Gear wear is proposed to be detected by the frequency shift of the maximum of the second harmonic of the vibration signal. OOO "PKF "TSK"" received a patent for a method of diagnosing gas turbine engine differential reducer gears, in which the meshing condition is determined by the maximum of the second harmonic of the vibration signal.
The method is designed for diagnosing GTD differential reducers and uses a vibro-transducer signal installed on the reducer housing.
During engine operation in "Acceleration" mode, the signal is subjected to spectral analysis. From it, the second harmonic of the series is extracted, the step of which is determined by the product of the number of planet gears by the rotational frequency of the sun gear in relative motion. Then, the frequency of maximum intensity of this harmonic is found and compared with a reference value, previously calculated from the statistics of healthy reducers.
The patent provides an example of a turboprop engine with a reducer having three planet gears. For the studied sample, the average value of the diagnostic parameter was 13.5 Hz, the root mean square was 31.5 Hz, and the reference value established by the given method was 138.98 Hz.
For two engines from the sample, the maximum frequency was higher than the reference; a crack in the blade of the seventh stage compressor working blade was subsequently found on one of the engines; in the patent, its occurrence is associated by the authors with resonant vibrations caused by the vibration of the worn gear pair,
The main difference between the new solution and the previously published method by the same "PKF "TSK"" lies in the diagnostic feature. In another patent, which we wrote about earlier, it was about analyzing the signal of a standard tachometric sensor and the shape of the spectral peak. The new patent uses a vibration signal, and the condition of the reducer is evaluated by the frequency of the maximum of the second harmonic.