CAVITATION TREATMENT

CAVITATION TREATMENT

S.I. Fishgal

1977

 ABSTRACT OF THE DISCLOSURE

    A method of producing physicochemical effects in liquids by directing pressurized liquid through a nozzle to form a stationary or pulsing jet entraining a relatively stagnant liquid, melt or gas. The velocity of the jet is sufficiently high increased by its restriction to cause cavitation in the jet itself or in the gap between a stationary or activated (e.g. by an ultrasonic transducer) obstacle. Multiple circular jets can be employed and impinged against each other. A vortex movement of the jet can be provided by a swirl inlet, spiral thread or spiral core of the nozzle.

For jet ventilation prevention, an annular stream is flowed alongside the surrounded jet at lower velocity and has a disc in its exit section. Also for this, an annular relatively hermetic envelope of relatively flexible material can be disposed between the nozzle and the obstacle.

For decreasing losses of jet energy, a substance with long-chain molecules (poly glycol, polyacrilamide, polysterene sulfonate, gelatine, polyethylene oxide, etc.) can be dissolved in the liquid. Cavitation can be enhanced by special temperature and static-pressure regimes and by irradiation providing the liquid with artificial cavitation nuclei.

Many heterogenous processes in liquid-liquid, liquid-solids systems are intensified: emulsification, dispersion (size reduction of suspended solids or destroying the obstacle), mixing, dissolving (including metals and non-metals in melts, e.g. nickel and chromium in steel, graphite in bronze, carbon in iron), mass and heat exchange, homogenizing, degassing (vacuum can be provided), electrochemical and chemical reactions (e.g. wastewater oxidation), special alloying (iron-lead, iron-zinc, copper-lead, aluminum-lead, aluminum-copper, aluminum-cadmium, zinc-tin, cadmium-aluminum-silicon), catalytic reactions (e.g. water-methane mixture with nickel, cobalt or iron catalyst, the result being hydrogen and carbon dioxide; cracking of hydrocarbons with nickel or iron catalyst, the result being hydrogen and carbon; dehydrogenizing of alcohol with nickel catalyst into aldehydes and ketone; oxidation and ozonation of COD-and BOD-containing water with nickel catalyst), spraying and aerosol production, destroying bio-organisms (e.g. bacteria and enzymes), depolymerization, aging of wines and spirits, extraction of biologically active substances (e.g. insulin from pancreas).

The surface treatment of solids is also achieved: impregnation and pressurization, laminating and aczoiling wood, soldering, filling holes and cracks of metallic castings, softening and corning meat, electrodeposition, flash-removing, flushing, polishing, grinding, spheroidizing, descaling, to-size treatment, hardening, cleaning, deburring, drilling, cooling and lubricating cutting tools, cleaning abrasive discs. The liquid therein is non-reactive, reactive or with a mixture of a free abrasive.

If the obstacle is a sieve, filter medium or porous membrane, sieving, filtering and ultrafiltration (reverse osmosis) are enhanced.

 BACKGROUND OF THE INVENTION

    This invention relates to methods of producing physicochemical effects in liquids by directing pressurized liquid through a nozzle-type device (orifice, pipeline or nozzle) to form a jet entraining a relatively stagnant liquid (in a larger chamber). In the treatment of liquids, such known methods are employed for mixing in tanks, piping, combustion, stack exhaust and solids suspension with jet mixers.

The mixing objective of the known jet method usually is to combine feed components, to suspend traces of solids or to blend the tank content. The suspension objective of the known method is generally to maintain the suspension or to eliminate contamination (solids containing in liquid, particularly in case of different bottom of a tank liquids, can settle and build-up a layer in the tank bottom thereby reducing the available tank volume). Jet mixers generally consume more energy than mechanical agitation (e.g. propeller mixers), but their operating and equipment cost can be less expensive.

The main objective of this invention is to widen greatly the possibilities of jet method by producing new physicochemical effects in liquids and solids, the known use of mixing and dispersion being also enhanced. These effects are heterogenous in liquid-liquid and liquid-solids systems: emulsification, dispersion (size reduction of suspended solids or destroying an obstacle), mixing, dissolving (including metals and non-metals in melts), mass and heat exchange, homogenizing, degassing, electrochemical and chemical reactions, special alloying, catalytic reactions, spraying and aerosol production, destroying bio-organisms, depolymerization, waste water treatment, aging of wines and spirits, extraction of biologically active substances, etc.; surface treatment of solids; impregnation and pressurization, laminating and aczoiling wood, soldering, filling holes and cracks of metallic castings, softening and corning meat, electrodeposition, flash-removing, flushing, hardening, cleaning, deburring, drilling, cooling and lubricating cutting tools, cleaning abrasive discs, etc. Sieving, filtering and ultrafiltration (reverse osmosis) are also enhanced.

In some cases, this invention is close to ultrasonic methods, but can be more suitable because of the absence of expensive ultrasonic energy sources. In comparison with known ultrasonic hydrodynamic oscillators (e.g. an ultrasonic whistle), there is no fusible wear or fatigue failure in the vibrating blade and, in many cases, it is possible to work on supercavitation regime without any wear.

SUMMARY OF THE INVENTION

The principal distinguishing characteristic of this invention is that the velocity of the jet is increased sufficiently high to cause cavitation in the jet itself (by restriction, e.g. with a core) or in the gap between a stationary or activated obstacle. Other distinguishing characteristics are enhancing the cavitation regime by special temperature and static-pressure regimes and by irradiation providing the liquid with artificial cavitation nuclei, pulsing the jet, dissolving a substance with long-chain molecules in the liquid, jet ventilation prevention by an annular stream flowing alongside the surrounded jet at lower velocity and having a disc form in its exit section, and by an annular relatively hermetic envelope disposed between the nozzle and the obstacle.

The invention has also many other distinguishing characteristics and objectives which will be more apparent from the followed detailed description, drawings and appended claims.

 IN THE DRAWINGS

   Figure 1 is a schematic diagram of the jet treatment in a tank.

Figure 2 is a design of a submerged nozzle device with a stationary obstacle.

Figure 3 is a design of a nozzle device with mutual colliding jets.

Figure 4 is the same as above with a mixing chamber (tank).

Figure 5 is a schematic diagram of cavitation process in the nozzle-obstacle gap.

Figure 6 is an exemplary graph of drainage-to-minimum pressure relationship (Pd/Pmin), the gap-to-nozzle one (h/R) and discharging coefficient (μ) according to Reynolds number (Re) in the nozzle-obstacle gap.

Figures 7 are appropriately the designs of a nozzle device with a swirl inlet, a spiral core and a spiral thread.

Figure 10 is a schematic diagram of producing cavitation in a nozzle with a core cavitator.

Figure 11 is a design of a device with above scheme.

Figures 12 and 13 are appropriately the designs of a nozzle device with the stream surrounding the jet, and with an annular envelope.

Figure 14 is an exemplary graph of decreasing treatment time for gelatine-water (line A) and polyethylene oxide-water (line B) solutions in comparison with that for water in dependence on their concentration.

Figure 15 is a design of a nozzle device with an activated obstacle.

Figure 16 is a design of a device with an obstacle to be destroyed (suspended in the liquid).

Figure 17 is a schematic design of a device for molten metal treatment.

Figure 18 is an exemplary graph of increasing the coefficient of filling the pores of sintered bearings at cavitation impregnation depending on treatment time in comparison with non-cavitation impregnation.

Figure 19 is a schematic view of a means for wood board cavitating jet impregnation.

Figure 20 is a schematic diagram of cooling and lubricating a cutting tool of a lathe.

Figure 21 is a schematic diagram of cleaning an abrasive disc.

Figure 22 is a graph with the percentage lines showing COD reduction depending on treatment time (t) for cavitation treatment (line A), cavitation ozonation (line B), catalytic (nickel) cavitation treatment (line C) and the latter with ozonation (line D).

Figure 23 is a graph with the percentage lines showing BOD reduction depending on treatment time (t) for the last three kinds of treatment.

Figure 24 is a graph with the percentage lines showing the influence of initial COD on treatment time (t) for cavitation ozonation (line B) and catalytical (nickel) cavitation ozonation (line D).

Figure 25 is a graph with the percentage lines showing the reduction of coliform organisms depending on treatment time (t) for cavitation treatement (line A) and the catalytical (nickel) (line C).

Figure 26 is a graph with the percentage lines showing phenol reduction depending on cavitation treatment time (t) with air (line E) and ozone (line B).

Figure 27 is a schematic diagram of ultrafiltration process.

Figure 28 is an exemplary graph of percentage decreasing liquid viscosity according to the quantity (N) of pressure oscillations and to a current-quantity (mc)-of-viscous-additive-to-maximum-one (m_max) relationship.

Figure 29 is a view of a portable installation for cavitation treatment with one tank.

Figure 30 is a design of the nozzle device of unsubmerged type.

Figure 31 is a view of a portable installation with the device of Figure 30, operating with two tanks.

Figure 32 is the same as above with an overhead funnel.

 DESCRIPTION OF THE EMBODIMENTS

    Physicochemical effects in liquid are producedby directing pressurized liquid through a nozzle 1 (Figure 1) to form a jet entraining a relatively stagnant liquid in a tank 2 provided with an outlet 3. The spreading tendency of the jet (its diameter is usually increased on the jet length with 14° angle) causes surrounding liquid to be sucked or entrained into the jet to conserve momentum.

Multiple circular jets can be also employed. In a cross flow they interact with each other in a complicated way. If the orifices are spaced too close together, the jets feed each other and inhibit mixing. In the opposite case, the cross flowing stream may pass between the orifices, thereby bypassing the device.

Either laminar (at the Reynolds number Re<300) or turbulent (at Re>1,000) jets are produced when a liquid flows through an orifice, nozzle or pipeline into a larger chamber. For the common axisymmetric (circular) jets, the characteristic Reynolds number, constant throughout the jet structure, is equal to that at the exit nozzle or orifice. At 300<Re<1,000, some disturbances in the flow are amplified, a developed turbulent flow not being sustained. Mixing by laminar jetting is not effective. A laminar jet of viscous liquid directed into a tank promotes the movement of the tank liquid not mixing, however, with the nozzle one on a molecular scale. Effective mixing takes place only through molecular diffusion occurring at a negligible rate in viscous liquids (unless the nozzle is extremely small).

For suspending the solids in a tank, a highly effective device is a radial wall jet. The latter can be formed by directing an axisymmetric jet flow to a wall and may consist of an axisymmetric free jet, a turning region and the wall jet one.

An open pipe or a nozzle can be centered on the tank axis and placed three nozzle diameters above the bottom of the tank. An impingement plate can be installed to protect the tank against jet erosion.

Mixing and jet penetration intensifies by increasing momentum ratio ρ_nv_n^-2/ρ_sv_s^-2, an orifice diameter and the orifice pitch-to-diameter ratio t/D_n. Here ρ_n and ρ_s are fluid densities appropriately in a nozzle stream and in a cross-stream; v_n and v_s are the velocities of the same streams.

At t/ D_n = 3-4, ρ_nv_n^-2/ρ_sv_s^-2>6 and a mixing cell height-to-diameter ratio H/D_c = 8, good mixing is achieved.

Strongly penetrating jets cause excessive pressure drop and develop an upstream recirculation pattern within the tank. Weak jets do not mix satisfactorily. Mixing is enhanced by swirling jets, but at this their velocity and concentration decay more rapidly. To obtain cavitation regime, the jet velocity is increased sufficiently high.

Cavitation results in formation and subsequent violent collapse of vapor-gas-filled bubbles in a liquid subjected to requisite pressure changes. The formation occurs if liquid is at or below its bubble point pressure. The collapse occurs if liquid is above that pressure. The collapse produces shock waves damaging the mechanical surfaces it contacts.

The solids suspended in liquids are subjected to a steady force which arises since the viscosity of liquid does not remain constant over a pressure cycle with temperature variations. The motion of the particles depends on their size and mass (the larger ones oscillate with smaller amplitude). This amplitude difference also increases probability of mutual collision of the particles.

During the process of forming cavities (gas-vapor bubbles) when local pressure reduces below the gas-vapor pressure, and subjecting the cavities by higher pressure at which they collapse (since the vapor within them condenses and gas dissolves), liquid particles move to the bubble center with great speed. As a result, the kinetic energy of the colliding particles causes local hydraulic impacts accompanied by high temperature and pressure sufficient to damage the hardest material of the solid boundaries exposed to the collapsing cavities.

At high temperature, chemical acting of atmospheric-oxygen bubbles (dissolved air contains 1.5 times more oxygen), electrolytic effect and oscillation fatigue the material. In addition, hydraulic micro impacts destroy the oxidation film delaying metal oxidation in usual conditions.

For the bubble formation, a nucleus is required. It may be a small bubble already existing in the liquid, a small pocket of gas in a crack in the suspended particles or in the wall of the vessel, the particle itself, some defect or void in the structure of the liquid, etc.

As the suspended solids are also nuclei of cavitation, it is very expedient to utilize this phenomenon for their size reduction and dispersing. In this case, the pressure pulses are generated right where they are needed (on the particle surface). This gives a great advantage to this method because the energy for the destruction is transferred directly to the particles and a minimum is lost by divergence of energy. The required one is relatively modest, but is concentrated over a small area and produces very high local stresses (the peak erosion intensity and jet power vary respectively with the sixth power and the cube of the jet velocity).

Any cavitation process is temperature dependent because it depends on the liquid temperature-dependent characteristics. Vapor pressure, surface tension, the diffusion rates of dissolved-in-liquid gases, and chemical activity of liquid increase when temperature is raised, the solubility of gases in the liquid decreasing. The temperature rise may, at first, lower the cavitation threshold and thereby intensify cavitation. The gas content of liquid reduces as the temperature rises and increases bubble compressibility and shock pressure. These actions provoke still more erosion intensification. However, further temperature rise increases the pressure of saturated vapor and lowers the pressure impact of slamming cavities. These contrary effecting factors may cause the optimal temperature interval of cavitation processes.

The dissolution of air is lower in organic-origin liquids (kerosene – 1.25 times, oil – 1.8 times, benzene – 10 times), than in water, and vapor pressure and surface tension are higher (alcohol and petroleum – 3 times, oil – 2). That is why the pressure of cavitation micro impacts and erosion in water are higher (in comparison with kerosene at the optimal temperature – 2 times, benzene – 5, alcohol and acetone – 6).

Higher viscosity liquids slow up the rate of bubble growth and lower cavitation intensity (also, because they have more dissolved air). Liquids of higher density show greater inertia and lower cavitation erosion.

If hydrostatic pressure rises, cavitation slamming pressure and erosion increase. However, sufficiently high pressure can suppress cavitation by raising the cavitation threshold too high. The optimal pressure interval may be 3-5 kgf/cm2.

Cavitation processes are determined by many factors with complicated dependencies. That is why the investigation of the cavitation process cannot give quantitative data of technological efficiency and erosion intensity. This investigation only points out the qualitative nature of the process.

The mechanism of dispersion and emulsification by the jet lies in its tendency to entrain large volumes of surrounding liquid, to move the solid and liquid particles, to create turbulence, to suspend them and to blend liquids. The effect of emulsification can be used not only for the production of new emulsions, but for improving the latter during the operation of the liquid system (water-oil fire-resistant hydraulic liquids, cutting fluids, cooling lubricants, etc.) Here cavitation can be produced by the same means.

For better dispersion (size-reduction) action, the nozzle can be provided with an obstacle 4 (Figure 2) against which the dispersed-in-jet particles are collided. The obstacle 4 is the part of a body 5 provided with slots 6 and a locknut 7 for fixing the distance between the nozzle 1 and the obstacle 4.

To avoid wearing action on the obstacle, the nozzles can be installed against each other (Figures 3 and 4). The jets from the nozzles mutually colliding, the solids are destroyed. In Figure 4 shows the treatment of liquid with a mixing chamber (tank) 2.

In systems with small consumption, pulsating jets can be applied to enlarge the small orifices required to provide the proper jet velocity and susceptible to blockage through dirt ingress, carbon deposit formation and obliteration.

The liquid system is subjected to minor pressure oscillations about the mean pressure level. The significant ones are forced at the nozzle, if the forcing frequency of the volumetric displacement is the resonating frequency.

Jets can be pulsated by known means, e.g. pumps with a pulsed delivery, multipliers, etc.

The submerged jet produces cavitation at the velocity

             v =[2(p_min - p_s)/σρ]^0.5,

where p_min is minimum pressure;

p_s is the sum of pressures of the dissolved gas and saturated vapor;

ρ is liquid density;

σ is cavitation number.

The force of the jet creates a high turbulent zone with a multitude of vortices around the periphery of the jet and shears the surrounding fluid. Low pressures in the vortices centers decrease below the vapor-gas pressure and additional cavities (vortex cavitation) are formed there. This increases the erosion and the dispersion effects.

Also, cavitation can be produced in the nozzle-plate gap (Figure 5) at

 h<0.5R (e.g. 0.1R>h>0.01R);

v>= [2 p_sμ (Re, h)]^0.5,

where h is the gap;

R is the nozzle orifice radius;

μ is discharge coefficient, depending on h and Reynolds number Re (Figure 6).

In many cases, cavitation can arise in regions below curves p_d/p_min (Figure 6) at

             Re = 2h[2(p_min - p_d)/ρ]^0.5/υ >250,

where p_d is drainage pressure;

υ is kinetic viscosity of the fluid.

Vortex cavitation can be also obtained by a nozzle with either a swirl volute inlet (Figure 7), or a spiral core 8 (Figure 8), or a thread (Figure 9). But in this case, collision with the plate is deteriorated.

The bubble cavitation (producing the vapor-gas liquid mixture) and the cloudy one (pulsating bubble systems and dispersed fluid drops) arise at 1>σ >0.5. These two cavitation forms create erosion, noise and the equipment vibration. The most radical means of fighting against this cavitation damage is transition into supercavitation regime (sheet cavitation with sharp interface between vapor-gas and fluid phases) with cavities closing behind the nozzle, but not on the obstacle (σ < 0.5). The supercavitation regime can be easily achieved by placing a core cavitator 8 into the orifice of the nozzle (Figures 10 and 11).

Cavitation intensifies heterogeneous processes in liquid-liquid systems and liquid-solids ones (emulsification, mixing, dispersion, dissolving, mass exchange, homogenizing, chemical and electrochemical reactions, degassing, etc.). In most cases, the rate of heterogeneous processes proceeding on a phase interface depends on the area of the latter. The solids disperse into liquid, and the phase interface is enlarged under the fatigue (described above) and hydro impacts (when cavities slam). Also, a diffusion boundary layer resisting to the transportation of reacting molecules to the phase interface is enlarged, and the products of reactions are carried away.

In a liquid layer adjoining a cavitation bubble, chemical bounds are broken and molecules are ionized, great voltage and electro breakdown arising. As a result, energy-rich free radicals, ionized molecules and ions are formed in cavities. Oxidation-reduction reactions and electrochemical processes are intensified in such a way.

The primary reaction in water:

H₂O -> H + OH.

   That is why due to the electrical discharges of cavitation bubbles, there is a noticeable oxidation by molecular oxygen (although to a lesser degree). Even if oxygen is almost absent, oxygen, hydrogen and hydrogen peroxide are produced.

The predominant reactions of free radicals after the primary water dissociation are the back reactions:

H + OH -> H₂O;

H + H -> H_2;

H₂ + OH -> H₂O + H;

OH + OH -> H₂O₂;

H + H₂O₂ -> H₂O + OH.

   Dissolved substances increase the possibility of other reactions.

Dissolved oxygen greatly increases the oxidation effects of cavitation and promotes direct activation of oxygen:

O₂ + H -> H₂O;

HO₂ + H -> H₂O₂;

O₂ -> O + O.

   The last reaction may be of secondary importance as the concentration of the dissolved oxygen is small in comparison with the quantity of the oxygen of water.

In this way it is possible to explain, e.g. wastewater oxidation under cavitation (see below).

In many cases, cavitation has combining effects (mechanical, physicochemical, etc.) with no visible strict line of demarcation between them. The intensity and duration of cavitation influence at dispersing has to be considerably higher than at emulsifying.

If cavitation occurs close to the atmosphere layer, the air tends to leak into the liquid and cushions the collapse, the shock and destructive force being consequently decreased. To increase the latter, it is necessary to prevent ventilation of the cavities.

If the cavitating jet cannot be submerged into a liquid (e.g. when a surface is treated in the atmosphere), the jet is provided with a surrounding liquid from an annular stream flowing alongside at a lower velocity than the jet (Figure l2). This annular stream has the form of a disc in the exit section created between the nozzle 1 and the body 5.

Another means for preventing the ventilation of the cavitating jet is to provide the nozzle with an annular relatively hermetic envelope 10 (Figure 13) disposed between the nozzle 1 and the obstacle 4. For better sealing, the envelope 10 can be made of a relatively flexible material such as rubber, plastic, canvas, etc.

Large gains in free stream persistence, improving jet characteristics and performance are realized by dissolving 0.3 – 3% synthetic or natural long-chain molecules in the liquid (Figure 14). The beneficial effects of drug reduction up to 40% are known, e.g. from irrigation and fire-fighting equipment, and result in an increase of jet forces, throw distance and volume. Jets containing very small amounts of polymer exhibit less free stream turbulence.

Among liquids with long-chain molecules are polyglycol, polyacrylamide, polystyrene sulfonate, etc.

Experiments, however, show the waste differences in performance. A 3% gelatine-water solution decreases the treatment time by 2 times in comparison with water (line A), whereas a 4% polyethylene oxide-water solution – 3 times (line B).

The obstacle 4 can be not only stationary (as described above), but also activated, e.g., by an ultrasonic transducer 11 (Figure 15). This greatly enhances all processes.

SOLIDS SIZE REDUCTION AND RELATED PROCESSES, PRODUCTION OF SUSPENSIONS AND ALLOYS

    Solids size reduction and related processes (grinding, polishing, spheroidizing, production of suspensions and alloys that cannot be produced by orthodox mixing) have become very important especially. In processing industries, size reduction is necessary for most reactions involving solid particles (because the rate is directly proportional to the area of contact between reacting phases, and size reduction enlarges the surface), for breaking a material (to separate its constituents), for considerable influencing the chemical reactivity and the color and covering power of a pigment, for more intimate mixing, etc.

In powder metallurgy (where solids are made of metallic and other material powders) invented probably by ancient Egyptians to fabricate implements from spongy iron, great progress has been made. In ancient times, products were shaped by hammering after iron-oxide reduction with charcoal. In the 18th century, powder metallurgy undertook work with platinum, in the 19th – the manufacture of incandescent filaments from carbon and osmium. (Later they were made of tungsten). Other early applications are cutting tools (tungsten carbide), magnets, radio tuning devices (iron, copper-nickel, and cobalt), filters, etc. Tungsten, molybdenum, chromium, beryllium, thorium, tantalum and other metallic and alloy powders are prepared for high performance parts, especially in space and nuclear technology. Also, aluminum powder is used not only in chemical processes, but is a component of rocket solid fuels.

The reasons for the use of powder metallurgy in jet-engine and gas-turbine discs and rings, nuclear reactor components, low and medium duty gears, dies, gas and oil drilling tools, cutting tools, filters, etc. include the ability to fabricate refractory, reactive and pure metals and alloys of given chemical consistency, to combine homogenously dissimilar materials not mixed when molten and not forming the solid solutions or intermetallic compounds (iron-head, tungsten-copper), to obtain the useful properties (porosity or permeability, etc.) otherwise not obtainable, to produce in service ready state, and so on.

A significant part of sliding bearings is made by powder metallurgy. These bearings are especially effective for friction units working at a restricted irregular lubrication when a lubrication film forms at the cost of the lubricant located in the pores of the sintered bearings. With the mechanical properties comparable with those of casting bearings, the porous ones have a better ability to be run-in, less friction coefficient, 2-3 times more wear-resistance and can work without regular lubricant delivery.

A newer lubrication technique employs finely ground particles (mainly of graphite-cadmium oxide) drawn into a carrier gas for high-temperature, space and radiation-resistance applications. The technique may be also economical for ordinary applications, e.g. lubricating the cylinder walls of engines in which the suspended particles are burned up during the combustion cycle after performing their duty as the lubricant.

Dispersion fuels (the compounds of small particles of fissionable fuel dispersed in a relatively inert matrix of metal, ceramic or graphite) are a significant part of fuel elements. They are excellent for research and test reactors, military and propulsion applications, etc. because of the high performance, reliability, economy, strength, good corrosion resistance, high thermal conductivity (in high heat flux applications), good fission product retention, dimensional stability in radiation exposure, etc. These properties exceed those of other fuel forms. However, dispersion fuels are difficult to fabricate and reprocess.

The extreme hardness and wear-resistance of diamond give it a high abrasive-grain qualification. Diamonds can be cut (ground) only by diamond dust, whereas other softer materials can have other means. Diamond grain is used as loose and bound. In some cases, pure diamond dust is too fierce and harmful for fine grinding and polishing, and the mixture of diamond dust with other abrasives is applied. Also, metal powder mixed with diamond dust or grain and sintered under pressure is used to form grinding and cutting materials.

This broad significance of powder production explains worldwide efforts devoted to this area, the more so as from the point of view of energy utilization, size reduction is a very bad process with 0.1 – 2% efficiency (supplied energy appears as increased surface energy of the solids) being less for fine products. Many methods of powder making are used: milling, machining, atomization, vapor condensation, reduction of metal oxides, decomposition of hydrides and carbonyls, precipitation, electrolytic deposition, etc.

For dispersion fuels, spheroidizing the fissionable particles is also important and achieved by rounding off corners by attrition of particles against each other. Rough spheroidizing by vibratory shaking is also employed (mainly for uranium dioxide UO₂ and bulk processing).

Colloidal suspensions and emulsions, with particle or droplet sizes less than one micron, are produced by colloidal mills, ultrasonics and jet pulverizers. The latter are also used for spheroidizing wherein solids are pulverized in jets of high pressure (up to 500 psi) superheated steam or compressed air. The pulverizing takes place in a shallow cylindrical chamber with a number of jets introduced tangentially at equal intervals around the circumference. The solid is thrown to the outside walls of the chamber. The fine particles are formed by the attrition and shearing action resulting from the differential velocities within the fluid streams.

In another method, particles are repeatedly driven by a high velocity gas stream through a long helical glass tube. This method is better suited to moderate volume grinding, but its production rate is still only a few kilograms per day. Both metallic and ceramic powders are spheroidized by grinding in the internal grinding wheel, but as to attrition in the helical tube, only ceramic powders are spheroidized because friability is essential to the process.

In all colloidal methods, power consumption is very high and materials should therefore be ground as finely as possible before they are fed to the colloidal process. Both uranium oxides and carbides have been granulated into roughly spherical shape by mixing the powders with a small amount of binder to make the material tacky and then forcing or shaking it through a sieve. The coarse granules are further densified and spheroidized by grinding and sintering.

According to this invention, the size reduction of solids, their descaling, grinding, polishing, spheroidizing, production of suspensions and the like are achieved by the cavitating jets of primary obtained (e.g. by mixing) rough suspension. Cavitation mechanism of acting for such processes has been explained above.

Another means is destroying the obstacle 4 (Figure 16) installed in a holder 12 of the tank 2 with screw leads 13 and 14. Liquid is pumped under high pressure through an outlet valve 15 maintaining excessive static pressure in the tank 2. At this the obstacle is dispersed in the liquid and powder (suspended in the liquid) is produced. Impinging rough suspension jets upon each other (Figures 3 and 4) can be also employed.

Uranium-containing particles treated to obtain dispersed fuels enhance cavitation process by irradiation provided the liquid with artificial cavitation nuclei. The applied liquids can be substantially non-reactive chemically, e.g. water-based or reactive solutions. The latter cause physicochemical effects and are described below.

For the production of metal mixtures (alloys) that cannot be produced by orthodox mixing (e.g. alloys of iron with lead or zinc, copper with lead, aluminum with lead, copper or cadmium, zinc with tin, cadmium with aluminum-silicon alloys, etc.), the breakup and cavitation erosion of suspended solids or an obstacle are applied. At this the melt of fusible metal is pumped through the nozzle and the powder or obstacle of the more refractory metal is added or installed. Therein dispersive effects, grain refinement and degassing are also improve the metal structure. The same procedure can be adopted for increasing the solubility of nickel and chromium in alloy steels, non-metals in melts (graphite in bronze for self-lubricating bearings, carbon in iron, etc.)

The incorporation of a small percentage of lead in aluminum and its alloys gives more malleable metal for lead-bearing alloys. This method is simpler than the orthodox ones incorporating lead in the form of chloride and subsequently reduce this to the metal.

The device for the treatment of metals may consist of a vacuum chamber 18 (Figure 17) with pipes 19 and 20 submerged into a ladle 21 with a liquid metal. The pipes 19 and 20 are equipped with nozzles 1 and electromagnetic induction pumps 22 circulating the metal through the vacuum chamber 18, the ladle 21 and the pipes 19 and 20. Electromagnetic field of the pumps also heats the metal.

Suspensions are used in a large quantity in cosmetic, toilet and pharmaceutical industries and this cavitation process can be applied for production of e.g. zinc oxide ointment, cream of magnesia, barium meal, antibiotic suspensions and dispersions, make-ups, disinfectants and insecticides, flour-in-water batter, etc.

 DEGASSING

    As it has been mentioned, cavitation degassing of molten metals can be used to avoid defects in structures (especially of aluminum and its alloys). Dissolved gas in the melt is liberated in regions of rarefaction. At this, produced small gas bubbles coalesce and drift, and the large ones rise to the surface, the gas being liberated.

Using pure aluminum and aluminum-magnesium alloys in 8-10 kg melts degassing can be completed in 30-60 minutes, the surface of the melt being protected by a fused salt.

The cavitation treatment of molten glass at temperature 1,350^oC during 30 minutes while it is cooled gives possibilities to manufacture glass with a completely homogenous structure required, for example, for optics. This technique can also be applied to degas resin solutions, transformer oil, viscose, soft drink and beverages, chocolate, orange oil, apple cider, cleaning solutions, water (elimination of oxides), electrochemical solutions (elimination of hydrogen at deposition process), drilling mud, etc.

The degassing degree can be judged by the shaft critical angular speed corresponding to the cavitation beginning of the degassed liquid.

  HOMOGENIZATION (EMULSIONS PRODUCTION)

    Emulsion products are made to obtain more palatable food, more effective remedies, smoother cosmetics, and many other mixtures of oil and water making the processes easier and used in large quantities as, e.g., dairy products, lubricant mould oils, batching, pharmaceutical emulsions and creams, flavoring emulsions for soft drinks, soups, baby foods, juices, pan greases and fat extenders for bakery, mayonnaise and salad cream, etc.

A good example of emulsions are the water-oil ones used not only as fire-resistant hydraulic liquids, but in many metal working operations such as cutting, grinding, broaching, tapping, rolling, drawing and extruding.

The role of a metal working lubricant is to form a protective film reducing metal-to-metal contact, dissipating heat and preventing welding and adhesion between the working tool and the metal removed or displaced from the work piece. Water improves metal working due to its superior heat extraction properties. Oils, alone or with various additives, provides lubrication. Synthetic materials (e.g. carbon tetrachloride) prevent welding and adhesion. Although all materials have been used, none is completely satisfactory. Water does not have sufficient lubrication and anti-welding properties. Carbon tetrachloride is too toxic for general use.

To combine the individual advantages of each liquid, various oil-water emulsions consisting of oil, water, emulsifiers and additives (not always) such as a bactericide, rust preventive, foam inhibitor; lard oil, sulfurized lard oil and chlorinated wax have been proposed.

Another example of emulsions are bituminous ones in which fluidity at atmospheric or slightly elevated temperatures is obtained by dispersing bitumen, generally asphalt, in water in the form of microscopic particles. Such emulsions are used in road-building, roofing, waterproofing, the manufacture of cements, adhesives, paints, coatings, paper, boards, etc.

Tar emulsions are applied as coatings over asphalt mixtures on parking areas, airport runways, etc. to prevent deterioration of the asphalt mixtures by gasoline, oil drippings and jet fuel spillage. Road emulsions (55-75% bitumen; 0.5-3% emulsifier; the rest water) are applied without heating and therefore allow lengthening the road-building season.

In food industry, animal fat-water emulsions increase the water-binding ability of sausage meat, elevate the production rate and quality.

Emulsions can be stable because of the rate of settling of the suspended liquid particles of colloidal size is directly proportional to the difference in density emulsion-forming liquids and to the square of the diameter of the particles, but inversely proportional to the friction in the medium. Also, there is random Brownian movement of the particles below 3 mkm. To protect emulsion against coagulation (the reverse process), a surface-active substance (emulsifier) is added and forms the film containing a mixture of all phases with interfacial tensions. Differences between the latter give one or another type of emulsion. If, for example, the interfacial tension between the water and the film is less than that between the oil, an oil-in-water system is more probable. In the reverse case, a water-in-oil system is more likely. Thus, emulsifier soluble in water produces the first emulsion, while that soluble in oil – the second one.

The dispersed liquid must be finely divided in the continuous medium by the energy supplied to the emulsion. Mechanical homogenizers, for example, require about 0.01 hp per hour.

Jet cavitation is very efficient for emulsification because of rough dispersion produced by forcing liquid through an orifice at high pressure. That reduces the quantity of applied emulsifiers and the energy requirements. The process can be continuous or semi-continuous.

The exemplary list of homogenized products (emulsions and several dispersions) for cavitating jet manufacture is following: adhesives, antibiotic dispersions, antioxidants, antiseptic creams, baby food, bitumen emulsions, canvas waterproofing, carbon black dispersions, cleansing lotions, condensed milk, coolant, cutting emulsion, deodorants, disinfectants, dye dispersions, emulsion paints, essential oil emulsions, flavorings, polishes, juices, gelatine dispersions, gravies, greases, gum dispersions, ice cream, insecticides, jute hatching emulsions, make-up, lubricants, margarine, mayonnaise, mineral oil emulsions, ointments, pan greases, paper coatings, peanut butter, inks, processed cheese, sauces, shampoos, soups, syrups, timber preservatives, titanium dioxide dispersions, cocktails, pastes, etc.

 SURFACE TREATMENT OF OBSTACLES (CLEANING, DEBURRING, TO-SIZE TREATMENT, POROUS CAPILLARY BODIES IMPREGNATION, COATING, SOFTENING MEAT, ETC.)

   Cavitating jets clean details off oxides, scales and lubricants used in many metal working operations (see above). However, better results are achieved with brittle contaminants. This cleaning is more effective than others as mechanically not abrading and chemically not dissolving the material, and giving the possibility to change inflammable toxic expensive frequent-regeneration-requiring organic solvents with alkaline solutions. Yet, a viscous insoluble film wetting the surface is hard to remove. As to the choice of cleaning solutions, there are no special requirements in this case, and alkaline, acidic and solvent type detergents and their variations can be employed.

Low-surface-tension solutions promote separation of pollutants and prevent their sticking together. For this purpose, soaps or surface-active additives are doped. Alkaline detergents (caustics, phosphates, silicates, carbonates, surface-active agents, etc.) speed the wetting, penetrating and the emulsifying action of the solution, accelerate lime-sequestering in hard water and maintain the pH of solution. However, applying alkaline solutions requires rinsing, passivation and drying.

At the same time, organic solvents have some advantages: chemical inertness to a cleaned surface, good fat-dissolving and volatility (easy disposal off the surface). Hydrocarbons (kerosene and benzene) and their chlorinated derivatives (carbon tetrachloride and trichloroethylene) are most frequently used. Freon (especially methylene chloride and trifluoro-trichloroethane) having small toxicity and explosion-and-fire safe are also acceptable. Their comparatively high cost can be compensated by continuous regeneration.

For iron-scale removing, pickling in the solutions of either sulphuric or muriatic acids, or 10% nitric and sulphuric acids and 50 g/l of potassium fluoride, or 10% sulphuric acid and 4% sodium chloride, etc. is used. At pickling, scale distends and its pores and cracks are saturated with hydrogen bubbles. Electro discharges arising as a result of the potential difference on the opposite walls of cavities form hydrogen peroxide, nitrogen oxides and increase the acid degree of dissociation.

If impurities have high adhesion to details surfaces, chemical pickling (e.g. in solution containing 30 g/l Na₃PO₄, 10 g/l Na₂CO₃ and 3 g/l surface-active additive) and posterior cavitation slime separation are applied. The liquid must be periodically cleaned, otherwise the quality of the process is deteriorated by absorption of the pollutants from the liquid by the already cleaned surface. If prior to the cavitation cleaning, the bulk soil has been removed by the normal dip cleaning, requirements to the filtering of solvents are not strict.

The jet energy acts on a surface impurity by cavitation erosion, dispersion, dissolving, mixing and promoting diffusion of a solid or liquid film. Cavitation action in the solid surface cleaning relies on intense hydro impacts. The latter initially press liquid away from the particles, and oscillating currents are set up in the liquid. The alternating pressure moves oscillating individual liquid centers. The detail surfaces covered with an oil film, air pockets and small metallic particles adhering to the surfaces are also cavitation sources (nuclei) adjacent to the surface. They produce the forces right where they are needed. Also, if oscillating cavitation bubbles are trapped between a dirt particle and the surface, they fatigue the material at the bond interface and break off.

Rough surfaces of the details give more nuclei for cavitation bubbles and hence greater action. That is why tank walls should be not rough to avoid the screening action of cavitation bubbles.

When liquid is degassing (gaseous cavitation), the gaseous bubbles absorb energy from the sound field. That is why fresh liquids should be degassed.

The same methods debur better by the mixture with abrasive slurry. As well as other surface defects, burrs are the nuclei of cavitation and promote the latter.

Cavitation hydro impacts penetrate into the pores and cracks of the surface which deforms resiliently in many cases. Due to the different elasticity of the material and a surface deposition (if there is any), the latter peels off and is turned into suspension or solution (depending on the working medium composition).

If abrasive suspensions are used, they have grooving effect and represent microscopic cutting tools. The best results of the to-size treatment of the surface with an abrasive are typical for brittle materials not undergoing to plastic deformation. Such treatment does not cause residual stresses, cracks, structural and microhardness changes, but can be great energy consuming and low productive. The addition to the liquid of finely disperse abrasive particles commensurate in size with the effective range of the shock waves created by the slamming bubbles enhances the erosive activity of cavitation and the jet itself at cleaning, deburring and to-size treatment.

The work with suspended free abrasive of the size of cavitation bubble order (3-10 mkm) is especially effective under elevated hydrostatic pressure (to 5 kgf/cm2) at deburring, cleaning (especially blind holes and recesses), grinding powdery materials, etc. By doing so the quantity is sharply increased and manual operations can be eliminated.

The strength of burrs’ connection is considerably lower than that of the detail material itself. That is why deburring occurs always before destroying the surface. Besides, cavitation micro impacts are considerably stronger just in the connection. Thus due to the selectivity of cavitation deburring, the junction between the burr and detail and its sharp edges are broken first of all as the cavitation bubbles are concentrated at the interface between the burr and detail. This interface is the place of stress concentrations.

Cavitating jets can be used to remove the flash off plastic details delivered into jets cavitation zones. Such treatment not only removes the flush, but also controls the quality of details because it destroys those having defective plastic bodies with cavities, cracks, etc.

Another application of cavitating jets is to flush porous and capillary filtering elements (e.g. pipe drains). Few examples in the industry are the production of woody plastics, antifriction metallic ceramic, electro carbon details, capacitors, rendering hydrophobic in electro and radio ceramic details, conservation and hydrolysis of wood, etc.

The duration of the impregnation and pressurization in the mixture of insulating varnishes and compounds subjected to cavitation is reduced. Impregnation is deepened because the pressure on the air in the pores is increased when the liquid penetrates into the latter under hydro impacts, the air being dissolved and taken away by the liquid.

The productivity of impregnation and oil quantity in the pores of sintered bearings are increased by about twice. At this the coefficient of filling the pores is also raised in comparison with impregnation without cavitation (Figure 18).

The cavitation impregnation of fibrous materials can be utilized in paper pulp industry. Therein the suspension of treated materials in a working solution is passed through the cavitating nozzle. Slamming cavitating bubbles distend the fibrous material and remove air out of it. This provides quick complete impregnation.

In impregnating and aczoiling laminated wood, a device for board cavitation impregnation is shown on Figure 19. A board 26 is impregnated on roller beds 27 and 28 from a frame 29 provided with nozzles 1 (the nozzles as on Figures 12 and 13 can be employed) connected with a pump installation 30 with a sump 31. Better results can be achieved by submerging the boards into a tank (under external static pressure) with nozzles. Yet, in some cases, such an installation may be too clumsy for continuous processing.

The heat exchange coefficient at natural and forced convection is increased under cavitation because a boundary layer and a laminar underlayer are deformed and mixed. Hardening liquids from cavitating nozzles have their cooling ability increased, a steam jacket formed on the detail surface at water hardening being destroyed. As a result, stress-strain properties and steel hardenability are improved.

Cavitating jets can be utilized also for cooling and lubricating cutting tools of lathes, planers, threaders, etc. Therein the cutting liquid improves the smoothness of the cut surface and increases the tool life.

In accordance with the invention, a cutting liquid is forced to penetrate more effectively to the cutting edge of a tool by issuing a cavitating jet from a nozzle. The dynamic pressure the jet and cavitation micro impacts force the liquid into the intimate contact with the tool close to the cutting edge thereof.

A workpiece 35 (Figure 20) is rotated against a cutting tool 36 in a holder 37 which can be moved toward and away from the workpiece 35 parallel to the axis of rotation thereof. A nozzle 1 is secured by an adjustable bracket 38 to the toolholder 37 generally beneath the tool 36 on the side facing the wedge-shaped opening formed between the tool 36 and the workpiece 35 and having the cutting edge as an apex.

The nozzle 1 can slide toward or away from the opening and fixed at the most effective distance by e.g. a thumbscrew (not shown). The transverse position of the nozzle can be varied within limits by the appropriate bracket. 38 (the means for mechanical adjustments is not shown). The nozzle 1 is connected to a pump 30 drawing a cutting liquid from a sump 31 beneath the workpiece 35 and supplies the same under pressure to the nozzle l.

The cutting liquid is vaporized in the wedge-shaped opening under high temperature adjacent the cutting edge. The heat required for the vaporization cools the cutting edge. The vapor passes through minute spaces caused by relative vibration between the tool and the workpiece or by slight irregularities in both the cutting edge and the work surface. Then the vapor condenses on the top of the tool underneath the chip that comes from the workpiece in an area where the cutting liquid is most effective in reducing the frictional resistance to the movement of the chip.

Cavitation micro impacts produced between the surfaces of the workpiece and the cutting tool increase intimate contact between them and the cutting liquid. An overhead coolant spray may be provided to catch the cutting liquid jet when the tool is not engaged with the workpiec and to absorb the smoke and vapor generated by the cutting operation. Likewise, a chip guard may be employed to prevent the chip from intercepting the jet.

The cavitating cutting liquid jet is employed to clean the working surface of an abrasive grinding disc if the latter is soiled by the details of viscous hard-machined materials. A pump 30 (Figure 21) delivers the liquid to an abrasive disc 40 through a nozzle 1 (which may be as in Figure 12 or 13). The liquid flows down on a table 41 with a ground detail 42 to a sump 31. As a side action, the cutting liquid is also improved because of its emulsification by cavitation.

Cavitation jet mixing in a bath intensifies electrodeposition on the metal surfaces of details, decreases porousness of coating and facilitates discharge of ions. Due to this, current density can be increased. Here operative factors are cavitation mixing (removing an attached-to-cathode layer enriched with the ions of deposited metal) and hydrogen depolarization due to cavitation degassing the electrolyte. However, too intensive cavitation treatment is able to suspend electrodepositeld metal and imposes an upper limit of the intensity.

At such treatment, the velocity of copper plating is 1.5 times higher, e.g. with electrolyte containing 200 g/l crystal sulphuric acid copper and 60 g/l sulphuric acid (the temperature is 55°C and the current density is 0.15 a/cm²). So is cadmium plating with the solution of 40 g/l cadmium oxide and 90 g/l sodium cyanide.

Light metals, like aluminum and its alloys, have difficulties with soldering due to the presence of thin, only a few molecule thick, oxide layer (mainly Al₂O₃) forming almost instantaneously on a freshly cut metal and preventing the wetting by tin and other soldering materials.

The metal surface eroding by cavitating jets of a lower melting point (cavitation being in a liquid adjacent to the oxide layer). Metal in its molten state removes the metallic oxide layer from the surface and thus facilitates the wetting of the surface. Cavitation erosion of the metal surface is characterized by the formation of pits with overhanging lips providing a keying action and mechanical bond between the solder layer and the metal.

Thus, cavitating jets can be used for the plating and soft or hard soldering of details and wires at 150-700°C. The lower range is known as soft solders and the higher one – as hard solders. They eliminate the need for a flux.

Cavitation must be not too violent as the solder can be thrown off the metal surface as well as the oxide. Impurities can be dispersed or emulsified with the solder thus weakening the joint. Also, there is a limitation to the thinness of details and wires which can be tinned by this technique as they can be broken down by the jet.

This technique can be also used to enable holes and cracks in metal castings to be filled.

Cavitating jets soften meat by breaking down the fibers of muscular and connective tissue and by intensifying biochemical processes and fermentation. Meat is treated in a pickle bath provided with cavitating jets. Diffusion processes at corning of meat are also accelerated by decreasing the boundary layer thickness and the depth of capillary penetrating thereto.

ACTIVATING CATALYTIC REACTIONS

    According to this invention, for enhancing the chemical reactions with a catalyst (a substance accelerating, retarding or providing the chemical reactions without change itself), catalytic powder is dispersed in the liquid subjected to cavitating jet action, or a catalytic obstacle is provided.

At this, a nickel, cobalt or iron powder in methane and water results in carbon monoxide and hydrogen, an iron or nickel powder can be used in the cracking of hydrocarbons to carbon and hydrogen. A nickel powder can be used in the dehydrogenation of alcohols into aldehydes or ketone, etc. An example of these processes is wastewater treatment (seen below).

 COD- AND BOD-CONTAINING WATER TREATMENT

   Common methods of treating of water containing chemical (COD) and biological (BOD) oxygen demands (the terms expressing the pollutant content of water) for removing the pollutants are biological oxidation of organic impurities, mixing with oxygen and/or ozone-containing gas, applying ionizing radiation, chlorination, etc. The treatment depends on the characteristics of the water to be treated, the purity of effluent required, the necessary rating and so on. The known methods do not achieve complete purification, or are much time consuming because wastewaters are very dilute solutions of pollutants with slow reactions at low concentrations. The effluent may contain residual oxidizable material (COD and BOD) and potentially pathogenic bacteria. That is why the post-treatment is often included.

According to this invention, the water is treated by cavitating jetting. Air, oxygen or ozone supply enhances the rate of oxidation which is still bettered by suspending powdery catalyst (e.g. nickel, stable under cavitation). At a proper regime, 2-3 hour treatment gives 40-80% COD (Figure 22), and 70-95% BOD (Figure 23) reduction (depending on the initial value – Figure 24) and eliminates coliform bacteria (Figure 25).

The bactericidal effect of ozone (a few percents of which are supplied with air or oxygen) is an alternative to chlorination. However, it is mainly employed for water sterilization. As to wastewater treatment, dosing with enough ozone for oxidation is not feasible for bulk processing because of the high cost and difficulties with the equipment. That is why the substitution of ozone can be recommended for this method only at the post-treatment.

Oxidation and especially ozonation of phenol wastes (phenol aqueous solutions) by the cavitation treatment rapidly decrease phenol concentration (Figure 26). Phenol is converted into higher oxidized compounds, carbon dioxide and water. At this, nickel catalyst increases the rate.

In industrial wastes, phenol and orthochloronitrobenzene are common aromatic compounds difficult to remove by biological processes. In this case, this method has especial value.

It should be mentioned that cavitation bacteria-destroying action may be harmful for the biological organisms and consequently cannot be applied in the processes wherein purification depends on them.

SIEVING, FILTRATION, ULTRAFILTRATION

    When the obstacle of a cavitating jet is a sieve, filter medium or porous membrane (ultrafiltration, separation, reverse osmosis, etc.), sieving, filtration and ultrafiltration (through porous membranes), separation of solids from suspensions and the like processes are greatly facilitated. Because of cavitating slamming bubbles, the obstacle is oscillating and casts away the particles of the solid phase of a pumped suspension or solution. The liquid phase passes freely and the obstacle is less obstructed.

The sieve and filter should be formed of some rather resistant material (stainless steel, powdered metal, etc.). For separating solvents from solutes in solution (ultrafiltration or reverse osmosis), a semi-permeable membrane is employed. In order to withstand the severe requirements of cavit.ation and high pressure (in comparison with an ordinary filtration), the membranes can be made of cross linked polymers (e.g. porous polyethylene), reinforced with glass fiber, powdered metal, etc.

In such processes, cavitation increases the flow of liquid (in many cases, water is treated) from the nozzle 1 (Figure 27) through a semi-permeable membrane 45 installed in a container 46 and provided with outlets 47 for treated liquid and 48 for the purified one. This can be employed to separate water from salt water, recovery of industrial wastes and water pollution, water softening, sewage water treatment, pulp and paper waste water treatment, saline water conversion, separation of substances in food processing (removing of water), e.g., concentration of juices, treatment of whey, concentration of latex, separation of certain hydrocarbons, etc.

 MISCELLANEOUS APPLICATIONS

    Cavitating jets cause depolymerization of high polymers. Cavitation breaks the chemical bonds in the chain, makes the molecules smaller and therefore decreases the viscosity (an example of hydraulic liquids with viscous additives consisting of long hydrocarbon chains is shown in Figure 28).

The cavitation jet aging of wines and spirits reduces the maturing time to days instead of months. At this, rearrangement of the alcohol/ester balance changes the taste.

The lethal properties of jet cavitat.ion can be used for the destruction of enzymes in sugar syrup to retard the inversion of sucrose into other products such as glucose.

The disintegration of bacteria suspended in solutions can be used for sanitary purposes.

Cavitating nozzles can be utilized for spraying and aerosol production wherein the liquid particles are so dispersed in the gaseous medium of the receiving atmosphere as to be most effectively and efficiently used for the purpose intended (e.g., fuel-air mixture production, cooling, etc.)

Cavitating jet intensification of the extraction of biologically active substances (e.g., insulin from pancreas reduced to fragments and dispersed in cavitating jets) is founded on breaking cells, stratification and liberation of hormones and ferments of tissue. At this, the latter preserve their initial biological activity.

The installation (Figure 29) can be portable and composed of the nozzle device 51 (as in Figure 2), a tank 2, a pump 30, pipes 52 and 53. The liquid to be treated is poured out into the tank 2 and circulates through the circuit; the tank 2 – the pipe 53- the pump 30 – the pipe 52 – the device 51 – the tank 2.

In many cases, from operational considerations, the nozzle device is better to be of an unsubmerged-into-tank type. This is easily achieved by sealing the body 5 and changing the outlet (Figure 30). Such a device can operate with two tanks (Figure 31) or with an overhead funnel (Figure 32). In he first case, the liquid to be improved is pumped out of one tank 2 into another through the pipe 53, the pump 30, the device 51 (as shown in Figure 30) and the pipe 52. In the second case, the liquid flow is the same, except there is no inlet pipe.

* * *

   It is to be understood that this description is exemplary and explanatory, but not restrictive. Also, the invention is not limited to the specific details shown and described. Departures may be made without departing from the scope of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A method of producing physicochemical effects in liquids by directing a pressurized liquid through a nozzle device, such as an orifice, an annular nozzle, forming a jet entraining a relatively stagnant fluid such as a liquid, a melt and gas wherein the velocity of said pressurized liquid is increased sufficiently high to case cavitation, said effects being such as emulsification, dissolving, heat exchange, mass exchange, homogenization, degassing, dispersion, alloying, mixing, depolymerization of high polymers, ageing of wines and spirits, crystallization of saturated solutions, intensification of chemical and electrochemical reactions such as diffusion.

2. The method of claim 1 wherein said jet collides against a solid obstacle to disperse the latter, impregnate and pressurize porous and capillary surfaces, to harden, clean, debur, descale, drill, grind, polish.

3. The method of claim 2 wherein said obstacle is activated by an ultrasonic transducer.

4. The method of claim 1 wherein at least two jets are formed and impinge against each other.

5. The method of claim 2 wherein said velocity increase is achieved in the gap between the nozzle and the obstacle.

6. The method of claim 1 wherein a vortex movement of the jet is induced in the nozzle inlet by at leas one member of the group consisting of a swirl nozzle inlet, a spiral nozzle thread and a spiral core installed in the nozzle.

7. The method of claim 1 wherein ventilation of the cavities is prevented by such method as surrounding the jet by an annular stream flowing alongside the jet at a lower velocity and having a disk form in its exit section, and providing the nozzle with an annular relatively hermetic envelope between the nozzle and the obstacle.

8. The method of claim 1 wherein the liquid suspends a powdery material to be treated with, the effect being such as size reduction, grinding, polishing, spheroidizing, producing alloys such as iron-lead, iron-zinc, copper-lead, aluminum-lead, aluminum-copper, aluminum-cadmium, zinc-tin, cadmium-aluminum-silicon, dissolving nickel in steel melt, chromium in steel melt, graphite in bronze, carbon in iron.

9. The method of claim 1 wherein the liquid is melt of a fusible metal, the solids being of more refractory material to be alloyed with.