Highly accurate differential pressure FBG gas flow sensor

Abstract

In this paper, the limitations of traditional electronic-type gas flow sensors for flow measurements in practical engineering applications such as flammable and explosive gas environments are discussed. Further, the importance and uncertainty of gas flow measurements in critical parts of industrial equipment are also discussed. In this work, a high-precision differential-pressure FBG gas flow and a temperature sensor with an embedded nozzle were designed using a long-diameter nozzle-type throttle tube with a fiber optic Bragg grating and an elastic-sensitive diaphragm composite strain mechanism. It was observed that the pressure difference between the two sides of the nozzle leads to the deformation of the elastic-sensitive diaphragm, and it results in a wavelength drift of the strain grating that is attached to the elastic diaphragm. Further, it also enables real-time monitoring of the gas flow value. Moreover, the temperature compensation grating which was attached to the side wall of the gas chamber was used to eliminate the cross-sensitivity of the strain grating as well as to improve measurement accuracy while implementing a temperature monitoring system. The experimental results showed that the Bragg wavelength drift in the fiber grating gas flow sensor acts as a quadratic curve with respect to the gas flow, and the experimental results were found to be highly compatible with the results of the theoretical analysis.