航空发动机涡轮叶片叶尖间隙呈三维变化特点, 传统光纤式叶尖间隙检测系统的测量结果受维间耦合影响精度差, 信息源单一。本文利用一种沿直角等腰三角排布的三路双圈同轴式光纤传感基元组成的传感探头, 通过BP神经网络解耦方法, 实现了从传感器输出到叶尖端面径向间隙、轴向倾角和周向倾角三维参量的解耦。设计加工三维测量光纤传感器和后续调理电路并对检测系统进行了静、动态实验验证。实验结果表明: 该系统径向间隙静态测量的最大误差为47 μm, 标准差为10 μm, 轴向和周向倾角的静态测量最大误差分别为0.49°和2.32°, 标准差分别为0.13°和0.36°。系统具有良好的重复性和可靠性, 径向间隙的动态测量标准差小于18 μm, 轴向和周向倾角的动态测量标准差小0.2°和05°, 能够满足航空发动机涡轮叶片叶尖间隙三维参量快速实时检测的需求。

Turbine blade tip clearance varies in a three-dimensional (3-D) direction in an aero-engine. The traditional fiber-optic sensor can only measure the radial clearance, and the results are affected by the interdimensional coupling effect. In this paper, a sensor array consisting of three of the two-circle coaxial fiber bundles, arranged along the isosceles triangle layout, was used to realize the decoupling of blade tip clearance 3-D parameters. These parameters included radial clearance, axial deviation angle, and circumferential deviation angle from the sensor outputs, leveraging a BP neural network method. A special fiber-optic sensor array and signal conditioning circuit were developed, and the experimental tests for static and dynamic properties of the measurement system were performed. Experimental results indicate that the maximum error of radial clearance static measurement is 47 μm with a standard deviation of 10 μm. The maximum error of axial and circumferential deviation angle static measurements are 0.49° and 2.32° with standard deviations of 0.13° and 0.36°, respectively; the measurement system performed well in terms of repeatability and reliability. The dynamic measurement standard deviation of radial clearance is less than 18 μm with axial and circumferential deviation angles of less than 0.2° and 0.5°, respectively. This satisfies the demand of real-time detection of blade tip clearance 3-D parameters of turbine blades of an aero-engine.