Observation of vibration velocity at many parts of wind turbine and relational analysis with propagated sound to surroundings

摘要

Authors had carried out many kinds of trial to understand characteristics of wind turbine noise. In this study, authors also newly tried measurements of the excited vibration on many parts of wind turbine such as outside surface of nacelle for storing power generation system and tall tower by using a laser Doppler vibration meter. Observation and analysis of the natural frequencies of blade vibration at rotation stopping state were done. Investigations on the noise in surroundings of wind turbine were also done. We tried the FFT analyses on them with high resolution to obtain detailed frequency characteristics. Then, relational analyses between vibration velocity and noise propagated to surroundings were added to ordinal spectral analyses only for the propagated wind turbine noise to make origins of tonal components clear. It first could be understood that both sharp spectra at near 1 Hz as slightly lower on a blade and higher on a tower were appeared in the analysed results. In analyzed results of the vibration velocity and propagated sound in the normal operation continued state, a lot of sharp spectral peaks with exceeding of 10dB from each base level of vibration and noise were recognized in the broad frequency range from very low to several hundreds of Hz's. It also could be understood that there were high coherencies between vibration velocity and wind turbine noise at frequencies with high spectral peaks. And certain values of coherency as exceeding 0.3 or up to 0.6 were remained even for the case of noise received at distance of about 200m from a wind turbine.