Qingrui Meng, Zhao Chenghao and Tian Zuzhi
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
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.
Details
Keywords
– The purpose of this paper is to reveal the effect of starting time on hydro-viscous drive speed regulating start.
Abstract
Purpose
The purpose of this paper is to reveal the effect of starting time on hydro-viscous drive speed regulating start.
Design/methodology/approach
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.
Findings
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.
Originality/value
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.
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The aim of this work is to reveal the temperature rise characteristics of the new designed disc during a braking process. In underground coal mines, the highest temperature of the…
Abstract
Purpose
The aim of this work is to reveal the temperature rise characteristics of the new designed disc during a braking process. In underground coal mines, the highest temperature of the disc brake used for inclined downward belt conveyors should be < 150 to prevent gas explosion during a braking process. To meet the requirements, a new type of disc was designed.
Design/methodology/approach
By using ANSYS software, the disc surface and interior temperature rise variations, effect of braking time and running speed on temperature rise are analyzed numerically.
Findings
The results show that the new designed disc can meet the coal mines’ requirements well, during the braking process the disc surface temperature increases at first and then decreases, there is an obvious temperature gradient in the axial direction; when running speed increases to two times of the rated one, the highest temperature nearly reaches 150; and a prolonged braking time can decrease the highest temperature effectively.
Research limitations/implications
It indicates that the disc brake should act as earlier as possible to slow down the belt conveyor when overspeed occurs; and when the running speed increases to two times of the rated one, the braking time must be prolonged to prevent gas explosion.
Originality/value
Research findings of this paper provides theoretical basis for the practical applications of the disc brake used for inclined downward belt conveyor.
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Keywords
Daoming Wang, Youfu Hou, Zuzhi Tian and Qingrui Meng
This study aims to reveal the temperature rise characteristic of magnetorheological (MR) fluid in a multi-disc MR clutch under slip condition, including the temperature…
Abstract
Purpose
This study aims to reveal the temperature rise characteristic of magnetorheological (MR) fluid in a multi-disc MR clutch under slip condition, including the temperature distribution regularity and the impact factors.
Design/methodology/approach
Three-dimensional transient heat conduction equation for the MR fluid in the working gap was derived based on the heat transfer theory. Then, numerical simulation was conducted to analyze the temperature field of MR fluid. Furthermore, an experimental study was performed to explore the temperature distribution of the MR fluid in radial and circumferential directions, as well as the effects of disc groove, slip power and gap size on temperature rise characteristic of the MR fluid.
Findings
The results show that temperature appears to be largest in the center of the working gap and the temperature difference increases with the slip time. However, the temperature field in a circumferential direction is basically the same, but it presents slightly lower in the groove area. The temperature of the MR fluid increases linearly with the slip time and the rise rate increases with the slip power. Moreover, the temperature rise value decreases with the increase of gap size.
Originality/value
In this paper, the temperature gradients, both in radial and circumferential directions, are experimentally measured going beyond the estimation by computer simulations. In addition, the factors that influence the temperature rise characteristic of MR fluid were fully analyzed. The results could provide a reliable basis for the development of cooling technology for high-power MR devices.
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Keywords
The purpose of this paper is to reveal the mechanism of effect of surface groove on speed‐regulating start.
Abstract
Purpose
The purpose of this paper is to reveal the mechanism of effect of surface groove on speed‐regulating start.
Design/methodology/approach
This paper investigates numerically and analytically the torque transfer and load capacity of oil film between separator and friction disc with grooves commonly used at present by solving simultaneous equations: modified Reynolds, energy, and temperature‐viscosity equations.
Findings
The results show friction discs with wider and deeper groove are not suitable for speed‐regulating start. To improve performance of speed‐regulating start, distribution and size of surface groove should be designed to obtain ascending trend of oil film load capacity during startup process.
Originality/value
This paper reveals the mechanism of effect of surface groove on speed‐regulating start and facilitates the conceptual design of speed‐regulating start control system.
Details
Keywords
The purpose of this paper is to reveal the effect of working oil temperature, load and starting time on hydro‐viscous drive speed‐regulating start.
Abstract
Purpose
The purpose of this paper is to reveal the effect of working oil temperature, load and starting time on hydro‐viscous drive speed‐regulating start.
Design/methodology/approach
The authors developed an experimental equipment and carried out a number of experiments under different temperatures, load and starting time.
Findings
The results show that both the temperature rise of working oil and the increase of load can induce fluctuations in output speed, but the effect of the working oil temperature rise is more serious; also the longer the starting time is, the more perfectly the output speed can trace the given speed.
Practical implications
It indicates that the working oil temperature should be kept in a certain range by using a cooling device in practical application; and that under this experimental condition, kinematics viscosity of the working oil should be greater than 45 mm2/s under rated working temperature, and the relatively suitable starting time should range from 90 to 120 s.
Originality/value
The paper explains the effect of various factors on speed‐regulating start, and provides the basis for the design and the application of hydro‐viscous drives.
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Keywords
Jun Zhao, Hao Zhang, Junwei Liu, Yanfen Gong, Songqiang Wan, Long Liu, Jiacheng Li, Ziyi Song, Shiyao Zhang and Qingrui Li
Based on the weak seismic performance and low ductility of coupled shear walls, engineered cementitious composites (ECC) is utilized to strengthen it to solve the deformation…
Abstract
Purpose
Based on the weak seismic performance and low ductility of coupled shear walls, engineered cementitious composites (ECC) is utilized to strengthen it to solve the deformation problem in tall buildings more effectively and study its mechanical properties more deeply.
Design/methodology/approach
The properties of reinforced concrete coupled shear wall (RCCSW) and reinforced ECC coupled shear wall (RECSW) have been studied by numerical simulation, which is in good agreement with the experimental results. The reliability of the finite element model is verified. On this basis, a detailed parameter study is carried out, including the strength and reinforcement ratio of longitudinal rebar, the placement height of ECC in the wall limb and the position of ECC connecting beams. The study indexes include failure mode and the skeleton curve.
Findings
The results suggest that the bearing capacity of RECSW is significantly affected by the ratio of longitudinal rebar. When the ratio of longitudinal rebar increases from 0.47% to 3.35%, the bearing capacity of RECSW increases from 250 kN to 303 kN, an increase of 21%. The strength of longitudinal rebar has little influence on the bearing capacity of RECSW. When the strength of the longitudinal rebar increases, the bearing capacity of RECSW increases little. The failure mode of RECSW can be improved by lowering the casting height of the ECC beam in a certain range.
Originality/value
In this paper, ECC is used to strengthen the coupled shear wall, and the accuracy of the finite element model is verified from the failure mode and skeleton curve. On this basis, the casting height of the ECC casting wall limb, the strength and reinforcement ratio of longitudinal rebar and the position of the ECC beam are studied in detail.