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1 – 10 of 399Jian Wei, XiaoYue Sun, Jing Tian and CaiHong Liu
This paper aims to study the impact of transient velocity changes on sealing performance during reciprocating sealing processes.
Abstract
Purpose
This paper aims to study the impact of transient velocity changes on sealing performance during reciprocating sealing processes.
Design/methodology/approach
Establish a model of transient mixed lubrication, solve the transient Reynolds equation, consider the effect of temperature rise at the seal interfaces, and determine the behavior of the seal interfaces, such as film thickness and fluid pressure. Evaluation with friction and leakage rate, calculate the variation of sealing performance with reciprocating velocity under different working conditions, and verify it through bench experiments.
Findings
Within a reciprocating stroke, the frictional force decreases with increasing velocity, and the frictional force of the outstroke is greater than that of the instroke; at the time of the stroke transition, the fluid pressure is smallest and the rough peak contact pressure is greatest. At present, the dynamic pressure effect of fluids is the largest, and the friction force also increases, which increases the risk of material wear and failure. Friction and leakage increase with increasing pressure and root mean square roughness. As temperature increases, friction increases and leakage decreases. In studying the performance variations of seal components through a reciprocating sealing experiment, it was found that the friction force decreases with increasing velocity, which is consistent with the calculated results and more similar to the calculated results considering the temperature rise.
Originality/value
This study provides a reference for the study of transient sealing performance.
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Keywords
Fatima Harbate, Nouh Izem, Mohammed Seaid and Dia Zeidan
The purpose of this paper is to investigate the two-phase flow problems involving gas–liquid mixture.
Abstract
Purpose
The purpose of this paper is to investigate the two-phase flow problems involving gas–liquid mixture.
Design/methodology/approach
The governed equations consist of a range of conservation laws modeling a classification of two-phase flow phenomena subjected to a velocity nonequilibrium for the gas–liquid mixture. Effects of the relative velocity are accounted for in the present model by a kinetic constitutive relation coupled to a collection of specific equations governing mass and volume fractions for the gas phase. Unlike many two-phase models, the considered system is fully hyperbolic and fully conservative. The suggested relaxation approach switches a nonlinear hyperbolic system into a semilinear model that includes a source relaxation term and characteristic linear properties. Notably, this model can be solved numerically without the use of Riemann solvers or linear iterations. For accurate time integration, a high-resolution spatial reconstruction and a Runge–Kutta scheme with decreasing total variation are used to discretize the relaxation system.
Findings
The method is used in addressing various nonequilibrium two-phase flow problems, accompanied by a comparative study of different reconstructions. The numerical results demonstrate the suggested relaxation method’s high-resolution capabilities, affirming its proficiency in delivering accurate simulations for flow regimes characterized by strong shocks.
Originality/value
While relaxation methods exhibit notable performance and competitive features, as far as we are aware, there has been no endeavor to address nonequilibrium two-phase flow problems using these methods.
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Jianping Zhang, Leilei Wang and Guodong Wang
With the rapid advancement in the automotive industry, the friction coefficient (FC), wear rate (WR) and weight loss (WL) have emerged as crucial parameters to measure the…
Abstract
Purpose
With the rapid advancement in the automotive industry, the friction coefficient (FC), wear rate (WR) and weight loss (WL) have emerged as crucial parameters to measure the performance of automotive braking systems, so the FC, WR and WL of friction material are predicted and analyzed in this work, with an aim of achieving accurate prediction of friction material properties.
Design/methodology/approach
Genetic algorithm support vector machine (GA-SVM) model is obtained by applying GA to optimize the SVM in this work, thus establishing a prediction model for friction material properties and achieving the predictive and comparative analysis of friction material properties. The process parameters are analyzed by using response surface methodology (RSM) and GA-RSM to determine them for optimal friction performance.
Findings
The results indicate that the GA-SVM prediction model has the smallest error for FC, WR and WL, showing that it owns excellent prediction accuracy. The predicted values obtained by response surface analysis are closed to those of GA-SVM model, providing further evidence of the validity and the rationality of the established prediction model.
Originality/value
The relevant results can serve as a valuable theoretical foundation for the preparation of friction material in engineering practice.
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Yangtao Xing, Fugang Zhai, Shengnan Li and Peng Gui
This paper aims to study the deformation mechanism of polytetrafluoroethylene (PTFE) oil seal under a wide temperature range cycle.
Abstract
Purpose
This paper aims to study the deformation mechanism of polytetrafluoroethylene (PTFE) oil seal under a wide temperature range cycle.
Design/methodology/approach
This study categorizes the oil seal operation into three states: assembly, heating-up and cooling. The deformation equation for the oil seal is developed for each state, considering the continuity between them. The investigation of the oil seal’s deformation trends and mechanisms is performed using the ANSYS Workbench.
Findings
The assembling process results in a radial shrinkage of the skeleton, causing the centroid to move toward the axis. During heating-up, the outer diameter of the skeleton slightly expands, whereas the inner diameter sharply contracts toward the axis, leading to a further reduction in the centroid’s distance from the axis. Upon cooling, both the inner and outer diameters continue to contract toward the axis, causing the centroid to persist in its movement toward the axis. Consequently, after undergoing a heating-up and cooling cycle ranging from 20°C to 180°C, the outer diameter of the PTFE oil seal reduces by 0.92 mm from its original deformation, ensuring minimal contact between the skeleton and housing. As a result of the reduced static friction torque at the skeleton, the oil seal rotates along the shaft.
Originality/value
The deformation mechanism of PTFE oil seals under a wide temperature range cycle was investigated, aiming to address the concerns related to the rotation along the shaft and leakage.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2023-0142/
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Shahe Liang, Zhiqiang Zhang and Aiqun Li
A new type of variable damping viscous damper is developed to meet the settings of different damping parameter values at different working stages. Its main principle and design…
Abstract
Purpose
A new type of variable damping viscous damper is developed to meet the settings of different damping parameter values at different working stages. Its main principle and design structure are introduced, and the two-stage and multi-stage controllable damping methods are proposed.
Design/methodology/approach
The theoretical calculation formulas of the damping force of power-law fluid variable damping viscous damper at elongated holes are derived, aiming to provide a theoretical basis for the development and application of variable damping viscous dampers. For the newly developed variable damping viscous damper, the dynamic equations for the seismic reduction system with variable damping viscous dampers under a multi-degree-of-freedom system are established. A feasible calculation and analysis method is proposed to derive the solution process of time history analysis. At the same time, a program is also developed using Matlab. The dynamic full-scale test of a two-stage variable damping viscous damper was conducted, demonstrating that the hysteresis curve is complete and the working condition is stable.
Findings
Through the calculation and analysis of examples, the results show that the seismic reduction effect of high and flexible buildings using the seismic reduction system with variable damping viscous dampers is significant. The program developed is used to analyze the seismic response of a broadcasting tower using a variable damping TMD system under large earthquakes. The results indicate that the installation of variable damping viscous dampers can effectively control the maximum inter-story displacement response of TMD water tanks and can effectively consume seismic energy.
Originality/value
This method can provide a guarantee for the safe and effective operation of TMD in wind and vibration control.
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Youjie Chen, Rong Fu, Junying Yang, En Zhang, Linlin Su and Fei Gao
This study aims to clarify the relationship between the coefficient of friction (COF) and temperature of aluminum-based brake discs.
Abstract
Purpose
This study aims to clarify the relationship between the coefficient of friction (COF) and temperature of aluminum-based brake discs.
Design/methodology/approach
Three friction blocks with different COFs are examined by a TM-I-type reduced-scale inertial braking dynamometer. On this basis, the thermo-mechanically coupled model of friction pairs is established to study the evolution of brake disc temperature under different COFs using ADINA software.
Findings
Results indicate that the calculated disc temperature field matches the experimental well. The effect of COF on the peak temperature is magnified by the braking speed. With the COF increasing, the rise rate of instantaneous peak temperature is accelerated, and the dynamic equilibrium period and cooling-down period are observed in advance. The increase in COF promotes the area ratio of the high-temperature zone and the maximum radial temperature difference. When the COF is increased from 0.245 to 0.359 and 0.434 at 140 km/h, the area ratio of high-temperature zone increases from 12% to 44% and 49% and the maximum radial temperature difference increases from 56°C to 75°C and 83°C. The sensitiveness of the axial temperature difference to the COF is related to the braking time. The maximum axial temperature difference increases with COF in the early stages of braking, while it is hardly sensitive to the COF in the later stages of braking.
Originality/value
The effect of COF on the aluminum-based brake disc temperature is revealed, providing a theoretical reference for the popularization of aluminum-based brake discs and the selection of matching brake pads.
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Ediomo-Ubong Nelson, Ogochukwu Winifred Odeigah and Emeka W. Dumbili
The purpose of this study is to understand the complex interplay between illicit opioids trade and consumption practices and state policies that aim to reduce their misuse.
Abstract
Purpose
The purpose of this study is to understand the complex interplay between illicit opioids trade and consumption practices and state policies that aim to reduce their misuse.
Design/methodology/approach
The study adopted an exploratory design. Data were gathered through in-depth interviews with 31 commercially oriented drug dealers in Uyo, Nigeria. The framework approach was used in data analyses, while “friction” provided the interpretive lens.
Findings
Accounts revealed public concerns over the misuse of tramadol and other opioids among young people and the associated health and social harms. These concerns provided support for enforcement-based approaches to prescription opioids control, including police raids on pharmacy stores. These measures did not curtail opioids supply and consumption. Instead, they constrained access to essential medicines for pain management, encouraged illegal markets and fuelled law enforcement corruption in the form of police complicity in illegal tramadol trade.
Research limitations/implications
The findings reveal the frictions of drug control in Nigeria, wherein enforcement-based approaches gained traction through public concerns about opioids misuse but also faced resistance due to the persistence of non-medical use and illegal supply channels made possible by law enforcement complicity. These indicate a need to prioritize approaches that seek to reduce illegal supply and misuse of opioids while ensuring availability of these medications for health-care needs.
Originality/value
The study is unique in its focus on the creative tension that exists between state control measures and local opioids supply and consumption practices.
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Biqing Ye, Kebiao Zhang, Qiang Zuo, Li Zhang and Xiaohang Shan
The purpose of this paper is to test and analyze the friction torque of double-row angular contact ball bearings under vacuum or ordinary pressure environment, horizontal or…
Abstract
Purpose
The purpose of this paper is to test and analyze the friction torque of double-row angular contact ball bearings under vacuum or ordinary pressure environment, horizontal or upright installation mode, and different rotational speeds, and to provide theoretical bases for the development of aerospace equipment.
Design/methodology/approach
The experiments were carried out to investigate the effects of vacuum or ordinary pressure environment, horizontal or upright installation mode and different rotational speeds on bearing friction torque. To explore the relationship between working conditions and bearing friction torque, firstly, based on the generation source of friction torque, the test principle was determined, a test system was developed and the reliability of data was verified. Secondly, the friction torque of bearing was tested, and the values under various working conditions were obtained. Finally, this paper compared and discussed the test results.
Findings
The test results show that the friction torque value of vacuum environment horizontal installation condition is the largest at different rotational speeds, and the rotational speed has the most significant influence on the friction torque.
Originality/value
The friction torque test system of double-row angular contact ball bearing under vacuum environment was designed and built. The influence rules of vacuum or ordinary pressure environment, horizontal or upright installation mode and different rotational speeds on bearing friction torque were obtained.
Peer review
The peer review history for this article is available at: http://dx.doi.org/10.1108/ILT-08-2023-0259
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Mohammadsadegh Pahlavanzadeh, Krzysztof Rusin and Wlodzimierz Wróblewski
The purpose of this study is an assessment of the existing roughness models to simulate the flow in the narrow gap between corotating and rough disks. A specific configuration of…
Abstract
Purpose
The purpose of this study is an assessment of the existing roughness models to simulate the flow in the narrow gap between corotating and rough disks. A specific configuration of the flow through the gap, which forms a minichannel with variable cross sections and rotating walls, makes it a complex problem and, therefore, worth discussing in more detail.
Design/methodology/approach
Two roughness models were examined, the first one was based on the wall function modification by application of the shift in the dimensionless velocity profile, and the second one was based on the correction of turbulence parameters at the wall, proposed by Aupoix. Due to the lack of data to validate that specific case, the approach to deal with was selected after a systematic study of reported test cases. It started with a zero-pressure-gradient boundary layer in the flow over a flat plate, continued with flow through minichannels with stationary walls, and finally, focused on the flow between corotating discs, pertaining each time to smooth and rough surfaces.
Findings
The limitations of the roughness models were highlighted, which make the models not reliable in the application to minichannel flows. It concerns turbulence models, near-wall discretization and roughness approaches. Aupoix’s method to account for roughness was selected, and the influence of minichannel height, mass flow rate, fluid properties and roughness height on the velocity profile between corotating discs in both smooth and rough cases was discussed.
Originality/value
The originality of this study is the evaluation and validation of different methods to account for the roughness in rotating mini channels, where the protrusions can cover a substantial part of the channel. Flow behavior and performance of different turbulence models were analyzed as well.
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Xiuwei Shi, Wujian Ding, Chunjie Xu, Fangwei Xie and Zuzhi Tian
In the process of conveying the solid–liquid two-phase medium of the centrifugal slurry pump, the wear of the flow-passing parts is an important problem affecting its life and…
Abstract
Purpose
In the process of conveying the solid–liquid two-phase medium of the centrifugal slurry pump, the wear of the flow-passing parts is an important problem affecting its life and safe operation. Therefore, a numerical investigation on the wear characteristics of the centrifugal slurry pump under different particle conditions was conducted.
Design/methodology/approach
A solid-liquid two-phase model based on CFD-DEM coupling is established and used to analyze the flow field and the wear characteristics of the flow-passing parts with different particle densities, volume fractions and sizes.
Findings
Particle conditions will affect the pump flow field. To analyze the pump wear characteristics, the wear distribution, wear value and cumulative force laws of flow-passing parts under different particle conditions are obtained. In each flow-passing part, with the increase of particle density, volume fraction and size, the wear area is concentrated and the wear depth increases. Under different particle conditions, the wear is mainly on the volute chamber and the blade pressure surface, and the tangential cumulative force of flow-passing parts is much larger than the normal cumulative force.
Originality/value
An accurate model and a coupled simulation method for predicting the wear of the slurry pump are obtained, and the wear characteristic law can provide a reference for the design of the slurry pump to reduce friction.
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