基于单频与扫频融合干涉的转静子轴向间隙测量方法研究

The rotor-stator axial gap of aero-engine is a key parameter related to the efficiency and size of aero-engine. To measure the rotor-stator axial gap, the sensor has to be installed inside the aero-engine where the space is extremely small. Besides, the sensor is required to be resistant to the extremely high temperature and temperature perturbation, and the sensing system needs to have characteristics of fast measurement speed, high measurement accuracy, and wide measurement range. Due to the extreme measuring environments and requirements, there is currently no effective measuring method for the rotor-stator axial gap, which has been a bottleneck in the aero-engine measurement field. To solve problems of the sensor and the sensing system, we propose a new measuring method that fuses the single frequency interferometer and sweeping frequency interferometer. In this method, an interferometric cavity is formed between the end-face of gold-coated graded index fiber and the surface of rotor to overcome the problem of extremely small space and high temperature, and the time-varying Doppler effect of sweeping frequency interference signal is estimated and eliminated by the single frequency interference signal to ensure the measurement accuracy. We are going to focus on investigations of theory and method of sensor design and fusion demodulation, which can establish a theoretical and technical foundation for the measurement of rotor-stator axial gap of aero-engine.

航空发动机转静子轴向间隙是关系发动机效率和尺寸的关键参数，而转静子轴向间隙测量不仅要求将传感器深入发动机内部的极小空间内，还要求传感器耐受极高温度及其干扰，更要求传感系统能够进行高速高精度和大范围测量。其极端的工作环境和苛刻的测量要求，使现有的间隙测试方法难以适用，是航空发动机测试的瓶颈之一。为突破传感器及其系统两方面的难题，本项目创新性地提出一种单频和扫频融合干涉测量的解决思路：采用镀金折射率渐变光纤端面与转子表面形成干涉腔，解决狭小空间极端环境的测量难题；采用单频干涉信息判断和消除时变多普勒效应，以保障扫频干涉的间隙测量精度。通过重点研究传感器的设计理论与方法，融合干涉解调的理论与算法，以为航空发动机轴向间隙测量奠定新的理论和技术基础。

航空发动机转静子轴向间隙与发动机的效率和安全性密切相关，对其进行精确测量可以为发动机的设计与加工提供重要参考。轴向间隙测量需要将传感探头引入发动机内部，由此形成了空间狭小、高温、高压、高速等极端的测试环境，以及传感探头小尺寸耐高温、测量系统高速高精度大范围的测试需求。极端的测试环境以及极高的测试需求导致目前没有测试方法能够适用于转静子轴向间隙测量，使之成为航空发动机测试的瓶颈难题之一。.针对上述难题，本项目从以下四方面开展了研究：(1)传感探头的设计理论与方法、制造工艺优化及性能测试，(2)扫频干涉间隙测量、单频与扫频融合干涉间隙测量的理论及方法，(3)单频与扫频融合干涉间隙测量系统的设计与研制，(4)单频与扫频融合干涉间隙测试系统的性能测试。通过系统性的研究，在理论模型层面上，提出了用于干涉测量的传感探头设计理论、扫频与单频通用的瞬态干涉模型、扫频干涉间隙测量的瞬态多普勒误差模型、以及扫频与单频融合干涉间隙测量原理；在技术系统层面上，研制出了小型(1.5mm直径)耐高温(500℃)的光纤传感探头、以及融合干涉间隙测量样机(测量范围大于10mm，测量速度5MHz，测量精度优于20μm)。本项目的研究成果不光为航空发动机转静子轴向间隙测量提供了一种新理论与新技术，在光纤珐珀/光纤光栅温度、压力、应变等多参数的高速测量领域也具有广泛应用前景。