| Grease is a kind of semi-solid lubricant which consists of base oil, gelatinizer and additive. It is widely used for open lubrication system with low-speed and heavy-load equipment, because of its excellent lubrication properties such as anti-extreme pressure,anti-wear and sealing performance. The higher reliability of grease lubricating are required for the large-scale, heavy load and automation trends of modern machinery and equipment.However, it is difficult for the present centralized grease-delivering devices to meet the requirements of delivering quantitative grease on time because of the problem of higher viscosity. There is an important significance to study the delivering system in order to protect the mechanical equipment lubrication and reduce wear.In order to solve this problem, the micro-structure of lubricating grease and flow characteristics in circular pipe was studied, and the results could provided the theoretical basis with developing new delivering system. Then, the design scheme of delivering system based on grease pump was put forward, and the theoretical and simulation analysis of the system were carried out. Finally, the feasibility and reliability of delivering system based on grease pump was verified based on the experimental results,The main research results are as follows:(1) The mechanism and main index of rheological property and the basic equations of grease motion were systematically analyzed. The flow characteristics model of grease was established based on the circular pipe flowing. The fitting rheological equation of grease was obtained by ways of rheological experiments of 3# lithium base grease, and the flow behavior of grease in circular pipe was predicted using the fitting parameters.(2) The new design scheme of delivering system based on grease pump was proposed,which used crankshaft as drive and combined hydraulic cylinder with grease pump to collaboratively delivery grease. The parametric geometric model of pump body was established. Structure optimization and stress and strain analysis of crankshaft were carried out. The simulation model of delivering system based on grease pump was set up by ways of the AMESim. The characteristic parameters of system including output pressure, flow characteristics and dynamic characteristics of crankshaft were analyzed. The results showed that the flow curve and the motion curves of crankshaft and piston were almost in accordance with the theoretical curves. The results meet the design requirements despitethe fluctuation error value of 12%. The output pressure and flow rate curve kept stable and meet the requirement of steady system.(3) The flow behavior of lubricating grease in the pump body was analysed by ways of the FLUENT software. And the cloud charts of grease’s pressure, velocity and viscosity in piston cavity in the process of suction grease were obtained. The results showed that there was not obvious pressure gradient and pressure surges at the beginning and the end of piston’s movement. The pump kept excellent stable condition. In the process of delivering grease, the viscosity of grease became decreased because of the shear effect, thus would have advantage in the delivering grease. The optimization is carried out to solve the problem of pressure and velocity mutation at the junction between grease cavity and the mouth.(4) The test rig of delivering system based on grease pump was set up. The validation about output flow, output pressure characteristics, the collaborative working reliability of hydraulic cylinder and grease pump were carried out by ways of the experimental results.The results showed that the output pressure values and flow rate values of grease could meet the requirements of working conditions and be almost in accordance with the theoretical and simulation results. The hydraulic cylinder and grease pump kept collaborative and reliable condition. The higher work efficiency was obtained for the delivering system based on grease pump. |
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