Design Method for Noise Reduction of Outer Duct of Turbofan Engine

Abstract

The invention discloses a noise reduction design method for an external bypass of a turbofan engine. The method comprises the steps of 1, finding out a locally optimal external bypass shape by using an adjoint method; 2, jointly optimizing a resistance value and a reactance value of an acoustic liner on the local optimal external bypass shape, and establishing a coupled database of the external bypass shape and the resistance and reactance values of the acoustic liner, namely, obtaining a certain amount of shape parameters and resistance and reactance value sample points by using an experimental design method; 3, performing calculation on all data points according to objective functions of shape and acoustic liner optimization to obtain values of the corresponding objective functions, and establishing a coupled response surface of the objective function values; and 4, achieving a globally optimal noise reduction effect under a combined action of shape optimization and acoustic liner optimization. According to the method, a large amount of design parameters can be processed, so that the noise reduction design time is greatly shortened.

Description

technical field [0001] The invention relates to a noise reduction design method for a turbofan engine. Background technique [0002] With the rapid development of the civil aviation industry worldwide, more and more attention has been paid to the noise problem, and the noise standards of civil aircraft have become increasingly stringent. Judging from the distribution of noise sources at each noise airworthiness observation point, for modern civil aircraft, the fan noise is the main noise source when the aircraft is circling, side-flying and approaching. [0003] Compared with the calculation of the engine bypass, the noise propagation calculation of the turbofan engine bypass is still a research hotspot and difficulty in the field of aerodynamic noise. The main complication is that a shear layer occurs between the external duct fluid and the external flow. Intrinsic aerodynamic instability occurs in shear flow (Kelvin-Helmhotz, Kelvin-Helmhotz instability wave). And it in...

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Problems solved by technology

[0007] 3) In the paper "Shape optimization of a general bypass duct for tone noise reduction using continuous adjoint method", Qiu et al. aimed at the single-frequency single-mode single-tone noise in the external duct of the engine, and derived the continuous adjoint equation based on the acoustic perturbation equation (APE) and continuous adjoint boundary conditions, which further improves the adjoint optimization method, but the adjoint optimization method can only obtain the local optimal low-noise external channel

The development of external duct noise reduction design theory and tools that can handle a large number of design parameters is crucial; however, there is no theory and method that is easy to operate and can efficiently carry out external duct noise reduction design with a large number of design parameters

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