Acoustic characteristics of a mean flow acoustic engine capable of wind energy harvesting: Effect of resonator tube length

Abstract

A mean flow acoustic engine based on the aerodynamic effects converts wind energy and fluid energy in pipelines into acoustic energy which can be used to drive thermoacoustic refrigerators and transducers without any mechanical moving parts. A mean flow acoustic engine with the resonator tube length regulated steplessly was developed for experimental study. Experimental results reveal the effects of the resonator tube length and the mean flow velocity. When the single end closed resonator length is between 150 mm and 230 mm, the acoustic field is in the fundamental mode; more odd acoustic modes appear in turn with the increase of the resonator length. There exist stable oscillation regions in certain ranges of the mean flow velocity. The critical lengths occurring between the transition points of acoustic modes are determined experimentally. Furthermore, the strong acoustic oscillation in the first hydrodynamic mode and the first acoustic mode is more likely to occur at short resonator. With the mean pressure of 106.36 kPa, the mean flow velocity of 50.35 m/s, and the single end closed resonator length of 190 mm, the mean flow acoustic engine demonstrates a pressure amplitude of 15.67 kPa, showing a great potential in mean flow energy harvesting.