Types Of Seals Research Articles

Aerodynamic instability of brush seals in gas turbine engines based on a fluid-structure interaction method

By brush seal, we mean a type of mechanical seal that uses a large number of closely packed, thin, and flexible bristles to create an outstanding seal between rotating and stationary components in gas turbine engines. However, at high levels of swirling and pressured environments in engines, bristles of brush seals tend to circumferentially slip, which leads to reduced sealing performance and seal failure. In this paper, the effects of upstream–downstream pressure differences Δp (0.2–0.5 MPa), downstream static pressure (0.1–1.0 MPa), and the coverage of bristles by a front plate (0%–90%) on the mechanical characteristics and deflections of bristles of a brush seal at highly swirling inlet were investigated based on a two-way fluid-structure coupling method. A key criterion for bristle instability, based on a simplified two-dimensional (2D) theoretical analysis, is obtained from the fluid-structure coupling simulations. The results indicate that a fundamental reason for the bristle circumferential slip is the ratio of the normal to the axial aerodynamic forces (Fn/Fax) acting on the first row of bristles. When this ratio exceeds 0.9, the bristles will slip circumferentially. The effects of the pressure differential across the seal, the downstream pressure, inlet swirl velocity, and front plate coverage of the bristles on bristle stability can all be explained through their influences on this force ratio. At relatively low outlet static pressure of 0.1 MPa, upstream bristles slip when the inlet swirl is in the range of 230–300 m/s and the bristle slip instability is more likely to occur at higher pressure difference conditions. However, at high downstream pressures, Fn/Fax declines with the growth of Δp, contributing to the stability tendency. With the constant Δp, the value of Fn/Fax significantly increases as the downstream pressure rises, and the critical swirl velocity required to trigger bristle slip is considerably reduced. Additionally, the front plate shields a part of the bristles away from pressure gradient in axial direction but leads to outward radial flow upstream of the bristle pack, thereby increasing the Fn/Fax. Thus, front plate does not offer protection to bristles under high inlet swirl conditions, on the contrary, it may cause early slip of the bristles.

Fog seal with polymer composite modified emulsified asphalt: Road performance and environmental adaptability

Three types of fog seals with polymer modified-emulsified asphalt were prepared to improve the durability of the fog seal and the maintenance quality of asphalt. Based on the skid resistance, water seepage, and wet wheel abrasion, the spraying scheme of the fog seal was determined. The variation of surface drying time under different temperatures and humidity was clarified. The road performance evolution law of fog seal under composite conditions and long-term abrasion was revealed, respectively. The results show that the optimal spraying amount of modified emulsified asphalt for three types of fog seals was 0.6 kg/m2. The optimal dosage of fine sand for fog seals with waterborne epoxy/polyurethane modified-emulsified asphalt (WER-WPU-JFC-EA) and waterborne epoxy/polyurethane/styrene-butadiene rubber-modified emulsified asphalt (WER-WPU-SBR-EA) was 0.6 kg/m2 and 0.4 kg/m2, respectively. Under average temperature and humidity, the traffic open time of the fog seal was 1.0–1.5 h. After the long-term action of thermal-oxygen/freeze-thaw and climate/freeze-thaw, the bonding strength of WER-WPU-JFC-EA and WER-WPU-SBR-EA fog seal was still greater than 0.34 MPa. After 50,000 times of wear, the mass loss of WER-WPU-JFC-EA and WER-WPU-SBR-EA fog seal was below 5.2 %, maintaining good skid resistance and waterproof performance.

Flow Characteristics of Asymmetric Plunger Pairs in High-Pressure Plunger Pumps

Abstract The deep-sea submersible is an essential piece of equipment for deep-sea development, serving as a crucial tool for conducting exploration and operations in the deep ocean. As the core component of the hydraulic system, the plunger pump is vital for ensuring the smooth lifting and lowering of the submersible. The plunger pair, which constitutes the most significant friction pair in plunger pumps, plays a pivotal role in determining both the service life and volumetric efficiency of the pump through its friction, lubrication, and sealing performance. This article proposes a flow model for the plunger pair in eccentric and inclined positions, considering its various orientations and placements. It elucidates the deformation and leakage characteristics of the plunger pair under different configurations, including various postures, material properties, and design parameters. The findings not only provide a theoretical foundation for the design of reciprocating seals and the evaluation of sealing performance but also contribute to the broader field of parameter design and performance assessment for other types of gap seals.

Dynamic Models of Mechanical Seals for Turbomachinery Application

One of the primary causes of mechanical face seal failure is rotor vibration. Traditional dynamic seal models often cannot fully explain failure mechanisms. The dynamic models of seals proposed in this paper, including those developed by the authors, are valuable for predicting seal dynamics during operation in specific turbomachinery and for explaining the causes of seal failure. The single-mass dynamic model is suitable for analyzing the dynamics of contact mechanical face seals and simply designed dry gas seals. The two-mass dynamic model is used to investigate the operational dynamics processes of classical dry gas seals under complex loading conditions. The three-mass dynamic model is used to study various complex types of mechanical face seals. This model can determine the normal operating condition range and explain leakage mechanisms in the presence of excessive rotor vibrations.

CALCULATION OF DYNAMIC CHARACTERISTICS OF A FACE GAS-BARRIER IMPULSE SEAL FOR PUMP AND COMPRESSOR SHAFTS

The article presents a combined mathematical model that allows us to determine and investigate the dynamic characteristics of the latest type of non-contact sealing for pump and compressor shafts, which eliminates leakage of pumped products, which are important from the point of view of safe operation. The proposed method is based on the laws of conservation of energy and conservation of matter. The model is based on static and dynamic calculation of operation characteristics, while its key feature is the combination of analytical, variational and numerical solutions. The materials of the article may be useful to developers of new types of contactless seals of centrifugal machines.

Sealing efficiency performance of four different rim seals in turbine cavity

In modern aero-engine, the turbine rim seals whose purpose is to reduce the ingress are located in a complex flow region between the mainstream and secondary air flows. The sealing air discharged from the compressor of engine is used to purge turbine cavity. In order to examine the effects of ingress through four distinct rim seals, a one-stage test rig was used in the experiments presented in this work. At a Reynolds number of 5.16 × 105 in the mainstream and (0.85–2.13) × 106 in the rotational, the radial pressure distribution on the stator was determined. To assess flow characteristics and sealing efficacy, measurements of the swirl ratio and CO2 concentration were made. The reliability of turbine rim-seals is determined by the locations of the hook and teeth, as well as their effect on hot gas ingestion. To evaluate the performance of four types of seals: a datum double-rim seal and three derivatives with different clearances, the data are employed. Due to the inlet air position, the swirl ratio exhibited a pronounced inflection for all the rim seals. The sealing efficiency can be decreased by putting the hook closer to the rim or by taking the teeth out. Static pressure measurements in the turbine cavity indicate that the seal position has a significant impact. The analysis results revealed that the existence of slot vortex is beneficial to improving efficiency.

A comparison of static and rotordynamic characteristics for two types of liquid annular seals with and without helical grooved stator

Less leakage is a benefit of parallel grooved liquid seals (labyrinth seals). But researches show that the liquid seal with parallel grooves on the rotor harms the rotor stability. The seal with helical grooves on stator performs well in terms of rotordynamics, and its leakage is sensitive to the rotating speed. To make use of the advantages of both seals and improve seal stability, based on the Smooth-stator/Parallel Grooved-rotor (SPG) liquid seal, a Helical Grooved-stator/Parallel Grooved-rotor (HGPG) liquid seal is designed. To evaluate two liquid seals’ leakage, rotordynamic characteristics and drag power loss, a transient computational fluid dynamics-based method is employed. This method is based on the multi-frequency elliptical-orbit rotor whirling model and the mesh deformation technique. The published experimental data of the leakage and rotordynamic force coefficients for an SPG liquid seal are used to validate the accuracy and dependability of the current method. Seal leakage and force coefficients are presented and compared for the SPG liquid seal and the HGPG liquid seal at various pressure drops. The influences of parallel groove depth on the leakage and rotordynamic properties for the HGPG liquid seals at two rotational speeds (2000, 6000 r/min) are analyzed. The numerical findings demonstrate that the novel HGPG liquid seal has a lower leakage flow rate (by ∼22.3%) than the traditional SPG liquid seal. There is an optimal parallel groove depth that minimizes leakage. The presented novel HGPG liquid seal significantly improves rotordynamic stability, due to the similar effective stiffness and the obviously larger positive effective damping. Reducing parallel groove depth can increase the positive effective damping. In terms of leakage and rotordynamic characteristics, the novel HGPG liquid seal is a better seal design for liquid turbomachinery.

ЭЖЕКТОРНОЕ УПЛОТНЕНИЕ ВАЛА РОТОРНОЙ МАШИНЫ

The analysis of designs and the principle of operation of contactless ejector shaft seals of rotary machines, fans, aerodynamic heating furnaces, blowers, turbochargers of gas pumping units and other injection machines is considered. A new type of non-contact ejector seal is shown, which in-creases its efficiency when changing the direction of rotation of the shaft and eliminates friction and sparking between sealing surfaces during operation of a rotary machine

Failure and Damage of Reciprocating Lip Seals for Pneumatic Cylinders in Dry Conditions

Lip seals are components subjected to high mechanical stress and they are responsible for many out-of-service in pneumatic cylinders. The aim of this work is the development of an experimental methodology to evaluate lifetime duration and analyse failures and damages of rod lip seals for pneumatic cylinders. A dedicated test bench was designed and manufactured which reproduces actual working conditions of the seals i.e., compressed air action (seal pressurisation) and relative linear reciprocating motion. Three types of seals made of two elastomers (NBR and polyurethane) were tested; dry condition was considered to speed up the tests. The influence of geometric parameters like seal seat dimension and seal axis misalignment with respect to the rod axis, was analysed by multiple experimental tests. Results in terms of seal life duration and failure modes are presented which allow comparison of seals performance and provide a helpful tool to end-users in a proper selection of seals geometry, material and key working parameters.

Characteristics of packing gland seals in hydraulic systems of quarry excavators and results of comparative analysis of experimental tests

The efficiency of quarry hydraulic excavators will depend on several factors, namely the climatic conditions of the area where hydraulic excavators are used, the degree of air pollution (pollination), the performance of the structural parts of the excavator, the reliability of the hydraulic system, the performance and cleanliness of the hydraulic working fluid. In this area, research was carried out on the performance of seals used in the hydraulic system of quarry excavators. The article presents the results of experimental tests of the existing type of oil seal a and b, as well as the proposed oil seal type c, shown in Fig. 1.

Investigation of operational fundamentals for vacuum-assisted headspace high-capacity solid-phase microextraction and gas chromatographic analysis of semivolatile compounds from a model solid sample.

Vacuum-assisted headspace solid-phase microextraction (Vac-HS-SPME) is a technique used to enhance SPME sampling of semi-volatile organic compounds. Here, it was combined with a high-capacity SPME Arrow, which features a larger volume of extraction phase and a more rugged configuration than traditional extraction fibers. An in-depth assessment of the critical parameters was conducted to achieve optimal extraction of representative compounds from a model solid sample matrix (Ottawa sand). Operational fundamentals investigated included the types of seals needed to create a leak-free environment under vacuum conditions; the magnitude of the vacuum applied and time needed to activate the Vac kinetics; order of sample vial preparation methods (VPMs); and other standard variables associated with extract analysis by gas chromatography-mass spectrometry. When exploring the limits of sample VPMs, results indicated an ideal workflow requires the solid sample to be spiked before sealing the vial, allow the sample to rest overnight, then apply vacuum at a pressure of -677mbar (out of -789mbar maximum possible vacuum with pump and compressor used), exerted on the vial for 90 s. This work provides the necessary workflow for the optimization of Vac-HS-SPME sampling of analytes from solid matrices.

Leakage flow-induced excitation behavior and rotor instability in the high-speed supercritical CO2 scallop damper seals

As an innovative type of damper seal, the scallop damper seal (SDS) has shown greatly improved sealing performance for the high-compactness supercritical CO2 (S-CO2) turbomachinery, but leakage-induced excitation forces have an impact on the rotor stability. In this research, we improve the rotordynamic solution based on the multi-frequency elliptic whirling model for the S-CO2 seals and investigate the leakage-induced excitation behavior of SDS depending on seal geometry and operating condition. By comparing the results of a labyrinth seal and a full-partition pocket damper seal, we prove that SDS has better rotordynamic performance for the S-CO2 compressor. The results show that increasing the pressure drop favors greater direct stiffness and effective damping of the SDS. Inlet preswirl changes the direction of fluid-response force to coincide with the rotor motion, which is detrimental to rotor stability. Changing the cavity depth has no significant effect on the dynamic characteristics of the SDS, but shortening the cavity length reduces the direct stiffness to below zero. Supplementing the number of circumferential cavities increases the direct stiffness and effective damping but results in SDS not being able to be machined directly by milling cutters. The design with 12 circumferential cavities is recommended for the 100-kW-class S-CO2 compressor.

Effect of light intensity and seal type on the in vitro elongation and adventitious rooting of Eucalyptus grandis × E. urophylla

Background: Rejuvenation/reinvigoration of tissues through micropropagation has become an important tool for clonal propagation in eucalypts species. This study evaluated the effect of photomixotrophism (i.e., light intensity and seal type) on in vitro elongation and adventitious rooting to identify the limiting factors on in vitro culture of the Eucalyptus grandis × E. urophylla hybrid. Methods: Nodal segments (i.e., explants) from ministumps grown in a semi-hydroponic system were collected. The effects of light intensity and seal type on in vitro elongation and adventitious rooting stages were evaluated from a 40 μmol m-2 s-1 fluorescent lamp and 20, 40, and 80 μmol m-2 s-1 red/blue LEDs, with (through porous membranes) and without gas exchange. Results: Based on the results at 35 d, 40 μmol m-2 s-1 fluorescent lamp and gas exchange combination was the most suitable for in vitro elongation and adventitious rooting of Eucalyptus grandis × E. urophylla. Both factors increased the vigour, shoot length, photosynthetic pigment content, xylem, phloem, stomatal number and density, root length, diameter, number of roots per explant, and adventitious rooting fraction. Conclusions: Light intensity and seal type influences the in vitro elongation and adventitious rooting of Eucalyptus grandis × E. urophylla. The results contribute to optimising the cloning of commercial eucalypts species by the micropropagation technique.

Introduction of Internal Circulation-Based Cooling Methods and Green Coolants in Milling via Cutting Tool and Tooling Design

This paper describes the process of the design and verification of a milling tool and tooling that may contribute to the renouncement of the flood cooling method when mineral oils and oil-in-water emulsions are used as coolants. The proposed solutions are based on the idea of coolant supply in internal channels created inside of a cutting tool. As an alternative to the aforementioned mineral oil-based coolants, liquids with higher cooling efficiency and environmental friendliness (green coolants) were considered. Given coolants’ possible lack of lubricating properties and negative (corrosive, etc.) influence on a machine tool’s units, tooling delivers these coolants to the cutting tool and bypasses the standard machine tool’s supply system. The geometry of the milling tool (a cutting insert with an internal channel) was tested in the framework of a stress simulation. To perform it, cutting force components Fz, Fy, and Fx were determined empirically and then applied to the simulated area of contact between the tool and the workpiece. Based on the obtained principal stress values P1, P2, and P3, the factor of safety was calculated with the Mohr–Coulomb, P1 max, and P3 min failure criteria. The proposed milling tool, equipped with a novel type of labyrinth seal with no friction between its components, was experimentally tested to confirm its ability to maintain leak-tightness at different values of spindle speed (200~2000 rpm) and coolant supply volume (1.0~10.0 L/min). Based on the results of the stress simulation and the leak-tightness experiment, conclusions were drawn about further modernization and utilization prospects of the proposed milling tool and tooling design.

Enhanced rotordynamic performance under various structural arrangements of hole diaphragm labyrinth seal

In this study, we study the influence of five drilling hole arrangements on the rotordynamic and leakage performance of hole diaphragm labyrinth seal (HDLS) type seals with precise CFD analysis. Key findings reveal that hole distance significantly affects direct and cross-coupled stiffness, thereby impacting stability and leakage. Notably, the smallest hole in rectangle four holes(RF)-HDLS does not yield the minimum leakage. Vortex structure analysis, employing the Q-criterion, elucidate horizontal two holes(HT)-HDLS's superior leakage reduction owing to enhanced turbulence eddy dissipation. Seals with larger hole diameters, down single hole(DS)-HDLS and up single hole(US)-HDLS, demonstrate stable rotordynamic performance, with DS-HDLS exhibiting a notable 106.3% improvement in cross-coupled stiffness. In contrast, seals with holes positioned farther away, DS-HDLS, US-HDLS and vertical two holes(VT)-HDLS, experienced increased leakage with whirl frequency. HT-HDLS and RF-HDLS displayed a decrease, attributed to the stronger centrifugal effect. Comparing to center single hole(CS)-HDLS, VT-HDLS and US-HDLS achieved a significant 159.3% direct stiffness improvement and 432.7% reduction in cross-coupled stiffness. Despite a maximum 4.2% leakage increase, this substantial enhancement in rotor stability should not be overlooked. Moreover, all seals exhibited lower leakage rates than the traditional labyrinth seal.

Design of the Springs Tightening for a Double Cartridge Mechanical Seal

Mechanical seals are used in a wide range of industrial applications, including pumps, compressors etc., in order to avoid leakage of the working fluid. The design construction, and the operation of the mechanical seals continue to evolve to meet the demands of new technologies and industries. These developments are the increase of operating parameters, in the condition of strictly respecting the environment protection. A mechanical seal consists of two rings, one being static and the other one dynamic, which are actioned by one or two fluid pressure, and an elastic force (or magnetic) which keeps the two faces of the rings in permanent contact. A direct contact between the frontal face of the rings will increase the surface temperature and the rings wear, so a small fluid film, as a lubricant and coolant, it is kept between the two face sealings. At modern mechanical seal are used also a secondary fluid. The tightening force in the seal, which it is very important, depends on seal construction, materials used, working fluid type, pressure and temperature, rotational speed, secondary fluid type, pressure, and temperature. Paper aims to present the studies made by the authors on a mechanical seal of the AESSEAL, cartridge seal type CDSA of a 1” in order to obtain the correct sealing pressure between seal rings. Calculation was made analytical, with the respect of regulations of the standards, and by FEA method. Was obtained a CFD model, to simulate the pressure inside the chamber of secondary fluid at different inlet/outlet pressures to determine the real value of it. The obtained results by CFD analyses were integrated in FEM analyses by ANSYS Static Structural to calculate the contact pressure on the rings faces and to calculate the minimum spring force for internal and external sealing cartridges for different working and secondary fluid pressure, also considering the seal construction design, materials, and rotational speed of 3000rpm. The results are very important in operation of the mechanical seal because the graphs presented in the paper give the operators the correct value of the spring tightening in the seal depending on the different ranges of fluids pressures.

Improved vibration performance of a nonlinear rotor-seal system with modified labyrinth seals by an interpolating database method

Traditional studies for seal evaluation primarily focused on rotordynamic coefficients. We previously introduced two innovative labyrinth seals, the diaphragm labyrinth seal (DLS) and hole diaphragm labyrinth seal (HDLS), featuring enhanced rotordynamic and leakage characteristics. To delve into the dynamic response of these circumferentially discontinuous seals, which cannot be reduced to a 2D model, an interpolation database method (IDM) is proposed. Improved vibration performances are obtained in a nonlinear rotor-seal system with modified labyrinth seals. The Muszynska seal force model is compared with IDM for verification of accuracy. Comprehensive insights into the system's behavior were provided through metrics like the maximum Lyapunov exponent, time-domain waveform, spectrogram, Poincaré, displacement orbits, and phase maps. Results underscored IDM's accuracy for circumferentially continuous seals vis-a-vis Muszynska's model, showcasing exceptional solving abilities for discontinuous seals. Local subharmonic vibrations in rotor-DLS and rotor-HDLS systems were identified. Notably, HDLS demonstrated a 56.6% reduction in maximum amplitude compared to labyrinth seal (LS) and a 24.6% reduction compared to DLS. Maximum Lyapunov exponent outcomes emphasized HDLS’s superior stability among the three labyrinth seal types in rotor-seal system. Especially, HDLS maintained stability across diverse unbalanced mass conditions, further highlighting its versatility and application potential.

Leakage and Rotordynamic Force Coefficients of a Labyrinth Seal and a Pocket Damper Seal Operating With Wet Gas

Abstract Subsea centrifugal compressors commonly using labyrinth seals (LS) and pocket damper seals (PDS) must withstand the flow of oil in gas mixtures with a liquid volume fraction (LVF) up to 5%. This paper presents experimental results for the leakage and rotordynamic coefficients of a uniform clearance PDS and a similar size LS both supplied with wet gas. The shaft diameter D = 127 mm and the seal axial length L = 48 mm. In the tests, the seals' pressure ratio (inlet/exit) = 2.5, and the shaft speed reaches 5.25 krpm (surface speed = 35 m/s). The LS has a 17% larger radial clearance (Cr,LS = 0.230 mm > Cr,PDS = 0.196 mm) due to a manufacturing error. This paper extends prior work by Torres et al. (2022, “A Stepped Shaft Labyrinth Seal versus a Pocket Damper Seal: Leakage and Dynamic Force Coefficients Under Wet Gas Operation,” ASME J. Eng. Gas Turbines Power, 145(1), p. 011006) for the same two seal types with a stepped clearance configuration that promotes damping. When supplied with a dry gas, the LS leaks more because of its larger clearance. A loss coefficient (cd) is a fraction of the physical clearance that characterizes a seal's effectiveness in reducing leakage. The cd of both seals is nearly identical for operation with pure gas; the small differences are well within the experimental uncertainty. For operation with wet gas, the PDS cd decreases as the LVF increases whereas the LS cd increases, thus indicating the PDS is more effective to restrict wet gas leakage. When operating with pure gas, the direct stiffness (K) and effective damping (Ceff) of both seals are small in magnitude (K < 0.5 MN/m, Ceff < 2 kN-s/m) and often less than the experimental uncertainty. For wet gas operation and with shaft speed = 3 krpm and 5.25 krpm, the PDS produces Ceff < 0 for whirl frequencies below 50 Hz. In contrast, the LS Ceff > 0, although small in magnitude. The experimental results under wet gas operation are similar for operation with LVF equal to 3% and 5%. Unexpected low-frequency broadband motions appear when supplying the PDS with a wet gas. Although small in amplitude (<5 μm), the motions increase in severity as the mixture inlet LVF and shaft speed increase. The motions are entirely absent for tests with the LS. Experiments in which the mixture is drawn from the PDS cavities rule out liquid accumulation as the cause of the observed motions. The current test results serve as a reference for turbomachinery design engineers and aid in the validation of analytical predictive tools.

Analysis of mechanical characteristics and normal operating conditions of magnetic seals

Aiming at the leakage failure problem caused by the accidental disengagement of the sealing interface due to the failure of the magnetic seal force balance system, taking a certain type of aero-engine magnetic seal as an example, the mechanical analysis model of the magnetic seal is established, and the mechanical conditions for normal sealing work are deduced according to the set of equilibrium equations of force. The analysis process of the normal operation is proposed, and the calculation method of the key mechanical parameters of the magnetic seal is determined. On this basis, the influence of operating conditions on the normal operating mechanical conditions is analyzed. The results show that the primary sealing face contact pressure, the maximum contact pressure of the secondary sealing face, and the traction torque of the rotor determine the normal operating condition of the magnetic seal. Excessive chamber pressure and rotational speed will increase the contact pressure of the primary sealing face, leading to increased wear of the face and slippage between the O-Ring 1 and the shaft; too little differential pressure and rotational speed will lead to the disengagement of the graphite ring/stator, which ultimately leads to the failure of the seal. Severe vibration reduces the contact pressure of the primary sealing face and increases the risk of the primary sealing face disengagement.

Performance Analysis of a Pressurized Assembly with a Reinforced O-ring

In industrial facilities, leaks from manufacturing equipment represent uncontrolled fugitive emissions. The most critical components in this equipment are the seals. Several types of seals are used and the most popular are flat seals and O-rings. These seals are subject to high clamping loads and pressures. The failure of the seals could seriously affect the safety of people, and also the environment by the leakage of toxic products. In this work, the analysis of the mechanical and leakage behavior of the O-ring seal reinforced by a metal core and a conventional one when placed either between two plates or in a rectangular groove is presented. Four finite element models, developed using Ansys software, are used to study the behavior of the assemblies in the four cases when clamping load and fluid pressure are applied. This study shows that the introduction of a metal core inside an elastomer O-ring improves the sealing in pressurized installations. The comparison between the assembly without and with a groove shows that the installation of the two studied seals in a groove can protect them against the high stresses which can cause their deterioration and thus increase the probability of failure.