【作者】 吴亚东；

【导师】 杜朝辉；

【作者基本信息】 上海交通大学 ， 动力机械及工程， 2009， 博士

【摘要】 动静干扰和尾迹是叶轮机械主要的非稳定流场形式,采用尾缘吹气能够降低动静干涉噪声、降低下游叶片的疲劳损失和降低机组总的气动噪声等,研究和掌握其流动特性和流动控制方式,对提高机组的整体性能意义重大。实验测量和数值模拟是研究叶轮机械内部流场的两种基本方法,随着科学技术的发展,各类先进的测量技术的不断发展,如热线风速仪和粒子图像测速仪,为实验研究提供了新的测量方式;同时计算机性能的飞速提高和计算流体力学技术的日趋完善,基于求解三维粘性Navier-Stokes方程的数值模拟方法为叶轮机械内部流场的研究提供了强大的手段。本文正是通过实验测量和数值模拟相结合的方法来研究尾缘吹气对低速风机气动噪声的影响。本文主要研究内容和研究成果如下:1、根据研究的要求,设计加工了实验用静子模型,并设计了静子尾缘吹气的装置,保证了静子尾缘吹气的连续性和均匀性,使静子尾缘在不同吹气条件下,能达到所需要的尾迹特征,即纯尾迹、弱尾迹、无动量亏损尾迹、喷射四种尾迹特征。2、根据国家通风机空气动力学性能测试标准,搭建了性能测试试验台,得到了在静子尾缘不同吹气条件下模型风机系统的空气动力学性能曲线,性能结果表明,静子尾缘吹气在吹气流量为模型风机设计流量的1.8%时达到无动量亏损尾迹时,动叶的气动性能变化不大,说明静子尾缘吹气对动叶的气动性能基本没有影响。3、使用热线风速仪和PIV测量了静子尾迹区的详细流动特征,得到了纯尾迹、弱尾迹、无动量亏损尾迹、喷射四种尾迹的流动特征。通过轴向速度分布、湍流长度尺度分布、尾迹特征长度等重要的尾迹参数描述了静子不同尾迹的流动特征。结果表明通过静子尾缘吹气,可以填平速度亏损区,获得无动量亏损尾迹。无动量亏损尾迹可以消除静子尾缘的涡脱落频率以及其谐波值,吹气改变了静子的涡脱落特性,吹气后可以减小静子的尾迹宽度。同时,使用了数值模拟对尾迹区的流动进行了进一步的研究,通过不同湍流模型计算结果的对比,发现SST湍流模型适合模拟尾迹区的流动。通过和实验结果对比,CFD模拟结果和实验结果吻合较好,并从数值计算中提取了速度、压力和湍动能等参数继续描述尾迹流动。4、使用热线风速仪和PIV测量了静子尾迹与动叶相互干涉的流场,得到了静子尾迹在下游动叶排中的传播规律。热线测量结果表明,静子尾缘吹气不但消除了静子尾缘的脱落涡,而且还减弱了下游动叶的周期性影响。通过静子与动叶的全流场数值模拟,详细给出了静子风机系统内的压力分布、涡量和湍动能等参数,对比了纯尾迹和无动量亏损尾迹状态时不同的分布规律。数值计算和PIV测量结果都揭示了静子尾迹在动叶流道内的传播规律,通过静子尾缘吹气,使动叶的入口流场均匀,速度波动较小。5、利用声级计和频谱分析仪测量了静子尾迹与动叶相互干涉的总声压级、噪声频谱,得到了模型风机系统噪声辐射的特性。对模型风机系统噪声预测方法采用CFD+FW-H混合方法,使用尾缘涡脱落噪声模型和Lowson关于离散频率噪声的点力模型预测了纯尾迹和无动量亏损尾迹与动叶相互作用的宽频噪声和离散噪声,实验测量和噪声预测结果均表明静子尾缘吹气能够降低系统的噪声,尤其离散频率噪声降低较为明显,最大降低幅度为3.65dB,而对宽频噪声的影响较小。6、提出和尝试了尾缘脉动吹气,使用数值模拟进行了初步的研究。并使用噪声预测模型预测了脉动吹气时脉动尾迹与动叶相互作用的噪声。结果表明,脉动吹气可以降低高阶处离散频率噪声值,从而降低离散频率噪声。更多还原

【Abstract】 Stator-rotor interaction and wake are the main unsteady flows of turbo machinery. The interaction noise between stator and rotor and high circle fatigue of rotor blade downstream will be reduced, and the total noise performance of the whole machine set will be improved using trailing edge blowing (TEB). It is very important to study and master the flow characteristic and control method of trailing edge blowing to improve the overall performance of the turbo machine set.Experimental measurement and numerical simulation are the two basic methods to study the internal flow of turbo machinery. With the development of technology, various advanced measurement techniques come forth to serve for the investigation, such as Hotwire Anemometer (HWA), and Particle Image Velocimetry (PIV), which supply experimental study for the new method and device of measurement. Meanwhile, with the rapid development of computer performance and gradual perfection of computational fluid dynamics (CFD), numerical simulation method based on solving 3D viscous Navier-Stokes equation supply a powerful tool for the investigation of internal flow of turbo machinery. Experimental measurement and numerical simulation are combined to study the effect of trailing edge blowing towards a low speed axial fan in this paper.Main contents and conclusions of the investigation are described in the following:1. According to the demand of study, an experimental stator is designed and manufactured. And the system of trailing edge blowing of the stator is designed to supply continuous and stable air flow for the stator. Under different flow rate of trailing edge blowing, four wake statuses can be obtained, that is pure wake (no blowing), weak wake (some blowing), momentumless wake (blowing adjusted to provide a thrust which exactly cancels the blade’s drag), and jet (more blowing than necessary to cancel the drag).2. The performance test facility is designed in according with the Chinese National Standard GB1236-2000. The aerodynamic performance curves of stator-rotor system under different trailing edge blowing rate are obtained. The results show that the mass flow rate is too small to affect the aerodynamic performance of stator-rotor system. When trailing edge blowing reaches momentumless wake status, the mass flow rate is about 1.8% of the designed flow rate of the rotor.3. HWA and PIV are used to measure the detailed flow of stator wake, the flow characteristics of four wake status are obtained through axial velocity profiles, wake characteristic length scale, turbulence length scale, etc. The results showed that through trailing edge blowing up to momentumless wake, the velocity deficit of the stator wake can be filled. The shedding vortex of stator was reduced through momentumless wake. The vortex shedding frequency and its harmonics are eliminated by trailing edge blowing up to momentumless wake. The turbulence length scale of pure wake is larger than that of momentumless wake, and it become larger with the increasing of axial position, and for momentumless wake case it become smaller contrarily. The wake characteristic length scales of pure wake and momentumless wake become larger with the increasing of axial positions, but at the same axial position, characteristic length scale of momentumless wake is smaller than that of pure wake. That is to say, trailing edge blowing can reduce the wake width of stator. Through the experimental result, the wake flow of pure wake and momentumless wake takes on similarity characteristic. At last, CFD simulation was carry out to simulation the wake flow of stator to gain more information about wake. SST turbulence model is found to suit for the wake flow simulation. And the results from this turbulence model agree well with the experiments. Through the CFD simulation, some information, such as velocity, pressure and turbulence kinetic energy, and so on, is abstracted to describe the wake flow of stator.4. HWA and PIV are used to measure the interaction flow between stator wake and rotor, the spreading rules of stator wake across the rotor row are obtained. The results of HWA measurement shows trailing edge blowing can eliminate shedding vortex of stator and weaken the periodicity effect of the rotor downstream. The results of PIV tests present the wake flow across the rotor row. Through trailing edge blowing, the inlet of the rotor is more uniform, and the fluctuation of velocity is small compared with non-blowing from the trailing edge of stator. A whole simulation including all stator and rotor blades is carried out to calculate the flow field of stator-rotor system with trailing edge blowing. And the results agree well with the experiments. Through the distribution of vorticity, pressure, turbulence kinetic energy, etc, the two wake flows are compared with each other. The results of PIV experiments and CFD simulation results reveal the flow characteristic of stator wake flowing across the rotor row. Through trailing edge blowing, the inlet of rotor can be more uniform, and the fluctuating of velocity is smaller.5. The sound pressure level and noise spectrum are measured using sound level meter and a dual channel real-time frequency analyzer in a semi anechoic chamber. A hybrid prediction method is adopted to predict the noise radiated from the stator-rotor system, i.e. CFD plus FW-H. For the trailing edge noise, the shedding vortex noise model developed by Fukano is adopted. And for the interaction noise between stator wake and rotor, the point force model for discrete frequency noise developed by Lowson is adopted. The prediction results agree well with the experiment. The noise test and noise prediction results show that trailing edge blowing can reduce the noise level, especially the discrete noise level; the effect to the broadband noise level is small.6. Pulsing blowing is brought forward in this paper. And CFD simulation is used for preliminary study. Meanwhile, the noise prediction is made using above noise prediction models based on CFD results. The noise prediction results show that pulsing blowing can reduce high order discrete noise, and then reduce the total discrete noise level.更多还原