Theoretical And Application Researches On Hydroviscous Drive

As the result of the rapidly improving productivity and increasing modernization, energy consumption has been dramatically increasing in the past a few decades, which has led to the steady rise in energy price and a worldwide energy crisis. Nowadays, energy conservation has become one of the major areas of research.Hydroviscous drive (HVD) is a new type of power transmission mechanism, which utilizes the shear of oil film between two sets of discs for power transmission. As a brand new subject in the field of Fluid Power Transmission and Control, HVD has tremendous potentials in a wide range of applications such as speed regulation and energy conservation in large fans and pumps. This dissertation explores the fundamentals of HVD using a range of theoretical and experimental studies. The main contribution of this dissertation can be summarized in the following aspects.First, we explore the fundamental theories of the mechanism of oil film drive, which is the basis of HVD. Specifically, we derive the practical analytic solutions to the pressure distribution of the oil film and the parameters of the oil flow in the viscous drive for typical frication disks with radial grooves, based on analyzing the oil film between two sets of smooth discs. We also obtain the close-form solution to the load carrying capacity of the oil film. In our analysis we use a unique superposition-by-steps method of boundary conditions, which is based on the dynamical lubrication theory of the sector-thrust-step bearing. AH the theoretical solutions by experiments are validated by experiments.Second, we study the dynamics of HVD. In particular, we derive the dynamic balance conditions of the oil film among several disc couples, establish the dynamic balance equations of the HVD system, and give the speed output transmission function and the torque output transmission function. All the conclusions above are also validated by experiments. Our analysis leads to the crucial conclusion that the open-loop HVD system is always stable with respect to the speed output and to the torque output. This provides the theoretical foundation for applying HVD in real life engineering situations.Third, we investigate the distortion of the friction discs in HVD devices. Specifically, we build the model of the thermodynamics and heat conduction, based on which we use numerical computations to derive the thermal loading distribution on the friction discs of a hydro-viscous drive, and to plot the curves of the instantaneous asymmetric temperature field along the radial direction of the discs as well as the instantaneous asymmetric thermal stress field. Our analysis unveils the main cause of the distortion of the discs and suggests methods for effectivelypreventing the distortion phenomena.Finally, we investigate the performance of the steady state open loop of HVD in real life applications. In particular, we analyze the effects of electro-hydraulic systems and lubricants on the performance of the steady state open loop of HVD and present our design of a new special-purpose, speed-regulating valve for HVD. We also give the ranges of the acceptable viscosity and viscosity- temperature coefficient of the lubricants to be used in a HVD and identify by experimentation the best substitute lubricant available in lack of special-purpose lubricants for HVD.To summarize, in this dissertation we further the fundamental theories of HVD and provide solutions to a range of problems that have arisen in the development of HVD devices. HVD devices developed based on the results reported in this dissertation have been used by a heating power plant and a waterworks for more than 15 months and have shown satisfactory performance and have yielded significant economic benefits. The research results presented in this dissertation are significant in both practice and theory for the improvement of the performance of HVD products.