油气润滑ECT传感器的轴向屏蔽电极及其影响

Axial Shield Electrode of Oil-Air Lubricated ECT Sensor and Its Influence

建立UMIST型(带轴向接地屏蔽电极)和METC型(带轴向驱动屏蔽电极)油气润滑ECT传感器的三维物理模型,根据三维物理模型推导电容值和灵敏度数学表达式,并分析轴向屏蔽电极对传感器的敏感性和灵敏度均匀性的影响;采用线性反投影算法(Linear Back Projection,LBP)进行图像重建,并比较重建图像与真实图像的相对误差和相关系数。结果表明:2种轴向屏蔽电极均可消除边缘电容并提高传感器的敏感性;带轴向接地屏蔽电极使得传感器的灵敏度更加均匀,而带轴向驱动屏蔽电极的传感器则相反。带轴向接地屏蔽电极的传感器更适用于油气润滑中环状流的识别,其重建图像与真实图像的相对误差降低了28􀆰79%,相关系数提高了14􀆰05%。

Three⁃dimensional physical models of oil⁃air lubricated ECT sensors of UMIST type(with axially grounded shield electrode)and METC type(with axially driven shield electrode)were established.Based on the three⁃dimensional physical models,the mathematical expressions of capacitance value and sensitivity were derived,and the influence of the axial shield electrode on the sensor sensitivity and the uniformity of sensor sensitivity was analyzed.Linear back projection(LBP)algorithm was used to reconstruct the image,and the relative error and correlation coefficient between the recon⁃structed image and the real image were compared.The results show that both axial shield electrodes can eliminate fringing capacitance and improve the sensitivity of the sensor.Sensitivity influence coefficient characterizes the uniformity of sensor sensitivity.The axially grounded shield electrode makes the sensitivity of the sensor more uniform,while the axial driving shielding electrode has the opposite effect.METC type ECT sensor is more suitable for the recognition of annular flow in oil⁃air lubrication,the relative error between the reconstructed image and the real image is reduced by 28􀆰79%,and the corre⁃lation coefficient is increased by 14􀆰05%.