A low-speed spindle running on air bearings is presented, it is used on rotary viscometer based on velocity attenuation of rotating cylinder. Principle of spindle is introduced, it is composed of a low speed motor and an air bearing. The low speed motor is a coupling of two motors. Design of the spindle shows the structure of it. Materials of the spindle are selected. The spindle is machined and operation process of it shows it is suitable for driving part of rotary viscometer based on velocity attenuation of rotating cylinder.
Value of viscosity of liquid at an arbitrary velocity is important in many manufacturing processes, method of rotation is used commonly to measure it at a scheduled velocity, but it is not convenient to measure it at an arbitrary velocity. A method based on cylinder rotation is presented in the paper and it is used to measure it at an arbitrary velocity. Derivation of mathematical models is executed and a simulation is carried in Matlab. Results show that the velocity of the cylinder in the liquid attenuates by exponential law and it is in accordance with mathematical models. Error analysis indicates that that the generation of them mainly results from unsuited velocity of cylinder, slippage between the cylinder and the liquid and misalignment between the cylinder and the cup.
A viscometer based on velocity attenuation is presented. It is used to measure viscosity of liquid at an arbitrary velocity. Structure of the viscometer is designed. A motor designed specially called Series-Motor is used as driven motor of the viscometer to keep the flow stability of test liquid. A solid rotor motor is adapted to reduce the cogging effect. Pressure-feed air bearing is adapted as support to minimize the resistance torque. Simulation is made in MATLAB. Results show that Series-Motor reduces the resistance torque besides the viscous torque and it provides slow speed motor to keep the flow stability.
A viscometer based on velocity attenuation of rotating cylinder is presented in the paper. A solid rotor motor drives the cylinder immersed in liquid in a cup to a scheduled velocity. The electricity supply of the motor is cut, the velocity of the cylinder with rotor of the motor attenuates with time because of viscous torque and other resistance torque. The velocity is measured by optical encoder. Viscosity of the fluid was calculated by a computer. Experiments are carried out and results show that deviation of viscosity beyond 1000 mPa•s are below 3%. The viscometer can be used in measurement of viscosity beyond 1000 mPa•s in industry.
An experimental device capable of producing uniform metal droplet stream and electric charging and deflecting has been developed. Uniform spherical powder of 180μm in diameter was obtained after cooling and solidification. Numerical models of heat transfer and solidification of droplets were established. The thermal history including solid fraction of droplets in uniform droplet spray process were calculated. Under the common processing conditions, the cooling rate of a droplet of 180μm diameter is of the order of 103−104°C/s. To obtain homogeneous and dense preforms, the substrate should be positioned at a distance of 1.1-1.3m from the nozzle.
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