水下高温高速射流噪声机理研究

High temperature and high-speed underwater jet mainly occurs in the firing process of submarine weapons. And it generates strong gas-liquid flow and noise. Underwater jet noises reveal the trail of underwater weapon, and generate bad impacts on military as well as environment. These problems can be attributed to the mechanism of high-temperature high-speed underwater jet noise problem. Here the mechanism of those underwater noises will be studied by experimental and theoretical tools. This project will establish models of underwater nozzle jet noise and bubbles noise, and also develop prediction model of gas-liquid mixing noise. The influences of injection gaseous characteristics (gas flow rate, gas pressure, gas temperature, heat exchange between gas and liquid, gas pulsation) on underwater nozzle jet noise are studied in this project. The influence of main factors, such as gas-liquid temperature difference, gas-liquid flow rate difference, gas-liquid viscosity difference, et al. on bubble group behavior (vaporization, collapse, merge, split) will be further analyzed in this project. And based on the above, underwater high-temperature high-speed jet noise prediction methods will be established, and noise suppression will be achieved. This project will provide not only worthy support for stable prediction of underwater jet noise, but also a practical means to solve similar scientific problems by the development models of jet noise and bubble noise. This is a key problem in academic and engineering application aspects.

在潜射武器发射过程中，发动机向周围水环境排放大量高温气体，形成强烈气液掺混和强烈的水下噪声。高强度噪声容易暴露水下武器踪迹，同时严重破坏我国军事及海洋生态环境影响。这些问题可归结为水下高温高速射流噪声机理问题。本项目拟通过机理实验和理论计算相结合的方法，建立水下射流管口喷注噪声预测模型及射流外围区的气泡噪声预测模型，发展水下高速高温射流噪声预测方法；研究喷注气体特性（流速、压力、温度、气液界面热交换率、气体脉动特性等）与管口喷注噪声的关系；分析气液温差、气液流速差、气液粘度差对单气泡、气泡群行为（汽化、溃灭、合并、分裂）影响规律；形成水下射流噪声预测模型，探索性提出水下气液掺混噪声抑制原理。该研究不仅为预测水下射流噪声的可靠性提供科学依据，研究的管口喷注噪声模型及汽化气泡噪声模型为解决类似的科学问题提供实用性很强的手段，具有重要的学术价值和工程应用价值。

本文以鱼雷排气噪声作为研究对象，针对鱼雷排气的高温、高压和多相特性，研究水下排气噪声的机理及主要影响因素。研究工作为认识鱼雷水下排气噪声机理和水下排气消声器的设计提供了理论基础和实验依据。主要内容包括以下四个方面：.1）建立水下气泡声压模型，分析了气泡演变状态的行为特征及对应的噪声特性（自振及噪声、双气泡耦合振动及噪声、汽化气泡及噪声、溃灭及噪声等）；搭建了气泡噪声测试装置，分析气泡噪声特性及各因素对其影响规律；依据实验数据，验证所提声压模型。结果发现：诸多气泡演变行为中，气泡破裂噪声最大；单气泡振动具有单频特性，气泡之间的相互作用诱发宽频噪声；气泡周边液体汽化导致气泡体积增加，但对气泡振动噪声影响较小。.2）针对鱼雷尾部排气阀的二次噪声问题，建立了排气阀与尾腔的排气噪声CFD计算模型；分析阀口结构和弹簧刚度对二次噪声的影响规律；发现了排气阀小开度下的高频脉动现象，以及开度和排气阀材料对排气尾腔噪声控制的作用规律。.3）针对鱼雷水下排气形成的气液混合噪声，通过数值模拟和水下排气机理实验研究水下气液气液两相流场特性和噪声特性及关键结构和参数对气液流场和水下噪声的影响；研究了排气温度、注入液体对排气噪声的影响规律。重点说明了排气温度对管口喷注噪声及气泡噪声的影响机理，阐述了注入液滴降低排气噪声的原理。.4）针对水下排气的气液混合特性，分析掺混少量液体对排气噪声的影响；设计分离装置，用于水下气-液混排的分离，达到降低排气噪声的目的；设计降噪阀口结构，改变气-液流态，达到降低排气噪声的目的。对结果表明,在气液两相水下排气条件下，消声器降低1000-8000Hz的排气噪声5 dB以上。

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