The Design Of Rotational Rheometer For Microgravity Environment

Microgravity fluid science is an emerging discipline to study the movement of fluid medium under micro-gravity environment.Microgravity fluid science in our country is still in its infancy,requiring a large number of scientific experimental data as a support.In order to promote the development of microgravity fluid science in our country,carry out the research and exploration of microgravity experiment and fill in the blank of microgravity rheological experiments,based on the “Microgravity Fluid Physics Experiment Program” of China's manned space project,this paper designs a self-locking structure of rotary rheometer and a high-precision shear structure which supports rapid replacement by using the worm wheel and Morse's taper.Built the prototype,and conducted a viscosity measurement experiment.The experimental results show that the measurement accuracy of the measurement system increases with the viscosity of the sample,which is suitable for the measurement of medium and high viscosity samples.The main contents of this paper are as follows:1)The mathematical relationship model of viscosity,shear rate and shear stress was established based on the simple shear flow.The influence of temperature and pressure on the viscosity and the boundary conditions of rheological measurement were analyzed.Based on the working principle of rotary rheometer,mathematical model of three rotor structure parameters and viscosity of the sample was established,the feature and application scope of different rotor structures were analyzed,laying a foundation for the development of the equipment.2)Through the analysis of special transportation conditions and application environment,the related functions for the microgravity environment were proposed,and the related indexes were analyzed.According to the related functions and indexes,the system design plan was made,the functions of each part were clarified,the method of realization was given,the selection of the required components was achieved by taking into account a number of indicators,and the vibration test of the torque sensor was carried out.3)A control board based on ARM was designed for the system.The design basis and functions of each module were analyzed in detail,and the circuit implementation was given.Completed the mechanical structural design of the rheometer.Self-locking structure and high precision rapid replacement shear structure were designed for the requirement of the project.Self-locking structure was achieved by turbine worm structure.Shear structure adopts the design of two stages separation with shear turntable by Morse taper sleeve,which can guarantee the alignment precision.4)The prototype of rotational rheometer was developed,and the viscosity experiment using different viscosity of silicone oil was conducted on the prototype.The experimental results show that measuring accuracy can reach 2.5% under 50000 cSt.The problems found during the measurement process are analyzed,feasible solutions are proposed,and the future work is planned.