Parametric Simulation of ‘Hot-wire’-based Gas Velocity Sensor Using Optical Fiber

Based on the lumped parameter method, the mathematical model of temperature field distribution of optical fiber hotline sensor is established in this paper, which provides a theoretical analysis for optimizing sensor design and improving performance. The relationship between the dynamic measurement range, sensitivity of the sensor and the surface heat transfer coefficient of sensor probe, wind speed is calculated, and the variation of radial temperature and the average axial temperature of the probe are analyzed by COMSOL simulation software. What the results show the larger thermal conductivity of the tube, the more uniform of sensor temperature distribution. Under the initial conditions of no wind, the average temperature of the probe surface has a good linear relationship with the pump source power. Moreover, a large heat capacity and a small heat exchange area of the probe, which will make the initial dynamic range larger. With the increase of wind speed, the average temperature of the probe decreases nonlinearly. Considering the influence of temperature on FBG, in order to avoid the chirp of FBG due to the excessive gradient of axial temperature distribution, the length of probe should be shortened and the thermal conductivity of sensor should be increased. Considering the temperature-dependent characteristics of the fiber grating, and avoiding the fiber grating defect caused by the excessive axial temperature distribution gradient, shortening the length of the probe, increasing the axial thermal conductivity, and reducing the heat capacity of the sensing probe will improve the performance of the sensor.