曲率连续造型方法对激波噪声的影响机理

Buzz-saw noise generated by fan/compressor blade tips is one of the main noise sources in high bypass ratio Turbofan engine. To reduce the noise, the detached shock-wave system at the blade leading edge of a relative supersonic and subsonic axial two-dimensional cascade is studied. First, based on the geometric hermit interpolation (GHI) method, a three-segment Bezier curve was proposed to construct a continuous-curvature leading edge, which has higher degree of freedom in modification design. Next, by changing the position of the transition points between the three Bezier curves on the leading edge, the effects of local curvature optimization, overall curvature optimization, and optimization with extra thickness upon the strength of the shock-wave and noise level at the leading edge were explored. A comparison of numerical results showed that the continuous curvature design could decrease the size of the over expanded zone at the leading edge of the blade, thus reducing the reverse pressure gradient. Through local curvature optimization and overall curvature optimization, noise level at one chord length upstream from the leading edge could be lowered by 1.6 dB and 4.6 dB.