On One Special Problem of Blades Identifi cation in Monitoring the Technical State of Gas Turbine Engine Air-Gas Channel

This article is devoted to the problem of "targeted" fixing of the measurement results of spatial position of the blades’ tips of compressor or turbine of gas turbine engine (GTE) to a specific struct ural element of the power plant (blade) in monitoring the state of engine’s gas-air channel under limitations on use of diagnostic equipment and, in particular, the impossibility of installing the shaft’s angular position sensor, that ensures the synchronization of primary converters polling with the rotation period of the turbomachine rotor. The diagnosis of disruptive and surging phenomena in GTE compressor, detection of foreign objects entering the gas-air path of the engine, determination of fatigue failure of the blades are the typical examples of the tasks that require binding of the measurement results to each individual blade on a rotor wheel. The proposed solution is based on the analysis of a unique set of radial clearance values for the complete ensemble of rotor blades with the comparison of the current and previously obtained "reference" images of the turbo compressor’s bladed wheel. Two algorithms for blades’ number determining are considered. The algorithms do not require a separate channel for synchronization and use the minimum Euclidean distance and the maximum value of the cross-correlation function between the elements of the "reference" and current arrays of codes as criteria for blades’ identifying. The results of the performance test of both algorithms on a laboratory bench with a real compressor wheel are presented. It is shown that the criterion based on cross-correlation function calculation has higher noise immunity, and therefore it is the most preferable for practical implementation in actual practice measurement systems. Low computational complexity of the criterion allows to use it at the microprocessor level and to reduce the measuring system hardware.