Research On Thermal Gas Flowmeter Based On Metallic-coated Fiber Bragg Gratings

A novel thermal gas flowmeter based on metallic-coated fiber Bragggratings (FBGs) with a fiber core-offset coupling is proposed. Thetemperature-sensing characteristic of FBG is what it is based upon. By makingcomprehensive utilization of the dynamic thermal equilibrium relation between thelaser energy absorbed by the metallic thin film and the heat taken away by the gasflow, the flow measurement for large-diameter(mainly50mm) and low-velocity gasflow is eventually realized.This article first reviews the development and application of optic fiber gratingsand the research status of thermal gas flow measurement technology. Variousnew-tape flowmeters based on the combination of both principles are introduced.Then the research on the sensing mechanism of this thermal gas flow meter is carriedout and the mathematical model is derived. The package structure is designed andoptimized by using the simulation software Fluent as well. Characteristicexperiments of multiple different sensing probes are launched, from which theoptimal probe is choosed to packing. All these compose the primary instrument ofthe flowmeter. After that another simulation is conducted on the temperature changesat work aroung the probe, contour maps of temperature are acquired to see thetemperature field distribution visually. Setting up the detection optical route,adopting Ethernet to communicate and employing VB6.0to carry out the display ofinstantaneous flow rate fulfill the design and prepare of this thermal gas flowmeter.A Standard Bell Porver is adopted to develop a series of calibration andmeasurement experiments. The results show that the measurable range is0~10m3/hand the minimum resolution can be defined as0.01m/s on the basis of the accuracyof OSA. This flowmeter performs well and is worth to be developed.