A rise in seawater salinity results in an increase in its viscosity, which presents a coupled influence on the distribution of fluid pressure, temperature and deformation at the sealing face, leading to fluctuations in sealing performance and forming the salinity effect in seawater thermoelastohydrodynamic lubrication (TEHL). Here, for a double spiral groove face seal, a TEHL model is established and numerical analysis is carried out, taking account of the salinity effect and cavitation effect, with the aim to ensure that the seal maintains stable performance under varying conditions of sea depth and speed. It is found that the effect of salinity on the opening force and leakage rate exhibits obvious nonlinear variations. As salinity rises from 0 to the standard 35 g/kg, the opening force changes by about 5%, and there is a transition between forward and reverse leakage, with variations of approximately ±100%. More importantly, the double spiral grooves offer the potential for a zero-leakage design in seawater face seals, even under pressures exceeding 4 MPa, through precise design. Additionally, the double spiral groove face seal shows excellent adaptability under multipoint conditions and can facilitate a zero-leakage design in varying pressure, speed and temperature conditions. This provides theoretical support for deep-sea equipment and applications in other extreme environments.

In a vacuum environment, reduced gas pressure alters the surface tension, dynamic viscosity, and wetting angle of oil, leading to distinct vacuum pressure effects when oil spreads on solid surfaces. This study experimentally investigated how surface tension and dynamic viscosity vary for three lubricating base oils—N60, N250, and N500—as well as their contact angles on three rough M50 steel surfaces under vacuum pressures. The spreading speed was also measured for these oils on the rough M50 steel surfaces and developed a theoretical model to predict spreading speed on rough surfaces in vacuum conditions. Experimental results indicate that vacuum pressure changes significantly affect surface tension, dynamic viscosity, and contact angle. Surface tension decreases monotonically with reducing environmental pressure, dropping by roughly 40% at 10 kPa compared to atmospheric pressure. Dynamic viscosity and contact angle, however, follow a nonlinear, non-monotonic trend, first increasing and then decreasing. Viscosity peaks between 80 kPa and 40 kPa vacuum pressure, rising about 7% above atmospheric values. For N60 oil, the contact angle increases to 17.66° at 60 kPa and falls to 11.75° at 10 kPa. These factors cause the spreading speed to vary nonlinearly and non-monotonically, initially increasing and then decreasing as environmental pressure drops. Spreading speed peaks at around 60 kPa, exceeding atmospheric speed by over 100%. At 10 kPa (higher vacuum), it declines by approximately 50% relative to atmospheric conditions. In vacuum environments, higher surface roughness correlates with faster spreading speeds. Surface geometric morphology thus appears to be a viable method for achieving micro-lubrication control in vacuum settings.

The thermal distortions of seal face caused by heat transfer directly affect the stability of seal operation. Here, a heat transfer analysis model of spiral groove gas face seal is established taking account of gas compressibility and choked flow effect. Then, a thermoelastohydrodynamic lubrication (TEHL) analysis is carried out based on the proposed heat transfer model, frictional heat flux, surface conduction heat flux, and film adsorption heat flux are calculated, and face distortions are also analyzed under different operating parameters including rotational speed, seal temperature and seal pressure. It is shown that, the adsorption heat induced by gas expansion makes the film cooling, which often leads complex temperature distributions and plays an important and non-ignored role in thermal distortions. For the spiral groove face seal, the increase of seal pressure and rotational speed makes the adsorption heat increase significantly due to pumping effect of grooves. The more important is that the thermal distortions may be controlled by changing seal width. Here, for the spiral groove face seal, the clearance can transfer divergent to convergent with increasing seal width from 5mm to 13.1mm. This provides a potential way for distortion control in gas face seal design.

High-speed valves (HSVs) often exhibit excessive steady-state temperature rise and sluggish dynamic response under rated current conditions, which constrain their performance and reliability in high-speed fluid control systems. This paper proposes an innovative magnetic isolation slice structure that significantly enhances the electromagnetic performance of HSVs while avoiding additional temperature rise and ohmic loss. A weighted function method is adopted to model the relationship among current, response time, and temperature, enabling the determination of an optimal operating current to achieve a trade-off between electromagnetic performance and thermal performance. Experimental results demonstrate that, compared with the original HSV structure operating at the rated current, the proposed design reduces the response time by 69.2%, steady-state ohmic loss by 53.3%, and steady-state temperature rise by 51.7%. These findings indicate that the magnetic isolation slice facilitates a coordinated control of thermal and electromagnetic behaviors, providing a practical solution for enhancing HSV performance in high-speed applications.

The upstream pumping effect of mechanical face seals has a significant influence on their sealing performance. In order to reveal the effect of deep grooves on upstream pumping effects, an experimental and theoretical analysis is carried out in this study. The main novelty of this paper is to analyze the feasibility of deep grooves in a mechanical seal design from the perspective of cavitation and leakage rate. Firstly, an upstream pumping spiral groove is designed and fabricated, with different groove depths from 2 μm to 90 μm. Then, testing is performed with water as the sealing medium. Finally, the cavitation phenomena are captured, and leakage rates are measured during the experiment. The obtained results show that the groove with a depth of tens of microns can be designed according to the laminar flow hypothesis, and Reynolds equation is still valid to predict the cavitation and leakage rate theoretically. The spiral groove with a depth of tens of microns shows a significant upstream pumping effect. Both the theoretical and experimental analyses show that under certain working conditions, deep grooves can realize the zero-leakage sealing design of liquid, which might provide significant guidance for the sealing design of mechanical face seals to enhance sealing performance.

With the increasing requirement of multi-point working conditions, the problem of lubrication heat in liquid face seals attracts more attentions, which often results in a high risk of seal failure due to unstable opening force and leakage. The precise design considering heating effect of face grooves under complex working conditions is necessary. Here, based on the fluid lubrication theory, a thermo-dynamic model for liquid face seals with elliptical groove was established to analyze the lubrication heat behavior. The novelty of this model is to take the complex seal structure, cavitation effect and fluid thermo-viscous effect into consideration together, which was validated by experimental work. The temperature distribution and temperature rise were investigated for both smooth and elliptical groove face seals. The effects of rotational speed, film thickness and sealing pressure on temperature distribution and sealing performance of liquid film were further studied. When the film thickness increasing from 2 to 5 mu m, the maximum temperature for face seals with elliptical groove and smooth surface decreases from 355.6 K to 350.45 K and from 354.9 K to 350.4 K, respectively. The values of maximum temperature present no obvious difference for both smooth and elliptical faces. However, it is found that elliptical groove presents an obvious influence on temperature distribution of liquid sealing film. The maximum temperature occurs near the inner diameter for the smooth face, but near the outer diameter for the elliptical groove face. The obtained results also suggest that the cavitation effect and hydrodynamic effect induced by shear effect make the sealing performance unstable, accompanying multi-peaks phenomena under multi-velocity and multipressure conditions. Face grooves could provide a potential way to control temperature distribution in precise sealing design.

The adhesive force between two contact surfaces often leads to an increase in the friction force of the rubber seal O-ring after a certain dwell time, forming dwell time effects and affecting the reliability of sealing. The dwell time effect may result in substantial instability with respect to the frictional behavior of rubber O-rings, which needs to be carefully taken into account in the design of rubber seals. Therefore, in this paper, the dwell time effect of the friction force was studied experimentally for intermittent reciprocating rubber seal O-rings coupled with stainless steel 316L and a sealing air medium. The friction force of three kinds of rubber materials, including fluorine rubber (FPM), silicone rubber (SI), and nitrile rubber (NBR), was measured under different dwell times, compression ratios, and seal pressure. The results showed that there was a rolling frictional force, and the second peak value of the frictional force caused by the O-ring’s rolling under shear action and after the maximum static frictional force was observed at the starting stage of reciprocating motion. For FPM O-rings, the rolling friction force was much greater than the maximum static frictional force at about four times the value of the compression ratio at 9% and seal pressure at 0; moreover, the force was much greater at greater compression ratios. The dwell time effect was significant in the friction forces of rubber O-rings. The friction force increases with an increase in dwell time. The increase in maximum static friction force exceeded 50% after 5 dwell days. The increase in seal pressure led to the disappearance of the rolling friction feature and the rapid increase in friction during the starting stage. Under gas seal pressure conditions, the dwell time effect still led to a significant increase in friction force. The obtained results might provide guidance for the material selection of sealing designs.

Friction and wear are the main failure sources of face seals. When the surfaces of sealing rings exhibit greater roughness, the level of friction might increase and lead to sealing failure. Therefore, in this paper, based on the elastic contact hypothesis of rough and wavy surfaces and the influence of temperature on the elastic modulus of materials, a thermoelastic contact lubrication model of a gas-lubricated end seal is established. The novelty and advantage of this study is that it takes the effect of surface roughness into consideration during thermoelastic analysis of gas-lubricated seals. The film pressure, temperature, contact force and deformation of a gas spiral groove-faced seal are numerically determined. The influence of surface roughness on the contact distribution, deformation and temperature of the end-face seal at different speeds and pressures is analyzed. The film thickness increases as the rotational speed increases from 1 rpm to 2000 rpm, while the contact pressure sharply decreases from 0.25 kPa to 0. The analysis shows that the roughness contact mainly happens on the inner side of the rings due to convergent distortion of the seal faces, which easily causes partial wear of the seal faces. Moreover, it can also be found that the spiral grooves on the sealing surface can produce obvious hydrodynamic pressure effect due to the function of shear speed when the speed increases to 2000 rpm, while the film temperature increases from 293.3 K to about 306 K. The greater surface roughness results in a larger temperature rise under low-rotational-speed and lower-seal-pressure conditions, which further increases the risk of severe wear or even failure of the seal faces.

Cavitation in micro-scale lubricating film could be determined by the fluid’s thermal properties, which impacts the hydrodynamic lubrication capacity dramatically. This study aimed to novelly investigate the impact of the thermal cavitation effect on the hydrodynamic performance of liquid face seals, employing the compressible cavitation model, viscosity–temperature effect, and energy equation. The finite difference method was adopted to analyze the thermal cavitation by calculating the pressure and temperature profiles of the lubricating film. The working conditions and geometric configuration of liquid face seals under different thermal cases were further studied to explore their effects on sealing performance. The results showed that thermal cavitation could reduce the temperature difference of liquid film at high speeds, and cavitation would be weakened under temperature gradients, which further dropped off the hydrodynamic performance. Contrary to the leakage rate, the opening forces tended to be lower with the increasing seal pressure and film thickness under high-temperature gradients. Furthermore, apart from the spiral angle of grooves, the hydrodynamic performance exhibited significant variation with increasing groove depth, number, and radius at high-temperature gradients, which meant that the thermal cavitation effect should be considered in the design of geometric grooves to obtain better hydrodynamic performance.

The property of vaporization phase transition in liquid oxygen face seals is a key factor affecting the stability of mechanical face seals in many fields, especially under cryogenic conditions. Here, a numerical model based on the saturated vapor pressure is established to investigate the vaporization phase transition property of liquid oxygen sealing film. The novelty of this model is to take the influence of heat transfer and face distortions into consideration at the same time. The pressure and temperature distributions as well as face distortions are calculated, and then the property of vaporization phase transition and sealing performance are analyzed. It is found that spiral grooves may lead to the complex film temperature distributions and irregular vaporization distributions. With the increase in seal temperature and decrease in seal pressure, the vaporization area extends from the low-pressure side to the grooves area, and the vaporization rate increases rapidly. The more important thing is that the vaporization often brings a drastic fluctuation and non-monotonic change in opening force. Specifically, with the increase inin seal temperature from 55 K to 140 K, the opening force fluctuates violently, and the fluctuation range is more than 50%, showing an obvious instability. Finally, this study provides a design range of pressure and temperature values for liquid oxygen face seals. In these ranges, this kind of face seals can have a stable operation, which is beneficial to the practice engineering related to the complex properties of sealing fluid.

Cavitation intensity variations in fluid lubrication may alter the mechanical and lubrication properties of the fluid. In this paper, a compressible cavitation model is presented to study the effect of fluid cavitation intensity on zero-leakage flow of upstream-pumping spiral grooves face seals (UPSGLFS). The pressure variation in cavities can be calculated considering the compressibility of the lubricating medium, the ratio of minimum pressure to cavitation pressure is further defined to characterize the cavitation intensity. A numerical analysis of the zero-leakage behavior of UPSGLFS is then performed based on its effect. Results show that cavitation plays a negative role in sealing performances. However, the groove’s configuration and working conditions have substantial effects on controlling the cavitation intensity. Meanwhile, whether a circumferential continuous pressure ring above the seal pressure can be formed is the design basis for judging the strict zero leakage of the medium, rather than only depending on the change of leakage rate parameter value. With suitable spiral groove parameter design, zero-leakage design for upstream-pumping seals may be achieved under multi-speed and multi-seal-pressure conditions. Here, a zero-leakage map is presented for working conditions with multi-speed ranging from 500 to 20,000[Formula: see text]rpm and multi-seal pressure ranging from 0.1 to 3.0[Formula: see text]MPa.

The Brayton cycle system, as a closed cycle working under high-temperature, high-pressure and high-speed conditions, presents significant prospects in many fields. However, the flow behavior and energy efficiency of supercritical CO2 is severely influenced by the structures of face seals and the sealing temperature, especially when the sealing gas experiment is the supercritical transformation process. Therefore, a numerical model was established to investigate the high-temperature flow behavior and energy consumption of face seals with different surface grooves. The effects of the operation parameters and groove structure on the temperature distribution and sealing performance are further studied. The obtained results show that the supercritical effect of the gas film has a more obvious influence on the flow velocity uθ than ur. Moreover, it can be found that the temperature distribution, heat dissipation and leakage rate of the gas face seals present a dramatic change when the working condition exceeds the supercritical point. For the spiral groove, the change rate of heat dissipation becomes larger, from 3.6% to 8.1%, with the increase in sealing pressure from 15 to 50 MPa, when the temperature grows from 300 to 320 K. Meanwhile, the open force maintains a stable state with the increasing temperature and pressure even at the supercritical point. The proposed model could provide a theoretical basis for seal design with different grooves on the supercritical change range in the future.

In order to obtain the leakage characteristics of an upstream pumping face seal with inclined ellipse dimples under high-temperature and high-speed liquid lubricating conditions, a thermo-hydrodynamic lubricating model is developed. The novelty of this model is that it takes the thermo-viscosity effect and cavitation effect into account. The influence of operating parameters, such as rotational speed, seal clearance, seal pressure, ambient temperature and structural parameters, such as dimple depth, inclination angle, slender ratio and dimple number on the opening force and leakage rate, is numerically calculated. The results obtained show that the thermo-viscosity effect makes the cavitation intensity decrease noticeably, leading to an increase in the upstream pumping effect of ellipse dimples. Moreover, the thermo-viscosity effect may make both the upstream pumping leakage rate and opening force increase by about 10%. It can also be found that the inclined ellipse dimples can produce an obvious upstream pumping effect and hydrodynamic effect. Based on the reasonable design of the dimple parameter, not only can the sealed medium achieve zero leakage, but the opening force can also increase by more than 50%. The proposed model has the potential to provide the theoretical basis for and guide the future designs of upstreaming liquid face seals.

Helium face seal as a key component of cycle engine, its stability and energy consumption have a significant influence on the working efficiency of high parameter energy equipment. Extreme working conditions may make this influence more obviously and seriously. In this paper, a numerical model of helium face seal with spiral grooves is established to investigate the heat dissipation property and energy transfer route at cryogenic condition. The obtained results show that with the growth of rotational speed from 1047.2 to 5236 r/min, the increase rate of heat dissipation for the cases of p0 = 1, 3, and 5 MPa reaches to 148%, 139%, and 129%, respectively. This may be induced by the increasing friction torque due to the high working condition. Moreover, the heat transfer direction is analyzed by analyzing the temperature distribution of helium lubricating film and sealing rings. It is found that the temperature of helium film near the rotor surface demonstrates a slightly increasing trend along the radius direction from outer to inner side. The heat transfer of rotor shows an obvious flow tendency along radial and axial directions, especially at the rotor surface. For the stator, the heat transfer just can be found along radial direction. Finally, the sealing performance of helium face seals are discussed with the increase of sealing pressure and rotational speed. The proposed model may improve the heat utilization of energy equipment and provide guidance for the future structure design of helium face seals in engineering applications at cryogenic condition.

The cavitation effect is an important factor affecting the leakage of liquid face seals. Especially for the upstream pumping seal, the cavitation intensity increases significantly since the groove is generally set at the low pressure side. Here, a numerical modeling of the zero-leakage upstream pumping liquid spiral groove face seal is presented, taking into account the cavitation intensity. The pressure variation in the cavitation region is computed, while the cavitation intensity is defined as the ratio of minimum film pressure to cavitation pressure. Numerical analysis of the zero-leakage behavior of upstream-pumping liquid spiral groove face seals has been performed. The results show that cavitation plays a negative role in the sealing performance of upstream pumping liquid spiral groove face seals. With the growth of cavitation pressure from 10 kPa to 90 kPa, the opening force presents a significant decrease, exceeding 70% in degree at 10,000 rpm, as well as the upstream leakage rate, exceeding 80% in degree. Meanwhile, whether a circumferential continuous pressure ring above the seal pressure can be formed is the design basis for judging the strict zero leakage of the medium, rather than only depending on the change of leakage rate parameter value. With suitable spiral groove parameter design, zero leakage design of the upstream pumping seal may be achieved under multi-speed and multi-seal pressure conditions. Here, a zero leakage map is presented for working conditions of multi-speed ranging from 500 rpm to 20,000 rpm and multi-seal-pressure ranging from 0.1 MPa to 3.0 MPa.

高参工况下密封环的弹性变形在一定程度上会影响密封性能.以波度端面机械密封为研究对象,考虑空化效应和弹性变形,对高速波度端面机械密封液体泄漏特性开展理论研究.采用有限差分方法数值求解密封的压力分布、开启力和泄漏量,重点分析密封端面波度几何参数以及密封工况参数对开启力和泄漏率的影响规律.结果表明:高速工况下波度密封端面空化加剧以及端面变形,使得密封端面承载力减小;当表面波度幅值较小时,考虑弹性变形时的密封开启力大于不考虑弹性变形时的密封开启力,而表面波度幅值大于0.2μm之后,两者呈现相反的结果;考虑弹性变形时的密封泄漏率则均大于不考虑弹性变形时的密封泄漏率;在弹性变形影响下,波度端面机械密封的密封性能主要受密封压力和密封间隙的影响;随着密封压力的增加,密封泄漏率增加;随着密封间隙的增加,考虑弹性变形前后的泄漏率差值逐渐减小.在文中计算条件下,弹性变形使得密封泄漏率增加可达50％以上.

Considering the roughness and circumferential surface waviness of seal face and cavitation effect, a mathematical model for the analysis of liquid circle-dimples face seal was established.The pressure distribution and leakage rate of liquid face seal under different circle-dimples arrangements were numerically solved, and the influence of geometry parameters of surface waviness and sealing condition parameters on opening force and leakage rate was analyzed.The results show that the circumferential surface waviness significantly changes the pressure distribution of the seal face.With the increase of waviness amplitude, the sealing leakage rate increases gradually, and the leakage rate of radial partial dimples face seal is smaller than that of radial fully dimples face seal.However, when the film thickness is 2 μm, the leakage rate is relatively large for the partial dimples face seal.The waviness number has no obvious influence on the leakage rate of the two kinds of arranged face seals at low pressure.With the increase of the pressure, the circumferential waviness number makes the leakage rate of the radial fully dimpled face seal decrease gradually.The leakage of liquid circle-dimples faces seal is affected by rotating speed, sealing pressure, and film thickness.The sealing leakage is increased with the increase of sealing pressure, and is gradually decreased with the increase of rotational speed and film thickness.At high speed, dimples arrangement of sealing face has little influence on the sealing leakage.

为了探究液体椭圆微孔端面密封特性,通过液体密封试验考察了微孔端面密封的泄漏控制规律,对2种椭圆微孔端面和1种光滑端面开展对比研究,研究了不同压力和转速工况下泄漏率和温升的变化规律.试验结果表明:密封表面双列椭圆微孔设计在高速下可明显降低摩擦温升,转速达到15000?r/min时,最高可降低80?℃;合理的反向椭圆微孔可以降低并控制密封泄漏;椭圆多孔密封端面在多转速工况时存在增加磨损的风险,通过合理的反向椭圆微孔设计可一定程度上减缓端面磨损.

The force equilibrium and moment equilibrium play a significant role on the sealing performance of gas split floating ring seals. A small deflection angle may generate seriously wear on sealing surface and cause seal failure. Therefore, the thermo-hydrodynamic lubrication analysis of gas split floating ring seal with Rayleigh grooves is investigated considering the deflection angle and frictional heat of surface contact, which is beneficial to grasp the hydrodynamic characteristics and rules under high-temperature and high-speed conditions. Pressure and temperature distributions of sealing rings are numerically calculated for the cases with different deflection angle, rational speed, seal pressure and ambient temperature. Then, the hydrodynamic effect and sealing performance are analyzed. The obtained results show that, the surface Rayleigh step grooves do not present obvious hydrodynamic effect when split seal ring has no deflection. While, a significant hydrodynamic effect can be obtained when the split seal ring presents a deflection angle about dozens of micro radians. Here, a 10% increase of opening force is achieved when the deflection angle reaches 80 μrad in the case of speed 30,000 r/min and seal pressure 0.2 MPa. Moreover, the hydrodynamic effect becomes obvious with increasing deflection angle as well as rotational speed. Meanwhile, the growth of rotational speed results in an obvious increase of film temperature. The increase of ambient temperature has a significant influence on the decrease of leakage rate. When the ambient temperature increases from 340 K to 540 K, the leakage rate reduces exceeding 50%, however, it does not present obvious effect on the opening force. The proposed model has the potential to provide the theoretical basis and design guidance for surface grooves of gas split floating ring seal in the future.

The thermo‐penetrative spreading behaviours of oil in microgrooves on stainless steel 316L surfaces were studied experimentally under temperature gradient conditions. An interface of smooth surface and microgrooved surface was designed to comparatively investigate the penetrative spreading of oil in microgrooves and the apparent spreading of oil on microgrooves and smooth surfaces. Then, microgrooves with different depths but a same width were laser processed to analyse the relationship between the actions of surface texture and temperature gradient on oil directional spreading. Results showed that the apparent oil on microgrooves extended directionally along the temperature gradient, leading to the lubricant loss from the high‐temperature region to the lower, while the penetrative oil in microgrooves could spread rapidly from the low‐temperature region to the higher under the obstruction of the thermocapillary effect, providing a potential method to enhance the lubrication.