分流三通气动噪声偶极子声源特性的数值分析

doi:10.11949/0438-1157.20191145

摘要/Abstract

摘要：

为研究空调通风系统中因存在三通等局部构件而引起的气流再生噪声产生机理，从声源处对其进行控制，采用声学有限元与计算流体动力学相结合的方法，对分流三通局部管段内气动噪声进行分析，获得了管道内表面气动噪声源的强度及其分布规律。探讨了支管前过渡倾角和支管流量分配比对声源强度与噪声传播特性的影响。研究结果表明：当气流流经分流三通管道时，由湍流运动引起的偶极子声源占主导地位，且主要噪声源位于支管处；在支管入口前增加倾角，可削弱声源强度，减少声波向声场传递的声能量，存在某个最优倾角角度使最大声源强度最低；若仅改变支管流量分配比例，声源强度改变，气动噪声主要声源位置不发生变化。倾角与流量分配比变化会导致管道内流体的非定常涡旋运动改变，从而影响到表面偶极子声源强度与噪声传播。

关键词: 空调系统, 三通气动噪声, 计算流体力学, 湍动, 偶极子声源特性

Abstract:

To explore the generation mechanism of airflow regenerative noise caused by the presence of local components such as T-elbow in duct systems and suppress it from the source, the distribution of aerodynamically generated sound on the inner surface of the local component pipe segment represented by the T-elbow pipe were obtained by using finite element method (FEM) and computational fluid dynamics (CFD) method jointly. The strengths and distributions of the aerodynamic sources on inner surface of T-elbows with different inclination angle of branch pipe and different airflow rate ratio of the branch pipe were investigated. Results show that the dipole source caused by the turbulent motion dominates the noise within the pipeline when the airflow through the T-elbow，and the main noise sources are located along the branch pipe. An inclination angle of 30° at the branch inlet can weaken the sound source intensity to the greatest extent and reduce the sound energy transmitted by the sound wave. A change in the flow rate ratio of the branch pipe can not cause the main positions of the aerodynamic sound source to change, but may bring about the change in intensity of sound source accordingly. The changes in the inclination angle and in flow rate ratio may lead to the change of unsteady vortex motion of the flow in the pipeline, thereby affecting the surface dipole source intensity and noise propagation.

Key words: air conditioning system, T-elbow aerodynamic noise, computational fluid dynamics, turbulence, dipole source characteristics

中图分类号:

TU 831

刘雅琳, 王珂, 赵蕾. 分流三通气动噪声偶极子声源特性的数值分析[J]. 化工学报, 2020, 71(S1): 194-203.

Yalin LIU, Ke WANG, Lei ZHAO. Numerical analysis on aerodynamically generated sound dipole source characteristics of shunt T-elbow[J]. CIESC Journal, 2020, 71(S1): 194-203.

图/表 13

图1 计算模型

Fig.1 Computation model

表1 不同网格方案的相关指标比较

Table 1 Comparisons of relevant indices for different schemes of grid configuration

网格数量/个	a (0,1080,1525)			b (0,2060,0)
网格数量/个	压力	速度	最大声压级	压力	速度	最大声压级
570000	-18.13	4.42	66.40	18.87	6.70	62.44
800000	-17.58	4.40	67.46	18.25	6.71	63.56
1040000	-17.56	4.39	67.49	18.25	6.71	63.60

图2 静压等值线与涡量云图（支管流量占比32%）

Fig.2 Static pressure contours and vorticities distributions (branch pipe flow accounts for 32%)

图3 管道内表面偶极子声源分布

Fig.3 Distribution of dipole sources on inner surface of tee pipe

图4 监测点声压级频谱图

Fig.4 SPL spectrum of monitoring points

图5 模拟与文献结果对比

Fig.5 Comparison of simulation and literature results

图6 模型二（α=30°）静压等值线和涡量云图（支管流量占比32%）

Fig.6 Static pressure contours and vorticities distributions of model 2 (Branch pipe flow accounts for 32%)

图7 不同模型下管道内边界偶极子声源分布

Fig.7 Distribution of inner dipole sound sources in pipelines under different model

图8 不同倾角下管道内各频率的声源强度最大值

Fig.8 Maximum sound source intensity at each frequency at different angles

图9 模型一与模型二（30°倾角）监测点声压级频谱对比

Fig.9 Comparison of SPL spectrum between model 1 and model 2 (30° inclination)

图10 压力等值线与涡量云图(支管流量占比20%)

Fig.10 Static pressure contours and vorticities distributions (branch pipe flow accounts for 20%)

图11 不同流量比下管道内边界偶极子声源分布

Fig.11 Distribution of inner dipole source in pipeline with different flow ratio

图12 不同流量比下监测点声压级频谱图

Fig.12 Monitoring point SPL spectrum under different flow ratios

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