气体介质对气动声源发声特性的影响

Influence of Gas Medium on Acoustic Characteristics of Air-jet Generator

为探究气体介质对气动声源发声特性的影响,该文选取空气、氮气及水蒸气3种介质,通过数值模拟的方法研究这3种气体作为介质驱动气动声源发声时的声音特性。研究发现,相同参数下,空气作为介质驱动声源发声时,声压级最高,频率最低;氮气作为介质发声时,其声压级和频率数据与空气相近;水蒸气作为介质驱动声源发声时,声压级最低,频率远远高于其余两者;声源发声时,声场空间分布明显,在谐振腔正后方(0°~15°方向)声压级最大,均在150dB以上,且声场分布特性与气体介质类型无关;声源发声效率随进气压力的增大而减小,但是水蒸气作为介质时的下降速率明显更大。此外,声源发声时,声音纯音度达81%~86%,其中空气纯音度最高,水蒸气最低。结果表明:不同密度的气体介质驱动气动声源发声时的声压级及声频也会有所不同。

In order to explore the influence of gaseous media on the sound characteristics of air-jet generator. Air, nitrogen and water vapor were selected as the media of air-jet generator, and the acoustic characteristics gained by numerical simulation was used to explore the effect of gas media on influence of the acoustic characteristics of the air-jet generators. The simulations were carried out with the same parameters. The result showed that the sound pressure level(SPL) of air-jet generator was the highest and the acoustic frequency was the lowest while the air was driving generator. Taking nitrogen as gas media, the SPL and acoustic frequency were like the air. After the media was changed into water vapor, the SPL reduced and the acoustic frequency significantly increased. The acoustic directivity was obvious with the air-jet generator running, the biggest SPL which exceeded 150 dB occurred in the direction behind the cavity(0°-15°) and it was not affected by the type of gas media. It is worth noting that the acoustic efficiency was decreased with the inlet pressure increasing. Moreover, the tonal amplitude of three gas media were ranging from 81%~86%. It shows that the sound pressure level and acoustic frequency of the air-jet generator driven by gas media of different densities will also be different.