Received on December 01, 2014

The article investigates the blade pitch effect on the measurements of the blade tips radial and axial displacements in the turbines of the gas-turbine engines and gives a model description of the electromagnetic interaction between the work and compensating sensitive elements of the eddy-current single-coil sensors in the amount of the distributed cluster of sensors and inspected and adjacent blades. By means of the developed model the families of the conversion functions as dependences of the equivalent inductances of the sensitive elements from the radial and axial displacements of the irregular shaped blades are defined. These conversion functions were later used for computation of the dominant functions of the adjacent blades at various blade pitches. The authors demonstrated that the adjacent blades effect on the compensating sensitive element is far greater than on the work of the sensitive element and it increases with the blade pitch decrease. A model of differential measuring circuit with pulsed power was considered. The inputs of this model are the modeling results of the electromagnetic interactions between the sensitive elements and the rotor blades presented as the equivalent inductances changing in time. The families of the conversion functions as dependences of the digital codes from the radial and axial displacements of controlled blades were obtained. They are used, as before, for computation of the dominant functions of the adjacent blades at various blade pitches. The method is presented for obtaining of the calibration characteristics of the systems for measurement of the blade tips' radial and axial displacements. It gives an opportunity to avoid possible errors, typical for the adjacent blades effect, during the system operation.

Keywords: turbine, irregular shaped blades, radial and axial displacements, eddy-current single-coil sensor, adjacent blades effect, electromagnetic interactions model, measuring circuit model, influence reduction, method for obtaining of the calibration characteristics

Acknowledgements: This work was supported by the Russian Foundation for Basic Research, project no. 14-08-00802

For citation:
Borovik S. Yu., Kuteynikova M. M., Podlipnov P.E., Raykov B. K., Sekisov Yu. N., Skobelev O. Р. Adjacent Blades' Effect on the Tip Clearance Measurements in Turbines, Mekhatronika, avtomatizatsiya, upravlenie, 2015, vol. 16, no. 5, pp. 327—336.
DOI: 10.17587/mau.16.327-336

Corresponding author:
Borovik Sergey Yu., D. Sc, Leading Researcher, Institute for Complex Systems Control of RAS, Samara, 443020, Russian Federation, e-mail: borovik@iccs.ru, phone: +7 (846) 3332677

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