Experimental Study On Correlation Between Sound Source And Dynamic Strain Distribution Of Wind Turbine

With the rapid development of wind power industry, more and more wind turbines are installed in areas with high density of wind energy, such as coastal areas and densely populated areas. The noise of the wind turbine seriously affects residents’ daily life. The size of wind turbine noise can seriously affect the normal daily life of the residents. The most important problems are vibration size, noise control and safety of the wind turbine which should be solved. There must be exists some contact between the working mode and noise of the operated wind turbine. Based on the open end of the wind tunnel test, the horizontal axis wind turbine blade surface noise source and dynamic strain are studied, the correlation analysis between the noise source and the strain distribution were carried. inner relationship between the sound source and the strain was found.By spectral analysis found that the main area of noise acoustic energy of the wind turbine comes from low frequencies. Below 200 Hz, the noise of wind wheel rotation takes the dominant which mainly consists by the blade rotation frequency and its harmonics group consisting of discrete noise broadband noise superimposed on top thereof. With the increase of tip speed ratio and wind speed, the rotating frequency has increased, and corresponding to the sound power level.Based on the results of our research group, the main source of noise in the root zone is a secondary mechanical noise which caused by vibration of the turbine wheel, and the main source of noise at the tip region caused by tip vortex shedding. Therefore, correlation analysis of acoustic information and operating mode at 0.17 R ~ 0.85 R region were carried out. Analysis of the location of sound source, at the same conditions, with the increasing of fundamental frequency and its harmonics the main source of noise moving gradually along the plane of rotation of the radial direction to near the middle of the blade, the corresponding acoustic energy is gradually reducing. The maximum noise sources are mainly concentrated at the central area(r / R = 0.54). With the increase of tip speed ratio and wind velocity, the maximum noise source location does not change. Analysis of strain along span direction, the strain amplitude is increasing and then decreasing, the maximum strain amplitude areas are mainly concentrated at the central area(r / R = 0.51)of blade, and with the increase of tip speed ratio and wind velocity, the maximum strain amplitude position does not change. the cross-correlation analysis of noise and maximum SPL strain amplitude along the blade span direction by SPSS software was carried, noise and maximum SPL strain showed a high degree of correlation characteristics at 0.17 R ~ 0.74 R area,and showing moderate correlation characteristics around 0.85 R area.Based on the low-speed wind tunnel laboratory, the noise source localization testing techniques and stress-strain test technology use in testing horizontal axis wind turbine, the simultaneous acquisition noise parameters and strain parameter has successful implemented, which put forward an innovated experimental means, in the latter process data also obtained the expected results.The experiments preliminary obtain the regular of noise radiation and the distribution of stress and strain in wake region, similar variation and presenting highly relevant cross-correlation characteristics indicate that the sound radiation relates to the stress and strain. The results show that the acoustic array and rotational mechanical stress and strain wireless telemetry means test can gather sound field and strain dynamic parameter information in near wake, which accumulated experience for rotating machinery aerodynamic noise test and analysis. And providing validation data for simulation on the horizontal axis wind turbine and accumulated experience for designing high-performance, low-noise wind turbine design.