Taking the input and reflected waves into account,the relationship between the acoustic impedance at the end and the input of a system were theoretically analyzed.Closed and open acoustic configurations that influence the pressure,volumetric velocity,impedance and acoustic work were compared in detail.Based on the above investigation,an open-air traveling-wave thermoacoustic generator was designed and fabricated.It is composed of a looped tube,a resonator open at one end,a regenerator,and hot and cold heat exchangers.It is a small scale and simple configuration.The resonant frequency is 74 Hz at 1 bar in air.The maximum acoustic pressures at the open end and 0.5 m far away from the open end are 133.4 dB and 101 dB from a reference value of 20μPa when the heating power was 210 W,respectively.Acoustic pressure is reasonable for practical application as a low-frequency acoustic source.In further work,we believe that the acoustic pressure at the open end can achieve 150 dB,which could be a solution to problems in existing acoustic generators.These problems include low acoustic pressure and system complexity.It can be used as a basic acoustic source for low frequency and long-range noise experiments,and as a supply for high acoustic pressures necessary for industrial sources.
