Tip Clearance Measurement Research Articles

414 静電容量式翼端すきま測定法の研究(計測・制御・ロボット)

414 静電容量式翼端すきま測定法の研究(計測・制御・ロボット)

High Temperature Proximity Measurement in Aero and Industrial Turbomachinery

The measurement of disc and shaft displacement has been performed for many years as part of the development, commissioning and monitoring of all classes of turbomachinery. This measurement has traditionally been performed using sensors that cannot operate above the curie point of rare earth magnets. In this paper a programme of work is described that was undertaken to develop a measurement system that could make a measurement of target proximity in a high temperature environment. The specific objectives were to make possible the measurement of turbine disc axial movement and shaft motion in the engine core, close to the combustion chamber or turbine; and secondly to make possible the measurement of tip clearance over shrouded turbine rotors.

Study on Tip Clearance Measurement System. 2nd Report. Characteristics of the System and Measurement.

Using the discharge-type blade tip clearance measurement system which was designed for testing, the following were clarified. According to Paschen's law, gas pressure exerts an effect on the measured values; however, the result of the experiment showed that the measured values were not affected by pressure with the minimum discharge voltage. It was confirmed that when the speed of the probe was high, sometimes the probe came in contact with the blade tip. Since there exists a time constant for voltage restoration in discharge signals, there is a limit beyond which the continuous signals can not be obtained. This was examined theoretically and confirmed experimentally. As a result of measuring the blade tip clearance at a peripheral speed of 400 m/s, the elongation of a rotating object due to peripheral speed could be measured.

Study of Tip Clearance Measurement System Using a Fixed Discharge Probe.

We have devised a new method for tip clearance measurement which does not require an actuator to move the discharge probe. The applications of this method and its characteristics were investigated, and tip clearance measurements were attempted. As a result, it was found that UV irradiation was indispensable for obtaining a constant discharge voltage in the range of 98kPa∼196kPa. The discharge characteristics varied with pressure, but a linear relationship could be obtained. The discharge characteristics varied with the shape of the rotor. Hence, this factor must be checked prior to measurement. The probes produced were not affected by the peripheral velocity of up to 80m/s. Measurement accuracy using a core-type probe was within ±0.05mm, and with a cylinder-type was within ±0.lmm. The cylinder-type probe was able to measure the tip clearance up to a peripheral velocity of 270m/s.

A Blade-by-Blade Tip Clearance Measurement System for Gas Turbine Applications

It is difficult to make a reliable measurement of running clearance in the hostile environment over the blading of a modern gas turbine. When engine manufacturers require the measurement to be made over every blade during live engine tests, system reliability, ruggedness, and ease of operation are of primary importance. This paper describes a tip clearance measurement system that can measure clearance over every blade around a rotor. The measurement system concept is presented, and the system design described in detail. Commissioning of the measurement system on a compressor test facility, and the results obtained are discussed. An analysis of system performance during the commissioning trials concludes the paper.

Study of Tip Clearance Measurement System.

Trial manufacture of a tip clearance measurement system with spark discharge has been conducted, through which the structure of this apparatus was clarified. The characteristics of spark gap between the probe and the blade that determines the measurement accuracy of this apparatus and the effect of UV irradiation were investigated. As a result, the measurement value was affected significantly by voltage which is one of the factors of the spark discharge law (Paschen's law) . When supply voltage is more than 900 V, the scatter of measurement value increases. However, this scatter, obtained when ultraviolet irradiation was used, was found to remain in the initial range of the minimum spark discharge voltage, and the spark gap corresponding to supply voltage was also observed to approximate the Paschen curve. The measurement value was affected by the shape of the blade, but the spark gap was observed to approximate the Paschen curve when ultraviolet irradiation was used. The peripheral velocity of the rotor within 140 m/sec did not affect the measurement value.

Fast Response Tip Clearance Measurements in Axial Flow Compressors—Techniques and Results

As part of an investigation of the effects of tip clearance performance of development axial flow compressors, a system for detecting rotor blade tip rubs has been developed and a tip clearance measuring system modified to detect clearance changes at a bandwidth of 500 Hz. Mean clearance changes have been measured as well as changes during surge. Rotor orbit has also been investigated and the system has become an important means of monitoring rotordynamic behaviour. Subharmonic components of rotor orbit have been discovered.