The cavitation development process in regulating valve under different inlet pressures is investigated experimentally and numerically in our paper. The influence of inlet pressure P_in on cavitation location, shape, area and intensity is studied in axial and radial directions, and the axial and radial pressure distributions are also analyzed. The cavitation is generally annular in shape radially and irregular polygon in shape axially. Cavitation bubbles occur at the throat entrance when the inlet pressure increases. The bubbles then accumulate, and a bubble ring is formed. The cavitation development process under different inlet pressures is separated into three stages, no-cavitation, initial cavitation and steady-cavitation stages. During the no-cavitation stage, no bubbles exist. During the initial cavitation stage, bubbles occur and the area and intensity of cavitation increase in the radial and axial directions with increasing inlet pressure. During the steady-cavitation stage, the calculation area and intensity of bubble rings reach their maximum values and then remain stable. The cavitation bubbles extend downstream, and the area of cavitation ring and cavitation intensity increase with increasing inlet pressure. A slit exists between the upper and lower parts of bubbles in the cavitation process, both parts touch each other forming a whole.

In order to improve the performance of the electromagnet for electro-hydraulic proportional valve used in shock absorber, the static and dynamic characteristics of the proportional electromagnet are simulated and analyzed, which provides theoretical basis for the design and optimization of structural parameters of the proportional electromagnet. In this paper, the magnetic circuit model and finite element simulation model of the proportional electromagnet used in shock absorber are established, and the Ansoft software is applied to analyze the influence of the key structural parameters of the proportional electromagnet on static output force and dynamic characteristics. The results demonstrate that with the increase of the depth of basin mouth, the effective travel of the proportional electromagnet increases, and the mean value of the electromagnetic force in the working range decreases. The larger the radial clearance between armature and guide sleeve is, the smaller the electromagnetic force in the effective travel is. When the depth of the basin mouth is 3.9 mm, the slope of the magnetic isolation ring is 35°, the chamfer length of the convex platform is 0.2 mm, and the radial clearance is 0.3 mm, the proportional electromagnet has good displacement-force and current-force characteristics. According to the further transient analysis, it is found that when the voltage amplitude is 24 V, the rise time of the electromagnetic force under step excitation signal is about 40 ms.

Taking account of temperature and the effect of pressure difference and inertia force on oil film, the analytic solutions for pressure, radial velocity, and transferred torque were derived. The results show that considering the effect of temperature, the pressure reduces at the same radius and inertia force makes the pressure decrease. Compared with the pressure decrease caused by the inertia force, the radial velocity caused by the pressure difference is very small and can even be neglected. As the rotational velocity difference increases, the transferred torque also increases. Meanwhile, the transferred torque reduces when considering the effect of temperature.

Considering the influence of the inertia item on temperature distribution of multidisk friction pairs in hydroviscous drive (HVD), transient temperature models are derived with the aim of revealing the effect of engagement pressure, lubricant viscosity, viscosity–temperature correlation, surface roughness and the ratio of inner and outer radius of disks on temperature distribution. The results indicate that unsteady temperature gradient can be avoided by matching the suitable materials for multidisk friction pairs. The average temperature for the case of neglecting the inertia item is lower than that of the case of including the inertia item. It is shown that during the soft-start, the temperature along the radial direction achieves its peak value near the outlet and keeps decreasing along the axial direction; while after the engaging process, the temperature distribution tends to be uniform. It is also shown that the decrease of engagement pressure, surface roughness and the ratio of inner and outer radius of disks can reduce temperature gradient effectively as well as the increase of lubricant viscosity. The average temperature for the case of including the viscosity–temperature correlation is much higher than that for other cases.

Purpose: The purpose of this paper is to study the working characteristics of hydro-viscous clutch at high rotational speeds and obtain the trend of flow field variation of oil film. Design/methodology/approach: The FLUENT simulation model of the oil film between the friction disks is built. The effect of variation of working parameters such as input rotational speed, oil flow rate and film thickness on two-phase flow regime and transmission torque is studied by using the volume of fluid model. Findings: The results show that the higher the rotational speed, the severer the cavitation is. In addition, the two-phase flow region makes the coverage of oil film over the friction pairs’ surface reduce, which results in a decrease in transmission torque for the hydro-viscous clutch. Originality/value: These simulation results are of interest for the study of hydro-viscous drive and its applications. This study can also provide a theoretical basis for power transmission mechanism of oil film by considering the existence of a two-phase flow regime consisting of oil and air.