Evaluation of the possibility of creating means of active protection of water areas based on the use of the electrohydraulic effect.

Evaluation of the possibility of creating means of active protection of water areas based on the use of the electrohydraulic effect..

ANTSELEVICH Mikhail Aleksandrovich, Doctor of Technical Sciences
UDINTSEV Dmitry Nikolaevich, Candidate of Technical Sciences

ASSESSMENT OF THE POSSIBILITY OF CREATING MEANS OF ACTIVE PROTECTION OF WATER AREAS BASED ON THE USE OF ELECTROHYDRAULIC EFFECT

Previous publications [17, 18] noted the importance of creating means of active protection of objects from water areas.

The main methods of counteracting underwater saboteurs (UD) are still diving surveys and preventive grenade throwing. The analysis showed the extreme scarcity of the arsenal of technical means of detection in water and the almost complete absence of technical means of active influence on the intruder in the water.

Currently, the main and most effective way to combat PD is an underwater explosion. The search for ways to protect against a shock wave (SW) has allowed the development of means that only weaken its effect. But the use of such methods of implementing the impact of SW, such as preventive grenade throwing, to protect objects is ineffective.

Considering that the peculiarity of these objects is the presence of a large amount of relatively cheap electrical energy (EE), it is most expedient to affect the PD either directly with it, or to find a way to most economically convert it into another form. For example, into mechanical.

Conversion of EE into mechanical energy without intermediate links with a high efficiency factor (EFF) can be implemented on the basis of the electrohydraulic effect (impact). The electrohydraulic effect is a pulsed electrical discharge in a liquid, during which a rapid, almost instantaneous, release of energy occurs in the discharge channel. As a result, the pressure in the discharge channel significantly exceeds the external pressure, the channel quickly expands, which leads to the emergence of a shock wave and liquid flows.

It has been documented [16] that electrical discharges in water were carried out more than 200 years ago, and the powerful hydrodynamic impulses that arose did not find practical application at that time. The discovered effect was forgotten for a long time. Later, as electrical engineering developed, when creating powerful high-voltage electrical installations (transformers, disconnectors, etc.), they again encountered electrical discharges in liquids used in these installations as dielectrics. The destructive effect that occurs during electrical breakdown of dielectric liquids formed a persistent opinion about the futility and even harmfulness of electrical discharge in liquid. For many decades, this opinion remained among scientists and electrical engineers.

In 1950, L.A. Yutkin [2] proposed using hydrodynamic impulses generated by an electric discharge in a liquid in technological processes. Thus, the “Method for obtaining high and ultra-high pressures” was invented. An electric discharge in a liquid is nothing more than an electric explosion. The high pressure generated by an electric explosion is transmitted through the liquid into the environment. L.A. Yutkin’s proposals for using the “electrohydraulic effect,” as the author of the invention called it, turned out to be very timely and were immediately in demand.

During the research of the processes occurring during electric discharge in liquids and the applied use of accompanying effects, more than 70 dissertations were defended, and hundreds of inventions were made at the same time. Licenses for a number of technologies were sold to Great Britain, Hungary, Germany, Spain, the USA, Japan and other countries.

Currently, this effect has found the widest application from compaction and crushing of reinforced concrete to waste recycling and metal processing [2, 3, 11, 13, 14].

Usually, an electrohydraulic unit consists of an energy storage NE (Fig. 1), a charger ZUand a technological unit TB containing a certain volume of liquid, a system of electrodes SE between which a pulse discharge is created, and a processed object located near the discharge channel K. The energy storage device, as a rule, is a battery of high-voltage pulse capacitors with a capacity of C. The capacitor bank is connected to the electrode system in the technological unit through a spark gap P, the presence of which allows charging the C tank to the required voltage from the ZU charger with a relatively small current. The technological unit may be absent and a movable electrode system immersed in a borehole filled with liquid or in a reservoir may be used instead.

 Fig. 1. Structural diagram of the electrohydraulic unit

It has been established [16] that electrical discharges in water are characterized by a significantly lower rate of energy release than in explosions of solid explosives (SE). Thus, electrical discharges in water usually occur over a period of tens to hundreds of microseconds. The time of energy release during an explosion of SE lies within the range from several microseconds to several tens of microseconds.

As a result of previously conducted studies [13, 14, 16], a connection was established between the energy stored in the storage device and that released in the discharge channel (in TNT equivalent). Thus, depending on the discharge conditions, 1 kW h or 3.6 MJ of energy stored in the storage device correspond to the energy of 72? 300 g of TNT released in the discharge channel:

W (kW•h) = G/(0.072   0.3) » 10G (1)

W( J) » 3.6х107хG, (2)

where W is the energy stored in the accumulator, kW•h or J;
G is the energy released in the discharge channel (in kg of TNT).

The dependence of the maximum pressure at the shock wave front on the TNT equivalent of the charge and the distance to the point in question is determined by the ratio [1, 12]:

, (3)

where P is the maximum pressure at the shock wave front, kg/cm2;
R is the distance to the point in question, m.

Based on the known relationship (1) and (2) of the stored energy with the released energy and the dependence (3) of the maximum pressure at the shock wave front on the TNT equivalent of the charge and the distance to the point in question, relations (4) and (5) were obtained, linking the energy stored in the accumulator with the maximum pressure at the shock wave front and the distance to the point in question.

(4)

(5)

The physiology of the impact of an underwater explosion on a person is a well-studied area [3, 4, 5, 6, 7]. It has been established that a shock wave causes the most severe damage to those human organs that have uneven density of their components or that contain air: the lungs, stomach, intestines, bone sinuses and auricles. In the lungs, with strong impact of a shock wave, ruptures of the lung tissue are found. The intestines receive severe damage in those places where individual air bubbles accumulate.

Analysis and generalization of the results of the studies conducted to date [3, 4, 5, 6, 7] made it possible to substantiate the pressure values ​​at the shock wave front corresponding to different thresholds of the physiological impact of an underwater explosion on a person. Thus, at an excess pressure of 0.2 — 0.3 kg/cm2, a person begins to feel a shock wave (Table 1). The threshold of pain occurs at 1 — 1.5 kg/cm2. For an intruder equipped with a lightweight diving suit, the shock wave pressure that leads to shock corresponds to 4 kg/cm2. 20 kg/cm2 is the shock wave pressure that leads to death. When using an anti-explosion suit, respectively 16 kg/cm2 and 40 kg/cm2.

Table 1. Thresholds of physiological effects of an underwater explosion on a person

From the graph shown in Fig. 2, it is clear that 9 kWh of EE stored in the accumulator is sufficient to cause damage within a radius of 10 meters from the point of discharge of the PD in an anti-explosive suit.

 
Fig. 2. Dependence of the maximum pressure at the shock wave front on the energy stored in the accumulator and the distance to the point in question

To justify the possibility of creating active protection means for water areas based on the use of the electrohydraulic effect, it is necessary to evaluate the weight and size parameters of the installation and its energy characteristics.

The element of the electrohydraulic installation that has a decisive influence on its weight and size parameters is the capacitor bank serving as an energy storage device. The capacity of the capacitor bank:

C=2Wи/U2, Ф (6)

where Wи is the energy of a single pulse, J;
U is the operating voltage of the installation, V.

The power consumed by the installation from the network is equal to the power of the charger:

, (7)

where h is the efficiency of the installation;
f is the pulse repetition frequency, Hz.

For example, for a unit with an operating voltage of 10 kV, a pulse repetition frequency of f = 0.01 Hz, capable of creating a shock effect in 1000 m3 of water, the capacity of the storage tank C = 8200 μF. Its mass, when implemented on high-voltage pulse capacitors K41I-7 [10], is 4920 kg with a volume of about 3 m3. The power of the charging device is 7 kW.

As an example, we will compare the cost of current expenses for defeating underwater swimmers with existing and proposed means. One of the hand grenades used for preventive grenade throwing RGD-5 has a radius of destruction of a swimmer equipped with an anti-explosive diving suit equal to 5 m. Its cost is about 70-80 rubles. To ensure a similar effect when using an electro-hydraulic strike, 1 kW•h of EE is sufficient, which has a cost of about 0.15 — 0.3 rubles per 1 kW•h, which is more than 200 times cheaper. An approximate estimate of the cost of such a technical means, the cost of its maintenance, on the one hand, and the costs of training and maintaining personnel, obtaining and storing ammunition, on the other, suggests that the costs can be recouped in no more than 10 years.

A patent has been received for a means of active protection of water areas based on the use of the electrohydraulic effect [15].

In order to reduce energy costs, improve the weight and size indicators and expand the functional capabilities of the means of active protection of water areas based on the use of the electrohydraulic effect, it is necessary to develop:

• a method for calculating the rejection of an intruder by an electrohydraulic strike;
• a method for calculating designs of linear parts allowing to concentrate energy in the required direction;
• methods of integration with detection means;
• circuit and design solutions of the source and converter of EE of the linear part of this means.

In conclusion, the authors express their gratitude to academician Salamakhin T.M. for the provided consulting assistance.

Literature

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