安装角及雷诺数对压气机叶栅气动噪声特性的影响

发布时间：2019-01-26 12:30

【摘要】：叶型/叶栅的气动参数对压气机气动性能有着很大的影响，研究人员通过实验和数值模拟方法致力于叶型/叶栅气动性能的研究，并取得了详实的研究成果。随着社会和经济的发展，人们对周围环境舒适性的要求越来越高，叶轮机械的气动噪声逐渐成为人们关注热点。因此，叶型/叶栅的流动诱导噪声与气动性能的关系也成为设计者必须了解的问题。气流流经叶栅表面时，形成紊流附面层并发生尾涡脱落，产生的压力脉动作用在叶栅表面，形成偶极子噪声源；当附面层发展到一定程度，或者来流攻角比较大时，叶栅表面将发生明显的流动分离，引起叶栅表面压力脉动特征改变，从而影响叶栅流场辐射噪声。本文在叶栅稠度为1.0的条件下改变安装角获得了三种不同的NACA651210平面叶栅，然后结合计算流体力学和边界元方法数值模拟叶栅通道内的湍流场及流场辐射的噪声，研究安装角、自由来流雷诺数和来流攻角对叶栅通道内非定常流动特征以及叶栅流场辐射噪声的影响。主要工作和结果如下： (1)本文重点研究网格尺度、声源信息采样点长度对流场以及声场计算的影响，并结合前人的实验数据对整个计算方法的精度及准确度进行了验证。 (2)在来流雷诺数为252000、安装角为30°、来流攻角为-5°~20°时，计算叶栅通道内的湍流场以及流场诱导噪声，分析涡量、瞬时流线、叶型尾缘点的压力脉动以及远场声压辐射随攻角的变化规律。计算结果如下：叶型尾缘点的涡脱落频率随着来流攻角的增大而降低，，大的正攻角下，低频脉动占主导成分。攻角为5°时，涡脱落频率呈现出明显的离散特征；而负攻角以及大的正攻角下，呈现出宽频特征。监测点压力脉动幅值随攻角的增大而减小。对于叶栅外场监测点的总声压级，在0°攻角下出现最小值，为6.5dB；攻角为-5°和5°时，总声压级急剧增大；随着攻角增大到5°~20°时，总声压增大趋势变缓。总声压级与阻力系数随攻角的变化趋势并不一致。 (3)在来流雷诺数为252000，安装角分别为45°、60°时，由流场和声场计算信息可知，叶型尾缘点的涡脱落频率随攻角的变化趋势同安装角为30°时基本一致，除负攻角外，涡脱落频率随着攻角的增大而降低。不同安装角下，叶栅外场监测点总声压级均是在0°达到最小值，且安装角为60°时的总声压级较其它安装角增加了近6dB；负攻角下，随着安装角的增大，总声压级逐渐增大；攻角为5°~20°时，安装角为60°的总声压级相对于其它安装角反而降低。结合流场信息，我们可以推测，安装角为60°时，大的正攻角下，叶栅吸力面的耗散现象变得严重，消耗一部分能量，从而使声压级降低。 (4)在安装角为30°，来流攻角为0°时，随着雷诺数的增大，叶型尾缘点的压力脉动幅值增强；外场辐射声压变大；边界层变薄，流动损失降低。
[Abstract]:The aerodynamic parameters of the blade / cascade have a great influence on the aerodynamic performance of the compressor. The researchers have devoted themselves to the study of the aerodynamic performance of the blade / cascade by means of experiments and numerical simulation, and obtained detailed research results. With the development of society and economy, people need more and more comfortable environment. The aerodynamic noise of impeller machinery has become a hot spot. Therefore, the relationship between flow-induced noise and aerodynamic performance of blade / cascade is also a problem that designers must understand. When the air flow through the cascade surface, the turbulent boundary layer is formed and the wake vortex shedding, resulting in pressure pulsation acting on the cascade surface to form a dipole noise source. When the boundary layer develops to a certain extent or the angle of attack is large, the flow separation on the cascade surface will take place, which will change the pressure pulsation characteristics of the cascade surface and affect the radiation noise of the cascade flow field. In this paper, three different NACA651210 planar cascades are obtained by changing the installation angle when the cascade consistency is 1.0. The turbulent field and the noise emitted from the flow field in the cascade channel are numerically simulated by using computational fluid dynamics and boundary element method. The effects of installation angle, free flow Reynolds number and angle of attack on the unsteady flow in the cascade channel and the radiated noise in the cascade flow field are studied. The main work and results are as follows: (1) this paper focuses on the effects of mesh scale, the length of sound source information sampling point and the calculation of sound field. The accuracy and accuracy of the whole method are verified with the experimental data. (2) when the flow Reynolds number is 252000, the installation angle is 30 掳and the attack angle is -5 掳~ 20 掳, the turbulent field and the induced noise in the cascade channel are calculated, and the vorticity and instantaneous streamlines are analyzed. The pressure pulsation at the tip of the blade and the variation of far field sound pressure radiation with the angle of attack. The results are as follows: the frequency of vortex shedding decreases with the increase of the angle of attack, and the low frequency pulsation is the dominant component at the large positive angle of attack. When the angle of attack is 5 掳, the frequency of vortex shedding is discrete, while the negative angle of attack and the large positive angle of attack show wide band characteristics. The amplitude of pressure fluctuation decreases with the increase of attack angle. For the total sound pressure level of the field monitoring point in the cascade, the minimum is 6.5 dB at 0 掳attack angle, the total sound pressure level increases sharply when the attack angle is -5 掳and 5 掳, and the total sound pressure increases slowly with the increase of attack angle to 5 掳~ 20 掳. The variation of total sound pressure level and resistance coefficient with angle of attack is not consistent. (3) when the flow Reynolds number is 252000, the installation angles are 45 掳and 60 掳, the calculated information of the flow field and sound field show that the vortex shedding frequency of the tip edge of the blade shape is basically the same as the angle of attack when the angle of attack is 30 掳, except for the negative angle of attack. The frequency of vortex shedding decreases with the increase of angle of attack. At different installation angles, the total sound pressure level of the monitoring points in the field of the cascade reaches the minimum at 0 掳, and the total sound pressure level at the installation angle of 60 掳increases by nearly 6 dB compared with the other installation angles, and the total sound pressure level increases gradually with the increase of the installation angle under the negative angle of attack. When the angle of attack is 5 掳~ 20 掳, the total sound pressure level of 60 掳is lower than that of other angles. Combined with the flow field information, we can infer that when the installation angle is 60 掳, the dissipation of the suction surface of the cascade becomes serious at the large positive angle of attack, and part of the energy is consumed, thus reducing the sound pressure level. (4) when the angle of installation is 30 掳and the angle of attack is 0 掳, with the increase of Reynolds number, the amplitude of pressure pulsation at the tip of the blade increases, the sound pressure of the external field radiation becomes larger, the boundary layer becomes thinner and the flow loss decreases.
【学位授予单位】：上海理工大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH45

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