深海条件下面向冲蚀行为的自振射流特性调制及建模方法研究

Self-oscillating jet has broad application prospects in the exploitation of deep-sea mineral resources. Modulating the jet characteristics according to different impingement and cavitation behaviors is the key issue to better apply the self-oscillating jet technology in deep sea mining.Currently, the study of modulation mechanisms of self-oscillating jet in complex deep-sea environment is imperfect. And impingment and cavitation behaviors of collecting objects with different physical properties are not studied intensively. In this project, the acoustic oscillation theory model containing different frequencies and amplitude of fundamental wave and harmonic components is established firstly based on the study of hydroacoustic characteristics of self-oscillating jet device. Secondly, the kinetic parameters of the actual jet are obtained using the detection method and time-frequency analysis method, which are used to modify the above mentioned theorectical model to a self-oscillating jet model with time-variant characteristics. On the basis of the above studies the interaction mechanisms between jet impingement and cavitation behaviors and the physical properties of seabed mineral resources, deep-sea environment conditions and cavitations are studied, and the characteristic parameters that match with different impingement and cavitation behaviors are proposed. Finally, the self-oscillating jet modulation model concerning impingement and cavitation behaviors is estabilished. This research is contributive to the accomplishment of the self-oscillating jet theory and will provide necessary theoretical basis for the application of this technology in the deep-sea area.

自振射流在深海矿产资源开采领域具有广阔的应用前景。实现不同冲蚀行为下射流特性的调制是自振射流技术在深海资源开采应用中的关键问题。目前，深海复杂环境下自振射流调制机理尚不完善，且对于不同物性采集对象的冲蚀行为缺乏深入研究。本项目将通过自振射流装置水声学特性研究，建立包含不同频率、振幅基波及其谐波分量的射流装置声谐振荡理论模型；运用检测手段和时频分析方法，获取实际射流的动力学参数，对上述理论模型进行修正，构建具有时变特征的自振射流模型；在此基础上，探究射流冲蚀行为与海底矿物物性、深海环境条件以及空化作用之间的作用机制，提出匹配不同冲蚀行为的特征参数，建立面向冲蚀行为的自振射流调制模型。研究成果不仅可以完善自振射流理论体系，且为该技术在深海中的应用提供必要的理论基础。

自振射流技术具有强烈的振荡特性和空化作用，是深海资源勘探开发装备中的关键技术，在结核采集系统中发挥了重要作用。针对围压下自振射流频率特性及冲蚀行为研究过程中存在的关键问题，本项目从射流装置声谐振荡模型、自振射流频率时变模型、面向冲蚀行为的自振射流调制模型等方面展开研究。首先，对射流装置的声谐固有频率特性开展理论分析，基于装置结构的声学特性，采用多种建模方法建立理论模型，探明装置声谐固有频率的宽带特征及频率范围。其次，提出一种基于管道流体压力信号的自振射流特性检测方法，将压力传感器从高压釜内移至高压釜外的前端管路上，使其不受实验围压的影响，据此搭建高围压自振射流特性检测平台，实现了高围压下自振射流特性的获取。通过围压下自振射流冲击试验，获取自振射流的全频谱结构，揭示了射流自激频率的影响因素及变化规律，最终建立实际射流的频率模型；对射流高频振荡模态进行了深入分析，依据三波共振理论确定射流自激频率及斯特劳哈尔数，通过研究斯特劳哈尔数的影响因素及变化规律，获得了斯特劳哈尔数随空化数的变化关系，进而建立实际射流自激频率的估算模型。基于自振射流冲蚀试验，获得自振射流冲蚀效果随环境参数的变化规律，定义了自振射流的三种冲蚀模式，并研究得到不同冲蚀模式的演化规律及生成机理，结合射流声谐共振特性，分析得到射流冲蚀行为与高频振荡特性的联系。基于高速粒子图像测速技术展开可视化研究，进一步探究了不同喷嘴结构下的自振射流涡环演变及流场特征，探究了喷嘴孔口结构对自振射流流场及涡环特征影响规律，揭示其内在机理。本项目研究成果不仅完善了自振空化射流理论体系，并进一步推动了该技术在高围压下的应用。