Research On Directivity Flextensional Ring Shell Transducer

Low-frequency active sonar,low-frequency long-range communication,deep and distant sea exploration and other fields have put forward urgent demand for small size,low-frequency,broadband,deep water,directional emission sound sources in recent years.The flextensional transducer is a kind of low-frequency and high power transmitting transducer which is widely used in underwater.There are many types of structure forms.The flextensional ring shell transducer is one of the low-frequency transmitting transducers with high quality factor and outstanding performance.This paper mainly studies how to realize the directional emission performance in deep-water under the conditions of low-frequency,small-size and high power of flextensional ring shell transducers.In this paper,it propose a structural form using two classes of flextensional ring shell transducer to achieve directional emission and an free flooded structure to achieve deep water operation,and finally design a directional flextensional ring shell transducer that can achieve excellent performance of low frequency,small size,broadband,high power,deep water,and directional emission.For technical advantage of flextensional transducer is to achieve low-frequency and high power emission,but generally due to the small-size,usually without directivity,and because of its own strength of the shell is hard to work under high pressure,pressure compensation is also difficult to do work of more than 500m depth,liquid type and free flooded and have their own performance flaws and difficulty of work,therefore,how to realize the deep-water,directional emission in conditions of low frequency and high power,is the key technology of expanding flextensional transducer applications.Flextensional ring shell transducer as one of the performance more superior types,this paper mainly study how the flextensional ring shell transducer surrounded by conditions of low frequency,broadband,high power to achieve deep water and directional emission.The details are as follows:Firstly,this paper presents a theoretical analysis of how the flextensional ring shell transducer can achieve low frequency,high power and broadband emission.The theoretical analysis shows that:the vibration frequency of the circular shell can be effectively reduced by using piezoelectric rings;broadband emission can be achieved by using the modal coupling of the second-order and third-order bending vibration of the shell;the output power and electroa-coustic efficiency can be improved by using the V-shaped circular shell driven by the mosaic rings;the directional circular shell can be achieved by using the superposition of the monopole and dipole acoustic radiation vibration modes of the upper and lower flextensional ring shell transducer.The free flooded structure can realize the deep water work of the directional flextensional ring shell transducer.On this basis,the structural model of the free flooded type directional flextensional ring shell transducer is determined,and the expected advantages are analyzed.On this basis,the finite element model of the pointing flextensional ring shell transducer is established,the performance advantages of the structural form using the class of flextensional ring shell transducer are calculated,the influence of structural parameters on the low-frequency emission performance of the pointing circular shell bent-tension transducer is analyzed,how to realize the cardioid pointing by using the acoustic radiation mode superposition is simulated,and the influence law of the main structural parameters on the pointing is analyzed.Finally,the schematic prototype of a directional flextensional ring shell transducer is optimized and designed.The electroacoustic characteristics of the schematic prototype in air and water are simulated and calculated,and it is verified that the directional flextensional ring shell transducer can achieve low frequency,high power,broadband and directional emission.Then,based on the above analysis,the finite element model of the free flooded directional flextensional ring shell transducer was established,and the influence of the location,dimension and quantity of the free flooded hole on its low-frequency performance was analyzed.On this basis,the transducer prototype was designed.The electro-acoustic characteristics of the principle prototype in air and water are simulated and calculated,and it is verified that the free flooded directional flextensional ring shell transducer can achieve low frequency,broadband,higher power,deep water,and directional emission.Finally,the principle prototype of the directional flextensional ring shell transducer was developed,which can have both air-backed and free flooded operating modes.The principle prototype of the directional flextensional ring shell transducer in both modes of operation was subjected to hydroacoustic measurements,and the test results showed that:the low frequency resonant frequency of the directional flextensional ring shell transducer was 320Hz,the maximum transmitting voltage response value at the resonant frequency was 123.1dB,the maximum transmitting voltage response in the bandwidth of 1600Hz-3800Hz was about 147dB,with an undulation of about 7dB,and the general amplifier The measured sound source level is not less than 170dB,and the maximum sound source level is not less than 195.8dB,which is better to achieve the low frequency,broadband,and larger power emission characteristics;the low frequency resonant frequency of the free flooded type directional flextensional ring shell transducer is 350Hz,and the maximum transmitting voltage response value at the resonant frequency is 109.5dB,and the maximum transmitting voltage response in the bandwidth of 1000Hz-4000Hz is about 141dB,and the minimum transmitting voltage response is about 130dB,with deep water,low frequency,broadband and high power transmitting characteristics.In addition,the two operating modes of the directional flextensional ring shell transducer developed in this paper are able to form low-frequency cardioid directivity using the superposition of acoustic radiation modes.The test results show that the maximum crater depth of cardioid directivity at 450Hz of the directional flextensional ring shell transducer reaches-15dB;the maximum crater depth of cardioid directivity at 360Hz of the free flooded directional flextensional ring shell transducer reaches-16dB,both forms of transducer have good unidirectional radiation sound field distribution.The test results show that the directional flextensional ring shell transducer has excellent low-frequency,broadband,high-power performance,through the structural design and mode superposition can also achieve deep water,low-frequency directivity characteristics,worthy of in-depth research,and combined with the actual application needs to further expand the application field.