Experimental Test Results for a Fiber Bragg Grating-Based Flow Sensor

Abstract

A fiber optic-based mass flow sensor has been developed that uses fiber Bragg gratings to deduce flow velocity. Flow velocity, local temperature, pressure measurements (that all can be extracted using fiber Bragg gratings) and geometric information can be combined to determine mass flow. A range of concepts have been investigated and compared using the same “design of experiment” for each sensor. The most promising concept has been further developed into a prototype. The working prototype successfully demonstrated a thermally insensitive sensor design that has the capability to track flow velocities. The sensor design is incorporated directly with a structural beam element to magnify the strain effect while simultaneously compensating for thermally-induced wavelength shifts in the sensor response. Further testing has been performed using three flexible beams at different angular positions showing that flow angles can be measured similar to the approach used for 3-hole pneumatic probes. As a final test, the sensor has been tested in a shock tube demonstrating superior performance compared to steady pneumatic measurements which rely on tubing to reach the measurement location.