Leakage Performance Research Articles

Analysis of internal leakage performance of spool valve based on size chain and part size distribution

Analysis of internal leakage performance of spool valve based on size chain and part size distribution

Sensitivity Analysis of Scallop Damper Seal Design Parameters for Leakage and Static Performance

The leakage characteristics and static stiffness of scallop damper seals have a significant impact on rotor vibration and stability. A parameter sensitivity analysis model for geometrical parameters in scallop damper seals was developed using a design of experiments (DOE) approach. The method employed a central composite design, integrating factorial, axial, and center points to assess non-linear effects efficiently. And the effects of radial clearance, cavity depth, and length–diameter ratios on leakage performance and rotor stability were investigated. The leakage rate, flow-induced force, and static stiffness coefficient for 15 different combinations of geometric parameters at eccentricities of 0.2 and 0.4 were numerically calculated. The results show that eccentricity has little effect on leakage and its parameter sensitivity. Larger cavity depths and length–diameter ratios are beneficial for seal leakage performance. The tangential force increases with increasing eccentricity but decreases with increasing radial clearance, while it first decreases and then increases with the increase in the cavity depth and length–diameter ratios. Additionally, the radial force decreases with the increase in the length-to-diameter ratio and increases first and then decreases with the increase in radial clearance. The parameter level in this study is defined as the ratio of the actual parameter value to the maximum parameter value. Static direct stiffness reaches its maximum value at a radial clearance level of 30.2%. It remains positive within a cavity depth range of 92.3~100%, as well as a length–diameter ratio range of 0~20.3%. The static cross-coupled stiffness gradually decreases with the increase in radial clearance but first decreases and then increases with the increase in the cavity depth or length–diameter ratio levels. The research results presented in this paper can serve as a reference for the analysis of the performance and design of scallop damper seals.

Levitation Performance of Radial Film Riding Seals for Gas Turbine Engines

Turbomachinery in gas turbines uses seals to control the leakage between regions of high and low pressure, consequently enhancing engine efficiency and performance. A film riding seal hybridizes the advantages of contact and non-contact seals, i.e., low leakage and low friction and wear. The literature focuses on the leakage performance of these seals; however, one of their fundamental characteristics, i.e., the gap between the rotor and seal surface, is scarcely presented. The seal pad levitates due to the deflection of the springs at its back under the influence of hydrodynamic forces. This study develops a test rig to measure the levitation of film riding seals. A high-speed motor rotates the rotor and gap sensors measure the levitation of the seal pads. Measurements are also compared with the predictions from a Reynolds equation-based theoretical model. Tests performed for the increasing rotor speed indicated that, initially, until a certain rotor speed, the pads adjust their position, then rub against the rotor until another rotor speed is reached, before finally starting levitating with further increased rotor speeds. Moreover, both the measured and predicted results show that pads levitated the most when located 90° clockwise from the positive horizontal axis (bottom of seal housing) compared to other circumferential positions.

Impact of high-k insulators on electrical properties of junctionless double gate strained transistor

High-k dielectric insulators are required to reduce leakage and increase transistor performance. They are able to impact the mobility of carriers in transistors positively, leading to better device performance in advanced transistor architecture. Nevertheless, an in-depth analysis of how high-k dielectric insulators influence transistor characteristics must be carried out to determine their suitability. The objective of this study is to investigate the impact of high-k insulators towards electrical properties of junctionless double gate strained transistor. The simulation works is done using process/device simulator Silvaco Athena/Atlas. Based on the retrieved results, the magnitude of I<sub>ON</sub>, on-off ratio, g<sub>m</sub>, and C<sub>int</sub> for TiO<sub>2</sub>-based device are approximately 63%, 99%, 62%, and 89% respectively higher than the lowest permittivity material-based device. The TiO<sub>2</sub>-based device also exhibits the lowest magnitude in I<sub>OFF</sub> and SS compared to others. However, a significant degradation in f<sub>T</sub> magnitude have been observed for TiO<sub>2</sub>-based device significantly due to its large capacitances

Improved energy storage properties in Pb0.82La0.12(ZrxTi1-x)O3 antiferroelectric films with different Zr/Ti ratios

Antiferroelectric (AFE) materials attract widespread attention due to their unique behavior under electric field. In this work, the Pb0.82La0.12(ZrxTi1-x)O3 (PLZT) films with Zr/Ti ratios close to the AFE region are deposited on the LaNiO3/SiO2/Si substrate through chemical deposition method. The dielectric, leakage, and ferroelectric performance of PLZT films are thoroughly examined. It can be concluded that the Zr content in PLZT films can effectively regulate their dielectric properties. At the same time, the increase of Zr/Ti ratio makes the double hysteresis loop of PLZT more obvious, leading to greater stability of the AFE phase, providing a significant advantage in energy storage. Notably, the PLZT film with a Zr/Ti ratio of 95/5 exhibits the highest recoverable energy storage density (Wrec) of 30.8 J/cm3 and energy storage efficiency (η) of 71.5 %. These results reveal that the Zr/Ti ratio in PLZT antiferroelectric films plays a critical role in enhancing their energy storage performance.

Rotordynamics of a Single-Stage Brush Seal in Isolation: The Effects of Variable Stiffness and Back Plate Geometry

Abstract Brush seals control leakage around rotating components from areas of high to low pressure inside turbomachinery. They are known to contribute to the overall stability of gas turbines, therefore their dynamic behavior is of particular importance to engine designers. Despite this, limited research exists in the literature on the rotordynamic behavior of brush seals. This paper aims to experimentally characterize the leakage and rotordynamic performance of two seals with different bristle diameters tested with both conventional and pressure-relieved back plates with a slight interference. A dynamic test facility was utilized to study the dynamic characteristics of an isolated seal with changes in excitation frequency, rotational speed, and pressure drop. Seal leakage increased with bristle diameter and with the use of the pressure-relieved back plate but reduced with increasing rotational speed for all tests. The direct dynamic coefficients were shown to increase with pressure difference. The back plate geometry influenced the change in stiffness coefficient with rotational speed. The larger bristle diameter resulted in a stiffer seal, however, the damping coefficient reduced with the reduction in packing density. The insight provided by these results will help inform engine manufacturers on the suitability of implementing brush seals in future gas turbine designs.

Composite Polymer Electrolyte Enabled through 2D g-C3N4 for All Solid-State Sodium-Ion Batteries

Coupling the advantages of sodium ion chemistry and solid-state batteries can circumvent challenges such as leakage, fire risk, cost, supply chain and better electrochemical performance compared to conventional non-aqueous Li-ion batteries. Here, the inherent low ionic conduction and poor mechanical strength of solid polymer electrolytes urges the necessity of coalescing of polymer with active or passive ceramic fillers to efficiently overcome the individual demerits by offering benefit of both counterparts. Hence, a composite polymer electrolyte through passive or functional fillers are explored due to their enhancements in the ionic conductivity, structural and electrochemical properties. It has been found that morphology, size, and shape of the fillers along with their concentration in the polymer host will have significant effect on the performance improvement of the electrolyte. Dimensional control such as aligned nanowires and two-dimensional clays have resulted in much improved ionic conductivity and battery performance. The filler addition firstly influences the crystallinity of the host and then ameliorates the mechanical strength to hinder dendrite growth and overall rigidity of the electrolyte. Furthermore, functional filler induced salt-filler interaction improves the dissociation ability, cation mobility and anion immobility. Morphology being a critical performance enabler, compared to 0D/1D/3D fillers, fillers with 2D morphology that possess abundant surfaces induce increased active interface that allows better transport network and mechanical strength.Herein, we have attempted to develop a unique functional filler, graphitic carbon nitride, g-C3N4 layered material based composite polymer electrolyte with PEO and salt for all solid-state sodium ion battery. As a two-dimensional filler, GCN synthesis is facile and scalable by simple thermal oxidative etching. Further, the functional N groups in the abundant surface of GCN allows increased interaction with Na salt that allows better ionization and transference. The 2D filler with high active surface properties can effectively create more nonslip region under load to augment the mechanical property. Additionally, unlike other 2D materials, GCN along with its high surface, also possess numerous defect regions that prospectively provide increased ion transport network for better ion migration through the created channels and thus efficiently improving the ionic conductivity of the composite electrolyte. Therefore, a ~60% increment in ionic conductivity (~4.5 × 10-6 S/cm) was observed for PEO-GCN composite compared to pure PEO electrolyte. Also, an assembled solid state sodium metal battery with the composite polymer electrolyte delivered an impressive discharge capacity of 102 mAh/g at 0.2 C operated at 60 °C using a functional composite NVP catholyte. References Ye, K. Liao, R. Ran, Z. Shao, Energy Fuels 2020, 34, 9189.Liu, W. Liu, D. Ba, Y. Zhao, Y. Ye, Y. Li, J. Liu, Advanced Materials 2023, 35, 2110423.Shen, Y. Cheng, S. Sun, X. Ke, L. Liu, Z. Shi, Carbon Energy 2021, 3, 482.Vijayakumar, M. Ghosh, K. Asokan, S. B. Sukumaran, S. Kurungot, J. Mindemark, D. Brandell, M. Winter, J. R. Nair, Advanced Energy Materials 2023, 13, 2203326.Wang, Y. Huo, Y. Fan, R. Wu, H. Wu, F. Wang, X. Xu, Journal of Photochemistry and Photobiology A: Chemistry 2018, 358, 61.

Analytical Model for Contaminant Transport in the CGCW and Aquifer Dual-Domain System Considering GMB Holes

Composite geomembrane cut-off walls (CGCW) have been widely used for the remediation of polluted sites, especially where the environmental conditions are complex. Accurate predictions of the GMB hole leakage and CGCW performance are essential for engineering design and cost control. This paper establishes empirical equations to predict the leakages through the CGCWs based on the numerical models. Additionally, an analytical solution for contaminant migration through the CGCW is proposed considering the effects of GMB holes. The accuracy of the established equations and analytical solution is verified by the numerical models. The key effects of the GMB thickness (TG), head loss (HG), cut-off wall hydraulic conductivity (kG), hole radius (rG) and shape on the leakage and CGCW performance are investigated. The results show that compared with other hole shapes, the leakage through the circular hole is lowest. This is mainly because the shape factor for the circular hole is 1.15–1.3 times lower than that for other shapes of holes with the same area. Additionally, the effects of the hole geometric properties and head loss on the CGCW performance can be more significant when the cut-off wall hydraulic coefficient is small. For example, the breakthrough time differences between the cases with rG = 0.005 m and 0.05 m are 0.8 and 5.0 years when kG = 10−10 and 10−9 m/s, respectively. This is because the impermeability of the CGCW is good when kG is small. This will weaken the impacts of the hole geometric properties on the leakage. The proposed empirical equations and analytical solution can provide effective suggestions for the design of the CGCW in different GMB hole cases.

Polypropylene membrane with gradient-distributed covalent organic framework for highly efficient blood oxygenation

Hollow fiber membrane (HFM) is widely used for extracorporeal membrane oxygenator (ECMO) because of large membrane area, high packing density, self-supporting structure and good flexibility. However, polymeric HFMs often suffer from a trade-off between gas permeability and anti-plasma leakage performance. In this study, HFMs with gradient structure were prepared by introducing COF-42 as fillers into the polypropylene (PP) matrix through surface segregation. The enriched COF-42 near the upper surface endowed the membrane a gradient structure to reduce the plasma leakage and improve gas permeability. Compared with PP membranes, PP/COF-42 oxygenation membranes retained good blood compatibility and higher mechanical properties. The PP/COF-42–0.5 HFMs exhibited O2 exchange rate of ∼ 342.6 ml min−1 m−2 and CO2 exchange rate of ∼ 989.6 ml min−1 m−2, which was about 218.7 % and 15.4 % larger than that of the PP HFMs, respectively. Moreover, the simulated plasma leakage time could reach 124 h, which was about 21 times longer than that of PP HFMs. The membranes exhibited excellent blood oxygenation performance and anti-plasma leakage performance, which had great potential in ECMO.

The impact of refrigerant leakage on the dynamic operating performance of R600a refrigerator systems

Refrigerant leakage in refrigeration and freezing systems reduces efficiency and even results in reliable risks like insufficient cooling and component damage. This paper establishes a dynamic model of a dual-temperature zone refrigerator that combines physical and control models. It investigates the impact of refrigerant micro-leakage on the system’s dynamic operational performance, studies the effects of different leakage areas and compressor speeds on leakage performance, and identifies the critical leakage area (Ac) and critical compressor speed (Rc) based on the temperature variation patterns within the cabinets. Furthermore, this paper analyzes the coupled influence of the compressor speed and leakage area on the cabinet’s temperature. The findings reveal that after leakage occurs, the first noticeable deviations are in system pressure and the amount of refrigerant in the accumulator. Once the refrigerant in the accumulator fully vaporizes, the temperature in the cabinets is affected. Throughout the leakage process, both the system pressure and the heat exchange capacity of the evaporator decrease. At a compressor speed of 2000 rpm, the critical leakage area is 0.013 mm2, and the maximum refrigerant leakage that allows the refrigerator cabinet to cool to the shutdown temperature is 67.6 %. If the leakage area is larger than Ac, it reduces the time for alternating cooling between the freezer and refrigeration cabinets, resulting in a rapid rise in the comprehensive weighted average temperature deviation (CATD). For smaller leakage areas (<0.015 mm2), Rc exists. Operating the compressor at Rc can significantly reduce CATD. For larger leakage areas (≥0.015 mm2), Rc does not exist, increasing compressor speed has a lesser impact on CATD. The research results provide guidance for establishing a refrigerant leakage detection system and improving its accuracy, enhancing the operational reliability of refrigeration systems.

Prediction of thermo-physical properties and evaluation of thermal energy storage performance of phase change materials based on silicone rubber/graphite (Q/G) composites

ABSTRACT Phase change composite materials (PCCMs) are a type of thermal energy storage system known for their high latent heat of fusion. In this study, PCCM samples based on peroxide-cured silicone rubber (Q) were prepared using a simple soaking procedure in molten Paraffin Wax (PW). At any fixed amount of peroxide, the rubber base samples were filled with varying amounts of graphite powder (G), 4 to 8 Wt.%, to improve the thermo-physical properties. The effect of peroxide and graphite content was then evaluated on the PW loading, PW leakage, and thermal storage performance of the resulting Q/G/PW composites. It was found that the highest ratio of the PW loading to PW leakage occurs at a peroxide content of 6 Wt.%. Moreover, the graphite particles demonstrate a significant role in PW trapping inside the rubber structure and lowering the PW leakage. Finally, the thermal studies showed that the Q/G/PW composite containing 6 wt.% of peroxide and 4 wt.% of graphite has the highest latent heat of 111.5 J/g with a PW loading of 15.2%. This sample also had the lowest thermal diffusivity and the slowest cooling and heating rate.

Precise and low-complexity method for underwater Doppler estimation based on acoustic frequency comb waveforms

Ocean observation has advanced rapidly in recent decades due to its crucial role in resource exploration and scientific research, with the Doppler factor being widely utilized. However, the precision of Doppler estimation is frequently constrained by frequency resolution. Traditional frequency estimation methods using single-tone signals face considerable challenges with low accuracy and poor robustness. In response, this paper introduces a novel Doppler-sensitive Acoustic Frequency Comb (AFC) for estimating the Doppler factor, enabling multiple measurements with a single transmission and reception of the signal. The proposed Combined Uneven Uncertainty (CUU) method based on AFC achieves a bias of less than 1.1×10-5, significantly surpassing the optimal result of 3.2×10-5 attained by other frequency estimation methods in the absence of noise. Compared to traditional single-tone methods, the AFC approach improves spectral leakage performance and enhances estimation accuracy without increasing computational complexity. Experimental results demonstrate that the CUU method realizes a difference performance of less than 3.4×10-6, notably lower than that of 3.2×10-5 induced by coherent spectral leakage in fast Fourier Transform (FFT).

A comparative study on rotordynamics characteristics of hole-pattern damping seals with different cavity shapes

PurposeThe purpose of this paper is to improve the seal performance by proper design of the cavity shape of the damping holes, especially the rotordynamics characteristics of the hole-pattern damped seal (HPDS).Design/methodology/approachA new damping seal structure that comprises a circle-shaped cavity and two directional leaf-shaped cavities with a dovetail-shaped diversion groove is proposed. The comparative study on the sealing characteristics of dovetail-shape, leaf-shape and classical circular HPDSs was carried out using ANSYS CFX.FindingsThe dovetail-shaped HPDS significantly outperformed two other damping seal designs in leakage and rotordynamic performance. At a rotating speed of 7,500 rpm, it showed a 25% reduction in leakage, a 23% increase in average effective damping and a 119% increase in average effective stiffness. The cross-coupled stiffness Kxy shifted from positive to negative, reducing circumferential flow. The dovetail's inclined leaf-shaped grooves create a double vortex that slows jet velocity in the seal clearance and alters spiral flow direction, resulting in a uniform pressure distribution and enhanced rotor stability at low frequencies.Originality/valueThis study proposes a novel HPDS with dovetail-shaped diversion grooves. The seal can realize the simultaneous improvement of rotordynamics and leakage characteristics compared to the current seal structure.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0127/

Leakage Retardation of Static Seals via Surface Roughness and Wettability Modification.

In this paper, the effects of surface roughness and wettability on the leakage performance of static seals were highlighted. The results show that the leakage rate is negatively correlated with the contact pressure and positively correlated with surface roughness. Surface wettability affects leakage performance. Leakage retardation is achieved by modifying the roughness and wettability at the interface. The seal interface consists of two oleophobicity surfaces and exhibits an excellent seal performance, of which the leakage reduction is approximately 64%. A theoretical model based on wettability is established to predict the leakage rates under varying wettability conditions, and its validity is confirmed. This research result is expected to be applied in the field of seals and predict the leakage performance of interfaces with different wettabilities to minimize and reduce the leakage of oil in static sealing systems.

A High-Linear Radio Frequency Quadrature Modulator with Improved Sideband Suppression and Carrier Leakage Performance

A High-Linear Radio Frequency Quadrature Modulator with Improved Sideband Suppression and Carrier Leakage Performance

Enhancing Fresh-Cut Apple Preservation: Impact of Slightly Acidic Electrolyzed Water and Chitosan-Apple Essence Microencapsulation Coating on Browning and Flavor.

Fresh-cut apple preservation is a critical concern in the food industry due to the rapid deterioration of texture, color, and flavor. While our previous study introduced apple essence microencapsulation (AEM) to enhance flavor during storage, its impact on overall storage quality was minimal. Thus, this study explores the application of two preservation techniques, namely, slightly acidic electrolyzed water (SAEW) and chitosan-apple essence microencapsulation (CH-AEM) coating, to enhance the quality of fresh-cut apples. Our findings reveal that SAEW treatment significantly reduces the browning index (from 65.38 to 57.36) and respiratory rate (from 5.10% to 4.30% of CO2), and maintains a desirable aroma profile compared to uncoated treatment during 10 days of storage. Additionally, the CH-AEM coating acts as a protective barrier, further preserving the sensory characteristics of fresh-cut apples. Notably, the SAEW-CH-AEM group exhibits superior performance in firmness (8.14 N), respiratory rate (3.37% of CO2), ion leakage (34.86%), and juice yield (47.52%) after 10 days. Our research highlights the synergistic effect of combining these preservation strategies, providing a promising approach for extending the shelf life of fresh-cut apples while maintaining their visual appeal and aromatic quality. These results offer valuable insights for the fresh-cut produce industry, contributing to improved apple product preservation and consumer satisfaction.

Effect of surface topography and roughness on the leakage of static seals

Static seal is widely used in modern machinery. Leakage of static seals would shorten the mechanical system’s service life and affect the environment. To understand the leakage characteristics of static seals, in this work, an experimental apparatus for leakage quantization was built. The effects of surface topography and roughness on the leakage performance of static seals subject to elevated pressure were highlighted. It was found that the leakage rate is negatively correlated with contact pressure. Orientation of surface topography affects the leakage, where the grinding scar parallel to the leakage direction contributes to the leakage, and the perpendicular grinding scar has an inhibiting effect. The leakage rate of irregular and discontinuous surface topography is lower than that of regular ones, and it increases with increasing surface roughness. Furthermore, the leakage mechanism of surface topography and roughness was revealed. This work provides general guidance for the parameters design of static seals.

Flow resistance enhancement for the leakage decrease of labyrinth seals using teeth tip winglets

A novel flow resistance enhancement technology is proposed to decrease the leakage flow for labyrinth seals adopting teeth tip winglets (TTW). The specially designed TTW is utilized to double the throttling effect at each teeth tip. In addition, the annular slots on the TTW can also generate teeth tip vertexes. These vertexes disrupt the direction of teeth tip leakage flow, enhancing the local flow resistance. To validate this concept, a three-dimension computational fluid dynamic model (CFD) is established. The flow field and leakage performance of the seal with TTWs are calculated with compassion to the baseline seal. Results show that the TTW seals increase flow resistance at the teeth tips, resulting in an extra dissipation effect. As a result, the maximum leakage decrease ratio reaches up to 15.1%

The concept of estimating the risk of water losses in the water supply network

One of the methods of increasing the availability of drinking water is to reduce water losses in existing water supply systems (WSS). The need to manage water losses in WSS is highlighted in the new Directive (EU) 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the Quality of Water Intended for Human Consumption. It was indicated that the main cause of water losses is underinvestment in the maintenance and renovation of network infrastructure. The new legal provisions require a risk assessment to be carried out in the water supply system, taking into account the risk of leaks. The paper presents the concept of estimating the risk of water losses in the water supply network using the three-parameter risk assessment method and risk maps. The framework of the water balance proposed by International Water Association (IWA) were also presented, including the Infrastructure Leakage Index (ILI) for assessment of the water supply system Leakage Performance Category (LPC). The analysis was carried out for a water supply system used by 200,000 inhabitants. The LPC of the system was determined based on the ILI index. Then the water supply network pipes that could potentially be a source of leaks were identified. The analysis of the risk of water losses for the examined pipes allowed to determine which pipes should be first chosen to reduce the risk of water losses, i.e. active search for leaks.

Enhancing the Forward Gate Bias Robustness in p‐GaN Gate High‐Electron‐Mobility Transistors through Doping Profile Engineering

This article presents a study on the improvement of the gate robustness and reliability of p‐GaN gate high‐electron‐mobility transistors (HEMTs) by doping profile engineering and by performing a thermal treatment. The reduction of the p‐doping concentration at the Schottky interface using a graded magnesium (Mg) profile in the p‐GaN layer and introducing a top Si‐GaN cap layer is proposed, combined with a high‐temperature anneal step after the gate patterning. The results show that the proposed approach enhances the gate breakdown voltage, reduces the gate leakage current, and increases the time to failure under constant voltage stress, while ensuring stable dynamic behavior and off‐state leakage performance under high‐voltage stress.