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首页> 外文期刊>Journal of Sound and Vibration >Effect of noise reducing components on nose landing gear stability for a mid-size aircraft coupled with vortex shedding and freeplay
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Effect of noise reducing components on nose landing gear stability for a mid-size aircraft coupled with vortex shedding and freeplay

机译：降噪部件对中型飞机前起落架稳定性的影响以及涡流脱落和自由游动

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摘要

In the pursuit of quieter aircraft, significant effort has been dedicated to airframe noise identification and reduction. The landing gear is one of the main sources of airframe noise on approach. The addition of noise abatement technologies such as fairings or wheel hub caps is usually considered to be the simplest solution to reduce this noise. After touchdown, noise abatement components can potentially affect the inherently nonlinear and dynamically complex behaviour (shimmy) of landing gear. Moreover, fairings can influence the aerodynamic load on the system and interact with the mechanical freeplay in the torque link. This paper presents a numerical study of nose landing gear stability for a mid-size aircraft with low noise solutions, which are modelled by an increase of the relevant model structural parameters to address a hypothetical effect of additional fairings and wheel hub caps. The study shows that the wheel hub caps are not a threat to stability. A fairing has a destabilising effect due to the increased moment of inertia of the strut and a stabilising effect due to the increased torsional stiffness of the strut. As the torsional stiffness is dependent on the method of attachment, in situations where the fairing increases the torsional inertia with little increase to the torsional stiffness, a net destabilising effect can result. Alternatively, it is possible that for the case that if the fairing were to increase equally both the torsional stiffness and the moment of inertia of the strut, then their effects could be mutually negated. However, it has been found here that for small and simple fairings, typical of current landing gear noise abatement design, their implementation will not affect the dynamics and stability of the system in an operational range (F-Z <= 50 000 N, V <= 100 m/s). This generalisation is strictly dependent on size and installation methods. The aerodynamic load, which would be influenced by the presence of fairings, was modelled using a simple vortex shedding oscillator acting on the strut The stability boundary was found to remain unaltered by vortex shedding. Significantly however, the addition of freeplay in the torque link was found to cause shimmy over the more typical operating conditions studied here. Unlike the no-freeplay case, there was a suppressed stabilising effect of increased torsional stiffness of the strut caused by the presence of fairing. No interaction between the vortex shedding and the freeplay on the stability threshold was observed. (C) 2015 Elsevier Ltd. All rights reserved.
机译：为了追求更安静的飞机，已经在识别和减少机身噪声方面做出了巨大的努力。起落架是进近时机身噪声的主要来源之一。通常认为，添加噪声消除技术（例如整流罩或轮毂盖）是减少这种噪声的最简单解决方案。着陆后，降噪组件可能会影响起落架固有的非线性和动态复杂行为（摆振）。此外，整流罩会影响系统上的空气动力学负载，并与扭矩连杆中的机械自由运动相互作用。本文提供了一种具有低噪声解决方案的中型飞机前起落架稳定性的数值研究，其模型是通过增加相关模型结构参数来建模的，以解决附加整流罩和轮毂盖的假设影响。研究表明，轮毂盖对稳定性没有威胁。由于支撑杆的惯性矩增加，整流罩具有去稳定作用，而由于支撑杆的扭转刚度增加，整流罩具有稳定作用。由于扭转刚度取决于固定方法，因此在整流罩增加扭转惯性而扭转刚度几乎没有增加的情况下，可能会产生不稳定的效果。替代地，对于整流罩要均等地增加扭转刚度和支柱的惯性矩的情况，有可能彼此抵消。但是，在这里已经发现，对于小型且简单的整流罩，这是当前起落架噪声消除设计的典型特征，它们的实施不会影响系统在运行范围内的动力和稳定性（FZ <= 50 000 N，V <= 100 m / s）。这种概括严格取决于大小和安装方法。通过使用一个作用在支柱上的简单涡旋脱落振荡器来模拟受整流罩的存在影响的空气动力学载荷。发现稳定性边界不受涡旋脱落的影响而保持不变。然而，重要的是，在此处研究的更典型的运行条件下，发现在扭矩连杆中增加自由游隙会引起摆振。与没有自由活动的情况不同，由于整流罩的存在，支柱的抗扭刚度增加的稳定性受到抑制。没有观察到涡旋脱落与稳定性阈值上的游隙之间的相互作用。 （C）2015 Elsevier Ltd.保留所有权利。

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