Application Of CFX In The Propagation Characteristics Of Acoustic Modes Calculate For Duct

The acoustics modes studied in this paper is a special acoustic phenomenon caused by the coupling of stator and rotor blades in turbo machines,and the fluctuation pressure formed by the acoustics modes in the duct and the turbo machines may cause damage to the blades due to transient forces.By understanding and analyzing the propagation mechanism of acoustics modes in turbo machines,a more secure and low-noise turbine mechanism can be developed.The current acoustic analysis software includes Vone,Sysnoise and Actran.These software mainly solve the phenomena of vibration and noise,acoustic and vibration coupling,acoustic fatigue,etc,but has not had the good numerical simulation analysis for the acoustic fluids.The preliminary research shows that the commercial software Ansys CFX can perform numerical calculations of sound modulus propagation and can add fluid motion to numerical calculations.Therefore,this paper will gradually explore the ability of CFX to calculate sound modulus propagation.The main work of the thesis is:(1)The pressure transfer equation of acoustic wave in cylindrical coordinate system was calculated based on the equation of acoustic wave transfer.The most important work is to fit the Bessel equation under different modal numbers(8),9)),and to use the calculated Bessel equation as the boundary condition in the initial calculation of CFX to explore the characteristics and mechanism of the transmission of different acoustics modes in the duct.By using CFX,the acoustic propagation modes and cutoff frequencies of duct with different wall conditions are numerically simulated and the accuracy of CFX to acoustic performance is validated.(2)This thesis analyzed the conditions of producing sound pressure reflection and resonance in duct,and probes into the characteristics of the transmission of acoustics modes in duct,mainly probes into the characteristics of CFX in different duct lengths and different modulus,and shows the extension of CFX to acoustic performance calculation.(3)By coupling sound with fluid,the transfer characteristics of acoustics modes under different working conditions were analyzed.The pressure attenuation of the sound fluid in the direction of propagation and the influence of the fluid on the wavelength of the sound in the Gaumach are mainly explored.In addition,the influence of different wall conditions and turbulence on the attenuation of sound pressure was demonstrated respectively,and the limitation of CFX calculation under large turbulence was obtained.The results show that CFX can accurately calculate the characteristics of acoustics modes in the duct,and can show the reflection and resonance in the duct.Under the condition of fluid participation,CFX can still maintain satisfactory results.Because there is no method based on CFX to study the transmission of acoustics modes in duct,this paper discusses the acoustic simulation of CFX duct in detail,which provides the best guidance and advice for computing and facilitates engineers to do further research in this area.