PRELIMINARY INVESTIGATION AND SIMULATION OF FBG CRYOGENIC FLOWMETERS

Abstract

The dissertation work in discussion describes a novel technique to measure cryogenic fluid flow rate using optical fiber Bragg grating (FBG) sensors. FBG flowmeters are a good replacement to the conventional flowmeters, which are based on pressure or electronic methods having disadvantages like high pressure loss or electromagnetic influence. The FBG sensors to be used in the flowmeter were calibrated for temperature and strain to ensure reliable results. Initial room temperature tests of the existing wall element (float) based FBG flowmeter were performed with Air, Nitrogen and Helium as working fluids. A wall element free flowmeter is also designed where the FBG sensors are directly subjected to the flowing fluid. The new flowmeter is numerically modelled to study the effects of fluid flow conditions on the FBG sensor. A commercial finite-volume simulation software package, ANSYS Fluent R15.0, is used to carry out simulations and predict the strain caused on the FBG sensor for various flow conditions. The corresponding Bragg wavelength shift is calculated based on the simulation results, which could be utilized as reference for the experiments after fabrication.