Study On Water Content Measurement Of Crude Oil By Microwave

In this paper,the principle and method of measuring the electromagnetic parameters of media by coaxial transmission line are studied.Firstly,the paper introduces the principle of traditional transmission reflection method and verifies it by HFSS simulation software.Considering the properties of crude oil liquid,the traditional transmission reflection method can not meet the measurement requirements,so it needs to improve its model.Here,a coaxial section made of two Teflon materials is used,and crude oil is placed between the two coaxial sections.Because the improved model has a transition section from the ideal coaxial line to another size coaxial line,it will cause fixture discontinuity and standing wave,and then there will be problems such as calibration.In order to reduce the impact of calibration problems on measurement accuracy,the length of the coaxial line in the transition section of the measuring fixture is equivalent to the standard coaxial line,and the equivalent standard coaxial line length is moved on the end face Through the calculation of the dielectric constant,it can be found that the error of the calculation result can be reduced by using this method.Then,two methods to calculate the relative permittivity based on the two port network matrix are derived and verified.These two methods can solve the calibration problem caused by the discontinuity of the measuring fixture.The first method to solve the relative permittivity of the medium by using the cascade of two port network depends on the simulation data of the simulation software,which is different from the data measured by machining.The second method is based on the measurement of multithickness medium to solve the relative permittivity.It no longer needs to calibrate the measuring fixture.Because of the measurement of two thickness medium,the solution process only involves the continuous part of the medium,avoiding the influence of the transition coaxial belt at both ends of the measuring fixture.In order to complete the measurement of water content in crude oil and combine the above theoretical analysis of the solution of relative dielectric constant of medium,a kind of coaxial measuring fixture is designed.The measuring fixture is divided into three parts,i.e.the left and right parts are symmetrical structures.They are used to transition the calibration port and the dielectric port to be measured,and the middle part is used to place the medium to be measured.Combined with the method of solving the relative permittivity of medium based on the measurement of multi-thickness medium,the relative permittivity of water is measured by using the measurement fixture and matlab program.From the measurement results,it can be found that the measurement fixture and calculation method are feasible,and the real part of the relative permittivity is roughly consistent with the actual value,but the virtual part is relatively different It is analyzed that the error of the measurement system has less influence on the real part of the dielectric constant,but more influence on the virtual part.Therefore,in the next study on the water content of crude oil,the real part of its relative dielectric constant is measured to establish the relationship with the water content.After comparing the measured data and the fitting data,the fitting error between the measured water content and the fitting water content is within ± 1%.Finally,based on the possible problems in the measurement process,and combined with the measurement results,the error analysis of the measurement system is carried out.