Rotary Seal Research Articles

Rotary shaft seals at high temperatures

Rotary shaft seals at high temperatures

Test and Identification Analysis of Wear Response Signal of Contact Interface of Rotary Seal

Test and Identification Analysis of Wear Response Signal of Contact Interface of Rotary Seal

Effect of rotating shaft vibration on lip seal performance

Rotary lip seals are important components in various rotating machinery and are inevitably affected by vibration. This paper introduces the first simulation model for rotary lip seals under radial sinusoidal vibration conditions based on the mixed lubrication theory. Using the proposed model, the effects of varying vibration amplitudes and frequencies on the tracking performance, leakage rate, and friction torque of lip seals were analyzed. The simulation results indicate that, the leakage rate exhibits an initial increase followed by decrease as the vibration amplitude increases, while the friction torque exhibits a decrease followed by increase. Excessively high vibration frequencies may induce separation between the lip and shaft surface, resulting in severe leakage.

Enhance the tribological performance of soft AISI 1045 steel through a CrN/W-DLC/DLC multilayer coating

Special equipment vehicles typically operate in complex environments, leading to wear and failure of the chassis's rotary seal shaft predominantly made of soft AISI 1045 steel. An effective approach to prolong the service life is to apply a hard coating on the working surface. Previous research have primarily concentrated on the coating for hard high-speed steel. However, the significant disparity in physical characteristics between soft AISI 1045 steel and the hard coating results in a weak interface adhesion. This study produces a CrN/W-DLC/DLC multilayer coating on the soft AISI 1045 steel with strong interfacial adhesion and superior friction and wear property through modulation of the CrN transition layer thickness. The multilayer coating consists of five layers, a CrN transition layer, a Cr layer, a Cr/WC alternating layer, a W-DLC/DLC alternating layer, and the topmost DLC layer. The thickest CrN interlayer coating achieves the Lc2 and Lc3 value of 13.9 ± 0.2 N and 20.4 ± 0.9 N. The optimized CrN/W-DLC/DLC coating reduces the internal stress of the DLC coating and enhances its adhesion. Importantly, the average friction coefficient and wear cross-sectional area of the CrN/W-DLC/DLC multilayer coatings decrease accordingly. The thickest CrN interlayer coating exhibits superior outstanding wear resistance evidenced by an average friction coefficient of 0.119, a steady-state friction coefficient of 0.097 and a wear volume of 1.508 × 106 μm3. The presence of a high proportion of sp2 bonds in the thickest CrN interlayer coating, which are susceptible to graphitization, along with a thicker transition layer that enhances the coating's support, leads to narrower wear traces. The primary wear mechanisms observed in the friction and wear test of CrN/W-DLC/DLC coatings are oxidative wear and tribo-abrasive wear. The work provides a significant promise for application in vehicle rotary seal components and a theoretical reference for enhancing the wear resistance of the seal surface.

Cooling method for the rotor of a superconducting motor

Electrification has been proposed as a route to decarbonizing air travel. Conventional electric motors are too heavy to achieve the power densities required for aviation so superconducting motors for aircraft are being developed. Superconductors however, work at cryogenic temperatures, which indispensably require a reliable and efficient cooling mechanism with a cryocooler. The Robinson Research Institute is developing a 3 MW superconducting motor using an HTS (High Temperature Superconductor) rotor operating at 50 K and MgB2 running at near 20 K for the stator. The motor is intended to run at a shaft speed of 4500-6000 rpm to directly drive a ducted fan. A key challenge is the removal of heat from a cryogenic spinning rotor to a stationary refrigerator so it can be rejected at ambient temperatures. Previous motors have utilized externally pumped or thermos-syphoned cryogens to cool the rotor, which require complex rotary seals. The aircraft application demands a compact and low weight solution. This paper presents a novel cooling design where a stationary cryocooler’s cold heat exchanger penetrates the rotor, and the relative motion of the two creates a pumping motion for cold helium gas to transfer heat from the rotor to the cryocooler. The sealing is low pressure and at ambient temperature and pressure with a temperature gradient in the helium adjacent to the cryocooler regenerator. Design and CFD modelling of the concept are presented showing the system can generate sufficient cold helium flow to transfer heat from the rotor to the cryocooler with a small temperature difference, resulting in a compact, efficient, and low-weight rotor cooling method.

Finite Element Analysis and Optimization of High Speed E-mobility Seal

Background: The use of electric vehicles is expected to increase day by day. The operating conditions of the rotary shaft seals used in the powertrain of electric vehicles are more challenging than those of internal combustion engines. The maximum operating temperature of seal used in electric vehicles is 150℃ and the maximum operating speed is 16,000RPM. It is impossible for a standard seal with a garter spring not to leak under these operating conditions, which has led us to turn to alternative designs. Objective: The objective of starting this study is to develop a new generation rotary shaft seal to be used in electric vehicles with finite element analysis (FEA) and optimization. Methods: During this study, finite elements, optimization and geometry development methods were used. First of all, alternative spiral knurled seal that can operate at high speeds was designed in this study. Secondly, our alternatively designed seal was tested to determine lifetime. Results: When we checked the results coming from test machines, the first design seal had approximately 5g of leakage at the end of 7 days. In the examinations made after the experiment, it was observed that the spirals were deleted at the end of 7 days. A finite element model of the first designed seal was created and radial load control was performed. When the radial load value obtained from the finite element model and the experimental radial load value are compared, it is seen that there is a deviation of around 4.3%. In the light of these data, the accuracy of the FEA model created in the Abaqus has been proven. The created finite element model was optimized within the boundary conditions with the help of Isight. A prototype of the optimized design seal was produced and a life-time test was carried out. The prototype seal of the optimized design had approximately 4g of leakage after 13 days under the same test conditions. Since the lifetime requested by the customer is 10 days, the optimization made on the seal is considered appropriate. The lifetime of the seal was approximately 95% improved. Conclusion: As a result, a new generation rotary shaft seal that can be used in electric vehicles, which is the aim of our study, has been developed. The prototype rotary shaft seal has been validated according to DIN 3761 specification.

Using Fluid Curtains to Improve Sealing Performance in Turbomachinery Applications

Abstract The results from an investigation into the physics of how fluid curtains can be applied to improve the aerodynamic performance of conventional turbomachinery shaft and rotor seals are described in this paper. Computational fluid dynamics and testing on two experimental facilities are used in the study. In the first part of the work, computational fluid dynamics simulations validated against experimental test data demonstrate the fundamental mechanism by which the presence of the curtain can act to reduce leakage flow through conventional seals. These results are consolidated into a single performance carpet map, showing how the leakage reduction performance and the curtain supply pressure needed to achieve it vary with changes in values of key geometrical parameters. In the second part of the work the effect of swirl in the seal inlet flow, as is often encountered in turbomachinery applications, on the performance of the fluid curtain is investigated experimentally. Test results show that if the swirl momentum in the inlet flow is greater than the momentum of the curtain flow, the performance benefit from applying the curtain is greatly diminished. Overall, the results provide some fundamental design rules for applying fluid curtains to enhance turbomachinery sealing performance for the general type of leakage path geometry (cylindrical channel, 45-deg jet angle, curtain upstream of a conventional seal) and working fluid type and conditions (air, ambient temperature, subsonic leakage channel flow) used in the study.

Experiment and Simulation on the Ferrofluid Boundary Deformation and Fluctuation Characters of a High-Speed Rotary Seal

Abstract A ferrofluid seal is a rotary seal widely used in the chemical industry, shipbuilding, aerospace, aviation, and other fields, demonstrating various advantages, such as high reliability, low wear, and low leakage rate. The reason for sealing is that the ferrofluid ring isolates the sealed gas from the atmosphere. Hence, boundary deformation and fluctuation are two significant factors to consider for the design of a ferrofluid seal. However, the ferrofluid boundary is wrapped in the shell and pole shoe, which poses a challenge in direct observation. In this paper, an experimental ferrofluid rotary seal device is presented, which can be used to monitor the boundary changes at different rotational speeds and pressure differences. According to the simulation result, the boundary fluctuation affects the pressure transfer and causes the sealing performance to deteriorate. The ferrofluid boundary obtained through the experiment is essential for an in-depth investigation into the rotary seal failure mechanism for improving the design of the ferrofluid rotary seal.

Numerical and Experimental Investigation of Nano zinc Oxide's Effect on the Mechanical Properties of Chloroprene and Natural Rubber (CR/NR) Composites

Nanocomposites, especially natural rubber (NR), have been extensively studied for their unique features and superior performance in tire applications. The present research investigated the impact of zinc oxide nanoparticles (ZnO) on the performance of typical rotary machine seals made of chloroprene rubber / natural rubber (CR/NR) composites. An ordinary standard rubber two-roll mill and hydraulic press were used to prepare high-temperature vulcanized CR/NR samples filled with ZnO nanoparticles. Tensile strength, tear resistance, abrasion resistance, resilience, and hardness were measured to determine the effects of nanoparticles on these physical and mechanical properties. Based on the various hyperelastic modeling schemes, enhancement in multiple characteristics of the control sample, such as overhaul properties, was observed. Furthermore, results show that increasing nanoparticle content in the vulcanisates increased the physicomechanical characteristics, such as hardness, resilience, tensile strength, and elastic Modulus at 200% strain. Moreover, hyperelastic analytical modeling shows that the differences with experimental results are less than 5%.

Study on performance optimization of double screw-magnetic fluid combination seal

The magnetic fluid seal (MFS) is a new type of sealing method that offers the advantages of no leakage and low wear. Hence, it is widely used in rotary seals in coal, chemical, and electric power fields. However, at high speeds, the degradation and even failure of the sealing performance severely limits the application of MFS in engineering. Therefore, this study designed a combined sealing device comprising a double screw seal and MFS and optimized the pressure resistance of the screw seal using an orthogonal test in combination with the response surface optimization method. Thus, the pressure resistance could be raised to 3.1 times that before optimization. The effect of the sealing gap on the sealing pressure of the MFS was analyzed by numerical simulation, and an optimal sealing gap value of 0.2 mm was obtained. The results of the verification test showed that the performance of the combined seal was significantly better than that of MFS alone. When sealing liquids, the pressure resistance of the combined seal reached 3.3 times that of the MFS at 3000 rpm, which indicates the application potential of MFS in high-speed working conditions.

Numerical simulation study of high-speed lip seal considering eccentricity

PurposeThis paper aims to focus on the high-speed rotary lip seal in aircraft engines, combining its service parameters, its own structure and application conditions, to study the influence of different eccentric forms, eccentricity, rotational speed and other factors on the performance of the rotary lip seal.Design/methodology/approachA numerical simulation model for high-speed eccentric rotary lip seals has been developed based on the theory of elastic hydrodynamic lubrication. This model comprehensively considers the coupling of multiple physical fields, including interface hydrodynamics, macroscopic solid mechanics and surface microscopic contact mechanics, under the operating conditions of rotary lip seals. The model takes into account eccentricity and uses the hazardous cross-sectional method to quantitatively predict sealing performance parameters, such as leakage rate and friction force.FindingsEccentricity has a large impact on lip seal performance; lips are more susceptible to wear failure under static eccentricity and to leakage failure under dynamic eccentricity.Originality/valueThis study provides a new idea for the design of rotary lip seal considering eccentricity, which is of guiding significance for the engineering application of rotary lip seal.

Study on the prediction of high-speed rotary lip seal wear in aero-engine based on heat-fluid-solid coupling

PurposeThis paper aims to investigate the effect of frictional heat on the wear of high-speed rotary lip seals in engines.Design/methodology/approachIn this research paper, the authors focus on the high-speed rotating lip seal of aircraft engines. Using the hybrid lubrication theory, a thermal-fluid-solid coupled numerical simulation model is established to investigate the influence of parameters such as contact pressure distribution, temperature rise and leakage rate on the sealing performance under different operating conditions. By incorporating the Rhee wear theory and combining simulation results with experimental data, a method for predicting the wear of the rotating seal lip profile is proposed. Experimental validation is conducted using a high-speed rotating test rig.FindingsThe results indicate that as the speed increases, the rise in frictional heat leads to a decrease in the sealing performance of the lip seal contact region. The experimental results show a similar trend to the numerical simulation results, and considering the effect of frictional heat, the predicted wear of the lip seal profile aligns more closely with the actual wear curve. This highlights the importance of considering the influence of frictional heat in the analysis of rotating seal mechanisms.Originality/valueThis study provides a reference for the prediction of wear profiles of engine high-speed rotary lip seals.

Influence of Shape, Installation and Rotation Motion Errors on Tin Bronze Clearance Seal of Rotary Joint

The rotary joint is the key device of the marine clutch. Once the seal fails, the power cannot be transmitted. In view of the above problems, this research studies the influence of shape, installation and rotation motion errors on clearance seal. The results show that compared with the absence of roundness error, the roundness error of the shaft will increase the leakage by about 2.5-4.9 %. The cylindrical error of the bushing will reduce the leakage, but it will bring more serious friction, wear and life problems. The existence of radial installation error will increase the leakage, and the larger the radial installation error, the more obvious the flow field extrusion, the higher the unevenness of the pressure field in the whole flow field. The existence of angular installation error will reduce the leakage, but it will cause more serious friction and wear, resulting in a sharp increase in temperature. The leakage increases by about 0.68 % when the radial installation error is 0.1 mm, and the rotary motion error further increases the leakage by about 0.15 %. The above research can provide theoretical support for the structural design and optimization of the rotary joint tin bronze clearance seal.

A quantitative safety assessment for offshore equipment evaluation using fuzzy FMECA: A case study of the hydraulic submersible pump system

The Hydraulic submersible pump system (HSPS) is integral to the offloading of oil on offshore platforms and oil tankers. Due to the inflammable and explosive properties of the oil, the working process of HSPS is of high risk. Therefore, this study focused on the safety assessment of HSPS, key potential failure modes of HSPS were identified. A Fuzzy Failure Mode Effects and Criticality Analysis (FFMECA) model was proposed based on fuzzy logic theory and failure mode effects and criticality analysis (FMECA) method. Fuzzy linguistic terms were used to assess the Occurrence (O), Severity (S), and Detection (D) of the identified failure modes. The weights for O, S, and D were calculated based on experts’ ratings and entropy theory. A case study was carried out and the Fuzzy Risk Priority Numbers (FRPNs) for the failure modes were obtained. The results highlighted that 5 failure modes, namely wear of bearings, failure of mechanical seal, failure of rotary seal, zero pressure on the outlet and influence of excessive temperatures, were of critical level and required immediate preventive action. Risk control measures were proposed to ensure the safety of HSPS in practical application and to improve the reliability of system operation.

Dynamic characteristics analysis of a rotor system with loose support considering internal friction in couplings

Along with the rotating machinery advances toward high speeds, the significance of the excitation force of the seal fluid in the rotor system is growing, which can cause serious accidents. Most of the previous research on rotors in rotating machinery has predominantly focused on the effects of misalignment in couplings. In this article, a novel model is proposed, introducing an analytical approach that combines both internal friction in couplings and loosening support faults. Additionally, an analysis and discussion of the vibration characteristics of the rotating system under the influence of internal friction are presented. This method allows for a more comprehensive assessment of the performance of rotors in engineering applications. Assuming that the left support of the rotor is loose, this model focused on how various factors such as rotor speeds, eccentricity, seal disc mass, and left-end support mass affect the labyrinth seal rotor system's dynamic characteristics. Based on the findings, The emergence of internal friction forces advances the chaos of the rotor. It seems that as the rotating speed increases, there will be a small frequency range, resulting in fluid oscillation, and the system stability will be reduced at this time. The improvement in the seal disc's quality has minimal impact on the stability of the left journal, but it will reduce the stability of the seal disc. The increase in the mass of the left end support will increase the stability of the movement at the left journal and reduce the stability of the movement at the seal disc.

Modeling the Pumping Behavior of Macroscopic Lead Structures on Shaft Counterfaces of Rotary Shaft Seals

The leak tightness of the sealing system rotary shaft seal is based on the formation of an active back-pumping effect of the sealing ring. Here, the sealing ring pumps the fluid in the sealing gap back into the housing. However, this active sealing mechanism is disturbed by so-called “lead structures”. Lead structures include all types of directional structures on the sealing counterface which create rotation-dependent axial fluid pumping. Lead-affected sealing counterfaces can thus cause leakage or insufficient lubrication of the sealing contact. To ensure leak tightness, lead must be avoided or tolerated. This article investigates how different structural characteristics of lead affect the amount of fluid pumped by the shaft surface. For this purpose, 26 shafts are subjected to surface analyzing methods and an experimental pumping rate test. The interaction of various geometric features of the lead structures and their combined effect on the pumping capacity is modeled based on the measured data. Appropriated correlation models are discussed and relationships between shaft lead and its pumping effect are shown. The aim is to estimate shaft pumping rates based on surface measurements in future. The results contribute to the derivation of measurable tolerance values for lead and to the prevention of leakage.

Tribological Characteristics of Rotary Vane Steering Gear Seals Under the Oil With Different Abrasive Particle Sizes

Abrasive particles often cause wear of the rotary vane seals during an operation process, and lead to seal failure and mechanical fault. Focusing on the wear mechanisms and extracting the tribological information during the friction are the prerequisites for extending the service life and carrying out the fault diagnosis prediction of rotary vane seals. Four different sizes of iron particles were selected to mix with the same volume of hydraulic oil to explore the effect of lubricating oil containing abrasive particles on the wear behaviors of the seal. The tribological behaviors during friction were comprehensively analyzed, including the coefficient of friction (COF), wear volume, surface topography, vibration, noise, and other information. The results demonstrated that the wear characteristics of the seal’s contact surfaces changed obviously. The wear morphologies, coefficients of friction, surface roughnesses, and vibration signals increased with the increase of the abrasive particles’ size, with the wear state gradually worsening. When the iron particle size reached 160 μm, the COF increased by 0.047, and the peak vibration signal increased from 4.31 to 36.97 m/s2, compared with pure hydraulic oil lubrication. This tribological information could disclose the wear mechanisms of thermoplastic polyurethanes (TPU) and reveal the TPU wear states. Determining the tribological information for the rubbing pairs was a potential and effective way for evaluating or predicting the rotary vane steering gear seals’ wear states or failure modes. This study lays the foundation for understanding the wear mechanisms and the fault diagnosis of steering gear seals.

Nonlinear Vibration Characteristics and Bifurcations of a Rotor System Subjected to Brush Seal Forces

In the paper, nonlinear vibration characteristics of a rotor system are investigated. Such a nonlinear rotor system is subjected to brush seal forces, which are obtained by integrating the bristle force along the entire ring. The nonlinear brush seal rotor system is constructed by merging a flexible rotor with nonlinear seal forces. The research is aimed at studying the nonlinear vibration characteristics and bifurcations of the motions under a variety of eccentricity circumstances. Different kinds of bifurcations are successfully obtained by mathematical discretization and mapping manipulation. Such a discrete mapping method successfully predicts the stable and unstable motions accurately. The period-doubling bifurcations and saddle node bifurcations of the rotor system are obtained. The sole unstable solutions are obtained, which are special, and a normal numerical integration method cannot solve this problem, which provides advantages in rotor design and motion control. According to the results, nonlinear resonances are found between the stable and unstable motions. The greater the eccentricity of the rotor, the greater the number of bifurcation points that occur during the rotor’s nonlinear motions, as well as the larger the ranges of speeds where the motions are unstable. Saddle node bifurcations generate unstable nonlinear motions and non-smooth motions, which may bring damage to the mechanical rotors. The period-doubling bifurcations produce the route from period-1 to period-2 motions in the nonlinear rotor system. The research provides a new perspective to study the bifurcations and stability of the nonlinear rotor systems.

Multiphase Conjugate Heat Transfer Analyses on the Assembly Situation of Rotary Shaft Seals

Rotary shaft seals prevent the exchange of fluid at shaft passages. Their function and service life depend decisively on the temperature in the contact area between the sealing edge and the shaft. Since the temperature depends on both the generation of frictional heat in the contact area and the heat transfer to the surrounding sealing system, the design of the sealing system is crucial. Within the scope of this work, multiphase conjugate heat-transfer analyses were performed considering different assembly situations. The computed results were presented and contrasted to experimental data. This resulted in a valid model for predicting the temperature in the sealing system, which provided insight into the influence of the sealing surroundings on the contact temperature.

Design and experimental investigation of symmetrical embedded magnetic fluid rotary seal with small gap

A novel symmetrical embedded magnetic fluid seal (SEMFS) structure was designed with the aim of enhancing the pressure resistance of the magnetic fluid (MF) seal with small gap under vacuum condition. The magnetic field distribution in the sealing gap (SG) was studied by numerical simulation, and the theoretical pressure resistant-withstanding of the SEMFS was obtained by combining the pressure resistance theories of stepped MFS. An experimental study was conducted to investigate the effects of magnetic fluid injection volume (MFIV), number of pole teeth, SG, and rotational speed of the rotating shaft on the seal's pressure resistance. The pressure resistant-withstanding values obtained were compared with those theoretically projected for the (SEMFS) and the ordinary magnetic fluid seal (OMFS), based on numerical analysis. The results indicate that the measured pressure value for the SEMFS matches well with the calculated pressure value. Furthermore, the SEMFS exhibits superior pressure resistance capabilities compared to the OMFS when subjected to the same parameters, which fully reflects the superiority of SEMFS structure. With an augment in the injection volume of MF, the pressure-withstanding performance of the SEMFS exhibits an initial upward trend followed by a gradual stabilization. Moreover, the pressure-withstanding performance of the SEMFS demonstrates a progressive enhancement with an increase in the number of radial pole teeth (RPT) and a corresponding increment in the number of axial pole teeth (APT). The ability to resist pressure of SEMFS decreases as the radial sealing gap (RSG) and axial sealing gap (ASG) increase. At low shaft speeds, the SEMFS's pressure resistance capability is not impacted by rotational speed and can be considered similar to a static seal.