﻿ 基于减小气泡直径的水下排气降噪技术
 舰船科学技术  2023, Vol. 45 Issue (10): 1-4    DOI: 10.3404/j.issn.1672-7649.2023.10.001 PDF

Research on underwater exhaust noise reduction technology based on microbubbles
ZHANG De-man, ZHAO Jun-tao, DENG Peng, ZHANG Lu-jing, WANG Bo
Wuhan Second Ship Design Research Institute, Wuhan 430064, China
Abstract: When the gas is discharged underwater, it will produce large noise and affect the working performance of the underwater device. The bubble diameter formed in the process of underwater emission is an important factor affecting the noise. In this paper, the diameter of underwater exhaust bubbles is reduced by means of bubble generator exhaust and water flow scouring. Through high-speed micrograph and underwater exhaust noise measurement experiments, the process of bubble formation in the process of underwater exhaust and the influence of different exhaust bubble diameters on noise are studied. The experimental results show that the bubble generator and the method of water flow scouring can effectively reduce the bubble diameter and exhaust noise. The low-frequency noise can be reduced by flow scouring, but the high- frequency noise will increase with the increase of flow velocity.
Key words: underwater exhaust     microbubble     noise
0 引　言

Minnaert[6]等研究结果表明，气体排入水中形成气泡的直径大小可由式（1）计算得到，其主要受水密度、气体密度、排气口直径等因素影响。

 $D = 2 \times {\left( {\frac{{3{D_0}\sigma }}{{4\left( {{\rho _l} - {\rho _g}} \right)g}}} \right)^{\frac{1}{3}}}。$ (1)

 $V = {V_e} + Q{\tau _f}。$ (2)

1 水下排气气泡生成特征试验 1.1 气泡生成器介绍

 图 1 气泡生成器示意图 Fig. 1 Schematic diagram of bubble generator

1.2 气泡生成过程高速显微摄像试验台架

 图 2 气泡生成过程高速显微摄像试验台架 Fig. 2 High speed micro camera test bench for bubble generation process

1.3 不同通气缝长度时气泡生成过程

 图 3 通气缝长度为2 mm气泡形成过程 Fig. 3 Bubble formation process with vent joint length of 2 mm

 图 4 通气缝长度为1 mm气泡形成过程 Fig. 4 Bubble formation process with vent joint length of 1 mm
1.4 水流冲刷的影响分析

 图 5 不同水流速度时气泡尺寸 Fig. 5 Bubble size at different water velocities

2 水下排气噪声测试试验

2.1 试验台架

2.2 试验结果

 图 6 气泡生成器与管路排气噪声对比图 Fig. 6 Comparison diagram of exhaust noise between bubble generator and pipeline

 图 7 水流对排气噪声的影响 Fig. 7 Influence of water flow on exhaust noise

3 结　语

1）采用气泡生成器可以有效降低水下排气时气泡的直径，通气缝长度为2 mm时气泡直径为1.5 mm左右，通气缝长度为1 mm时气泡直径为0.5 mm左右。

2）减小排放气泡直径可以降低中低频排气噪声，气泡直径越小，排气噪声越小。总排气流量为60 m3/h时，相对于内径为25 mm的管路直接排放，采用通气缝长度为2 mm排气装置排放时排气噪声降低18 dB，采用通气缝长度为1 mm排气装置排放时排气噪声降低21 dB。

3）采用水流冲刷的方法可以使排气气泡直径进一步降低，并降低低频排气噪声，增加0.3 m/s水流时，噪声总级降低了6 dB。但是水流增大时，水流自身的中、高频噪声会随之增大，总噪声降低幅度较小，水流从0.3 m/s增加到0.9 m/s，总噪声降低2 dB。

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