| With the rapid development of civil aviation industry,aircraft noise is gradually attracting attention;the increasingly stringent noise regulations on the demand for aircraft power plant noise level has put forward higher requirements.Fans are one of the main sources of noise for civilian large culverts than for turbofan engines;fan afterburner noise accounts for a large proportion of aircraft noise in all operating conditions.Optimizing the external engine culvert shape and laying the external culvert sound lining is the trend and measure to suppress the noise transmitted after the fan,the pipe shape has an important influence on the noise propagation path,and the sound lining is the arrangement of sound-absorbing materials on the sound propagation path,through the optimization of the structure and parameters of the sound lining to achieve the purpose of noise reduction.The main research in this paper is as follows.(1)Noise reduction design optimization of turbofan engine bypass geometry is complicated under the single mode tone noise,considering aerodynamic characteristics which include thrust and mass flow rate.Geometry of bypass duct is designed by coefficients,and gradient computation is solved by continuous adjoint method.Bypass geometry optimization with24 design variables is finished based on steepest descent method.The result of the optimal procedure,the final bypass duct can satisfy both the aerodynamic characteristics and noise request.(2)Optimization design of bypass duct single-degree-of-freedom liner test piece in fan test bench of whole engine is complicated under broadband noise condition.Design variables are chosen as structure coefficients of singledegree-of-freedom liner,then calculation of objective function based on design variables is finished.Response surface of structure parameters to the objective function is established,and optimal structure parameters based on the response surface is completed.Comparison between the optimal structure parameters and the solid wall indicates that noise reduction was obviously achieved. |
