Researches On Sound Radiation Of Rotor Blade-tip Near-wake Field Based On Grid Test

Relatively high running speed and aerodynamic load of rotor blade tip region is the main source of acoustic radiation area, but also the main areas of converting wind energy to mechanical energy. So the blade tip region is regarded as the main focus to improve wind turbine performance and to explore noise reduction, become a hot research of wind turbine noise reduction. While the physical mechanism of blade-tip noise generated has not yet entirely clear. therefore the noise of blade-tip area is worth to pay close attention to. Author built on simple, effective and relatively easy to achieve acoustic test platform, based on BSWA VS302USB Noise Vibration Acquisition and Analysis System at opened experimentation segment of wind tunnel,The near-wake noise radiation acoustic field of rotor blade-tip downstream was measured over a range of tip speed ratios of windwill.The noise of blade-tip downstream pressure and spectrum were analyzed. And explore the structure of rotor blade-tip to achieve improvements,by installed V-and S-type tip vane region,improving the flow field, to study the near-wake of the rotor round sound radiation characteristics of situation.Experimental results show that: the rotor spinning process, rotor blade-tip noise radiation spectrum is composed by the fundamental frequency and the harmonic of discrete noise frequency superposition in broadband noise,and of the rotating blades, discrete rotation noise in total noise levels are dominant. Due to the tip vortex and adhesion vortex at the blade-tip airfoil trailing-edge downstream exist, induced effects on the flow field in the rotor blade tip disturbances, blade area with high pressure pulsation of the surrounding areas, most of the noise is mainly produced by the outer part of the blade.Rotor blade-tip with V-and S-type tip vane can augment effective the rotor power. The result show that the acoustic radiation law with tip vane is similar to without tip vane by rotor near-wake acoustic radiation testing, but the installation of V-or S-type tip vane rotor blade-tip area has a different degree of noise reduction. Installation of S-type tip vane rotor is better than the average noise reduction V-type. While sub-optimal S-type installation of rotor the best noise reduction, noise in the test within the range of 2 ~ 7dB. Special structure of tip vane improves the aerodynamic characteristics and reduces the frequency of the blade-tip vortex; destroy the blade-tip vortex structure. It also improves the speed of the flow field distribution. So the blade-tip flow field pressure fluctuation region is more uniform and stable, and the rotor internal downstream wake region is smaller, to reduce energy loss tip. Reduce the intensity of acoustic radiation.Blade-tip noise radiation of rotor near-wake is closely related to flow field of rotor near-wake and effects of wind energy transfer of rotor. To carry out horizontal axis wind turbine near-wake research in acoustic radiation,The experimental data are important for improving the horizontal axis wind turbine design and noise reduction to provide a reference calculation.