The efficiency of a gas turbine engine is directly dependent on the clearance between the rotational blade tip and the engine casing. Therefore, actual gas turbine engines make an effort to minimize tip clearance and, generally, the tip clearance measurement is widely done. Typically, tip clearance measurement is made by the use of sensors, applied magnetic-electric phenomenon, such as eddy-current type, electrical capacity type and spark/discharge type, etc. However, these sensors cannot be used for a non-metal blade measurement, such as the measurement principle. 'Research and development of the ceramic gas turbine' was carried out from 1988 to 1999 in the old Ministry of International Trade and Industry and Agency of Industrial Science and Technology, and National Aerospace Laboratory, based on results of the current gas turbine engine development. In the projects, turbine blade material was ceramic (non-metal) so a current tip clearance sensor could not be used. Then the method of assuming the distance measurement by the reflection of light was adapted as a measurement principle which can fundamentally measure tip clearance for a non-metal blade. Finally, sensor for trial purposes was made, with the aim of installing it in the real machine engine, and the performance of the sensor was proven with a simulated rotational blade device and high-speed rotational metal disk equipment.
光反射方式による非金属動翼の翼端すきま計測
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