The effect of hemispherical surface on noise suppression of a supersonic jet

Abstract

High pressure gas venting operations, known as blowdowns, such as from natural gas pipelines, are known to produce significant noise. One device which has shown some potential for noise abatement is a hemispherical acoustic reflector, which has been observed to be effective for pressure ratios from 2 to 4. However, typical pipe-line venting operations occur at pressure ratios far exceeding this. Therefore, the present study aims to experimentally investigate the influence of hemispherical noise reduction reflector on sonic jet flows at pressures more typical of pipeline venting operations. Results of experimental noise measurements from blowdowns with and without two different size acoustic reflectors are presented. The smaller acoustic reflector was found to strongly interact with the jet, in a manner making it unsuitable for extended use without a significant increase in structural support. The larger reflector showed levels of noise reduction on par with those seen at lower pressures. This suggests that acoustic reflectors of suitable scale, when appropriately structurally supported, are a suitable noise reduction method for the high pressure venting typical of blowdown operations.