The Key Technique Research Of Blade Tip Clearance Measurement For Rotational Blades

It's a problem desiderating solution for power industry, energy industry, aviation and shipping to real-time measure the rotating blade tip clearance. The conventional measurement technique mostly comprises discharging probe measurement, eddy current measurement, microwave measurement, ultrasonic measurement, capacitance measurement, X-radial measurement and optical trigonometry measurement. All these methods have different limitation.To achieve applied level for tip clearance measurement technique, foreign and domestic scholars have been applying them to research a new non-contact tip clearance measurement technique using optical fiber sensor. This dissertation researches the tip clearance measurement technique according to the requirement and parameter of New Century Excellent Talents in University Supporting Program"The key technique research of tip clearance measurement based on optical fiber"sponsored by National Ministry of Education. The main work in the dissertation is shown as follows:1. Based on the optical fiber sensor with two groups of receiving fiber, three groups of fiber were adopted to realize the measurement of tip clearance. The sensor can not only eliminate the effect to measurement results of light source fluctuation and reflectivity variety of tip surface, but also reduce the effect of angle between the tip surface and sensor end face to measurement result.2. The mathematic model of tip clearance sensor, which is based on a single bundle of fiber to transmit laser and three groups of fiber to receive reflected light, is designed; and with the model, the sensor was designed and optimized, the configuration of fiber arranging and parameters of original clearance and linear range were determined.3. The magnifying and processing circuit of high precision under static state was designed to measure the tip clearance effectively. By spatial surface fitting with lots of experiment data, within the measurement range, the effect of angle between the tip surface and sensor end face to measurement result was avoided.4. By analyzing the signal characteristic of one group, two groups and three groups receiving fiber, the sensor precision comparing and validating method is done with light power ratio of three-group fiber. Then combined with the experiment data, the performance of sensor was analyzed, within the linear measurement range of fiber-optic sensor, the measurement precision is up to 25um.