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The purpose of this paper is to reveal the effect of starting time on hydro-viscous drive speed regulating start.

The modified transient Reynolds equation, thermal energy equation and temperature–viscosity equation were solved simultaneously by using finite element method. And then variations of the oil film load capacity, variations of temperature and variations of the torque generated by the oil film during the starting process were obtained.

The results show that during the starting process, both the oil film load capacity and the temperature show an upward trend, the torque increases during the beginning period and then decreases during the latter part of the starting process. When the starting time is less than 60 s, variations of the oil film load capacity and temperature show fluctuations, which decrease with the starting time. For any output speed, the corresponding oil film load capacity, temperature and torque decrease with the starting time, and the decreasing amplitude also decreases with the starting time.

This paper indicates that the starting time can be set to 60-90 s to obtain a perfect starting process. The simulation results are verified by the speed regulating start experiments. Research findings of this work provide theoretical basis for the design and practical application of the hydro-viscous drive equipments.

The purpose of this study is to investigate the application of non-destructive testing methods in measuring bearing oil film thickness to ensure that bearings are in a normal lubrication state. The oil film thickness is a crucial parameter reflecting the lubrication status of bearings, directly influencing the operational state of bearing transmission systems. However, it is challenging to accurately measure the oil film thickness under traditional disassembly conditions due to factors such as bearing structure and working conditions. Therefore, there is an urgent need for a nondestructive testing method to measure the oil film thickness and its status.

This paper introduces methods for optically, electrically and acoustically measuring the oil film thickness and status of bearings. It discusses the adaptability and measurement accuracy of different bearing oil film measurement methods and the impact of varying measurement conditions on accuracy. In addition, it compares the application scenarios of other techniques and the influence of the environment on detection results.

Ultrasonic measurement stands out due to its widespread adaptability, making it suitable for oil film thickness detection in various states and monitoring continuous changes in oil film thickness. Different methods can be selected depending on the measurement environment to compensate for measurement accuracy and enhance detection effectiveness.

This paper reviews the basic principles and latest applications of optical, electrical and acoustic measurement of oil film thickness and status. It analyzes applicable measurement methods for oil film under different conditions. It discusses the future trends of detection methods, providing possible solutions for bearing oil film thickness detection in complex engineering environments.

To solve the problem of oil film thinning when hydrostatic thrust bearings are overloaded or rotating at high speed, the dynamic pressure formed by tiny oil wedges is used to compensate, and the optimum height of oil wedges is determined by the compensation rate to improve the bearing capacity of hydrostatic thrust bearings.

This research method is aimed at the new type of double rectangular cavity static bearing with microbevel surface of q1-205. The wedge parameters of oil film were defined. The oil film lubrication performance of the bearing with the wedge parameters of 0, 0.02, 0.04, 0.06, 0.08 and 0.10 mm was simulated by the finite volume method, the comprehensive influence law of the wedge-shaped parameters on the vorticity and flow rate of the oil cavity pressure fluid was revealed. Finally, the oil cavity pressure changes of oil films with different wedge parameters under certain load and speed were tested by design experiments, and the theoretical analysis and simulation were verified.

This study found that the oil film wedge shape can well compensate the static pressure loss caused by the high-speed or heavy-duty operation of the bearing, but the dynamic pressure effect of the wedge shape does not always increase with the increase of the wedge height. The oil film exhibits superior lubrication performance in the range of 0.06–0.08 mm.

The original hydrostatic oil pad was designed as a microinclined plane, and the dynamic pressure caused by the microwedge of the oil pad was used to compensate the static pressure loss of the bearing. The lubrication performance of the oil film under the condition of varying viscosity was obtained by using the simulation method.

The purpose of this paper is to propose an adjustable oil film thickness test rig for detecting lubrication characteristics of the slipper. The mathematical analysis of lubrication is introduced. Based on the results from the test rig, the results comparison from test rig and mathematical analysis is carried out.

This paper introduces a mechanism which can adjust the oil film thickness between the slipper and swash-plate. Feasibility is ensured, and the accuracy of test rig is guaranteed by the three-coordinate measuring machine. Three displacement sensors show the oil film thickness and its shape. The reacting force and torque resulting from oil film can be achieved by three S-type force sensors and a torque sensor, respectively.

The relative error of the reacting force is small. The relative error reduces and is acceptable when the deformation of retainer is taken into account. The thickness and tilt angle of oil film have less effect on the reacting force. However, they are significantly impact on torque.

The test rig proposed in this paper is able to adjust the oil film thickness, which is used to detecting the lubrication characteristics in pump design.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2020-0166/

The purpose of this paper is to study the influence of structural parameters of oil groove (such as central angle number, depth and so on) on pressure, flow, load capacity and transmitted torque between friction pairs of hydro-viscous clutch.

According to the working process of friction pairs of hydro-viscous clutch, mathematical models of hydrodynamic load capacity and torque transmitted by the oil film were built based on viscosity-temperature property. Then analytical solutions of pressure, flow, load capacity and transmitted torque were obtained; effects of central angle of oil groove zone and friction contact zone, oil film thickness, number of oil grooves on pressure, flow, load capacity and torque were studied theoretically.

The research found that the central angle of oil groove zone, number of oil grooves and oil groove depth have similar effects on flow, which means that with the increase of central angle, number or depth of oil grooves, the flow also increases; pressure in friction contact zone and oil groove zone drops along radial direction, whereas its value in oil groove zone is higher. With the increase of the central angle of oil groove zone, pressure in friction contact zone and friction contact zone rises, and the load capacity increases, whereas the transmitted torque drops. Number of oil grooves has little effect on load capacity. When the oil film thickness increases, its flow increases accordingly, whereas the pressure, load capacity and transmitted torque drops. Meanwhile, the transmitted torque decreases with the increase of number of oil grooves, whereas the oil groove depth nearly has no effects on transmitted torque.

In this paper, mathematical models of hydrodynamic load capacity and torque transmitted by oil film were built based on viscosity-temperature property in the working process of hydro-viscous clutch, and their analytical solutions were obtained; effects of structural parameters of oil groove on transmission characteristics of hydro-viscous clutch based on viscosity-temperature property were revealed. The research results are of great value to the theory development of hydro-viscous drive technology, the design of high-power hydro-viscous clutch and relative control strategy.

Friction pairs of the hydro-viscous drive speed regulating start device should be designed based on the rated torque. To obtain design basis of the rated torque of the hydro-viscous drive speed regulating start device, studies on effect of torque ratio (a ratio of the load torque to the rated torque) on speed regulating start were carried out theoretically and experimentally.

Under different torque ratio, the modified Reynolds, the thermal energy and the viscosity-temperature equations were solved simultaneously by using finite element method to reveal variation laws of the oil film load capacity and torque transmission during the starting process. Then, speed regulating start experiments were carried out to study the following performance of the output speed.

The results show that oil film thickness decreases with the increase of the torque ratio; when oil film thickness is less than 0.05 mm, oil film temperature increases rapidly with the decrease of oil film thickness, which eventually deteriorates performance of the speed regulating start; when the torque ratio decreases to about 0.3, output speed shows a better following performance.

It indicates that, to acquire a better speed regulating start, the rated torque of the hydro-viscous drive speed regulating start device should not be less than three times of the load torque. Achievements of this work provide theoretical basis for optimal design of the friction pairs of the hydro-viscous drive speed regulating start device.

Current lubrication analyses of misaligned journal bearings are generally performed under some given preconditions. The purpose of this paper is to calculate the lubrication characteristics of a journal bearing with journal misalignment caused by shaft deformation under load, considering the surface roughness, thermal effect and (thermal and elastic) deformation of bearing surface simultaneously.

The lubrication of bearing was analyzed by average flow model based generalized Reynolds equation. The deformation of bearing surface under pressure or heat of oil film was calculated by compliance matrix method. The compliance matrix was established by finite element analysis. The temperature distributions of oil film and bearing were calculated by energy equation and heat conduction equation.

When the thermal deformation of bearing and journal surface is considered, the radius clearance affects not only the value of the maximum oil film pressure and minimum oil film thickness, but also the distribution of oil film pressure and thickness of misaligned bearing. The effect of thermal deformation of bearing on the performance of misaligned bearing is larger than that of elastic deformation of bearing. Whether or not the surface roughness affects the performance of misaligned bearing and the affecting level depends greatly on the condition of deformation of bearing surface.

The surface roughness, thermal effect and (thermal and elastic) deformation of bearing surface were considered simultaneously in the thermoelastohydrodynamic lubrication analysis of bearing with journal misalignment caused by shaft deformation under load. The results of this paper are helpful to the design of the bearing.

The hydro-viscous drive (HVD) has been widely used in fan transmission in vehicles, fans, and scraper conveyors for step-less speed regulating and soft starting. It is an efficient method to save energy and reduce consumption. This study aims to analyze the influencing factors of oil film shear torque accurately.

The shear torque calculation model of double arc oil groove friction pairs was established. The influence of groove structure parameters on shear torque was analyzed. The interaction between viscosity temperature and shear torque was considered. Meanwhile, the equivalent radius was calculated when the rupture of oil film appeared. Finally, the test rig of torque characteristics was set up. The variance of shear torque with the input rotation speed under different oil film thickness, different oil temperature, and different flow rate was seen.

The results show that the shear torque increases with the growth of rotation speed. However, the increase of torque is quite gradual because of the effect of the change of viscosity, which is caused by the rise of temperature. The shear torque increases with the decrease of thickness, the increase of inlet flow rate, and the decrease of inlet oil temperature. Meanwhile, when the feeding flow rate is less than the theoretical, the oil film gets ruptured and the shear torque decreases sharply.

The influence on shear torque during full film shear stage in HVD can be achieved much more accurately through both experimental research and theoretical modeling in which groove parameters, influence of temperature, and oil film rupture are considered. Therefore, the shear torque of HVD can be predicted by theoretical model and experimental research in full film shear stage.

This study and its centering device with Archimedes spirals designed on hydrodynamic lubrication aims to reduce the deviation of deep holes because the drill tube is long and easy to deviate in deep hole machining.

The centering device with Archimedes spirals was designed and fixed between the drilling tool and the drill tube. The wall of the deep hole and the novel centering device formed three wedge-shaped oil films. When the workpiece rotated relative to the centering device, pressure was generated in the oil films; therefore, three oil films supported drilling system as oil films support rotating journal in the full-film hydrodynamic bearing.

When the Boring and Trepanning Association (BTA) drilling system was equipped with the centering device, the cutting oil flowed smoothly and carried all the iron chips; the motors run normally; no additional vibration or sound was detected during processing; the surface of the centering device was smooth; and the deviation of the drilled deep hole decreased with a high probability.

To the best of the authors’ knowledge, no one has designed and made the centering device with Archimedes spirals to reduce the deviation of deep holes in deep hole machining. Three oil films formed by the centering device with Archimedes spirals support drilling system and prevent it from deviating, which has never appeared before and is creative.

Piston ring dynamic problem plays an important role in the lubricant characteristics of a reciprocating engine, which lead to engine wear and the increased consumption of lubricating oil. A cavitation analysis of the piston ring lubrication with two-dimensional Reynolds equation has rarely been reported owing to the complex working condition. The purpose of this study is to establish a precise model that can provide guidance for the design of the piston ring.

In this paper, a cavitation model and its effect on the piston ring lubrication was studied in a simulation program based on the mass-conserving theory which is solved by means of the Newton–Raphson method. In this study, some models such as mixed lubrication, asperity contact, blow-by/blow-back flow and cavitation have been coupled with the lubrication model.

The established model has been compared with the traditional model that deals with cavitation by using the Reynolds boundary condition algorithm. The cavitation zone, pressure distribution and density distribution between the piston ring and the cylinder have also been predicted. Studies of the changing trend for the pressure distribution and the cavitation zone at few typical crank angles have been listed to illustrate the cavitation changing rule. The analysis of the results indicates that the developed simulation model can adequately illustrate the lubrication problem of the piston ring system. All the analyses will provide guidance for the oil film rupture and the reformation process.

A two-dimensional cavitation model based on the mass-conserving theory has been built. The cavitation-forming and -developing process for the piston ring–liner lubrication has been studied. Non-cavitation occurs in the vicinity of top dead center and bottom dead center. The non-cavitation period will be longer in the vicinity of 360° of crank angle. The density distribution in the cavitation zone can be obtained.