【作者】 曹素芝；

【导师】 段发阶；

【作者基本信息】 天津大学 ， 测试计量技术及仪器， 2007， 硕士

【摘要】 叶尖间隙是影响发动机性能的重要参数,旋转叶片叶尖间隙在线实时检测系统对航空发动机的高效、安全运行至关重要,也是近几年国内外研究的热点。基于对国内外现状的分析,本文对光纤法和电容法进行了详细研究和论证。光纤法用于测量环境较好,温度较低的压气机;电容法用于测量温度较高的涡轮机高压级。本文的目标主要是解决光纤式叶尖间隙测量系统中光纤束传感器的数学建模和结构优化问题,以提高传感器性能;探索电容式叶尖间隙测量法的整体方案,为研制实用的电容式叶尖间隙测量样机奠定基础。本文建立了基于光线跟踪理论的光纤传感器的三维数学模型,结合实际工艺,设计出具有补偿功能的四叉型光纤束传感器;探索出一套适于测量环境的调频电容式叶尖间隙测量的整体方案,采用混频下变频来提高测量系统灵敏度的方法。本文的研究内容主要有以下几个方面:(1)建立了基于光线跟踪理论的三维数学模型,用于分析光纤传感器的受光特性以指导传感器设计。(2)设计了适于高转速、高精度测量的四叉型光纤束式叶尖间隙传感器,该传感器对光源波动、叶尖表面反射特性,光纤传光损耗,叶尖表面微倾斜引起的与传感器端面夹角等影响因素有补偿功能。经过静态实验,证明了其工作的可靠性。(3)根据涡轮机高压级的测量环境,设计了长电缆单屏蔽的耐高温电容传感器,以及配套的调频用高稳定度的LC振荡电路。(4)电容传感器长电缆引入的大空载电容,影响测量灵敏度和精度,设计了混频下变频电路,用于增大调频信号的相对频偏,以提高测量系统的灵敏度。(5)设计了基于锁相环的鉴频系统,完成了对FM信号的解调。经过静态实验,验证了电容传感器及接口电路工作的可靠性。更多还原

【Abstract】 Blade tip clearance is an important parameter that influences the performance of aero-engine. On-line and real time measurement system of rotating blade tip clearance in a gas turbine is essential to the safe and efficient operation of aero-engine.Based on analysis of research status at home and abroad, optical fiber measuring method and capacitive measuring method is developed and demonstrated. The first method is applied to compressor stage under the appropriate circumstance of low temperature.The latter one is suited to high-pressure stage of gas turbine with high temperature. One of our research objectives is to build up a mathematic model of optical fiber bundle sensor and to optimize its sensor configuration. The other is to explore the whole scheme of capacitive probe tip clearance measurement system. According to measured environment, which build up a solid foundation to develop a practical blade tip clearance measurement prototype.Innovation points are as followings. Three-dimensional mathematic model based on ray tracing theory is proposed and demonstrated, and four-furcated optical fiber bundle sensor with compensated capability is developed combined with arts and crafts. The whole scheme of capacitive probe tip clearance measurement system is developed and mixer method is employed to improve sensitivity of measurement system.The research work in this paper mainly includes the following several parts.(1) Three-dimensional mathematic model based on ray tracing theory is built up and applied to analyze receiving light characteristic and designation of optical fiber bundle sensor.(2) Four-furcated optical fiber bundle sensor is designed. It’s independent of light source fluctuation, target surface reflectivity and optical fiber loss during transmitting light, but dependent of tip clearance and small inclined angle between tip plane and sensor plane. By means of static and dynamic stimulant experiment, it is proved to be reliable.(3) According to measured environment of high-pressure stage of gas turbine, capacitive sensor that can resist heat with long cable is designed and connected to LC oscillatory electric unit with high stability.(4) Large capacitance is introduced by long cable of capacitive sensor, which influences sensitivivity and precision of the sensor. Mixer circuitry is employed to enhance sensitivity of measurement system by increasing relative frequency offset of FM signal.(5) Demodulated system of FM signal based on PLL is developed. The working reliability of capacitive sensor and interface circuitry is demonstrated by means of static experiment.更多还原