Electrohydrodynamic equipment

Electrohydraulic effect is a new industrial method of transforming of electrical energy into mechanical one, produced without mediating of the intermediate mechanical links, with high efficiency.

The essence of this method consists in the fact that at realization in bulk of the fluid which is in an open or barred bulb, specially generated pulsing electric discharge round allowed band of its formation there are hydraulic pressures, capable to commit the useful mechanical operation and tracked by the complex of physical and chemical appearances.

The essence of electrohydraulic effect is an earlier unknown appearance of sharp magnification of hydraulic and hydrodynamic effects and amplitude of percussion at realization of pulsing electric discharge in ions conductive fluids under condition of the maximum linear shrinkage of pulse duration, as much as possible steep front of a pulse and a pulse shape, close to aperiodic one.

It means, that the major factors determining originating of an electrohydraulic effect are amplitude, front steepness, form and duration of an electrical pulse of current. The current pulse duration is metered in microseconds, therefore the instantaneous power of current pulse can reach hundreds thousands of kW. A current pulse front steepness determines the velocity of spreading of the discharge channel. When applying voltage to discharge welding rods in some tens kilovolts the amplitude of a current in a pulse reaches tens thousands of amperes. All it conditions a sharp and significant ascending of pressure in the fluids, provoking in its turn a powerful mechanical effect of the discharge.

Realization of electrohydraulic action relates to a rather slow accumulation of energy in a power source and its almost instant release in liquid medium.

The basic operating factors of electrohydraulic effect are high and superhigh pulsing hydraulic pressures, resulting in emersion of shock waves with acoustical and hypersonic velocities; significant pulsing movements of bulks of fluids produced with velocities reaching hundreds of meters per second; powerful cavitations processes of pulsewise origin, capable to encompass rather great volumes of fluid; infrasonic and hypersonic emissions; mechanical resonance phenomena with amplitudes allowing to realize mutual shelling of multicomponent solid bodies from each other;

All these factors allow exerting rather miscellaneous physical and chemical effects on fluids and objects placed in it.

Technology equipment

Electric hydraulic hammer drilling units:

crushing principle: electrohydraulic

instantaneous pulse power: up to 1 gW

frequency of pulses: 1 to 10 Hz

generator power supply: 400V, 50 Hz

input power: up to 10 kW

Equipment:

a) Pulse generator

b) Granulating machine

Borehole electrohydrodynamic equipment:

Performances:

Maximum pulse energy (discharger), 1 kJ

Frequency of pulses, 0,1-10 Hz

Submersible (borehole) instrument (discharger):

Length, 2500 mm

Diameter, 78 mm

Weight, 20 kg

Cable requirements: high-voltage monoconductor with puncture isolation up to 60 kV

Operating conditions: up to 150 atm

Power source:

Power 6 kW

Three phase supply voltage 400V/50Hz

Output voltage 30 kV

Charge current 200 mА

Adjustable discharge circuit.

Borehole module:

Discharge Power 1 kJ.

Capacitors charge voltage 30kV

Capacitors charge current 200mA

Adjustable discharge circuit.

Velocity of well water treatment is 1-3 metres per minute.

Module diameter - 76 mm

Module length - 2500 mm

Water treatment of solid deposits from interior surfaces of metallic tubes in wells

Deposits of 8-10 mm width
Tube (steel) of 150 mm diameter
Destruction of deposits and separation of large pieces of deposits from pipe walls

Discharge of 500 J, frequency of 1 Hz.

In 10 seconds a mass separation of deposits from pipe walls starts.

In 15-25 seconds deposits are separated completely from pipe walls.

Essence of electrohydraulic effect

Realization of electrohydraulic action relates to a rather slow accumulation of energy in a power supply source and its almost instant release in liquid medium.

The basic operating factors of electrohydraulic effect are high and superhigh pulsing hydraulic pressures, resulting in to emersion of shock waves with acoustical and hypersonic velocities; the significant pulsing movements of bulks of fluids produced with velocities reaching hundreds of meters per second; powerful cavitation processes of pulsewise origin, capable to encompass rather great volumes of fluid; infrasonic and hypersonic emissions: mechanical resonance with amplitudes, allowing to realize mutual shelling of the multicomponent solid objects from each other ;

All these factors allow exerting of rather miscellaneous physical and chemical effects on fluid and objects placed in it.

Branches of application of electrohydrodynamic technics (equipment)

Thanks to particular features, EH-technics allow to carry out effectively problems not solved or solved with difficulties by traditional methods. EH-technics help to solve problems in engineering industry and machinery reconditioning, in agriculture and melioration, in construction and in extraction of minerals, in mining and hydrometallurgical production, in medicine. Some concrete instances are mentioned below.

Manufacturing engineering

As it is known, in engineering industry details and their stock material are produced more often by casting, drop forging, welding, powder pressing. Let us consider some effective EH-processes used in the enumerated technics.

Casting is produced by pouring hot metal in specially prepared molding boxes. For large details which do not require precise accuracy of dimensions, made of earth (usually consisting of arenaceous quartz) molding boxes are used. After concreting and cooling the cast should be extracted from the molding box by means of special shakers. However the sand burns and partly remains on the cast. It is especially difficult to remove rods (molding box elements) installed for producing vacuities and openings. Difficulties are related to the fact that the rod is enclosed by molten metal and consequently works at elevated temperatures, not only burns more, but also is fabricated of a stronger material. Traditionally water treatment of casts from the scorched sand is produced by an operator in a breathing mask a with a buster or a pneumochisel (the work is harmful and unproductive).

A EH-technology allowing to solve the problem efficiently [1; 2] was designed. The cast is installed on a grating which is descended to tank with water, electrodes are connected to cast from above, the earthed cast is effected by discharges. A contraction shock wave, going on through the metallic cast, on boundary turns to an extension wave which shatters the scorched sand and all non-metallic stratifications having other acoustic features. The hydraulic current carries up all exfoliating out of bins and openings.

A crushing serves for cases of refinement (mechanical) of diamonds and solid diamond-like materials, for production of chemically pure powders and relates to resistance capacities of the instrument. EH-crushing solves all problems. A portion of material is loaded to the camera-granulating machine (fig. 3) which is treated in water. At the expense of shock waves effect the material is shattered and crushed. For deriving of fragments of the given size a sieve is installed at the bottom of the granulating machine. EH-process ensures: - Refinement of fragments of solid materials (diamonds, carbides, nitrides, ceramics, elbora) to 1-10 microns; - production of sharp unrounded facets indispensable in production of abrasive tools (for example, adamantine drills); - High chemical cleanness of the crushed material (water is the process working tool).

Water treatment from technological and production stratifications.

The problem of strife with stratifications, produced on midwalls of tubes of various devices is widely known. Special problems appear at the usage of hard (containing salt of calcium, predominantly lime carbonate) waters water supply and in calorific heaters (heat sinks, dryers, boiler equipment). "Hardness" salts are being precipitated during the water boiling, which produces strong deposits similar marble by its properties. This sediment (often called as incrustation) obstructs currents, having the thermal conductivity in 200-300 times worst, sharply lower a convective heat exchange (at 3 mm of of a sediment width - power loss amounts to 25 ). EH-discharges a tube filled with water, or on a tube in a tank with water easily shatter deposits which then are carried up by water current.

Agriculture and melioration

Boulders on fields sometimes cannot be removed out of the field - they should be shattered on site. Usage of explosives results in pollution of the field with splinters. The EH-technology ensures shatterproof breaking down of rocks of several cubic meters. Openings-boreholes of 25 mm in diameter and 500 mm length are drilled in stones. The borehole is filled with water, and an exploder (it can be two insulated cables the extremities stripped of which are installed with the set interval) is installed. There is produced a discharge which shock wave reshapes a fracture and the hydrocurrent moves apart the fracture, ensuring a breaking down that is a splitting of a rock.

Screens of water supply wells are silted in the course of operation i.e. sealed therefore the flow rate (efficiency) drops, frequently such holes should be closed down. EH-treatment of allowed range of the screen by special discharge devices pulled down in the well, produces it unsealing (4). Flow rate augmentation in 2,5-3 times is attained.

Construction

At redesigns there is a problem of breaking down of old reinforced concrete foundations and buildings. Application of explosives without stopping of production and specially in buildings is unsafe, therefore busters are used traditionally. EH-technics frequently helps to solve this problem in shatterproof and secure manner: blastholes are drilled and EH-shocks shatter the integrity of the construction which then is being knocked down faster by means of busters.

Rejected and wasted reinforced concrete articles is a problem of cities and reinforced concrete production plants where about 2-5% of discard were allowed. Breaking down of reinforced-concrete articles by EH-units analogous to the used in water treatment of casting, allows breaking down and utilizing concrete rocks and reinforcement.

cavitation electrohydrodynamic water treatment experiment of precision casting cleaning

Article before the water treatment

Article after the water treatment

Time of water treatment is 3-7 minutes.

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