Study On Online Measurement Method Of Liquid Viscosity Based On Fiber Bragg Grating

The liquid viscosity measurement is of great significance,which is bound up with the development of national economy and people's daily life.It has an important role on many areas such as the oil transportation industry,blood medical treatment,food processing and industrial textile production et al.This paper introduces several traditional methods of viscosity measurement,such as capillary method,rotation method,falling method,vibrating string method and other methods of viscosity measurement.The advantages and disadvantages of the traditional viscosity measurement methods are analyzed,some new methods of viscosity measurement at present stage are also introduced,such as electromagnetic method,acoustic method and micro mechanical method et al.On the basis of the above,a new method of on-line viscosity measurement based on fiber Bragg grating(FBG)is eventually proposed.This method combines the cantilever beam with the Newtonian viscosity law,an online,passive measurement method of liquid viscosity when the liquid flowing is proposed,and the mathematical relationship between the center wavelength shift of the FBGs and the liquid viscosity is established.An online measurement of liquid viscosity based on FBG is proposed.Through this method,the liquid viscosity can be derived from the variation of the FBG center wavelength.Using FBG to sensing the stress change of cantilever beam caused by viscous force on the surface of the blocking element with the liquid flowing.Then,the stress change will be calculated by the center wavelength variation obtained from the FBG interrogator,thereby the corresponding viscosity value can be gotten.Through the experimental study,the flow-blocking element is pasted on the cantilever beam,the FBG is bonded on the upper part of the cantilever beam,and the blocking element is the main part of the measurement system.First of all,the measurement system was calibrated by the standard viscosity liquids,meanwhile the mathematical model between the center wavelength variation and the liquid viscosity was established.Then,the verification experiments,test results of a group of liquid viscosity from this measurement system comparing with the result from the standard viscometer,has verified the feasibility of the experimental method.The repeatability of the measurement system is verified by a large number of experiments and the temperature compensation is carried out.In the end,the qualitative analysis of the induced experimental error is made,and the whole measurement system is improved so as to facilitate the further experiment.This method,the viscosity can be obtained by the fluid flowing,is a new exploration and breakthrough.