为了使低频主动声纳在深海能够利用海底弹射方式探测水下目标，提高声纳作用距离，需要水声发射换能器及基阵的垂直指向性可以偏转，同时发射声源级尽可能高。针对该国家重大战略需求，本项目旨在突破水声发射换能器及基阵的技术瓶颈，研究垂直指向性可调的弛豫铁电单晶溢流环换能器及基阵。研究内容主要包括通过使用弛豫铁电单晶材料构成镶拼溢流环换能器，利用单晶溢流环的径向谐振，替代传统压电陶瓷溢流环的液腔谐振，大幅提高溢流环换能器的发射电压响应和声源级。利用一定特性的声学波导结构，对弛豫铁电单晶溢流环换能器的垂直指向性进行调控，使发射指向性偏转到所期望的方向。建立弛豫铁电单晶溢流环换能器阵的集总参数模型，考虑阵元间的互耦作用，对阵列发射指向性进行优化。进行消声水池和湖上实验，对所研究的原理和方法进行实验验证，使得垂直指向性可调的弛豫铁电单晶溢流环换能器及基阵获得良好的性能，为深海远距离目标探测创造条件。

In order to enable low-frequency active sonar to detect underwater targets by means of bottom bounce of sound in deep sea,and increase the sonar detection range, it is required that the vertical directivity of the underwater acoustic transducer and array can be deflected, and the acoustic source level can be as high as possible.In response to the national major strategic needs, the project aims to break through the technical bottlenecks of underwater acoustic transducers and arrays, and to investigate the free-flooded ring transducers and arrays made of ferroelectric single crystal material with adjustable vertical directivity.The contents of research mainly include the following aspects. First,the ferroelectric single crystal material will be used to form the segmented free-flooded ring transducer. And the radial resonance of the single crystal ring will be used to substitute the conventional liquid cavity resonance of the piezoelectric ceramic ring,in order to greatly increase the transmitting voltage response and acoustic source level of the free-flooded ring transducer.Second,the vertical directivity of the ferroelectric single crystal free-flooded ring transducer will be controlled by an acoustic waveguide structure with a certain characteristic, to make the transmitting directivity deflected to a desired direction.Third, the lumped parameter model of the ferroelectric single crystal free-flooded ring transducer array will be established. The array directivity will be optimized considering the mutual coupling effect among array elements.At last, experiments in the anechoic water tank and lake will be carried out, to verify the principle and methods of the research. The research can make the free-flooded ring transducers and arrays made of ferroelectric single crystal material with adjustable vertical directivity obtain good performance, and create condition for long range target detection in deep sea.