Fiber Grating Flow Measurement System

The flow measurement plays an essential role in the petrochemical field. Since most of the measured medium is not only flammable, explosive and corrosive but used in a poor environment. Because it is difficult to fight off the possible explosion of the traditional electronic flow-meter, along with a relatively low level in automation of mechanical flow-meter, so this kind of field need a flow measurement system urgently, this is of high intelligence as well as good security. Focusing on meeting the actual demand, this research made use of fiber grating sensor that is corrosion-resistant and safe intrinsically to achieve new flow measurement system.Based on a deep study of theoretical measurement of flow and sensing principle, this paper had an analysis of the advantages and disadvantages in different types of flow measurement methods. According to the structural characteristics of fiber grating sensors, the combination of fiber grating and vortex flow sensor was carried out to achieve the flow measurement. This fiber Vortex flow-meter has the advantages that include simple structure, convenient installation and precise measurement. Some theoretical analysis about vortex flow sensor and the basic principles of fiber grating sensor were made. Additionally, we also conduct a dynamic analysis in vortex flow field, using dedicated fluid simulation software FLUENT, numerical simulation of the vortex formation and transfer process, and got the curve of the pressure of the point with force-time, namely, indirectly obtain the information upon frequency generated by vortex. We designed and produced a fiber grating Vortex Flow sensor system, including sensor package flange, uniform intensity cantilever, vortex generating body et al and other critical sensing units. There is a high-speed dynamic demodulation of the high-frequency vortex signal by fiber Bragg grating sensor perceived in the experiment, which took advantage of the Coarse Wavelength Division Multiplexing (CWDM). Through the air flow measurement calibration system, the fiber grating Vortex Flow Measuring System has been tested and calibrated successfully, and the flow and the curve of vortex street information upon frequency was observed by us. Experimental data and theoretical values proved a good match, and a curve of the sensor output owned a good linear relationship. It was well-demonstrated in the test and calibration results that the fiber grating can replace piezoelectric devices to achieve vortex flow measurement. Occupying certain advantageous features such as simple structure, low cost and the high-speed wavelength demodulation, this system has a broad application in the flow and measurement field.