The Diagnostic Of Technical Condition Of Turbine Engine's Bearing By Means Of Method Of Alternator Frequency Modulation

The paper has been intended to discuss an application of a diagnostic method based on measurements and analyses of frequency modulation. The method has been developed at Instytut Techniczny Wojsk Lotniczych – ITWL (Air Force Institute of Technology, Warszawa, Poland). It has been based on measurements of pulse-frequency modulation of a DC generator or that of an AC alternator. The method has been intended to determine the usual wear-and-tear of a subassembly under examination and to locate defects, both of them in the course of normal operation of an aircraft power plant. The diagnostic system is connected to any terminal supplied with DC or AC voltage. Results of performance tests of the turbine engine have been presented. An airborne D.C. generator and a threephase rate A.C. alternator were used as generators-observers. Subsequent stages of the wear-and-tear of rolling bearings, the turbine unbalance, and the misalignment were observed while taking measurements during both flight and bench tests. What was observed first was some increase in the amplitude of braking the bearing induced by the increasing resistance to motion due to the wear-and-tear of the bearing’s components. Then, the amplitude was observed to decrease due to the wearing-in of the bearing’s components. At the beginning of operation, the rolling-friction coefficient was 0.4, then this value kept increasing with time until some rapid decrease beyond any mathematical meaning. This decrease resulted from the extension of radial clearances. Such being the case, the bearing’s operation had to be stopped to avoid intense destructive effects.