A comparison between aeroacoustic source mapping techniques for the characterisation of wind turbine blade models with microphone arrays

Gianmarco Battista,Marcello Vanali,Paolo Castellini,Paolo Chiariotti

doi:10.21014/acta_imeko.v10i4.1142

Gianmarco Battista, Marcello Vanali + Show 2 more

Open Access

https://doi.org/10.21014/acta_imeko.v10i4.1142

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Abstract

<p class="Abstract">Characterising the aeroacoustic noise sources generated by a rotating wind turbine blade provides useful information for tackling noise reduction of this mechanical system. In this context, microphone array measurements and acoustic source mapping techniques are powerful tools for the identification of aeroacoustic noise sources. This paper discusses a series of acoustic mapping strategies that can be exploited in this kind of applications. A single-blade rotor was tested in a semi-anechoic chamber using a circular microphone array. <br />The Virtual Rotating Array (VRA) approach, which transforms the signals acquired by the physical static array into signals of virtual microphones synchronously rotating with the blade, hence ensuring noise-source stationarity, was used to enable the use of frequency domain acoustic mapping techniques. A comparison among three different acoustic mapping methods is presented: Conventional Beamforming, CLEAN-SC and Covariance Matrix Fitting based on Iterative Re-weighted Least Squares and Bayesian approach. The latter demonstrated to provide the best results for the application and made it possible a detailed characterization of the noise sources generated by the rotating blade at different operating conditions.</p>

Highlights

The growing interest in renewable energy sources is requesting advances on several disciplines in order to reduce technological barriers and improve energy conversion efficiency
This is caused by the localisation mechanism adopted by CLEAN-SC, that relies on the spatial resolution of Conventional Beamforming (CB)
A measurement campaign has been conducted in a semianechoic chamber on a single blade rotor, for its aeroacoustic characterisation with acoustic imaging techniques exploiting microphone arrays

Summary

Introduction

The growing interest in renewable energy sources is requesting advances on several disciplines in order to reduce technological barriers and improve energy conversion efficiency. It is well evident that the worldwide installed capacity of wind energy assets is growing exponentially since early 2000's. In order to mitigate wind turbine blade noise, the identification of location and strength of aeroacoustic noise sources is mandatory. This knowledge makes it possible to improve blade profiles and design effective aerodynamic appendages, such as trailing-edge serrations. Acoustic imaging techniques, based on microphone arrays [1], have been used to characterise a scale single-blade rotor, installed in a semi-anechoic chamber, in different operating conditions. The requirements of a mapping technique for this application are:

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Results

Conclusion