Analysis of leakage characteristics for bent-axis piston pump based on elastohydrodynamic deformation

Purpose This paper aims to revel the leakage characteristics of the bent-axis piston pump considering elastohydrodynamic deformation via a dynamic leakage model. Design/methodology/approach A dynamic leakage model of bent-axis piston pump based on elastohydrodynamic lubrication theory is proposed, which is used to present the leakage characteristics of bent-axis piston pump. The model is composed of three parts. First, the dynamic gap in the piston ring-cylinder bore interface (PRCB) is described via the elastohydrodynamic lubrication equations. Then, the PRCB leakage is presented based on the dynamic gap. Finally, combined with leakage equation of the valve plate-cylinder block interface (VPCB), the total leakage model is proposed. Through the numerical simulation and experiment, the leakage characteristics of bent-axis piston pump considering elasto-hydrodynamic deformation are studied. Findings The PRCB leakage is negatively correlated with VPCB leakage under the range of 800–1400 r/min and 1–25 MPa. When the discharge pressure is less than the critical pressure, the PRCB leakage is the main factor affecting the total leakage in bent-axis piston pump. On the contrary, the VPCB leakage is the main factor. The critical pressure increases with increasing speed Originality/value The effect of operating parameters has a significant effect on the elastic deformation of piston ring without considering wear of friction pairs in bent-axis piston pump. There is a critical phenomenon in the leakage, which is related to the operating parameters, and provides a novel idea for extracting wear information from leakage and evaluating the status of bent-piston pump.

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A leakage model of metallic static seals based on micromorphology characteristics of turning flange surface

Industrial Lubrication and Tribology ◽

10.1108/ilt-04-2015-0049 ◽

2015 ◽

Vol 67 (6) ◽

pp. 572-581 ◽

Cited By ~ 2

Author(s):

Chuanjun Liao ◽

Xibao Xu ◽

Hongrong Fang ◽

Hongrui Wang ◽

Man Man

Keyword(s):

Contact Pressure ◽

Leakage Rate ◽

Content Type ◽

Leakage Model ◽

Viscous Compressible Gas ◽

Leakage Mechanism ◽

Total Leakage ◽

Experimental Values ◽

First Time ◽

Practical Implications

Purpose – The purpose of this paper is to develop a leakage model of metallic static seals, which can be used to accurately predict the leakage rate and study the corresponding seal characteristics. The metallic static seal is effectively applied to severe rugged environments where conventional seals cannot meet the needs. More research efforts for deepening the understanding of its seal characteristics are important for its effective and safe applications, of which the study about its leak is one key component. Design/methodology/approach – In the microscopic observations of the turning surface that is general in the processing of flange surfaces, it is found that the spiral morphology is dominant, which had been also obtained by other researches. There are two potential leakage paths for the flange surface of spiral morphology, one is the radial direction perpendicular to the spiral ridges and the other is the circumferential direction along the spiral groove. Based on the microgeometry characteristics of spiral morphology, the micromorphology of turning flange surface is simplified for the calculation of leakage rate, and the simplified methods of the radial and circumferential leakage paths are presented separately. The topography of flange surface studied in this paper is actually measured, and the Abbott bearing surface curve is adopted to represent the micro-profiles parameters. The radial and circumferential leakage models are further developed based on the assumption of laminar flow of the viscous compressible gas. Findings – The experiments used to verify the leakage models were carried out, and the experimental values are well agreed with the calculated values. As the contact pressure increases, the change rules of both radial and circumferential leakage rates are obtained and the obvious transition from radial leak to circumferential leak can be found. Using the proposed leakage models, the effects of the key micro-profiles parameters on the leakage rates are studied, and some specific conclusions are given simultaneously, which are favorable for the theoretical study and practical application of the metallic static seal. Practical implications – By the interpretations of the micromorphology characteristics of turning flange surface, the leakage mechanism of the metallic static seal is further made clear. The proposed leakage model reveals the relationships between the key micro-profiles parameters and some sealing performances about the leakage and can predict the leakage rates of the metallic static seal used in various working conditions. Originality/value – For the metallic static seal, the simplification of the radial leakage path and the radial leakage model are put forward for the first time, so the total leakage model can be systematically reported based on the micromorphology characteristics of turning flange surface. The effects of the key micro-profiles parameters on the seal behaviors including of the leak rate, critical contact pressure and transition from radial leak to circumferential leak etc are also clarified firstly.

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Human rights of people with mental illness diagnosis: perceptions among service users, family members and health professionals in Tunisia

Journal of Public Mental Health ◽

10.1108/jpmh-06-2020-0075 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Mayssa Rekhis ◽

Sami Ouanes ◽

Abir Ben Hamouda ◽

Rym Rafrafi

Keyword(s):

Mental Illness ◽

Human Rights ◽

Family Members ◽

Mental Illnesses ◽

Service Users ◽

Content Type ◽

People With Mental Illness ◽

The Family ◽

The Right ◽

Main Factor

Purpose This study aims to assess the awareness about the rights of people with mental illness in the main psychiatric hospital in Tunisia among the service users, the family members and the staff. Design/methodology/approach The Convention of Rights of People with Disabilities mandates that State Parties initiate and maintain campaigns and human rights training to promote understanding of the rights of people with mental illnesses, considered as a main factor for their fulfillment. Service users, family members and staff evaluated, through a survey, the importance of ten rights for persons with mental illness, stated in the convention. Findings Disparities were found in the perception of the different rights by and between the three groups. The highest levels of awareness were associated with the freedom from torture or degrading treatment and the right to live with dignity and respect, whereas the lower importance were assigned to the right to participation in recovery plans, to give consent and to exercise legal capacity. Originality/value The lack of awareness and the poor perception of rights of people with mental illness is one of the barriers to their achievement. More training and awareness raising is necessary.

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Effect of tooth waist order parameters of double involute gears on lubrication performance of gear drive

Industrial Lubrication and Tribology ◽

10.1108/ilt-09-2015-0133 ◽

2016 ◽

Vol 68 (6) ◽

pp. 671-675 ◽

Cited By ~ 1

Author(s):

Zhimin Fan ◽

Wanfeng Zhou ◽

Ruixue Wang ◽

Na Wang

Keyword(s):

Elastohydrodynamic Lubrication ◽

Reference Value ◽

Tooth Profile ◽

Order Parameters ◽

Content Type ◽

Oil Film ◽

Gear Drive ◽

Involute Gear ◽

Lubrication Performance ◽

Involute Gears

Purpose The purpose of this paper is to derive a new lubrication model of double involute gears drive and study the effect of the tooth waist order parameters of double involute gears on lubrication performance. Design/methodology/approach The new lubrication model of double involute gears drive was established according to the meshing characteristics of double involute gears drive and the finite length line contact elastohydrodynamic lubrication theory. Numerical calculation of the lubrication model of gear drive was conducted using the multigrid method. Findings The results show that the oil film necking phenomenon and the oil film pressure peak emerged at the tooth waist order area and the tooth profile ends, and when compared with involute gear, the lubrication performance at the tooth waist order area is better than that at the tooth profile ends. The effect of tooth waist order parameters on lubrication performance at the tooth waist order area was greater than that at other areas. Originality/value This research will promote the application of the double involute gear as soon as possible, and it has the reference value for other types of gears.

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Wear of different material pairings for the cylinder liner – piston ring contact

Industrial Lubrication and Tribology ◽

10.1108/ilt-07-2017-0218 ◽

2018 ◽

Vol 70 (4) ◽

pp. 687-699 ◽

Cited By ~ 8

Author(s):

Thomas Wopelka ◽

Ulrike Cihak-Bayr ◽

Claudia Lenauer ◽

Ferenc Ditrói ◽

Sándor Takács ◽

...

Keyword(s):

Steady State ◽

Wear Mechanisms ◽

Piston Ring ◽

Cylinder Liner ◽

Wear Behaviour ◽

Special Focus ◽

Intermediate Step ◽

Piston Rings ◽

Content Type ◽

Cylinder Liners

Purpose This paper aims to investigate the wear behaviour of different materials for cylinder liners and piston rings in a linear reciprocating tribometer with special focus on the wear of the cylinder liner in the boundary lubrication regime. Design/methodology/approach Conventional nitrided steel, as well as diamond-like carbon and chromium nitride-coated piston rings, were tested against cast iron, AlSi and Fe-coated AlSi cylinder liners. The experiments were carried out with samples produced from original engine parts to have the original surface topography available. Radioactive tracer isotopes were used to measure cylinder liner wear continuously, enabling separation of running-in and steady-state wear. Findings A ranking of the material pairings with respect to wear behaviour of the cylinder liner was found. Post-test inspection of the cylinder samples by scanning electron microscopy (SEM) revealed differences in the wear mechanisms for the different material combinations. The results show that the running-in and steady-state wear of the liners can be reduced by choosing the appropriate material for the piston ring. Originality/value The use of original engine parts in a closely controlled tribometer environment under realistic loading conditions, in conjunction with continuous and highly sensitive wear measurement methods and a detailed SEM analysis of the wear mechanisms, forms an intermediate step between engine testing and laboratory environment testing.

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Optimization of injection parameters for ethanol blends of plastic oil in VCR engine using RSM and ANN

World Journal of Engineering ◽

10.1108/wje-12-2020-0626 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Datta Bharadwaz Yellapragada ◽

Govinda Rao Budda ◽

Kavya Vadavelli

Keyword(s):

Compression Ratio ◽

Fuel Injection ◽

Injection Pressure ◽

Operating Parameters ◽

Injection Timing ◽

Oxides Of Nitrogen ◽

Operational Parameters ◽

Content Type ◽

Injection Parameters ◽

Ethanol Blends

Purpose The present work aims at improving the performance of the engine using optimized fuel injection strategies and operating parameters for plastic oil ethanol blends. To optimize and predict the engine injection and operational parameters, response surface methodology (RSM) and artificial neural networks (ANN) are used respectively. Design/methodology/approach The engine operating parameters such as load, compression ratio, injection timing and the injection pressure are taken as inputs whereas brake thermal efficiency (BTHE), brake-specific fuel consumption (BSFC), carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and smoke emissions are treated as outputs. The experiments are designed according to the design of experiments, and optimization is carried out to find the optimum operational and injection parameters for plastic oil ethanol blends in the engine. Findings Optimum operational parameters of the engine when fuelled with plastic oil and ethanol blends are obtained at 8 kg of load, injection pressure of 257 bar, injection timing of 17° before top dead center and blend of 15%. The engine performance parameters obtained at optimum engine running conditions are BTHE 32.5%, BSFC 0.24 kg/kW.h, CO 0.057%, HC 10 ppm, NOx 324.13 ppm and smoke 79.1%. The values predicted from ANN are found to be more close to experimental values when compared with the values of RSM. Originality/value In the present work, a comparative analysis is carried out on the prediction capabilities of ANN and RSM for variable compression ratio engine fuelled with ethanol blends of plastic oil. The error of prediction for ANN is less than 5% for all the responses such as BTHE, BSFC, CO and NOx except for HC emission which is 12.8%.

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Size effect on thermal elastohydrodynamic lubrication of industrial chain bush-pin hinge pair

Industrial Lubrication and Tribology ◽

10.1108/ilt-10-2018-0369 ◽

2019 ◽

Vol 71 (9) ◽

pp. 1080-1085 ◽

Cited By ~ 2

Author(s):

Mingyu Zhang ◽

Jing Wang ◽

Yi Liu ◽

Longjie Dai ◽

Zhaohua Shang

Keyword(s):

Friction Coefficient ◽

Film Thickness ◽

Temperature Rise ◽

Elastohydrodynamic Lubrication ◽

Curvature Radius ◽

Line Contact ◽

Content Type ◽

Oil Film ◽

Industrial Chain ◽

Infinite Line

Purpose The purpose of this paper is to use elastohydrodynamic lubrication (EHL) theory to study the variation of the equivalent curvature radius “R” on the change of oil film thickness, pressure, temperature rise and friction coefficient in the contact zone between bush-pin in industrial chain drive. Design/methodology/approach In this paper, the contact between bush and pin is simplified as infinitely long line contact. The lubrication state is studied by numerical simulation using steady-state line contact thermal EHL. The two constitutive equations, namely, Newton fluid and Ree–Eyring fluid are used in the calculations. Findings It is found that with the increase of equivalent curvature radius, the thickness of oil film decreases and the temperature rise increases. Under the same condition, the friction coefficient of Newton fluid is higher than that of Ree–Eyring fluid. When the load increases, the oil film thickness decreases, the temperature rise increases and the friction coefficient decreases; and the film thickness increases with the increase of the entraining speed under the condition “R < 1,000 mm”. Research limitations/implications The infinite line contact assumption is only an approximation. For example, the distances between the two inner plates are 5.72 mm, by considering the two parts assembled into the inner plates, the total length of the bush is less than 6 mm. The diameter of the pin and the bore diameter of the bush are 3.28 and 3.33 mm. However, the infinite line contact is also helpful in understanding the general variation of oil film characteristics and provides a reference for the future study of finite line contact of chain problems. Originality/value The change of the equivalent radius R on the variation of the oil film in the contact of the bush and the pin in industrial chain drive was investigated. The size effect influences the lubrication characteristic greatly in the bush-pin pair.

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Demarcation boundary between region dominated by elastohydrodynamic lubrication and that by the surface force action for different elliptical ratios

Industrial Lubrication and Tribology ◽

10.1108/ilt-01-2016-0003 ◽

2017 ◽

Vol 69 (2) ◽

pp. 215-224

Author(s):

Mohamed Abd Al-Samieh

Keyword(s):

Van Der Waals ◽

Elastohydrodynamic Lubrication ◽

Hydrodynamic Pressure ◽

Surface Force ◽

Van Der Waals Force ◽

Line Contact ◽

Force Action ◽

Content Type ◽

Combined Action ◽

Ellipticity Ratio

Purpose This paper aims to investigate the effect of changing speed of the entraining motion on the formation of ultra-thin lubricating films under different elliptical ratios. The ellipticity parameter (K) varied from 1 (a ball-on-plate configuration) to 6 (a configuration approaching line contact). The influence of the ellipticity parameters, the dimensionless speed and the effects of surface forces on the formation of the minimum film thickness has been demonstrated. The demarcation boundary between region dominated by elastohydrodynamic lubrication (EHL) and that by the surface force action has been demonstrated for different elliptical ratios. Design/methodology/approach The numerical solution has been carried out, using the Newton–Raphson iteration technique, applied for the convergence of the hydrodynamic pressure. The film thickness and pressure distribution are obtained by simultaneous solution of the Reynolds’ equation, the elastic deformation (caused by hydrodynamic pressure, surface force of solvation and Van der Waals force) and the load balance equation. The operating conditions, load and speed of entraining motion, promote formation of ultra-thin films that are formed under the combined action of EHL, surface contact force of solvation and molecular interactions due to presence of Van der Waals force. Findings The paper provides insights about the transition between region dominated by EHL and that by the surface force action for changing ellipticity ratio (K) from 1 (a ball-on-plate configuration) to 6 (a configuration approaching line contact). Originality/value This paper fulfils an identified need to study the effect of changing ellipticity ratio on the formation of ultra-thin films that are formed under the combined action of EHL, surface contact force of solvation and molecular interactions due to presence of Van der Waals force.

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Research on sealing performance of oil seals with micro-dimple texture on lips

Industrial Lubrication and Tribology ◽

10.1108/ilt-06-2020-0198 ◽

2020 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Fuying Zhang ◽

Yuanhao Zhang

Keyword(s):

Peer Review ◽

Surface Texture ◽

Elastohydrodynamic Lubrication ◽

Friction Torque ◽

Pumping Rate ◽

Content Type ◽

Rotation Direction ◽

Sealing Performance ◽

Pumping Efficiency ◽

Shaft Seals

Purpose The purpose of this paper is to study the pumping efficiency of oil seals with different surface textures at different speeds, and the influence of the rotation direction of triangular texture on the sealing performance was further analyzed. Design/methodology/approach Based on the theory of elastohydrodynamic lubrication and the pumping mechanism of rotary shaft seals, establishing a numerical model of mixed lubrication in oil seal sealing area. The model is coupled with the lip surface texture parameters and the two-dimensional average Reynolds equation considering the surface roughness. Findings The results show that the application of lip surface texture technology has obvious influence on the oil film thickness, friction torque and pumping rate of oil seal. The triangular texture has the most significant effect on the increase of pump suction rate. When the rotation direction of triangular texture is 315 degrees, the pumping rate of oil seal is the largest compared with the other seven directions. Originality/value The model has a comprehensive theoretical guidance for the design of new oil seal products, which provides a certain basis for the application of surface texture technology in the field of sealing in the future. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2020-0198/

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A numerical method to investigate the mixed lubrication performances of journal-thrust coupled bearings

Industrial Lubrication and Tribology ◽

10.1108/ilt-02-2019-0063 ◽

2019 ◽

Vol 71 (9) ◽

pp. 1099-1107

Author(s):

Guo Xiang Guo Xiang ◽

Yanfeng Han ◽

Renxiang Chen ◽

Jiaxu Wang Jiaxu Wang ◽

Ni Xiaokang

Keyword(s):

Thrust Bearing ◽

Load Capacity ◽

Elastohydrodynamic Lubrication ◽

Hydrodynamic Pressure ◽

Mixed Lubrication ◽

Hydrodynamic Effect ◽

Asperity Contact ◽

Content Type ◽

Lubrication Regime ◽

Coupled Effect

Purpose This paper aims to present a numerical model to investigate the mixed lubrication performances of journal-thrust coupled bearings (or coupled bearings). Design/methodology/approach The coupled hydrodynamic effect (or coupled effect) between the journal and the thrust bearing is considered by ensuring the continuity of the hydrodynamic pressure and the flow field at the common boundary. The mixed lubrication performances of the coupled bearing are comparatively studied for the cases of considering and not considering coupled effect. Findings The simulated results show that the hydrodynamic pressure distributions for both the journal and thrust bearing are modified due to the coupled effect. The decreased load capacity of the journal bearing and the increased load capacity of the thrust bearing can be observed when the coupled effect is considered. And the coupled effect can facilitate in reducing the asperity contact load for both the journal and thrust bearing. Additionally, the interaction between the mixed lubrication behaviors, especially for the friction coefficient, of the journal and the thrust bearing is significant in the elastohydrodynamic lubrication regime, while it becomes weak in the mixed lubrication regime. Originality/value The developed model can reveal the mutual effects of the mixed lubrication behavior between the journal and the thrust bearing.

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