The Development Of High Pressure Rotating Viscometer And Research On Pressure Viscosity Response Of Synthetic Oils

The research on the characteristic of lubricant rheology under high pressure is an important investigation problem in lubricant field. One of the main research contents is the relationship between viscosity of lubricant and pressure which called pressure-viscosity properties. The viscosity and pressure-viscosity coefficient of a lubricant has a major influence on film thickness and traction in an EHL contact. There are many factors which influence the viscosity of lubricant, and pressure is the most important one. Therefore, it is great significance to determine the effects of pressure on the pressure-viscosity properties of lubrication oil.The high pressure rotating viscometer was designed by principle of rotation in this paper, which is mainly used to test the relationship between viscosity of lubricant and pressure and the influence on pressure-viscosity properties of shear rate. The high pressure chamber body was designed with double shrink jacket structure to solve the strength problem, which is not only meet the required strength but also greetly reduce the weight and volume of the instrument. Piston seal using the improved Bridgman seal and lead seal used the o-ring and cone to realize; To realize the end face sealing, the cylinder interference fitted was applied as well as using cone as block circle to press the seal ring. Many experiments proving that all the seals are well used.High pressure rotating viscometer is used magnetic coupling to realize transmission without contact, so as to solve the rotatory sealing problem under high pressure. using theoretical calculation, finite-element analysis and experiment to calculate the transmission torque of magnetic coupling and ensure that the transmission torque meet the requirements. The pressure device was designed by the principle of back pressure, therefore the press machine only need to offer little pressure can make the viscometer reach a high pressure; Based on germany DIN53019 standards to design the test cavity and the materials of its rotor and stator were used tungsten copper alloy because of the lower thermal conductivity which greatly decrease the influence on the test results.The testing system's hardwear and softwear of high pressure rotating viscometer were designed in this paper. The torque signal, pressure signal and speed signal can be collected with hardwear; PC softwear was written by delphi which is easy to use and realize the datas display and storage.Finally, this paper using the high pressure rotating viscometer to measure the viscosity of several domestic synthetic oils. The results show that the viscosity and its increasing rate increase with pressure; and the variation tendency becomes flat with the increasing shear rate; In addition, the viscosity of lubricating oil decreases rapidly with the increasing shear rate under high pressure, and non-newtonianism is obvious.