Seal Wear Research Articles

Multi-scale modeling and mechanical performance analysis of finger seals with plain woven C/C composite

The application of carbon fibers reinforced carbon matrix (C/C) composite can solve the local wear of metallic finger seals effectively. However, the performance of C/C composite finger seal is complex and variable, which further decreases the sealing performance and life. Therefore, a method of multi-scale modeling and mechanical performance analysis for plain woven C/C composite finger seals was conducted. The circumferential finger beams of C/C composite were modeled by multi-scale structural analysis and weaving simulation. The radial static and dynamic stiffness characteristics of finger beams were investigated. The results showed that the radial static stiffness of the finger beam with three layers was about 3 times that with single layer. The radial stiffness of circumferential finger beams presented a periodic distribution pattern with a period of 90°. The radial dynamic stiffness of C/C composite finger beams increased with the excitation displacement amplitude and rotor speed. But the magnitude and fluctuation degree of dynamic stiffness were greater than those of static stiffness. A large difference in radial stiffness will lead to local wear and hysteretic leakage. This study lays a foundation for the analysis and optimization of the hysteresis and wear characteristics of C/C composite finger seals.

INCREASING THE DURABILITY OF HYDRAULIC CYLINDERS OF LIFTING AND TRANSPORTING MACHINES

Most lifting and transporting and loading and unloading machines have a hydraulic drive. One of the most common actuators that perform reciprocating and rotary movements are hydraulic cylinders, characterised by one-sided wear of the rod seals. Known rod assemblies are elastic sleeves mounted in the hydraulic cylinder housing, which covers the rod with a guaranteed gap. During the unit operation, a gap seal forms in the gap between the rod and the sleeve, which prevents the leakage of the working fluid from the high-pressure cavity and centres the rod in the sleeve. However, to ensure the reliable centring of the rod, the intensive flow of the working fluid through the gaps is required, which leads to significant leaks of the working fluid and a decline in the unit efficiency. The optimal gap does not ensure centring, leading to reduced unit durability due to uneven wear of the sleeve and rod. Therefore, the development of new designs of rod seals that ensure self-centring is an urgent task. The development trends of modern hydraulic drives of construction, track, and loading and unloading machines aim at increasing the pressure of the working fluid up to 32 MPa. It imposes specific requirements on the designs of seals of hydraulic cylinders – the core executive bodies. The analysis of the factors that reduce the durability of reciprocating pair seals shows that it is possible to divide them into several types: wear, aging, operational, and design factors. The article aims to develop and describe a fundamentally new design of a self-centring rod seal, which can increase the durability of hydraulic cylinders of lifting-transporting and loading-unloading machines without using additional devices. The analysis of trends in the development of constructions of rod units of hydro cylinders showed that fundamentally new types have emerged among the existing designs, which simultaneously perform two functions – rod guides and sealing. The most notable among them are combined active and passive rod seals. Passive combined seals of rod assemblies of hydro cylinders differ from traditional ones in that they allow rod movements in the radial direction and allow slight distortions of the rod, compensating for assembly and installation inaccuracies of the assembly. Active combined seals have the same advantages as passive combined seals but additionally compensate for the wear of the guide sleeve, which increases the durability of the entire rod assembly of the hydraulic cylinder. Keywords: hydraulic drive of lifting and transporting machines, hydraulic cylinder rod assembly, sealing, one-sided wear of the rod assembly, self-centring.

Study on the wear performance of V-combined tandem seals

In this thesis, a numerical simulation model of tandem reciprocating sealing system is established for a V-type combination seal for large-size piston rods according to the material and structural characteristics of the seals to achieve the quantitative calculation of leakage rate, friction and other sealing performance indexes; Based on Rhee's wear theory, combined with the hybrid lubrication model, a wear life prediction method for V-type combination seals is proposed to predict and analyse the evolution of lip profile with working time, and a V-type combination seal bench is built for experimental verification.The results show that: with the increase of lip wear, the contact pressure decreases, the contact width increases, the wear is maximal at the lip, the friction of seals decreases gradually, the leakage rate increases gradually, and the total leakage meets the working requirements. Comparison of experimental and simulation results with high degree of overlap, the life prediction method has high reliability; this paper proves that, in 300 h service cycle, the V-type combination seals have good abrasion resistance and wear compensation ability, the seals have good sealing performance, meet the requirements of work use. This study provides a reference for predicting the wear of V-combination tandem seals.

Failure analysis and structural improvement of helicopter landing gear seals based on experiments and three-dimensional numerical simulation

The utilization of O-ring seal structures in landing gears has historically been associated with high rates of failure. Therefore, this study analyzes helicopter landing gear friction failures based on experimental and numerical simulations. The model is designed to replicate the failure phenomena including “seal extrusion”, “seal leakage”, “seal wear”, and “seal distortion”, and to further investigate causes of failure. Corresponding failure criteria are also presented. Addressing the deficiencies inherent in the original O-ring structure, three composite seal structures—namely, the VL seal, double triangle seal, and T-seal—are introduced to enhance the respective seal structure of the buffer pillar. The findings exhibit that, following the transition to the composite seal structure, the strain peaks are optimized. Finally, this paper offers optimal contact pressure ranges for the optimized seals.

Computational studies of stuffing box packing seal wear mechanism using the Archard model

Computational studies of stuffing box packing seal wear mechanism using the Archard model

Thermal accumulation effects modelling of investigate radial shaft seal wear and lubrication transition mechanism

A radial shaft seal (RSS) model is established to reveal mixed thermal lubrication (MTL) and wear performance at speeds ranging from 3000 r/min to 7000 r/min. The model takes into account the initial temperatures of the oil medium and the running time of the RSS to investigate the transition limit of lubrication. Then a thermal fluid-solid method was developed to simulate the lubrication performance of RSS, which shows lubrication transition boundaries through rough micro convex bodies for wear deformation. The RSS deforms wedge-shaped during the wear process and a localized fluid pressure is created on the convex bodies. Considering the wear deformation of the convex bodies due to the wedge effect, the micro performance of the RSS can fully describe the mechanism of the leakage rate. As the dynamic pressure decreases and the leakage rate increases with the temperature of the medium, the RSS lubrication gradually transitions from MTL to EHL. Thus, the initial medium temperature should be considered to maintain the RSS under the mixed lubrication regime with low friction.

An Experimental Study of the Influence of Cold Head Displacement Speed on Single-Stage Gifford-McMahon Cryocooler System Performance

In positive displacement cryocooler systems, the cooling performance is generally driven by the interaction between the compressor’s displacement and the cold head’s displacement. An experimental investigation explored the relationship between performance and cold end displacement speed for a single-stage gas-driven GM-type cold head operated at different frequencies. As loss mechanisms can be frequency related, the investigation also compared varying the cold end displacement by changing stroke length instead of changing operating frequency. Results showing these relationships are presented, and their impact on seal wear and variable-speed operation are discussed.

Predictive method of pressure loss in wet clutch caused by seal wear based on stacking ensemble learning

The harsh operating conditions of heavy-duty vehicles accelerates the wear of the sealing ring in the transmission, leading to increased oil leakage and a reduction of the operating pressure in the piston cylinder of wet clutch. This impairs the proper functioning of the transmission in the heavy-duty vehicle. Therefore, it is necessary to predict the pressure loss inside the transmission quickly and effectively after the wear of the sealing ring. The wear of the sealing ring under different operating conditions is calculated through the modified Archard model. The relationship between the oil leakage and pressure loss after the wear of the sealing ring is analyzed using Fluent software. The analysis involves the effects of different wear levels of the sealing ring. The simulation results are validated through a high-speed oil cylinder performance test rig. Based on the validated simulation data and test data, a prediction model for pressure loss is established by using stacking ensemble learning with MLR (multiple linear regression), DTR (decision tree regression), and SVR (support vector regression) as the base learners and RF (random forest) as the meta-learner. The risk of model overfitting is reduced through k-fold cross-validation. The research results indicate that the fused stacking ensemble learning algorithm fully utilizes the advantages of each base learner and can effectively predict the pressure loss after the wear of the sealing ring, and achieve a higher accuracy. The establishment of this model provides theoretical support for real-time prediction of pressure loss after the wear of the sealing ring in actual heavy-duty vehicles.

Fault Diagnosis of Dry Gas Seal Operation Status Based on Acoustic Emission Monitoring

A dedicated test bench is employed to record acoustic emission signals from dry gas seals under various operating conditions. Time-domain and frequency-domain analysis methods are utilized to process and analyze the acoustic emission signals during start/stop, stable operation, and two common fault states (end-face defects and compensation spring failure). Furthermore, feature recognition research is conducted. A method for identifying the operational states of seals (low-speed friction, gradual detachment, stable operation) based on the root mean square (RMS) was established, with transition points at speeds of 100 and 1000 RPM, respectively. Additionally, spectral analysis is conducted using Fourier transform to determine the frequency band of acoustic emission signals (240–320 kHz) generated during contact wear of dry gas seals. Investigation into two typical faults of dry gas seals reveals that the RMS value of the acoustic emission signal gradually increases with the rotational speed during the operation of dry gas seal end-face defects. This is attributed to the insufficient dynamic pressure effect on the end face, resulting in long-term wear and tear. When the dry gas seal compensates for spring failure, the RMS value of the acoustic emission signal initially increases, then decreases, and finally increases again as the speed increases. It reaches the stable operating inflection point when the end-face speed is 800 r/min.

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.

ИЗМЕНЕНИЕ ТЕХНИЧЕСКОГО СОСТОЯНИЯ ДВИГАТЕЛЕЙ ЛЕГКОВЫХ АВТОМОБИЛЕЙ В УСЛОВИЯХ ЭКСПЛУАТАЦИИ

This study presents the results of collecting and analyzing statistics on the wear of pistons of budget-class passenger car engines during active operation. The devices and methods of collecting experimental data on the wear of the cylinder-piston group of engines are described. The main ones were: measuring piston wear in four projections with a micrometer MK-100 GOST 6507-90 with a measurement error of ± 0.005 mm and measuring the compression properties of engines with a compressor, the latter showed low accuracy of displaying the technical condition according to the results of the study. The purpose of the study was to verify the effectiveness of common methods of diagnosing internal combustion engines, as well as to identify the dependence of wear on the frequency of oil change, the design features of the engine lubrication system (the presence of oil nozzles cooling pistons). As a result of the study, the inefficiency of the diagnostic method by measuring compression with various devices was revealed, since when the cylinder-piston group wears out with simultaneous wear of the rubber seals of the valves, the oil acts as an additional seal in the engine cylinder and "masks" the actual compression index of the internal combustion engine. In addition, the results of the study confirmed the effectiveness of the presence in the design of the lubrication system of piston cooling oil injectors designed to supply oil when a certain pressure in the lubrication system is reached to a more loaded cylinder wall and piston bottom – based on the revealed fact, it becomes possible to make recommendations on the refinement of the engine design during major repairs at automobile enterprises, service stations by introducing oil injectors into the engine block, which will lead to an increase in the life of the cylinder-piston group and longer trouble-free operation of the engines.

Hybrid lubrication model study of slip ring combination seal under the influence of frictional heat

This paper presents an experimental and theoretical investigation into the factors influencing the sealing performance of combined slip rings. Factoring in the frictional heat from micro convex bodies and convective heat exchange between the slip ring, oil film, and air, we formulate a thermoelastic flow hybrid lubrication model for the combined slip ring seal. This model calculates the distribution of oil film thickness, pressure, temperature, velocity, and viscosity in the sealing zone, drawing on the generalized average Reynolds equation and the transmembrane average energy equation, in conjunction with the heat conduction equation of the slip ring. Utilizing the Archard wear model, we also examine the wear characteristics of the combined slip ring seal, providing insights into seal wear under these conditions. The model enables an analysis of the interplay between parameters and their impact on seal performance. The method proposed accurately predicts friction and leakage in line with experimental data, thereby providing a theoretical foundation for further numerical investigation of seal characteristics.

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.

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.

A Hydraulic Reciprocating Rod Seal’s Life Evaluation Method Incorporating Failure Mechanism Analysis and Test Observation Data

Reciprocating rod seals are widely used in hydraulic systems. Their useful life and reliability affect that of the system. Degradation modeling is necessary to evaluate the useful life of the seal. Seal wear is one of the important forms of hydraulic reciprocating rod seal degradation, yet it is difficult to measure through direct methods. Because seal wear determines the leakage of the seal, we therefore consider the seal leakage as the performance degradation index. Furthermore, the degradation of the seal is always associated with random effects, which cannot be considered by theoretical failure mechanism analysis. Hence, stochastic processes are applied to consider the random effects. Considering the error between the measured value and its real degradation state caused by the measurement environment or other factors, we introduce the measurement error term into the Wiener process model and develop the corresponding Wiener process life prediction model. Finally, the failure mechanism analysis and test measurement data are fused to predict the life cycle of the hydraulic reciprocating rod seals. The effectiveness of the proposed method is verified by comparing the predicted degradation and the experimental observations.

Numerical Calculation Method of Multi-Lip Seal Wear under Mixed Thermal Elastohydrodynamic Lubrication

The multi-lip combined seal has the advantages of multi-lip coupling, large supporting force, and can withstand high-pressure shocks. It is an irreplaceable structure for single-lip seals. However, most of the seal wear analysis focuses on the simulation method of the single-lip seal under the influence of macro factors, and very little involves the wear characteristics of multi-lip seals. In this paper, a micro numerical method is established, which combines the elastohydrodynamic lubrication theory with the modified Archard equation. The performance of a multi-lip combined seal under different working conditions is analyzed through simulation, including macro and micro factors. It is found that some of the characteristics of single-lip seals are also reflected in multi-lip seals, and there is a critical speed that makes the sealing behavior of each seal lip different.

Radial shaft seals: How ageing in oil and hyper-viscoelasticity affect the radial force and the numerically predicted wear

In this paper, a comprehensive finite element model is revised and improved to investigate the role of ageing and viscous effect in the clamping force decrease and the predicted wear. The finite element model considers the effects of actual seal geometry, seal wear, shaft wear, temperature, rubber viscoelasticity and ageing. The comprehensive modelling approach, the application of actual seal geometry determined by newly developed measurement approaches, and temperature- and ageing-dependent hyper-viscoelastic constitutive constants obtained by simultaneous consideration of quasi-static and dynamic test results are the novel characteristics of this study. It was found that the applied ageing has a moderate while the viscous nature of rubber has a significant effect on the clamping force and predicted wear of seals.

The Particle Breakage Effect on Abrasive Wear Process of Rubber/Steel Seal Pairs under High/Low Pressure.

Pressure has a significant effect on rubber seal performance in the abrasive environments of drilling. The micro-clastic rocks intruding into the seal interface are prone to fracture, which will change the wear process and mechanism, but this process is not yet known at present. To explore this issue, abrasive wear tests were carried out to compare the failure characteristics of the particles and the variation wear process under high/low pressures. The results show that non-round particles are prone to fracture under different pressures, resulting in different damage patterns and wear loss on the rubber surface. A single particle force model was established at the soft rubber-hard metal interface. Three typical breakage types of particles were analyzed, including ground, partially fractured, and crushed. At high load, more particles were crushed, while at low load, shear failure was more likely to occur at the edges of particles. These different particle fracture characteristics not only change the particle size, but also the state of motion and thus the subsequent friction and wear processes. Therefore, the tribological behavior and wear mechanism of abrasive wear are different at high pressure and low pressure. Higher pressure reduces the invasion of the abrasive particles, but also intensifies the tearing and wear of the rubber. However, no significant differences in damage were found for steel counterpart throughout the wear process under high/low load tests. These results are critical to understanding the abrasive wear of rubber seals in drilling engineering.

Wear and Leakage Behaviors of Brush Seal Considering Eccentricity and Radial Deformation

Brush seals can improve engine performance by reducing leakage. Wear models of brush seals provide methods to predict wear and leakage. However, rotor eccentricity, radial deformation, and hysteresis effect of bristles are not considered systematically in the existing models, which may lead to large errors in some cases. To investigate the influence of rotor-stator eccentricity and radial deformation on the wear process and leakage performance of brush seal, a brush seal test was planned and executed, in which the air leakage rates were measured at different testing times and operating conditions, the eccentricity and radial deformation was measured using eddy current sensors. The test results showed that the eccentricity and radial deformation significantly affected the wear behavior and leakage performance. In the theoretical research, the abrasive wear equation is adopted to describe the material loss of bristles, and a simplified description is used to express the rotor-stator eccentric motions. To describe the effect of hysteresis on wear behavior, the deformation of the bristle pack is divided into rebounding deformation and locked deformation, and the two deformation modes are modeled separately. Then a brush seal wear model considering rotor-stator eccentricity and radial deformation is obtained, in which the hysteresis effect is especially represented. The wear model was verified quantitatively based on the brush seal test data, and the results show that there is an error of 20% with the calculated wear loss when rotor eccentricity, radial deformation, and hysteresis effect are comprehensively considered. In contrast, ignoring the hysteresis effect may increase the error by several times. This study provides a quantitative and practical method for predicting the wear and leakage of brush seals.

A multifunction flow channel switching module for multi-column capillary gas chromatography using silicon pneumatic microvalves

Decades ago, multi-column GC was developed for separating analytes which cannot be separated with a single column by switching the flow channels and introducing them into multiple columns. Formerly, a channel switching system consisted of stainless-tube-type packed columns and multi-port switching valves which were connected by stainless-steel pipes. These systems utilizing packed columns are still widely used today, mainly for gas analysis, especially for refinery gas analysis and natural gas analysis related to oil refining. However, there have been no new development updates in terms of hardware for decades. Since multi-port switching valves are used, there are problems such as the high frequency of valve replacements due to wear of seals, high running costs as well as long downtimes. In recent years, a heart-cutting multidimensional capillary GC using pressure switching devices such as the Deans switch has been put into practical use. Compared to the switching valves, the pressure switching devices have no wearing parts and are maintenance-free. Multi-dimensional capillary GC using the pressure-switching method cannot be applied to the analysis of low-boiling-point gasses because the retention capacity of the capillary column is low and the column inlet pressure is far from the optimum value for switching. Because of this another related factors, it has not been able to completely replace the traditional methods. In this study, an ON/OFF type silicon pneumatic microvalve was designed and fabricated by semiconductor manufacturing technology, and a flow channel switching module was developed by mounting microvalves on a metallic channel plate which is made by diffusion bonding. The flow channel switching module using silicon pneumatic microvalves has a heat resistance of up to 310 °C, can withstand pressures up to 1.5 MPA or more, and a durability that can withstand over 2 million opening and closing operations. In addition, the reproducibility of the gas sample analysis showed good reproducibility values of RSD 0.1% or less for peak areas and RSD 0.01 to 0.04% for retention time. Flow path switching without the use of pressure switching simplifies method development in several ways. For instance, by incorporating the use of valves that can be opened and closed independently, it was possible to integrate several methods such as heart cut, precut, column switching, and backflushing flow path layouts.