RU2236768C1 - Hydroacoustic radiating antenna of towed submersible craft - Google Patents

Abstract

FIELD: linear radiating antennas mounted on board towed submersible craft.

SUBSTANCE: novelty is that axes of sectionalized annular piezoceramic radiators are parallel and in towing they are disposed horizontally to plane normal to towing direction. Each radiator has alternating sections made of piezoceramic and passive material. Young's modulus of the latter is lower by minimum an order of magnitude than that of piezoceramic. Height of radiators is smaller than their diameter and distance between their centers is shorter by half-wavelength of sound propagating in water at operating frequency. Inner cavities of radiators accommodate screens in their diametric planes which are made in the form of acoustically soft plates.

EFFECT: reduced drag and, hence, reduced mass and size of towed craft at same directional properties of antenna.

1 cl, 2 dwg

Description

The present invention relates to the field of sonar, in particular to the creation of radiating linear antennas mounted on towed vehicles under water.

Such antennas are widely used in search active-passive sonar stations of submarines or helicopters to improve tactical and technical data, in particular for measuring the distance to the target.

Known hydroacoustic antennas of underwater towed vehicles, in which annular piezoelectric electro-acoustic transducers are used as emitters, assembled coaxially in a linear antenna whose axis is perpendicular to the direction of towing [1], [2]. Such an arrangement of the antenna is explained by the fact that in order to increase the target search speed, the antenna must be non-directional in the horizontal plane and at the same time possess directional properties in the vertical plane in order to reduce the level of reverberation interference.

The patent [1] describes an underwater towed vehicle containing a radiating antenna, which is covered by a hollow body with a cable-cable fixed to it. A radiating antenna is a linear antenna assembled from a series of ring emitters, the heights of which are smaller than their diameters and located coaxially at equal distances from each other, less than half the wavelength of sound in water at the operating frequency. In the working position, when towing the device, the antenna axis is vertical.

The main disadvantage of this antenna is its large drag when towing, which is determined by the cross-sectional area of the antenna in a direction perpendicular to the direction of movement. So, at a sonar operating frequency of 1.5 kHz (the characteristic frequency in the search mode), the average diameter of an individual ring emitter, which is part of it and made of piezoceramic TsTBS-3, is about 70 cm. This size, along with the total height, determines the transverse area section of the antenna in a plane perpendicular to the direction of towing. A large frontal resistance leads to increased loads on the towing cable-cable, a decrease in towing speed, and to certain difficulties when lifting the underwater vehicle to the deck of the ship after the end of work.

According to the largest number of common features with the invention, the hydroacoustic emitting antenna of the underwater vehicle according to the patent [2] is selected as a prototype. The patent describes a vertical linear antenna assembled from a series of annular piezoceramic sectioned emitters, in which the height is less than the diameter and installed coaxially and equidistantly at a distance from each other less than half the wavelength of sound at the operating frequency. Each emitter is equipped with an acoustic screen designed to form a radiation pattern. Screens (reflectors) are installed on the outer surface of the emitters. Each screen covers about half of the side (working) surface of one emitter. The screens of two adjacent emitters are located on their opposite sides. Thus, each group of emitters alternately emits an acoustic signal towards the port side of the underwater vehicle, and the second toward the port side. Thus, according to the authors, the bearing on the target is unambiguous in the direction of the left and right sides when receiving an acoustic signal reflected from the target.

The main disadvantage of the prototype as well as the analogue is the large drag of the antenna for the reasons mentioned above. The situation is aggravated by the fact that the outer screens increase the outer diameter of the emitters and, consequently, the antenna, that is, increase its cross-sectional area in a plane perpendicular to the towing direction. At the same time, it should be noted that at low operating frequencies of modern towed search sonars, comprising 1-2 kHz, the outdoor screens are inefficient, and as a result, the radiation pattern differs little from a circular one, as a result of which the bearing on the target is not unambiguous.

The task of the invention is the creation of a highly effective sonar emitting antenna of an underwater towed vehicle, which provides reduced drag when towing.

To solve the problem in a hydroacoustic emitting antenna of an underwater towed vehicle containing a number of piezoelectric sectional ring emitters, the height of which is less than the diameter, located equidistantly, while the distance between their centers is less than half the wavelength of sound in water at the operating frequency, and acoustic screens, new features have been introduced, namely: annular piezoceramic sectioned emitters are installed so that their axes are parallel and when towed horizontally o in the plane normal to the towing direction, part of the sections is made of passive material, the Young's modulus of which is at least an order of magnitude smaller than the elastic modulus of piezoceramics, and the acoustic screens are installed in the inner cavity of the ring piezoelectric sectioned emitters and are made in the form of plates of acoustically soft material fixed along the axes of these emitters and placed in diametrical planes.

The technical results from the use of the present invention are a significant decrease in drag when towing a hydroacoustic emitting antenna and, as a result, a decrease in the weight and size characteristics of the towed vehicle while maintaining the directional properties of the radiating antenna, in particular, close to a circular radiation pattern in the horizontal plane.

The achievement of these technical results is explained by the following. The proposed arrangement of ring emitters with a height of an individual ring emitter less than its diameter (usually the height is not more than half the diameter), allows to reduce the cross-sectional area of the proposed antenna in a plane perpendicular to the direction of towing, and, therefore, to reduce drag, at least twice as compared to the prototype. However, with this arrangement of the ring emitters in the proposed antenna, one should also fulfill other conditions necessary for its normal and efficient operation.

Firstly, it is necessary to reduce the so-called wave size of the emitters in diameter. It is known that the diameter (D) of an annular radiator is related to its resonant (actually working) frequency by the ratio

D = C _k / π f,

where C _k is the speed of sound in the material of the emitter (piezoceramics);

f is the resonant frequency.

At the same time, the wavelength of sound in water λ _in = C _in / f, where C _in is the speed of sound in water. From these relations it is easy to obtain the expression D = C _k λ _in / π C _in .

For the commonly used composition of piezoceramics TSTBS 3-titanate-lead zirconate C _k = 3200 m / s, for water _C = 1500 m / s. Hence, D = λ _in / 1.5.

In the proposed antenna, this size determines the minimum distance between the centers of individual emitters. With such a distance between the centers of individual emitters, greater than λ _in / 2, during operation of the antenna, additional maximums of the radiation pattern in the vertical plane are formed, close in magnitude to the main maximum. This is extremely undesirable, as it reduces the energy characteristics of the antenna, in particular the concentration coefficient.

A reduction in the wave size of an individual emitter is achieved by using piezoceramic rings, in which some sections of the piezoceramics are replaced by flexible sections of passive material with a Young's modulus of at least an order of magnitude smaller than the elastic modulus of piezoceramics [3].

Secondly, it is necessary to ensure radiation of the signal in the direction of the ends (in the traverse directions of the antenna) so that the radiation pattern in the horizontal plane remains close to circular.

A circular pattern is achieved by using internal acoustically soft screens. Screens located in the inner cavity of the annular emitter, due to the complex interaction of their individual elements, water cavities and the oscillating surfaces of the annular emitter, provide radiation to the ends of the emitter, which allows to obtain a directivity pattern of the antenna in the horizontal plane close to circular.

The invention is illustrated in figure 1 and figure 2, while figure 1 schematically shows the proposed antenna, and figure 2 is an annular piezoceramic sectioned emitter in section.

The antenna in this particular embodiment consists of two ring piezoelectric sectioned emitters 1 with acoustic screens 2. The emitters 1 are attached to each other by metal strips 3 and are connected to the body of the towed body using a flange 4. The electric signal is supplied to the emitters 1 by cables 5. Each emitter 1 contains a ring glued from piezoceramic sections 6 of the composition of TsTBS-3 (lead zirconate-titanate), alternating with sections 7 of passive material. In this example, a PTK brand textolite whose Young's modulus is an order of magnitude smaller than the elastic modulus of piezoceramics was selected as a passive material. Each emitter 1 is sealed with a layer of compound 8 based on polyurethane and an external sealing layer of rubber 9. Acoustic screens are installed in the internal cavities of each emitter. They are made in the form of plates 10, fixed along the axes of each emitter 1 and placed in its diametrical planes. Each plate 10 is a composite structure containing a rubber layer with cylindrical channels filled with air (acoustically soft layer), and thin outer layers of metal, providing mechanical strength and tightness of the structure [4].

The antenna works as follows. An electrical signal is sent via a cable 5 to the ring emitters 1. Due to the inverse piezoelectric effect, the emitters 1 have alternating mechanical tensile-compression stresses and they begin to oscillate. The oscillations of the ring piezoelectric sectioned emitters 1 create an acoustic signal that is radiated into the environment (water). This signal is used to detect the target and determine the distance to it.

This design of the antenna of an underwater towed vehicle can significantly reduce drag when towing a radiating antenna while maintaining the basic parameters, in particular, close to a circular radiation pattern in the horizontal plane. At an operating frequency of 1.5 kHz, the emitter diameter was reduced from 0.7 m to 0.45 m, which ensured normal (without large additional highs) antenna patterns in the vertical plane. At the same time, the height of an individual emitter (antenna width) was 0.22 m. This means that the drag of the proposed antenna decreased by more than 3 times compared with the drag of the prototype (width 0.7 m). Reducing drag allows you to increase the towing speed of the antenna, i.e. expand the tactical capabilities of the sonar station, for example, reduce the time required to survey a given water area. This allows us to consider the problem of the invention solved.

Sources of information

1. The Federal Republic of Germany patent No. 19719306 A1, 12.11.98, according to class 63 V 21/66, G 01 S 7/521, Towed vehicle.

2. The patent of Germany No. 19516727 C1, 22.02 96, according to class G 01 S 7/521, Underwater sound emitter.

3. R.P. Pavlov, Z.P. Shalaeva. On the efficiency of cylindrical transducers with a periodic structure. "Report at the IX All-Union Acoustic Conference, Moscow, 1977.

4. V.E. Glazanov. Shielding of hydroacoustic antennas, pp. 57-87. L .: Shipbuilding, 1986.

Claims (1)

A hydroacoustic emitting antenna of an underwater towed vehicle, containing a series of annular piezoceramic sectioned emitters, the height of which is less than the diameter, located at distances between their centers, less than half the wavelength of sound in water at the operating frequency, and acoustic screens, characterized in that the annular piezoceramic sectioned emitters are installed so that their axes are parallel and when towing are located horizontally in a plane normal to the direction of towing, each ring The piezoelectric ceramic sectional emitter consists of alternating sections made of piezoceramics and passive material, whose Young's modulus is at least an order of magnitude smaller than the elastic modulus of the piezoceramic, and the acoustic screens are installed in the inner cavity of the ring piezoelectric ceramic sectioned emitters and are made in the form of plates of acoustically soft material, fixed along the axes of annular piezoceramic sectioned emitters and placed in their diametrical planes.

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