BLADE VIBRATION MEASUREMENT OF TURBO PUMP INDUCER IN LIQUID HYDROGEN CONDITION

摘要

The tip displacement measurement of LE-7A turbo pump inducer has been performed using eddy current NSMS (Non intrusive Stress Measurement System) system in actual liquid hydrogen condition. The system has been developed in IHI, especially used for the measurement of rotor blade tip displacement caused by blade vibration for jet engines and gas turbine engines. Optical probes are normally used for tip timing detection, because the feature, which has smallest spot area and higher frequency response, are match for these kinds of measurement. In liquid hydrogen condition, it is very difficult for optical probes to separate the actual blade position and liquid surface, and in the case of cavitation condition it would be almost impossible. The eddy current sensor was developed to solve these difficulties. The eddy current sensor only generates the signals while the metal blade is passed in front of the sensor, and there are no influence caused by cavitation bubbles. The eddy current sensor has wider sensing area, which comes from bigger sensor diameter compared with optical probes that has very small sensing point generated through fine optical fiber. For above reasons, , the eddy current sensor was not suitable for blade tip timing detection until recent years. However, we have confirmed that eddy current system also have a performance to measure the blade tip timing detection almost same as optical systems, through many bench tests , cryogenic condition tests, improvement of electronics and sensor materials. Through these preparations, we could measure the turbo pump inducer blade vibration, and could get the useful data for development of liquid hydrogen turbo pumps.