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Laser optical measurements of the acoustic particle velocity at bias flow liners with grazing flow

激光光学测量偏流衬管处掠流声粒子速度

基本信息

批准号：
196686122
负责人：
Professor Dr.-Ing. Jürgen W. Czarske
金额：
--
依托单位：
Bremer Institut für Messtechnik, Automatisierung und Qualitätswissenschaft (BIMAQ)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2011
资助国家：
德国
起止时间：
2010-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/196686122?language=en
关键词：
Laser optical measurements acoustic particle

项目摘要

For a stable and low-noise operation of a modern jet engine, especially in case of lean combustion, highly efficient sound attenuators with bias flow (bias flow liners) are needed, since on the one hand, the combustion chamber of such an engine tends to suffer from combustion oscillations, on the other hand less air mass flow is available for the damping. However, the optimization of the damping efficiency of these bias flow liners requires a deeper understanding of the physical damping mechanisms. The damping performance of such a liner is determined by complex phenomena of interaction between the incident sound field and the flow field. Therefore, the goal of the research project is to reach a better understanding of these phenomena. For this end, an energy balance of the transfer from the sound field to the flow field is aspired. On the one hand, this necessitates three-dimensional measurements of the acoustic particle velocity and the flow velocity field. To achieve this, the Doppler global velocimetry with sinusoidal laser frequency modulation (FM-DGV) will be applied, which has been proven suitable already during the first funding period. However, the current FM-DGV system has to be extended for volumetric measurements at first. In doing so, it is planned to integrate a high speed camera to increase the efficiency, which represents an alternative to the detector array used so far. Moreover, it is intended to accelerate the signal processing by parallelization. On the other hand, the challenge concerning the evaluation of the velocity fields measured above the bias flow liner is to separate the acoustically induced hydrodynamic oscillations from the primary sound and flow field. For this purpose, different analysis and separation methods (e.g. Helmholtz Hodge decomposition, spectral analysis and wavenumber filtering) have to be tested and to be applied. Here, the aim is to develop the energy transfer from the acoustic to the flow field based on the amount of energy of the separated fields. This transfer will be proven by a comparison with the sound energy dissipation of the liner obtained by microphone measurements. As a last step of this second funding period, the qualified measurement techniques and analysis methodology are applied at a simplified bias flow liner at the specifically built DUCT-R (duct acoustic test rig - rectangular cross section). Using the measured velocity field data, the energy transfer from the sound field to the flow field can be balanced which enables gaining new insights concerning the physical damping mechanisms at bias flow liners.

为了使现代喷气发动机稳定低噪声运行，特别是在稀薄燃烧的情况下，由于发动机的燃烧室容易发生燃烧振荡，另一方面可用于阻尼的空气质量较少，因此需要带有偏压流的高效减声器（偏压流衬板）。然而，为了优化这些偏置流衬垫的阻尼效率，需要对其物理阻尼机制有更深入的了解。这种衬垫的阻尼性能是由入射声场和流场相互作用的复杂现象决定的。因此，研究项目的目标是更好地理解这些现象。为此，期望从声场到流场的能量转移达到平衡。一方面，这需要对声粒子速度和流速度场进行三维测量。为了实现这一目标，将采用多普勒正弦激光调频（FM-DGV）全球测速技术，该技术在第一个资助期已经被证明是合适的。然而，目前的FM-DGV系统必须首先扩展到体积测量。在此过程中，计划集成高速摄像机以提高效率，这是迄今为止使用的探测器阵列的替代方案。此外，它旨在通过并行化来加速信号处理。另一方面，评估偏置流衬板上测量的速度场的挑战是将声诱导的水动力振荡与原始声流场分离开来。为此，必须测试和应用不同的分析和分离方法（例如亥姆霍兹霍奇分解、光谱分析和波数滤波）。在这里，我们的目的是根据分离场的能量大小来发展从声场到流场的能量传递。这种传递将通过与由传声器测量得到的衬垫声能量耗散的比较来证明。作为第二个资助期的最后一步，合格的测量技术和分析方法应用于专门建造的duct - r（管道声学试验台-矩形截面）的简化偏置流衬里。利用测量的速度场数据，可以平衡从声场到流场的能量传递，从而使人们对偏置流衬里的物理阻尼机制有了新的认识。