| Hydro-viscous clutch(HVC),transmits power by using fluid shear force between multiple sets of rotating friction disks,uses viscous fluid as its working medium.As a new type of fluid power transmission.HVC has tremendous potentials in a wide range of applications such as fans,pumps or wind power generation.The thesis focuses on researching MW HVC.The structural parameters of the friction pairs are optimized,and the efficiency of single and double controlled MW HVC is further analyzed based on the results of optimization.Main contents are as follows:On the basis of flow equation,the temperature equation of friction pair is deduced,3-D model of oil film with radial oil groove on the surface of steel disk is established.Theoretical model under speed regulation conditions is solved using finite element method,and the distribution of temperature is obtained.The influence of outer diameter and inner diameter ratio on the temperature rise of oil film is analyzed.The results show that when the input speed is constant,the increase of the ratio leads to the increase of the temperature rise of the oil film,and the reduction of the ratio leads to the increase of the temperature rise rate.On the basis of Newton's law of viscosity,objective function is based on transmission torque of MW HVC,and the model of structural optimization of friction pair is built and inner penalty function is used to calculate the model.When the number of friction pairs is 8,the inner diameter is 0.385 m,the outer diameter is 0.528,and the ratio of inner diameter to outer diameter is 0.73,all the constraints can be satisfied and the transmission torque and service life are optimized.Based on transmission torque characteristics and oil velocity formula,the relation between input speed and out speed of single-control HVC is obtained.The transmission efficiency formula for multiple sets of friction pairs is derived and the mathematical model for the transmission efficiency of a single-control HVC is built.The influence of oil film thickness between the friction pairs,the rotational speed of the active and passive steel disks,and the inlet pressure of the lubricating oil on the transmission efficiency is mainly analyzed.A single-control HVC test-bed is developed.and the transmission efficiency of HVC at different speeds is studied.Based on the coMParison between test results and theoretical results,the law of the improvement of transmission efficiency by means of increasing the rotation speed and reducing the lubricating oil inlet pressure between the friction pairs is obtained.On the basis of the film bearing capacity.The dynamic balance equations for single-control and double-control HVC,natural frequency and damping ratio of steel dicks' engagement are obtained.Based on the dynamic simulation of friction disks engagement,the result shows that the time of double-control HVC friction disks' engagement is significantly shorter than the time of single-control friction disks' engagement.Based of the research of transmission efficiency of double-control MW HVC,the influence law of the effect of piston thrust on transmission efficiency is obtained,and it is found that the transmission efficiency of double-control MW HVC is always higher than that of single-control HVC under speed-regulating conditions. |
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