【作者】 王阳；

【导师】 徐国华；

【作者基本信息】 南京航空航天大学 ， 飞行器设计， 2010， 博士

【摘要】 旋翼气动噪声的计算及降噪方法研究是直升机空气动力学领域具有挑战性的课题。本文一方面开展了旋翼流场CFD方法建模研究,发展了基于FWH和Kirchhoff方程的旋翼气动噪声计算方法和模型,并对旋翼气动噪声特性进行了计算和分析。另一方面,针对大气与地面对旋翼噪声的影响进行了分析,发展了直升机噪声源的分辨方法,同时针对直升机旋翼降噪新方法进行了较深入的研究。主要工作包括以下方面:作为前提和背景,本文首先阐述了论文的研究目的,并对旋翼流场的数值模拟、旋翼气动噪声计算、大气和地面对旋翼噪声的影响、旋翼降噪方法等研究的国内外现状进行了概述,指出了现有研究中存在的不足,提出了本文拟采用的研究方法。为了获得旋翼噪声计算所需的流场信息,本文第二章基于非结构嵌套网格和N-S方程,建立了一个适用于旋翼噪声计算的流场CFD方法,并进行了不同旋翼的算例验证。结合该流场计算方法,本文发展了一个新的基于FWH和Kirchhoff方程的直升机旋翼气动噪声的计算方法和模型。该模型可适合于直升机亚音速至跨音速状态的旋翼气动噪声计算。应用该方法和模型,对不同状态的旋翼噪声特性进行了研究,并分析了桨叶表面粘性力对旋翼气动噪声的影响,得到了一些有实际意义的结果。在上一章的基础上,本文又建立了一个新的用于分析大气吸声和地面声学效应对旋翼噪声影响的模型。该模型改进了NASA用于飞行器地面反射、吸声的传统算法。应用所建立的模型,对旋翼气动噪声在大气中传播及地面的反射、吸声影响进行了计算与分析,获得了一些新的结论。基于二维频谱分析方法,本文还发展了一种从直升机总噪声中分离出旋翼和尾桨噪声的方法,而且针对剪刀式尾桨直升机噪声信号进行了分辨研究,在此基础上分析了剪刀式尾桨的降噪机理。然后,本文着重开展了旋翼噪声的降噪方法研究。在对桨尖控制源的旋翼单极子和偶极子降噪方法进行研究后,推导了一种同相角参考点位于桨毂的旋翼噪声解析表达式,以此为基础,提出了一个新的利用旋翼和尾桨噪声叠加相互抵消的降噪方法。同时,建立新的用于降噪研究的桨-涡干扰噪声简化计算模型。应用该模型对旋翼桨-涡干扰噪声进行了分析,给出了出现强烈桨-涡干扰噪声辐射的飞行参数,研究了通过小范围调整飞行参数来显著降低斜下降飞行桨-涡干扰噪声的方法,得到了一些新的结论。更多还原

【Abstract】 The calculation and debasement for rotor noise is a challenging subject in the field of helicopter aerodynamics. In this thesis, on the one hand, the CFD method for rotor flow field is modeled, and the method for the calculation of rotor aerodynamic noise is developed on the basis of FWH and Kirchhoff equations. By the method, the characteristics of the aerodynamic noise for rotors are computed and analyzed. On the other hand, the effects of the atmosphere and ground on rotor noise are analyzed, and a method for separating the overall helicopter noise is developed. Also, the new methods of helicopter rotor noise reduction are studied. The major contributions of the author’s research work are as follows:As the background of present work, the objectives of the research are firstly described. Then the researches and developments in the domain of numerical simulation of rotor flow field, the calculation of rotor aerodynamic noise, the effects of atmosphere and ground on rotor noise as well as the rotor noise reduction methods are briefly reviewed. The deficiencies in the current research are also pointed out, and the methods used in the present research are briefly introduced.In order to get the detailed information of the flow field for the rotor noise computation, a CFD method which is suitable for the calculation of rotor noise is presented based on the unstructured overset grid and N-S equation, and the comparisons with the available experimental data for different rotors are made to show the capability of the method. Then, a new model for the calculation of helicopter rotor aerodynamic noise is established based on the FWH and Kirchhoff equations, which is suitable for the calculations of subsonic and transonic rotor aerodynamic noise. The properties for rotor noise in different flight conditions are deeply studied by applying the method and model, and the effects of viscous force on the calculations for rotor aerodynamic noise are also analyzed, then some results of practical significance are obtained.On the basis of last chapter, a new model is established for the analysis of atmospheric absorption influence and ground acoustic effects on the rotor noise. The traditional algorithms used by NASA are improved in this model. By the developed model, the effects of atmospheric absorption as well as the ground reflection and absorption on rotor aerodynamic noise are calculated and analyzed, and some new conclusions are obtained. Afterwards, based on the 2-D frequency analysis, a method which can separate main and tail rotor noise from the helicopter overall noise is developed. The method is applied to separate the noise of the helicopter with scissors tail rotor, and the noise debasement mechanism of the scissor rotor is investigated.Then, the noise reduction methods are emphatically studied. The research on rotor noise reduction method, which has control sources of the monopole and dipole on the blade tips, is made. On the basis of method above, a new analytical expression for rotor noise is derived with the reference source location set on the rotor hub. From the new analytical expression, a new noise reduction method is proposed by the use of the cancellation of two noise waves of main and tail rotors. In addition, a new simplified calculation model for BVI noise is established. Applying this model, the BVI noise is analyzed, and the flight parameters causing strong BVI noise are given, then the methods for avoiding strong BVI noise by the slight adjustment of flight parameters are studied and some new conclutions are obtained.更多还原