A Research Of Fiber Fluid Velocity Sensor Based On The Doppler Effect

The parameter of fluid velocity is very important parameter index in the production of industry. The accuracy of the parameter measurement can effectively improve the efficiency of industrial production and quality. Compared with the traditional velocity sensor, the fiber fluid velocity sensor has many advantages: high accuracy, large dynamic range, intrinsically safe, resistance to electromagnetic interference, etc. It also can be used in bad working environment like high temperature or high pressure. The research of theoretical model, optical path structure and signal processing is carried out in this paper based on the Doppler Effect. Fiber fluid velocity sensor is developed arming at the fluid velocity measurement. The main research work is as follows:(1) Based on the optical Doppler Effect and combined with the optical coherent signal detection, the theoretical analysis model of the fiber fluid velocity sensor is set up. Various factors influencing the performances of the sensing system is analyzed by the simulation, which provides the basis for designing the sensing system.(2) Traditional Laser Doppler Velocity structures are compared and analyzed in detail. Then the theoretical analysis, optimization and production of the sensor structure suitable for fluid flow velocity measurement are carried out. A kind of two point measuring structure has been put forward. Based on the theoretical study, the structure can effectively enhance the Doppler scattering light signal collection without increasing the number of light source and detector.(3) Based on the optical heterodyne detection method, high speed data acquisition combined with computer software of Doppler frequency shift signal processing method is studied. According to the fast Fourier transform(FFT) method, the signal processing algorithms and measure control software are designed.(4) Two different kinds of velocity measurement experimental platforms are set up. And the experiments of solid and fluid flow velocity measurement are carried out. The performance indicators like measurement precision, stability, response time and so on are studied. The experiment of solid velocity measurement showed that the mean square error is less than 0.06, the repeatability error is less than 0.10 m/s, response time is less than 1.00 second, work time length has no effect on system performance; Fluid velocity measurement experiment showed that the mean square error is about 0.05, the repeatability error is about 0.10 m/s. Finally, the reasons of the measuring error are analyzed in detail and the two point measuring model is proved by experiment preliminary.A kind of fiber fluid velocity sensor which can effectively measure solid and fluid flow velocity is put forward in this thesis. The study provides important reference value for the practical application of optical fiber fluid velocity sensor.