Seal Leakage Research Articles

Thermal contact of roughness macro and micro model to reveal seal leakage mechanism under mixed lubrication

Research on numerical methods for reciprocating seals, including revealing leakage rate mechanism under the elastic-hydraulic lubrication (EHL) regime are mature. However, micro convex bodies contact behaviors and their effect on lubrication transition mechanism are still used under the mixed lubrication (ML) and wear model insufficiently. Seal model with micro convex bodies deformation should be updated to reflect the lubrication transition from EHL to ML and reveal leakage failure mechanism. Reciprocating speed ranging from 0.1 m/s to 0.2 m/s and working pressure of 100 MPa can characterize the seal performance and failure of leakage mechanism especially in low speed and harsh film formation condition. The updated leakage rate formula and the Reynolds equation are modified considering contact factor and reveal leakage mechanism through macro and micro numerical method.

Quantification of face seal leakage using parallel resistance model

Mask-wearing emerged as the key safety measure to prevent the spreading of COVID-19. In this study, we hypothesized a model to quantify the leakage flow rate through the face mask based on a parallel resistance model. The tests were performed in two ways: (I) mask material test, in which all masks were sealed to a flange to measure transmission through a full mask and prevent leakage around the edges, and (II) mannequin mask test, in which masks were fitted to a mannequin head tightly. For all masks, the pressure drop was measured at eight different flow rates between 5 and 85 LPM, and it was increased linearly with the flow rate (r2 > 0.98). The results of the study showed that the leakage flow rate was 10% of the total flow rate, even for the best-fitted N95 filtering facepiece respirators (FFRs) and KN95 masks. They showed higher resistance to the leaks. The procedure masks and cloth masks showed a leakage flow rate of 25% of the value of the total flow rate, quite a large proportion of the flow. They had lower resistance to leaks.

Implementation of a Reduced Order Model for rotating seal annular leakage flow inside a centrifugal pump

Sustainability and net zero emissions targets drive the importance of turbomachinery design, optimisation, and efficient operation in modern geoenergy systems. To further enable integration of advanced large-scale technologies, accurate and resource-efficient simulations of complex equipment and systems need to be completed readily. An approach to simulate internal leakage flows of centrifugal pumps is presented, an important factor that influences equipment operation efficiency.One significant challenge when internal leakage flow is investigated is achieving sufficient simulation detail in the flow regions separating rotating and stationary components where close-running clearances are present. Computational fluid dynamics (CFD) meshes typically require excessively fine resolutions of node points in these situations for accuracy. For example, the typical annular suction wear ring clearance ranges between 0.1–0.5 mm, whilst impeller diameters and other geometric properties have length scales from 600–1200 mm or even larger.A reduced order model (ROM) of an annular seal configuration was developed that allows for analytical calculation of the leakage flow by implementing user scripting in the CFD solver setup. The ROM implementation has a low symbol count and does not require any type of logic and/or recursive and iterative functionality. Thus, fine and resource-intensive meshing can be robustly eliminated and replaced by a sufficiently detailed ROM that contributes leakage flow effects to the overall simulation.Leakage flow through the suction wear ring of a high differential head (ΔH), high flow rate, double suction centrifugal pump with water as working fluid was used as a case study for ROM development. The calibrated model was verified against a commercial fluid dynamics software package and achieved a level of precision of 2.4% with σ=0.0118 in a wide operating range of 10m⩽ΔH⩽350m and fluid temperature (T) of 283.15K⩽T⩽353.15K.The leakage flow calculated by the ROM was proven to be accurate and therefore capable of accounting for a range of pressure heads, incorporating surface roughness effects and temperature variations, and adaptable for various fluids. Guidance for the implementation of the ROM in the Ansys CFX solver environment is also provided to aid future work.

Simulation and Experimental Study on Sealing Characteristics of Hydro-Pneumatic Spring GS Seal Rings

Hydro-pneumatic springs often work under high pressure and alternating load conditions, which can easily cause seal damage, leakage, and serious failure. Relevant studies have shown that the dynamic seal failure of hydro-pneumatic springs is the main cause of hydro-pneumatic spring failure, and the sealing performance of GS sealing rings directly determines the service life of hydro-pneumatic springs. The influence of different sealing structure parameters on the sealing performance of GS sealing of hydro-pneumatic springs has been studied, which can provide effective theoretical guidance for the design of sealing structures related to hydro-pneumatic springs. However, the existing research on hydro-pneumatic springs mainly focuses on the characteristics of damping and stiffness; there is a relative lack of research on sealing performance and sealing structure, and the performance change law of GS seals under different working conditions is unclear. In this paper, a GS seal ring is selected as the main seal of the hydro-pneumatic spring, the material parameters of the GS seal ring are obtained via the single-axis compression test, and the finite element simulation method is used to establish the sealing model under different compression ratios of 10–30% and different pressure impacts of 5–30 MPa. By doing so, the stress nephogram, sealing ring shape, and sealing contact pressure of the GS sealing ring under different simulation parameters are obtained. From the test results, the decrease in compression ratio after the wear of the sealing ring is the main reason for the seal leakage of the hydro-pneumatic spring. The maximum contact stress of the sealing ring occurs at the lip of the step ring, and the maximum sealing pressure of the sealing ring is determined by the contact pressure of sealing surfaces II and III. The sealing performance of the GS-type combination sealing ring is affected by the compression ratio of the sealing ring and the impact pressure; when the compression ratio of the sealing ring is 15%, the sealing ring can meet the sealing work needs below 25 MPa. The research results provide a theoretical basis for the design of GS sealing of hydro-pneumatic springs and the effective improvement of the life and reliability of related equipment.

Optimization of Cargo Pump Treatment by Hydrochloric Acid (HCl) Loading at MT. Cipta Anyer

The research is motivated by the occurrence of mechanical seal leakage in cargo pumps, which hampers the efficiency of the loading and unloading process. A mechanical seal is a mechanical component used in various industrial applications, such as pumps, to prevent leakage from the rotating shaft and stationary wall.
 The research method used in this thesis is qualitative descriptive, employing the SWOT (Strengths, Weaknesses, Opportunities, and Threats) approach to facilitate data analysis. The data collection methods utilized by the author include observation, interviews, and documentary studies to strengthen the data analysis. The objectives of this research are to identify the causes of damage to the mechanical seal, the handling of mechanical seal damage, and the efforts/methods to prevent mechanical seal damage on MT. Cipta Anyer.
 The conclusion revolves around the causes of mechanical seal damage, the methods to handle such damage and preventive measures. The causes of damage include surface wear connected to the pump shaft, direct contact of hydrochloric acid (HCl) with the cargo pump, and incorrect installation of spare parts for the mechanical seal. Solutions to address the damage involve identifying the specific issues, replacing them with genuine and compliant spare parts, and ensuring proper and procedure-compliant installation. To prevent damage, it is advisable to utilize modern equipment, maintain supervision by engineers, and select experienced crew members.

Research on Prediction Model of Interlayer Leakage in Separate Injection Wells in Offshore Oilfields

In order to ensure effective layered water injection, it is of great significance to establish the functional relationship among the equivalent diameter of damage, leakage and pressure of sealing cylinder. In this paper, the experimental and numerical simulation experiments were carried out to study the relationship between gap flow rate, pressure drop and equivalent diameter of sealing cylinder under the conditions of uniform corrosion, fracture non-uniformity and random groove non-uniform distribution and scratches in different tubing, equivalent diameters and gap widths. Through a lot of data analysis, the relationship between the damage state and the leakage quantity is established and evaluated by physical simulation test. The research shows that the error between the established model function relation and the test data is no more than 10%. By simulating the damage condition of the shock sealing cylinder and quantitatively detecting the defect of the sealing cylinder, the model function relation can well predict the corresponding damage situation. Therefore, this model function can be used to solve sealing cylinder inspection problem, so as to judge the seal defect and leakage quantity which is independent of the experience of the person in charge of the site and able to use the data as a basis for judgment. This research provides a new technology for the effective prediction of the damage of sealing cylinder, and provides theoretical guidance for selecting matching sealing tools and realizing layered mining.

On flow of power-law fluids between adjacent surfaces: Why is it possible to derive a Reynolds-type equation for pressure-driven flow, but not for shear-driven flow?

Flows of incompressible Navier–Stokes (Newtonian) fluids between adjacent surfaces are encountered in numerous practical applications, such as seal leakage and bearing lubrication. In seals, the flow is primarily pressure-driven, whereas, in bearings, the dominating driving force is due to shear. The governing Navier–Stokes system of equations can be significantly simplified due to the small distance between the surfaces compared to their size. From the simplified system, it is possible to derive a single lower-dimensional equation, known as the Reynolds equation, which describes the pressure field. Once the pressure field is computed, it can be used to determine the velocity field. This computational algorithm is much simpler to implement than a direct numerical solution of the Navier–Stokes equations and is therefore widely employed by engineers. The primary objective of this article is to investigate the possibility of deriving a type of Reynolds equation also for non-Newtonian fluids, using the balance of linear momentum. By considering power-law fluids we demonstrate that it is not possible for shear-driven flows, whereas it is feasible for pressure-driven flows. Additionally, we demonstrate that in the full 3D model, a normal stress boundary condition at the inlet/outlet implies a Dirichlet condition for the pressure in the Reynolds equation associated with pressure-driven flow. Furthermore, we establish that a Dirichlet condition for the velocity at the inlet/outlet in the 3D model results in a Neumann condition for the pressure in the Reynolds equation.

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.

A flow control method for the leakage reduction of annular gas seals using the helical gas curtain generator

Advanced sealing technology is crucial for turbine efficiency. To reduce seal leakage, the flow control method based on gas injection is an attractive solution. The traditional flow control methods primarily focus on blocking the axial leakage flow, neglecting the helical flow effect of the leakage flow at the design stage. In this paper, a novel flow control method is proposed for the leakage reduction of annular gas seals using the helical gas curtain generator (HGCG). The helical flow effect of the leakage flow is first considered for further sealing enhancement. The design conception of the HGCG involves connecting seal cavities and teeth tips using the specially designed pad with helical injection slots. Driven by the intrinsic pressure difference between the connected areas, helical gas curtains are passively generated, producing multi-row fluidic barriers against the helical leakage flow at each teeth tip. Numerical investigation of a labyrinth seal with HGCGs shows that the proposed method effectively enforces flow resistance at teeth tips, resulting in an extra dissipation effect. The performance of the HGCG is enhanced as the helical flow effect increases. The maximum leakage reduction ratio reaches 59.2%, over eight times higher than that of the traditional air curtain technology (ACT). In addition, the HGCG increases the effective damping coefficient by 45% compared to the ACT. The proposed HGCG presents significant superiority in sealing improvement and rotordynamic stability enhancement.

A non-uniform pressure distribution model on the end face in screw expander and shaft seal leakage characteristics{fr}Etude des paramètres de la Structure sur les fuites d'arbres dans un expandeur à vis basé sur un nouveau modèle de distribution de pression non uniforme sur la face d'extrémité

Pressure distribution on the end face of screw expanders is the primary premise for calculating shaft seal leakage and axial force. Different from other types of expanders, pressure distribution on the screw expander end face is not only affected by operating conditions but also closely related to rotor geometric parameters. To illustrate the leakage characteristics of shaft seal in screw expanders, a non-uniform pressure distribution model on the end face was proposed, and a thermodynamic leakage model in the shaft seal was established. Labyrinth seal, the most widely used sealing assembly, was taken as an example to study the effects of shaft seal parameters on leakage. The influence of four main parameters, namely tooth tip clearance, cavity depth, cavity width, and clearance on the rotor end face, on the leakage of the shaft seal was studied. The results show that pressure on the screw expander end face is non-uniformly distributed, and the average pressure is far less than the highest operating pressure. Moreover, the leakage through the shaft seal rises rapidly with the increase of end face clearance and tooth tip clearance, and a 0.1 mm increment of them can lead to increased leakage up to 108.6% and 52.5%, respectively. And the leakage drops with the increment of cavity width. There is an optimal depth-to-width ratio of about 0.13 for minimum leakage. Clearance on the rotor end face has the most significant influence on the leakage of the seal, followed by the tooth tip clearance, cavity width, and cavity depth.

Effects of High Rotational Speed on Leakage and Windage Heating of Staggered Labyrinth Seals With Smooth and Honeycomb Lands

Abstract Being an important component of aero-engines, the labyrinth seal has always been the focus of research for leakage characteristics. Rotation is usually neglected or taken for minimal effect on seal leakage in previous studies. However, the effect of high rotational speed is inevitable to understand the leakage characteristics of labyrinth seal accurately. Meanwhile, due to high rotational speed, viscous heat is generated massively to result in the rapid temperature rise of leakage flow. Also, the influence of rotational speed on windage heating inside the seal clearance has not been indicated completely. Therefore, the leakage and windage heating of staggered labyrinth seals with smooth and honeycomb lands were experimentally and numerically studied. The large-scale and multifunctional sealing test rig were employed to carry out the experiments with rotational speed 12,000 rpm and pressure ratio range 1.1–2.2. The simulation data obtained by three-dimensional computational fluid dynamics methodology show great agreement with experimental results. Notably, the leakage coefficient is not monotonically decreasing with increased rotational speed, but exists a maximum peak at RPM = 8000. The variation of axial kinetic energy in seal clearance entrances provides a clear explanation of the phenomenon. Rotational speed plays an important role in windage heating, and honeycomb cell size is of secondary importance. Based on simulation data, the calculating formula of windage heating is fitted and shows great performance. This study can provide theory and data support for the follow-up structural optimum design of the labyrinth seal.

Failure mechanism of magnetic fluid seal for sealing liquids

Magnetic fluid seals are contact-free rotary seals widely used to seal gas and vacuum. However, their effectiveness declines when utilized to seal liquids due to the inherent incompatibility and instability at the interface between the two liquids. The underlying mechanism for this premature failure remains incompletely comprehended, posing a significant challenge to their widespread use for sealing liquids. Here we demonstrate a novel pole structure featuring a non-magnetic shaft, which creates a closed magnetic circuit without requiring the magnetic circuit to pass through the rotating shaft. This innovative approach enables the observation of the failure processes of the seal through a hollow transparent shaft, utilizing an endoscope. The results show that the static seal failure occurrs in two stages: extrusion, infiltration, and magnetic fluid barrier rupture. In the first stage, a leakage channel opens cyclically, whereas in the second stage, the seal leaks completely once the critical pressure is surpassed. Dynamic failure arises from the intricate interplay between dissolution, extrusion, and interface instability. Upon attaining the critical speed, the flow at the interface transitions from laminar to turbulent, leading to apparent delamination fluctuations. At this point, the magnetic fluid film becomes unstable and instantly leaks from the seal upon exceeding the critical speed. This research has unveiled crucial inducing factors for seal failure that have significant implications for the design of liquid seals. The intricate and complex nature of the failure mechanism emphasizes the need for a comprehensive understanding of the interplay between the seal design, magnetic fluid properties, and operating conditions to develop efficient liquid seals with superior performance.

Respiratory protection strategies for the public in emergency response.

A strategy was established to minimize the stochastic effects of internal and external exposure to radioactive substances by wearing respiratory protection equipment (RPE) during an emergency evacuation. During the evacuation of residents in the event of a nuclear power plant accident, the stochastic effects of internal exposure caused by the inhalation of radioactive aerosol and external exposure due to accumulated radioactive particles in the filter medium of a mask must be minimized. The radioactivity concentration along an evacuation route considers atmospheric dispersion and the resuspension of particles deposited on surfaces. The effective dose due to internal exposure is evaluated using inhalation dose coefficients for each particle diameter. When the face seal leakage and filter medium penetration ratio for each particle diameter of the RPE (N95) is taken into consideration, the internal dose is reduced by 97.2%. Furthermore, the accumulated radioactivity in the filter medium decreases by 91.4% when the respirator is replaced every 48h.

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

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

Detailed Simulations of a Three-Stage Supercritical Carbon Dioxide Axial Compressor with a Focus on the Shrouded Stator Cavities Flow

This paper describes the findings of detailed simulations performed to investigate the impact of seal teeth cavity leakage flow on the aerodynamic and thermal performance of a three-stage supercritical CO2 axial compressor. The study compares a shrouded stator configuration (with cavities) to a cantilevered stator configuration (without cavities) to highlight their differences. High-fidelity computational fluid dynamics simulations were performed using non-linear harmonic (NLH) and mixing plane assumptions, considering various possible rotor/stator interface configurations for mixing plane calculations. The key performance parameters for each case were compared, and the best-performing configuration selected for further analysis. The individual stage performance parameters are also examined and compared between the cantilevered and shrouded configurations. It was observed that in the shrouded case, the leakage flow enters the cavity downstream of the stator trailing edge and gets entrained into the primary flow upstream of the stator, leading to boundary layer changes at the hub and degradation of stator and downstream rotor performance. Vortical flow structures were also observed in the stator wells, which tended to change the flow angles around the region, thereby affecting mixing and velocity distribution, resulting in a slight deterioration of compressor performance. Additionally, the study examines windage heating due to shear work from rotating walls, including the seal teeth surface. The amount of shear work done on the leakage flow and the corresponding rise in fluid temperature were quantified, tabulated, and further compared with a simple analytical model, showing good agreement between them and, hence, validating the numerical approach used.

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.

Method of predicting valve seal leakage considering deflection of the spool

The small angular deflection of the spool under the action of non-equilibrium force is a main reason for valve seal failure. In the present study, a prediction model of the valve seal leakage was established considering the sectional shape and channel height of the leakage channel. The effect of spool deflection on the leakage rate was analyzed quantitatively from the results of three-dimensional finite element mechanical analysis. The microscale leakage channel of a contact deformation surface was then generated through the reconstruction of the rough surface with nanoscale precision, deterministic rough-peak contact analysis, and lattice leakage theory. The results showed that the spool deflection was the key factor affecting the leakage rate. The leakage rate was measured on a self-built experimental platform, and the experimental results verified the accuracy of the theoretical calculations.

Design and Reliability Analysis of Integrated BOP

This article in view of existing BOP seal leakage point, low service life, large volume,high weight, height and installation of time-consuming to faults, the annular BOP and ram preventer, one-piece BOP design scheme is put forward, and seal the mouth of the well on the whole, 21 mpa pressure blowout limit design conditions for structural reliability analysis of one-piece BOP.The analysis results show that because the integrated BOP uses the integrated shell, does not need to use the flange connection, less leakage points, can greatly improve the traditional BOP short life, easy to leak and other shortcomings, and the maximum stress and maximum deformation displacement meet the design requirements.

Development of a New Loss Model for Turbomachinery Labyrinth Seals

Abstract The preliminary design of labyrinth seals requires fast and accurate estimate of the leakage flow. While the conventional bulk flow models can quickly predict labyrinth seal discharge characteristics, they lack the accuracy and pragmatism of modern computational fluid dynamics (CFD) techniques and vice-a-versa. This paper presents a new one-dimensional loss model for straight-through gas labyrinth seals that can provide quick seal leakage flow predictions with CFD-equivalent accuracy. The present seal loss model is developed using numerical experimentation technique. Multiple CFD computations are conducted on straight-through labyrinth seal geometries for a range of pressure ratios. A distinct postprocessing methodology is developed to extract the through-flow stream tube in seal. Total pressure losses and flow area variations experienced by the flow in seal stream-tube are systematically accounted for based on the well-known knife-to-knife (K2K) methodology. Regression analyses are conducted on the trends of variations of loss and area coefficients to derive the independent pressure loss and flow area correlations. These novel correlations can predict the bulk leakage flow rate, windage flow rate, and interknife static pressures over a wide range of variations of flow and geometry parameters. Validation study shows that the leakage mass flow rate predicted by this model is accurate within ±8% of measured test data. This fast and accurate model can be employed for various applications such as in seal design-analysis workflows, for secondary air system (SAS) performance analysis, and for the rotor-dynamic and aeroelastic assessments of seals.

Performance of Magnetic Fluid and Back Blade Combined Seal for Sealing Water

When sealing liquids with magnetic fluid, the interfacial stability problem caused by the interaction between the magnetic fluid and the sealed liquid leads to poor sealing performance. Centrifugal force is generated by the rotation of the sealed liquid in the back blade seal, which forms back pressure to reduce the load of the seal or prevents the sealed liquid from leaking. To reduce the influence of the shaft speed on the sealing performance, a combined magnetic fluid and back blade seal was designed for sealing liquids and a combined seal experiment stand was set up. Theoretical and experimental studies were carried out. The results showed that under a higher shaft speed, the combined seal structure had better sealing performance in which the back blade seal played the main role; the magnetic fluid seal played a major role in stopping and lowering the speed to prevent seal leakage. The combined seal could run stably under different shaft speeds.