Acoustic Analysis of the Transfer Parameters of Leading Edge Serration as an Application for Low Pressure Axial Fans

前缘锯齿传递参数在低压轴流风机中的声学分析

• 批准号: 427028547
• 负责人: Professor Dr.-Ing. Frank Kameier
• 金额: --
• 依托单位: Fachbereich Maschinenbau und Verfahrenstechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/427028547?language=en
• 关键词: Acoustic; Analysis; Transfer; Parameters; Leading

At high-turbulent inflow conditions, the blades of axial fans are known to emit a significantly increased amount of leading edge broadband noise due to the impingement of turbulent structures on the solid surface. Recent research has firmly confirmed sinusoidal leading edges (Leading Edge Serrations) to be an effective passive treatment in both, noise reduction and in increasing specific parameters of the aerodynamic performance. However, albeit intended for turbomachinery, fans and blowers, Leading Edge Serrations were up to now mainly analysed in rigidly mounted settings by investigating the noise radiation of mostly NACA65(12)-10 high-lift aerofoils. This project aims at describing the acoustic and aerodynamic effects of Leading Edge Serrations as an application for low-pressure axial fans but also considering a more universal transfer to axial flow machines in general. In particular, it aims at defining and quantifying transfer parameters from the rigid to the rotating frame and focusses on insights in the underlying physical principles, leading to a noise reduction. In order to benefit from the previously carried out extensive analyses of rigidly mounted aerofoils with leading edge serrations, NACA65(12)-10 aerofoils are utilised and scaled accordingly to serve as rotor blades of a low-pressure axial fan, where the rotor itself allows for an exchange of the blades and a continuous adjustment of the stagger angle. With this purpose a test rig according to DIN ISO 5136 and ISO 5801 is established, allowing to measure both, acoustic and aerodynamic performance of the fan simultaneously. Subsequent to analyses with straight rotor blades, leading edge serrations are introduced by varying the serration amplitude and wavelength in order to define the noise reduction capability and to draw conclusions on transfer losses from the rigid to the rotating domain. During the further procedure, the complexity of the rotor in form of blade sweep and skew is increased successively to gain knowledge on possible masking effects and to assign noise reduction phenomena to the tested influencing parameters.Consecutively, Leading Edge Serrations are increased in complexity by adding additional design parameters, such as a flow-specific spacing and alignment of serration amplitude and serration wavelength in accordance to the fan design point. Leading Edge Serrations featuring secondary amplitudes and a combination of serrations and porous materials are tested in a one-to-one scale in a rigid setting using phased-array beamforming as well as in the rotating setup, giving direct conclusions on the efficiency and losses/ winnings due to the transfer.

在高湍流入流条件下，已知轴流风扇的叶片由于湍流结构在固体表面上的撞击而发出显著增加的前缘宽带噪声量。最近的研究已经坚定地证实了正弦前缘（前缘锯齿）是一种有效的被动处理，既能降低噪音，又能提高空气动力学性能的特定参数。然而，尽管前缘锯齿是为涡轮机、风扇和鼓风机设计的，但到目前为止，主要是通过研究大多数NACA 65（12）-10高升力翼型的噪声辐射，在刚性安装的情况下进行分析。本项目旨在描述前缘锯齿的声学和空气动力学效应，作为低压轴流风扇的应用，但也考虑到更普遍的转移到一般的轴流机器。特别是，它旨在定义和量化从刚性到旋转框架的传递参数，并专注于基本物理原理的见解，从而降低噪音。为了从先前对带有前缘锯齿的刚性安装翼型进行的广泛分析中获益，使用NACA 65（12）-10翼型并按比例缩放，以用作低压轴流风扇的转子叶片，其中转子本身允许更换叶片并连续调整交错角。为此，根据DIN ISO 5136和ISO 5801建立了一个测试台，可以同时测量风扇的声学和空气动力学性能。在对直转子叶片进行分析之后，通过改变锯齿幅度和波长引入前缘锯齿，以确定降噪能力，并得出从刚性域到旋转域的传递损失的结论。在进一步的过程中，转子的复杂性以叶片掠角和偏斜的形式连续增加，以获得关于可能的掩蔽效应的知识，并将降噪现象分配给测试的影响参数。因此，通过增加额外的设计参数，前缘锯齿的复杂性增加，例如根据风扇设计点的锯齿幅度和锯齿波长的特定于流动的间隔和对准。具有次级振幅的前缘锯齿以及锯齿和多孔材料的组合在刚性设置中使用相控阵波束形成以及在旋转设置中以一对一的比例进行测试，从而直接得出关于传输效率和损失/收益的结论。