靶式光纤光栅流速传感器在裂隙水模型试验中的应用

结合等强度悬臂梁和光纤Bragg光栅(FBG)设计了靶式FBG流速传感器,用于在线测量管道及裂隙的流场流速。传感器将流体中靶片的受力转化为该流速下对应FBG中心波长的漂移,并自动实现温度补偿。采用FLUENT6.3对被测裂隙及管道流场进行有限元仿真,确定裂隙中靶片受力特性及相同受力条件下的等效管道内径,并求得过流断面5mm×2000mm的裂隙中传感器的灵敏系数为8.71×10-4 s2/m2。在管道系统中进行传感器标定实验,传感器在0～1.20m/s范围内,最大误差为0.02m/s。将该传感器应用于裂隙水模型引流试验,实验结果表明,关键点流速随着进水阀门开度逐渐增大而提高。打开引流管道阀门,引流管道布设处后方各点流速降低,且同一断面流速变化趋势保持一致。

Application of target-type FBG flow velocity sensor in fracture water model test

Combining equal strength cantilever with Fiber Bragg Grating(FBG),a target-type FBG flow velocity sensor is developed to monitor the pipeline and the fracture flow velocity on-line.The force produced by flow works on the special shape target,then the level and cantilever structure transform the force into the wavelength shift of the FBG and the dual FBG structure is adopted to eliminate temperature effect.In order to determine the target force characteristics in the fracture and the equivalent pipeline diameter under equal force,finite element simulation is carried out using FLUENT6.3.Simulation results show that the velocity sensitivity of the sensor is 8.71×10-4 s2/m2 in the fracture at the flow section of 5 mm×2000 mm.The pipeline calibration experiments indicate that,in the measuring range of 0 m/s~1.20 m/s,the maximum error of the sensor is 0.02 m/s.The sensor is used in the drainage experiment of simple fracture water model.The results indicate the velocity increases when the inlet valve is enlarged.After the valve is turned on,the velocity in the rear drainage pipeline decreases.The trend of velocity change at the same section is in agreement with each other.