Face Seal Research Articles

The Rotating Liner Engine (RLE) Diesel Prototype: Reducing Internal Engine Friction by about 40% under Idle Conditions

The Rotating Liner Engine (RLE) concept is a design concept for internal combustion engines, where the cylinder liner rotates at a surface speed of 2–4 m/s in order to assist piston ring lubrication. Specifically, we have evidence from prior art and from our own research that the above rotation has the potential to eliminate the metal-to-metal contact/boundary friction that exists close to the piston reversal areas. This frictional source becomes a significant energy loss, especially in the compression/expansion part of the cycle, when the gas pressure that loads the piston rings and skirts is high. This paper describes the Diesel RLE prototype constructed from a Cummins 4BT and the preliminary observations from initial low load testing. The critical technical challenge, namely the rotating liner face seal, appears to be operating with negligible gas leakage and within the hydrodynamic lubrication regime for the loads tested (peak cylinder pressures of the order of 100 bar) and up to about 10 bar BMEP (brake mean effective pressure). Preliminary testing has proven that the metal-to-metal contact in the piston assembly mostly vanished, and a friction reduction at idle conditions of about 40% as extrapolated to a complete engine has taken place. It is expected that as the speed increases, the friction reduction percentage will diminish, but as the load increases, the friction reduction will increase. The fuel economy benefit over the US Heavy-Duty driving cycle will likely be of the order of 10% compared to a standard engine.

A numerical solution of temperature distribution in the clearance and the sealing rings of the non-contact face seal

The study presents a numerical analysis of the temperature distribution in the clearance and the temperature distribution in the rings of a non-contact face seal. Non-contact face seals designed for turbine pumps to meet the requirements of lower leakage, longer life, and more frequent starting and stopping are included in this test. A thermo-hydro-mechanical model of the non-contact face seal clearance has been presented. Based on this model, dimensionless differential equations were derived to determine the temperature distribution in the clearance seal gap and the temperature distribution in sealing rings. The numerical solution of differential equations allowed the presentation of temperature characteristics for different parameters of the analyzed non-contact face seal. The analysis took into account hydrodynamic and thermodynamic phenomena in the clearance of the face seal depending on pressure, leakage flow rate and temperature of the sealing fluid, clearance dimensions, thermal parameters of the sealing rings, and operation parameters of the rotating machine. The temperature distribution in a non-contact face seal can also be used to determine the thermal deformation of the sealing rings. The presented numerical model is useful in the design of non-contact face seals because it allows the selection of parameters stabilizing the thermo-hydro-mechanical state of the two mating sealing rings.

Dynamics of impulse seals with tubular feeders

The paper presents a technique for calculating forced axial oscillations and stability of impulse seals with tubular feeders. Unlike the existing methods of calculation, wherein, for the sake of simplicity, the influence of the feeder conductance is neglected, this article describes a conductance effect on the dynamic characteristics of the impulse face seal. The proposed calculation technique makes it possible to determine amplitudes of forced oscillations of the axially movable bushing and stability limit for the geometric parameters chosen in the static calculation. As an example, the authors described a calculation of the impulse face seal of the rotor of the main Reactor Coolant Pump (RCP 20000-100). The amplitude and phase-frequency characteristics for different values of the nominal gap are constructed.

The State-of-the-art and Future Development of Mechanical Face Seal Intelligentization

The State-of-the-art and Future Development of Mechanical Face Seal Intelligentization

Physical Model and Calculation of Face Packing Seals

Increasing the reliability and service life of dynamic-pump shaft seals is the most important requirement for their creation. The most common type of seals is still traditional stuffing box seals, which are controlled leakage assemblies that are periodically restored during operation. A radical change in the design of standard stuffing box seals is the transition to face packing seals with a constant pressure against the packing. It is shown that face packing seals can successfully combine the advantages of mechanical face seals and the simplicity and relatively low cost of traditional stuffing box seals. Mechanical face seals, in which one of the packing rings is replaced by a stuffing box packing, have advantages that significantly expand the application of traditional stuffing box seals. A scheme and a physical model of the face packing seal operation are described. During the operation of the seal, the packing is pushed away from the mating metal surface by the pressure of the medium. In this case, a confusor gap is formed, the length of which is proportional to the ratio of the sealed pressure to the pre-compression pressure of the packing. The calculation of the distribution of the hydrostatic pressure and gap along the radius of the face joint of the seal is presented. The irregularity of the contact pressure along the radius, caused by the pressing out of the packing by the sealed inlet pressure, causes premature wear of the overloaded areas of contact surfaces. Expressions are proposed for estimating friction power losses in face packing seals. It is shown that these losses are significantly lower in comparison with the power losses in traditional stuffing box seals. Assessment of the thermal state of face packing seals has been carried out. An expression has been obtained for determining the flow rate that provides the average contact-surface temperature not exceeding the permissible value. Our studies have shown that the load factor of face packing seals, in contrast to mechanical face seals, must be close to unity. The obtained dependencies make it possible to calculate face packing seals at their design stage.

The "double eights mask brace" improves the fit and protection of a basic surgical mask amidst COVID-19 pandemic.

Study objectiveThe COVID‐19 pandemic has resulted in widespread shortages of personal protective equipment, including N95 respirators. Although basic surgical facemasks are more commonly available, their efficacy is limited due primarily to their poor face seal. This pilot study examined the impact of a rubber band mask brace on a basic surgical mask, as determined by quantitative fit testing.MethodsSubjects wearing a basic surgical facemask and the rubber band mask brace underwent quantitative fit testing using machinery designed to certify N95 mask fit. Subjects were tested with the brace anchored behind their ears, with a paperclip behind the head, and on the side knobs of their face shields. The primary outcome measure was whether the subject passed the quantitative fit test at or above the Occupational Safety and Health Administration (OSHA)‐verified standard for N95 masks.ResultsSubjects (n = 11) were 54.5% female, with a median height of 70 inches (interquartile range [IQR] = 68–74), weight of 170 pounds (IQR = 145–215), and body mass index (BMI) of 24.6 (IQR = 22.2–27.2), and encompassing 5 distinct N95 mask fit types. We found that 45%, 100%, and 100% of subjects passed the quantitative fit test when the brace was anchored behind the ears, with a paperclip and on a face shield, respectively.ConclusionOf the 11 subjects included in the analysis, across a range of body habitus and N95 mask fit types, all passed the quantitative fit test when the mask brace was anchored on either face shield or with a paperclip. This data suggests that although the brace does not create an N95 equivalent in terms of filtration, it would offer improved protection from airborne viruses when worn with a basic surgical mask.

Development of an Apparatus for Testing of High-Temperature Static Seals

A test apparatus is described that evaluates the performance of static aviation seals under an environment similar to the lubrication system in gas turbine engines. The seals can be tested at operating temperatures as high as 400 °C in a static seal rig (SSR). Incorporating an air–oil mist generating system, the test facility exposes the seals to degraded oil, which can deteriorate the performance of seals through chemical attack. The test rig provides representative operating conditions to test four piston and four face seals at the same time. Throughout the aging process of seals, the rig carries out pressure decay leak tests at regular intervals and monitors temperature and pressure at several locations in the test chamber. The capabilities of the rig are demonstrated by presenting the results of durability testing with five types of seals. The results obtained with both successful and failed seals indicate that regular leak testing along with real-time measurement of temperature at the outlet of the low-pressure cavity can provide adequate information as to the operating status of the seals at different stages of testing and operating conditions.

COVID-19 global pandemic planning: Performance and electret charge of N95 respirators after recommended decontamination methods.

Shortages of N95 respirators for use by medical personnel have driven consideration of novel conservation strategies, including decontamination for reuse and extended use. Decontamination methods listed as promising by the Centers for Disease Control and Prevention (CDC) (vaporous hydrogen peroxide (VHP), wet heat, ultraviolet irradiation (UVI)) and several methods considered for low resource environments (bleach, isopropyl alcohol and detergent/soap) were studied for two commonly used surgical N95 respirators (3M™ 1860 and 1870+ Aura™). Although N95 filtration performance depends on the electrostatically charged electret filtration layer, the impact of decontamination on this layer is largely unexplored. As such, respirator performance following decontamination was assessed based on the fit, filtration efficiency, and pressure drop, along with the relationship between (1) surface charge of the electret layer, and (2) elastic properties of the straps. Decontamination with VHP, wet heat, UVI, and bleach did not degrade fit and filtration performance or electret charge. Isopropyl alcohol and soap significantly degraded fit, filtration performance, and electret charge. Pressure drop across the respirators was unchanged. Modest degradation of N95 strap elasticity was observed in mechanical fatigue testing, a model for repeated donnings and doffings. CDC recommended decontamination methods including VHP, wet heat, and UV light did not degrade N95 respirator fit or filtration performance in these tests. Extended use of N95 respirators may degrade strap elasticity, but a loss of face seal integrity should be apparent during user seal checks. NIOSH recommends performing user seal checks after every donning to detect loss of appropriate fit. Decontamination methods which degrade electret charge such as alcohols or detergents should not be used on N95 respirators. The loss of N95 performance due to electret degradation would not be apparent to a respirator user or evident during a negative pressure user seal check.

Thermal mixing effect and heat transfer in U-shaped notch on the mechanical seal face

A three-dimensional thermohydrodynamic (THD) model of a notched mechanical seal is developed based on the commercial software ANSYS Fluent. The flow behavior of hot and cold fluid in and around the notch, namely, the thermal mixing effect, is detailly analyzed. The heat transfer between the notch fluid and the seal rings as well as the cooling effect mechanism of the notch are discussed. Finally, a parametric analysis is conducted to study the effect of notch size, rotational speed and seal gap on heat transport. The results show that the notch fluid locally decreases the notched stator face temperature around the notch boundaries. The reflux occurs between the sealing chamber and notch, which brings the most cooling effect to the notch. The notch depth and width have a significant effect on the heat transfer between the fluid and sealing rings. Because of the non-simplified THD model, the proposed research provides increased reliability of understanding the flow and temperature behavior in the notch.

Controversies in airway management of COVID-19 patients: updated information and international expert consensus recommendations

Controversies in airway management of COVID-19 patients: updated information and international expert consensus recommendations

Experimental Study of Abrasive, Mechanical and Corrosion Effects in Ring-on-Ring Sliding Contact.

This article presents the application of the ring-on-ring test to investigate some of the important factors affecting the abrasive and corrosion wear of a face seal used in the sugar industry. The test involves the sliding contact between two steel rings working in different conditions such as mechanic, abrasive, corrosive extortions and its combination. Rings were made of the C45 steel and the surface layers were modified by heat and thermochemical treatment such as normalizing, flame hardening, nitriding and chrome diffusion. Maximum wear of the sample after tests under mechanic, abrasive and corrosion extortion were obtained. For C45 steel without surface modification the biggest wear was obtained for mechanical, abrasive and corrosive extortion and equals 0.0138 g. This value was three times bigger than the result for the mechanical extortion and ten times than for the corrosive conditions. For individual research options the percentage increase or decrease in wear resistance in relation to the normalized surface layer was determined. In the corrosive extortion the highest increase (90%) of wear resistance was recorded for the chrome layer relative to normalizing sample. The main conclusion of the paper is that the wear effect caused by all factors—mechanical, abrasive and corrosive—is not a straight sum of values of wear.

A leakage model for a seal-on-seal structure based on porous media method

The main interface docking seal (MID seal) is one of the key components in the developing low impact docking systems for future space vehicles, and its sealing property is crucial to the spacecrafts docking in space. A seal-on-seal structure is one of the mainstream designs of the MID seal, and is generally made of rubber materials that can adapt to the complex space environment. For the MID seal of the seal-on-seal structure, it is further confirmed that the porous media theory is suitable to study the sealing property by investigating the micromorphology characteristics of seal contact faces, which based on a leakage model is proposed by this paper. In this model, both the primary seal and the secondary seal are considered as a whole, which is more consistent with the structure and the physical process of sealing face leakage. By comparison with the performed experiments, the leakage model was verified. Based on the proposed leakage model, some simulation results about the studied MID seal are presented and discussed, which mainly correspond with pressure distributions, compression levels, design parameters and operating temperatures. These analyses clearly present some intrinsic relationships implicated in the leakage model. This study is favorable for the mechanism researches, designs, assemblies, and applications of the MID seal, and other seals like that are also included.

Influence of Thermoelastic Phenomena on the Energy Conservation in Non-Contacting Face Seals

The purpose of this study was to develop a mathematical model for non-contacting face seals to analyze how their performance is affected by thermoelastic phenomena. The model was used to solve thermal conductivity and thermoelasticity problems. The primary goal was to calculate the values of thermal deformations of the sealing rings in a non-contacting face seal with a flexibly mounted rotor (FMR) for a turbomachine. The model assumes the conversion of mechanical energy into heat in the fluid film. The heat flux generated in the fluid film is transferred first to the sealing rings and then to the fluid surrounding them. Asymmetric distribution of temperature within the sealing rings leads to the occurrence of thermal stresses and, consequently, a change in the geometry of the rings. The model is solved analytically. The distributions of temperature fields for the sealing rings in the cross-sections are calculated using the Fourier-Bessel series as a superficial function of two variables (r,z). The thermoelasticity problems described by the Navier equations are solved by applying the Boussinesq harmonic functions and Goodier’s thermoelastic displacement potential function. The proposed method involves solving various theoretical and practical problems of thermoelasticity in FMR-type non-contacting face seals. The solution of the mathematical model was made use of analytical methods, and the most important obtained results are presented in graphical form, such as the temperature distributions and axial thermal distortions in cross-sections of the rings. The calculated thermal deformations of the sealing rings are used to determine the most important seal performance parameters such as the leakage rate and power loss. The article also presents a multi-criteria analysis of seal rings materials and geometry, which makes it easier to choose the type of materials used for the sliding rings.

Under-mask beard cover (Singh Thattha technique) for donning respirator masks in COVID-19 patient care

Tight-fitting filtering facepiece (FFP3) face masks are essential respiratory protective equipment during aerosol-generating procedures in the coronavirus disease 2019 (COVID-19) environment, and require a fit test to assess mask–face seal competency. Facial hair is considered to be an impediment for achieving a competent seal. We describe an under-mask beard cover called the Singh Thattha technique, which obtained a pass rate of 25/27 (92.6%) by qualitative and 5/5 (100%) by quantitative fit test in full-bearded individuals. Sturdier versions of FFP3 were more effective. For individuals for whom shaving is not possible, the Singh Thattha technique could offer an effective solution to safely don respirator masks.

Experimental study on friction coefficient of liquid film lubricated mechanical seals with laser micro-texturing

The friction coefficient was a key parameter for expressing the friction characteristics of the seal faces. The friction coefficient of the end faces of unbalanced mechanical seals with laser-textured micro-pores surface and spiral grooves surface were tested on the self-designed mechanical seal testing device, and compared with conventional smooth surface contacting mechanical seal. The experimental sealed medium was 25 °C water, the sealed medium pressures p=03 ∼ 0.9 MPa, and the rotating speeds n=1000 ∼ 3000 rpm. A series of experimental data of friction coefficient were obtained through experiments under different medium pressures and rotating speeds. The experimental results show that the friction coefficient of mechanical seals with laser surface micro-texturing were significantly lower than that of smooth surface mechanical seal, and the effect of spiral grooves end face on improve friction characteristics was better than that of micro-pores end face. Both medium pressure and rotating speed had influenced on the friction coefficient of mechanical seals with laser surface micro-texturing. The friction coefficient of micro-textured end face decreased with the increasing medium pressure, and it first decreased with the increasing rotating speed, and changes little when the rotating speed reaches a certain value.

Thermoelastohydrodynamic characteristics of supercritical CO2 spiral groove face seals

PurposeThe purpose of this study is to determine the sealing performance of face seals by numerical analysis of thermoelastohydrodynamic characteristics of supercritical CO2 (S-CO2) spiral groove face seals in the supercritical regime.Design/methodology/approachThe spiral groove face seal was used as the research object. The distribution of lubricating film pressure and temperature was analysed by solving the gas state, Reynolds and energy equations using the finite difference method. Furthermore, the influence law of sealing performance was obtained.FindingsClose to the critical temperature of S-CO2, face distortions produced by increasing pressure lead to divergent clearance and resulted in reduced opening force. In the state of S-CO2, the face distortions generated by increasing seal temperature lead to convergent clearance, which enhances the opening force. In addition, near the critical temperature of S-CO2, the opening force may be reduced by 10%, and the leakage rate of the seal sharply increases by a factor of four.Originality/valueThe thermoelastohydrodynamic characteristics of supercritical CO2 face seals are illustrated considering the actual gas effect including compressibility, heat capacity and viscosity. Face distortions and sealing performance were calculated under different seal pressures and seal temperatures in the supercritical regime, as well as with N2 for comparison.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2020-0169/

Reduction of allergic rhinitis symptoms with face mask usage during the COVID-19 pandemic

Reduction of allergic rhinitis symptoms with face mask usage during the COVID-19 pandemic

Methods and Means of Reducing Friction Torque in Face Seals

Methods and Means of Reducing Friction Torque in Face Seals

Fluid flow regime transition in water lubricated spiral grooved face seals

Spiral grooves are used to enhance the generation of a fluid film between the sliding surfaces of a mechanical face seal when fluids with poor lubrication properties are to be sealed. This technical solution allows reducing asperity contact, wear, and friction during operation, due to the full film between the surfaces. However because of the thickness of the film, the fluid flow regime can turn from laminar to turbulent. This transition can significantly affect the performance of the seal and needs to be evaluated. Simulations have been performed of a water lubricated seal with spiral grooves. The numerical model solves the Reynolds equation and the energy equation in the fluid film. The thermo-mechanical fluid–solid coupling is considered. The theoretical predictions of the temperature are compared with experimental findings obtained on a dedicated test rig with face seals of different groove depths. This comparison allows to identify the critical Reynolds numbers corresponding to a transition of the fluid flow regime.

Gas Flow Simulation in the Working Gap of Impulse Gas-Barrier Face Seal

Abstract Numerical simulation method of the working process of a centrifugal unit contactless face impulse seal is proposed. A seal functioning physical model was created. Its operation key aspects that are not taken into account in the traditional methods of calculating contactless impulse seals are identified. A numerical simulation of seal working process based on the Reynolds equation solution for the medium vortex-free motion in the gap between moving surfaces is proposed. Hypothesis that simplify the equation’s numerical solution for the face impulse seal is formulated. The numerical solution is obtained using the boundary element method. Based on the obtained numerical solution, the distribution of the working medium pressure field in the seal gap is simulated.