination optimization parameters of the seal were obtained. The rationality of the seal structure is verified through the gate sealing performance test. It provides reference for the design and optimization of the sealing structure used in deep-sea tunnel shield.

Performance of the ferrofluid-spiral labyrinth combined seal for sealing liquid

When the ferrofluid is used to seal liquid, the relative movement between the ferrofluid and the sealed liquid causes the stability problem of their interface, and the sealing performance is poor. However, the spiral and the spiral sleeve of the spiral labyrinth seal interact with the sealed liquid to make it reverse flow to prevent leakage when the shaft rotates. In order to improve the performance of rotary ferrofluid seal, the ferrofluid-spiral combined seal structure and the ferrofluid-spiral labyrinth combined seal structure are designed. A combined seal test-bench is built. The pressure resistance experiments and seal life experiments of ferrofluid seal and two type of combined seals are carried out. The theoretical and experimental results show that the sealing performance of the ferrofluid-spiral labyrinth combined seal is better than that of the ferrofluid-spiral combined seal ferrofluid seal. Ferrofluid-spiral labyrinth combined seal can not only solve the failure problem of ferrofluid seal at high speed, but also solve the leakage problem of spiral seal at shutdown and low speed, so as to achieve a more stable sealing effect at different speeds. The higher the speed is, the better its sealing performance is.

Research on Aging State Detection Method of Rubber O-ring Sealing Structure

The rubber seal structure is used extensively in mechanical devices, long-term use may bring major safety hazards and economic losses. In order to ensure the healthy operation of machinery and equipment, it is necessary to test the aging condition of the rubber sealing structure nondestructive online. In order to address the problem of unsteady vibration signals, a complex nonstationary signal is degraded into the sum of multiple product functions by means of global local mean decomposition, and then the energy features in these PF components are extracted, and the first three components with the largest energy eigenvalues are selected to form a sensitive feature vector set. Overall, the results of the search data show that the proposed method can efficiently extract energy features from a large set of original features, and the first three largest energy features can be selected to form a sensitive feature set, which can provide effective data information for the detection of the aging state of Rubber O-ring Sealing Structure (ROSS) in the next step.

System analysis and experimental investigation of a pendulum-based wave energy converter

Global economic development and environmental protection requirements are increasing the demand for renewable energy rapidly. Wave energy converters are a hotspot in research, and many designs have been proposed. Pendulum-based wave energy converters, because of their sealed structure and high reliability, are drawing researchers' attention. This article considers the concept of a Vertical Axis Parametric Pendulum Wave Energy Converter (VAPPWEC) and focuses mainly on the characteristics of the pendulum system. The dynamic function of the pendulum is proposed. A new evaluation indicator, Cumulative Frequency curves of Angular Velocity (CFAV) is introduced to analyze pendulum motion accurately and evaluate the harvesting performance conveniently. The model test shows the parametric resonance zone of the pendulum with a notable boundary and the pendulum's stability under power take-off (PTO) damping. Additionally, a large-range analysis method based on the Prescribed Excitation Model (PEM) is proposed, and the output power is assessed. Linear damping performs better than constant damping, with a maximum capture width ratio of 39.05%.

Experimental Research on Divergent Embedded Magnetic Fluid Static and Dynamic Seals with a Large Gap

Magnetic fluid sealing (MFS) is one of the most advanced applications of magnetic fluids (MF). To improve the pressure resistance of the traditional MFS with a large gap, this paper proposes a large-gap divergent embedded magnetic fluid seal (DEMFS) structure with radial and axial sealing capabilities. Through the simulation analysis of the radial and axial seal gaps (0.5–0.8 mm) and the number of radial and axial pole teeth (PT), the theoretical pressure resistance was obtained. A large-gap DEMFS test bench was built to experimentally verify the simulation results, and the effects of the MF volume and shaft speed on the pressure resistance of the sealing device were also experimentally investigated and compared with the theoretical pressure resistance of the traditional MFS structure. The numerical simulation and experimental results that the experimental values of the DEMFS are in good agreement with the theoretical values. When the MF injection volume was 2.5 ml, the pressure resistance reached the maximum and tended to be stable. With the change in the size of the seal gap and the number of PT, the variation trend of the pressure resistance of the DEMFS was different from that of the traditional MFS. When the shaft speed was low, the low speed had almost no effect on the pressure resistance of the DEMFS. The axial seal gap and axial PT were beneficial to the sealing effect.

A Novel Design of Rim Sealing Flow for Improving Sealing Effectiveness

AbstractRim seal structures and sealing flows are essential in aero engines for preventing hot gas ingestion from mainstream to turbine disk cavities. A novel design method of rim sealing flow path based on auxiliary sealing holes and sealing air re-distributions has been proved to improve sealing effectiveness. The present paper uses this method to re-design the axial rim sealing flow in a high-pressure turbine front cavity in an engine turbine. The incidence angle of the auxiliary sealing air has been proved to have a significant influence on sealing performance. Three different incidence angles, 0-deg, 35-deg, and 70-deg, with the maximum angle close to the vane exit flow angle, are investigated using unsteady computational fluid dynamics methods validated by experimental data. Sealing effectiveness, swirl ratio, unsteady flow structures in both rim clearance and wheel space cavity are considered. The auxiliary sealing air with a swirl in the circumferential direction is proved to improve and uniform swirl ratio and suppress flow instabilities. This results in a reduction in hot gas ingestion and a considerable improvement in sealing effectiveness. The mechanisms of improving sealing effectiveness using this novel method are explained. The conclusions may support the understanding of the complex flow mechanisms near the rim seal, provide references for the design of this novel structure and give possibilities to improve rim seal performance and engine efficiency.