CN103072084B - Nano-fluid electrostatic atomization controllable jet micro lubricating grinding system - Google Patents

Abstract

The present invention relates to a kind of nano-fluid electrostatic atomization controllable jet micro lubricating grinding system, the droplet of injection can be made to realize controlled distribution by principles of electrostatics, thus reduce the pollution to environment, for staff provides better health care.Its grinding system is provided with corona charging nozzle, the nozzle body of corona charging nozzle is connected with liquid-supplying system, air supply system, the high-magnitude DC electrostatic generator of nozzle body bottom is connected with the negative pole of adjustable high voltage D. C, the positive pole of adjustable high voltage D. C is connected with workpiece power-up device, and workpiece power-up device is attached to the not finished surface of workpiece; Grinding nanometer fluid liquid sends into corona charging nozzle by liquid-supplying system, compressed air is sent into corona charging nozzle by air supply system simultaneously, grinding nanometer fluid liquid by compressed air drive export ejection atomization from nozzle body while by high-magnitude DC electrostatic generator charged be controllable jet, the grinding area being distributed to processing work controlled under the effect of electric field force and aerodynamic force.

Description

Nano-fluid electrostatic atomization controllable jet micro lubricating grinding system

Technical field

The present invention relates to grinding fluid feedway in a kind of machining, be specially a kind of nano-fluid electrostatic atomization controllable jet micro lubricating grinding system.

Background technology

Minimal Quantity Lubrication Technology is also known as MQL(Minimal Quantity Lubrication) technology, the lubricating fluid of denier mixes with the compressed air with certain pressure and is atomized by he, be injected into grinding area, effectively lubricating is carried out to the contact surface of emery wheel and abrasive dust, emery wheel and workpiece.This technology, under the prerequisite ensureing effective lubrication and cooling effect, uses minimal grinding fluid (being about the some thousandths of of traditional cast-type lubricating system consumption), to reduce costs and the pollution to environment and the injury to human body.

Nanometer jet micro lubricating is set up based on enhanced heat exchange theory, and from enhanced heat exchange theory, the heat-transfer capability of solid is much larger than liquids and gases.The thermal conductivity factor of the solid material several order of magnitude larger than fluent material under normal temperature.In micro lubricating medium, add solids, significantly can increase the thermal conductivity factor of fluid media (medium), improve the ability of convective heat transfer, greatly make up the defect of micro lubricating cooling capacity deficiency.In addition, nano particle (referring to the ultra-fine minute solid particles being of a size of 1-100nm) also has the tribological properties such as special antiwear and antifriction and high bearing capacity in lubrication and friction.Nanoscale solids particle adds in micro lubricating fluid media (medium) by nanometer jet micro lubricating exactly makes nano-fluid, namely sprays into grinding area with pattern after nano particle, lubricant (oil or oil water mixture) and gases at high pressure mixed aerosol.

Inventor has carried out deep theory analysis and experimental verification to micro lubricating grinding feed system, achievement in research has applied for relevant patent, the patent of invention of being applied for by invention designer, application number: 201210153801.2 disclose a kind of nano particle jet micro lubricating grinding lubricant supply system, nanoscale solids particle is added the lubricant making micro lubricating grinding in degradable grinding fluid by it, from micro-feedway lubricant become and there is fixation pressure, pulse frequency is variable, the pulse drop that liquid-drop diameter is constant, grinding area is sprayed into pattern under the air barrier effect that gases at high pressure produce.But it is not adopt the formation of electrostatic atomization to produce the controlled fine droplets of jet, and atomizing principles is different with drop control mode; Application number: the patent of invention of 201110221543.2 discloses a kind of nano particle jet micro lubricating grinding three-phase stream feed system, nano-fluid is delivered to nozzle place through fluid path, gases at high pressure enter nozzle through gas circuit simultaneously, gases at high pressure and nano-fluid be abundant mixed aerosol in nozzle mixing chamber, minor air cell is entered after accelerating chamber accelerates, Compressed Gas enters through minor air cell's passage simultaneously, three-phase flow is further rotated and mixes and accelerate, then three-phase flow is injected into grinding area with the form of atomized drop through jet expansion.But the principle of electrostatic atomization neither be adopted in disclosed technical scheme to form charged fine mist, more can not accomplish that jet is controlled, atomizing principles is all different with drop control mode.

At present, in micro lubricating grinding, micro lubricating agent can't realize effectively controlled injection grinding area under the rolling action of gases at high pressure, i.e. the wedge area of emery wheel/workpiece interface, and therefore, nanometer jet can be dispersed in surrounding environment.Nowadays we just to show great attention to when using Minimal quantity of lubrication oil lubricating fluid and cooling fluid to the impact of operator ' s health, as, operating personnel can obtain various respiratory disease, comprise occupational asthma, hylactic pneumonia, PFT forfeiture and skin disease as allergy, oily acne and cutaneum carcinoma etc.The industrial focus of micro lubricating take air as the potential health hazard that the droplet of power brings to operating personnel.At micro lubricating be that in the injection of power, droplet no longer suffers restraints after ejecting with compressed air, its motion is no longer controlled, can spread, the series of problems such as drift.But the appearance of these problems can make the small droplet of particle be diffused in working environment, not only environment is caused and pollute greatly but also great health hazard can be caused to staff.Even various occupational disease can be caused when the size of droplet is less than 4 μm.Even if expose according to the reality report short time and also may damage PFT in such a case.The exposure limit concentration of U.S.'s occupational safety and health research institute suggestion mineral oil droplet is 0.5mg/m for this reason ³.In order to ensure the health of staff, must be controlled fine droplet in micro lubricating process, be reduced diffusing capacity.But from the document retrieved at present, have not been reported for research in this respect, the research therefore for the problems referred to above is extremely urgent.We conducted based on such present situation and the controlled distribution of mist droplet in micro lubricating process is explored.

Summary of the invention

The present invention is for solve the problem to a certain extent, provide a kind of nano-fluid electrostatic atomization controllable jet micro lubricating grinding system, the droplet of injection can be made to realize controlled distribution by principles of electrostatics, the uniformity of spectrum of fog drop, deposition efficiency and liquid effective rate of utilization can be improved, and effectively can control the characteristics of motion of droplet, thus the pollution reduced environment, for staff provides better health care.

For achieving the above object, the present invention adopts following technical scheme:

A kind of nano-fluid electrostatic atomization controllable jet micro lubricating grinding system, it comprises grinding system, grinding system is provided with corona charging nozzle, the nozzle body of corona charging nozzle is connected with liquid-supplying system, air supply system, the high-magnitude DC electrostatic generator of nozzle body bottom is connected with the negative pole of adjustable high voltage D. C, the positive pole of adjustable high voltage D. C is connected with workpiece power-up device, and workpiece power-up device is attached to the not finished surface of workpiece; Grinding nanometer fluid liquid sends into corona charging nozzle by liquid-supplying system, compressed air is sent into corona charging nozzle by air supply system simultaneously, grinding nanometer fluid liquid by compressed air drive export ejection atomization from nozzle body while by high-magnitude DC electrostatic generator charged be controllable jet, the grinding area being distributed to processing work controlled under the effect of electric field force and aerodynamic force.

Described high-magnitude DC electrostatic generator comprises the electrode tray being arranged on corona charging nozzle bottom, and electrode tray is made up of insulating materials, and along the multiple electrode slot of its circumference array, needle electrode is arranged in electrode slot; In electrode tray central diameter, place has wiring duct, installation high-voltage electric wire in it, and on electrode tray, has a high-tension bus-bar pallet pick out through hole, and each needle electrode is all connected with high-tension bus-bar, and high-tension bus-bar is connected with adjustable high voltage D. C negative pole; Electrode tray bottom is positioning threads ring, and positioning threads adopts ceramic material to make, and with the external screw thread coordinated with corona charging nozzle, positions electrode tray.

Described workpiece power-up device comprises workpiece power-up device insulation shell, foundary weight, permanent magnet, holddown spring; Permanent magnet is arranged on workpiece power-up device insulation shell periphery; In the middle part of workpiece power-up device insulation shell, have opening, foundary weight stretches out workpiece power-up device insulation shell from one end and is set with holddown spring; Foundary weight has split pin slot, and for insertion opening pin, foundary weight is connected with the positive pole of adjustable high voltage D. C.

Described adjustable high voltage D. C comprises transformer, primary is connected with AC power, two secondary lines are respectively as direct-flow voltage regulation unit V1 and direct-flow voltage regulation unit V2, direct-flow voltage regulation unit V1 is connected with self-maintained circuit, self-maintained circuit is connected with power amplification circuit, high-frequency impulse stepup transformer and voltage doubling rectifing circuit, constant current automatic control circuit, constant current automatic control circuit is connected with direct-flow voltage regulation unit V2, and direct-flow voltage regulation unit V2 is connected with power amplification unit; The adjustable voltage scope of adjustable high voltage D. C is between 2KV to 120KV; Direct-flow voltage regulation unit V1 is as the operating voltage of self-maintained circuit, direct-flow voltage regulation unit V2 is the main energy sources of power transfer, pulse signal is obtained by self-maintained circuit, after power amplification circuit amplifies, under the boosting of high-frequency impulse stepup transformer, final output high-voltage signal, through voltage doubling rectifing circuit thus export high direct voltage; Constant current automatic control circuit samples the electrostatic operating current of voltage doubling rectifing circuit automatically, when constant current, when workload normally strengthens, can not cause the rising of operating current; When outer load exceedes permission electric current, self-maintained circuit stops shake, and high pressure is cut off.

The grinding nanometer fluid liquid of described atomization is charged in the drift region of needle electrode corona discharge and the electron collision of drift, controlledly under electric field force, aerodynamic force and Action of Gravity Field after droplets sprays to surface of the work.

Be interference fit between described needle electrode and electrode slot, clamp needle electrode by the elastic deformation force of insulating materials.

The discharge tip radius of described needle electrode is 0.5mm, and die opening is 20-30cm, and discharge inception voltage scope is 15.2848-16.2064KV.

The nozzle angle of described nozzle body remains on 30 ° to 45 °, and nozzle body outlet is 20-30cm with the jet length of workpiece.

The carrying capacity computing formula of described droplet corona charging is as follows:

$q=f[1+2\frac{k-1}{k+2}]{4\mathrm{\π\ϵ}}_0{\mathrm{Er}}^2$

In formula $f=\frac{\frac{\mathrm{NeKi}}{{4\mathrm{\ϵ}}_0}t}{\frac{\mathrm{NeKi}}{{4\mathrm{\ϵ}}_0}t+1}$

Q---droplet carrying capacity, C;

K---droplet dielectric constant;

ε ₀---dielectric constant of air, is about 8.85 × 10 ^-12, c ²/ nm ²;

The electric-field intensity that E---corona discharge is formed, V/m;

R---droplet radius, μm;

N---charged ions concentration, population/m ²;

E---electron charge, 1.6 × 10 ^-19, C;

Ki---charged ions mobility, m ²/ (Vs);

T---charging holdup time, s.

Described liquid-supplying system is connected with nozzle body by nano-fluid conveying coiled pipe, and air supply system is connected with nozzle body by Compressed Gas conveying coiled pipe.

The beneficial effect of this device is: nanoscale solids particle and lubricating fluid are mixed and made into nano-fluid, form with jet after nano-fluid electrostatic atomization is injected to grinding area, what realize the controlled olderly flowage of charged nanosize fluid droplet enters into emery wheel/workpiece interface, thus nano particle participation enhanced heat exchange can be played to a greater extent and form lubrication antifriction oil film in emery wheel/workpiece interface, and the drift effectively reducing minor diameter droplet is scattered and disappeared, realize the clean efficient micro lubricating grinding of low-carbon (LC).

When the droplet of nozzle ejection is by after charged, displacement under the effect of electric field force, what make its maximum is covered in surface of the work.In charged process, because nanoparticle surface is larger, surface polarity is stronger, after charged, its charge-mass ratio is larger than the charge-mass ratio of droplet, so nano particle is tending towards more early arriving surface of the work, cover oil film lower floor, the exchange capability of heat that can better utilize it desirable like this.In electrostatic field, there is " electrostatic is encircled " effect, therefore when droplet and nano particle are more easily enter into workpiece to have certain roughness depression in the surface place to workpiece motion s, thus expand relative area coverage, better lubrication and heat exchange effect can be played.

Nano-fluid is atomized jointly by Compressed Gas and high-pressure electrostatic, can reduce its mist droplet particle size.Nano-fluid is charged under being sprayed at high-pressure electrostatic effect, and can be effectively directed under electric field force effect be distributed in grinding area, greatly reduce the drift value of spraying, thus greatly enhance the utilization rate of nano-fluid, and then improve lubrication effect reduce particulate expanding pollute.Spray by after charged, encircle effect due to the repulsive interaction of like charges and electrostatic and spraying distribution can be made more even.

Accompanying drawing explanation

Fig. 1 is the assembled shaft mapping of this embodiment;

Fig. 2 is fluid path and the gas circuit system schematic of this embodiment;

Fig. 3 is the circuit decorum block diagram of this embodiment;

Fig. 4 is the nozzle general assembly sectional view of this embodiment;

Fig. 5 is the nozzle body sectional view of this embodiment;

Fig. 6 is the nozzle rotation direction passage sectional view of this embodiment;

Fig. 7 is upward view and the revolved sectional view of the electrode tray of this embodiment;

Fig. 8 is the electrode tray internal wiring schematic diagram of this embodiment;

Fig. 9 is front view and the sectional view of the positioning threads ring of this embodiment;

Figure 10 is workpiece power-up device sectional view and the top view of this embodiment;

Wherein, 1-air compressor, 2-fluid reservoir, 3-air accumulator, 4-hydraulic pump, 5-filter, 6-Pressure gauge, 7-choke valve, 8-turbine flowmeter, 9-turbine flowmeter, 10-choke valve, 11-pressure regulator valve, 12-pressure regulator valve, 13-overflow valve, 14-fluid recovery case, 15-nozzle body, 16-electrode tray, 17-needle electrode, 18-positioning threads ring, 19-nano-fluid entrance, 20-rotation direction Compressed Gas passage, the built-in hoop compression gas passage of 21-, 22-nano-fluid and Compressed Gas mixing chamber, 23-Compressed Gas entrance, 24-minor air cell Compressed Gas passage, 25-three-phase flow accelerating chamber, 26-minor air cell, 27-high-tension bus-bar passage, 28-high-tension bus-bar pallet picks out through hole, 29-screws groove, 30-some work platform, 31-wheel guard, 32-emery wheel, 33-workpiece, 34-magnetic suction disc, 35-nano-fluid conveying coiled pipe, 36-Compressed Gas conveying coiled pipe, 37-adjustable high voltage D. C, 38-workpiece power-up device, 39-high-tension bus-bar, 40-nozzle, 41-insulating sheet material, high-tension bus-bar in 42-electrode tray, 43-workpiece power-up device insulation shell, 44-foundary weight, 45-permanent magnet, 46-holddown spring, 47-split pin slot.

Detailed description of the invention

Below in conjunction with accompanying drawing the present invention done and illustrate.

As shown in Figure 1, grinding machine some work platform 30 is covered with this new material of insulating sheet material 41(can magnetic conduction, but non-conductive, thus not only can ensure the installation of workpiece but also can ensure to form consistent electric field between nozzle and workpiece).Magnetic suction disc 34 is adsorbed on wheel guard 31 side, be used for fixing nano-fluid conveying coiled pipe 35, Compressed Gas conveying coiled pipe 36 and be connected with nozzle in high-tension bus-bar 39 that.Nano-fluid conveying coiled pipe 35 one end is connected with nano-fluid entrance 19, and one end is connected with turbine flowmeter 9.Compressed Gas conveying coiled pipe 36 one end is connected with Compressed Gas entrance 23, and one end is connected with turbine flowmeter 8.High-tension bus-bar 39 wherein one end of one picks out through hole 28 with high-tension bus-bar pallet be connected with needle electrode 17 afterbody each in electrode tray 16 through high-tension bus-bar passage 27, and the other end is connected with the cathode output end of adjustable high voltage D. C 37.Another one end of high-tension bus-bar 39 other end that is connected with foundary weight 44 is connected with the cathode output end of adjustable high voltage D. C 37, and carries out grounding.Workpiece power-up device 38 is adsorbed in workpiece not finished surface, thus workpiece and adjustable high voltage D. C 37 positive pole are connected.

As shown in Figure 2, in view of this invention nozzle used is pneumatic nano-fluid spray charging nozzle, therefore grinding nanometer fluid liquid and compressed air are introduced nozzle through fluid passage and gas passage by this programme respectively, and mix in nozzle, the droplet then nozzle being sprayed by the method for corona charging is charged.Gas circuit is formed by air compressor 1, filter 5, air accumulator 3, pressure regulator valve 11, choke valve 7, turbine flowmeter 8.Fluid reservoir 2, hydraulic pump 4, pressure regulator valve 12, choke valve 10, turbine flowmeter 9 form fluid path.By adjustable high voltage D. C 37, provide high pressure negative electricity to needle electrode 17.The compressed air produced by air compressor 1 enters air accumulator 3 through filter 5, then through pressure regulator valve 11 and choke valve 7, flows through turbine flowmeter 8 and enter Compressed Gas entrance 23; Nano-fluid in fluid reservoir 2 is extracted out by hydraulic pump 4, then through pressure regulator valve 12 and choke valve 10, flows through turbine flowmeter 9 and enter nano-fluid entrance 19.Wherein overflow valve 13 and fluid recovery case 14 form protective loop, and Pressure gauge 6 is used for monitoring the air pressure of air accumulator 3.

As shown in Figure 3, adjustable high voltage D. C is made up of AC power unit, direct-flow voltage regulation unit V1, direct-flow voltage regulation unit V2, self-maintained circuit, power amplification circuit, high-frequency impulse stepup transformer, voltage doubling rectifing circuit and constant current automatic control circuit.

As shown in Figure 4,5, the not easily processing and manufacturing of nozzle body complex structure, and require that there are certain insulating properties, therefore use ceramic material by quick shaping process processing and manufacturing.The Compressed Gas entered by Compressed Gas entrance 23 is via built-in hoop compression gas passage 21, enter mixing chamber by rotation direction Compressed Gas passage 20 with certain tangential velocity v and be mixed to form three-phase flow with the nano-fluid entered by nano-fluid entrance 19, accelerated by three-phase flow accelerating chamber 25, enter minor air cell 26 after acceleration and form eddy current at this and the compressed air entered by minor air cell's Compressed Gas passage 24, three-phase flow is mixed further, then exports ejection through nozzle body 15 and form droplet.Charged through the drift region of needle electrode 17 corona discharge and the electron collision of drift after droplet ejection, controlledly under electric field force, aerodynamic force and Action of Gravity Field after droplets spray to surface of the work.

As shown in Figure 6, rotation direction Compressed Gas passage 20 is along hybrid outer wall array arrangement, inlet axis and mixing chamber inner chamber wall tangent, Compressed Gas enters in nano-fluid and Compressed Gas mixing chamber 22 with tangential velocity v through rotation direction passage.

As shown in Figure 7, electrode tray 16 is made up of insulating materials, circumferentially array 8 electrode slots, and in electrode tray 16 central diameter, place has wiring duct, and on electrode tray 16, has a high-tension bus-bar pallet pick out through hole 28.

As shown in Figure 8, interference fit by needle electrode 17(it and electrode slot, clamped by the elastic deformation force of insulating materials) be arranged in electrode slot, with the high-tension bus-bar 42 in electrode tray, each needle electrode 17 is together in series, and picks out through hole 28 from high-tension bus-bar pallet and pick out.

As shown in Figure 9, positioning threads ring is also made up of ceramic material, with the external screw thread coordinated with nozzle body 15, and have in lower end two screw groove 29 be convenient to install.Positioning threads ring 18 mainly plays the effect of keeper electrode pallet 16.

As shown in Figure 10, workpiece power-up device 38 is made up of workpiece power-up device insulation shell 43, foundary weight 44, permanent magnet 45, holddown spring 46.By its near workpiece not finished surface time, permanent magnet 45 can produce attraction with workpiece 33 and compress holddown spring 46, and holddown spring 46 provides reaction force simultaneously, and guarantee foundary weight 44 is closely connected with workpiece 33.Foundary weight 44 has split pin slot 47, and its effect is insertion opening pin, and during to ensure that workpiece power-up device 38 does not adsorb with workpiece 33, foundary weight 44 and holddown spring 46 can not come off from workpiece power-up device insulation shell 43.

This programme specific works process is as follows;

Nano-fluid is via fluid path: fluid reservoir 2, hydraulic pump 4, pressure regulator valve 12, choke valve 10, turbine flowmeter 9 enter into nano-fluid entrance 19, and compressed air is via gas circuit: air compressor 1, filter 5, air accumulator 3, pressure regulator valve 11, choke valve 7, turbine flowmeter 8 enter into Compressed Gas entrance 23.Nano-fluid and Compressed Gas enter in nano-fluid and Compressed Gas mixing chamber 22 simultaneously.The aperture of nano-fluid and Compressed Gas mixing chamber 22 is greatly to ensure blending space than nano-fluid entrance 19 aperture.Due to rotation direction Compressed Gas passage 20 inlet axis and nano-fluid and Compressed Gas mixing chamber 22 inner chamber wall tangent, Compressed Gas enters in nano-fluid and Compressed Gas mixing chamber 22 through passage with tangential velocity v, because of its velocity attitude and axial centre non-intersect, therefore there is a moment of momentum to axial centre in inlet air flow, air-flow is impelled to rotate around axial centre in passage, advance to outlet simultaneously, thus drive nano-fluid rotation to form eddy current.

Nano-fluid enters after flowing out from nano-fluid and Compressed Gas mixing chamber 22 in the three-phase flow accelerating chamber 25 that taper shrinks, and accelerates.Three-phase flow flows in minor air cell 26 after acceleration.Minor air cell 26 inwall is made up of the conical surface that cylinder is different from axis angle with two, and Compressed Gas, by minor air cell's Compressed Gas passage 24, enters into the cylindrical zone that diameter is minimum, and immediately to adjacent two tapered zones that diameter is larger diffusions.This will inevitably cause the diffusion of eddy current, thus three-phase flow is mixed further.Through being sprayed by jet expansion after further mixing, form spraying.

The electrode slot of electrode tray 16 can according to circumstances clamp 2,4,8 quantity needle electrode 17 not etc.Needle electrode 17 discharge tip radius is about 0.5mm.Needle electrode 17 connects high-tension bus-bar 39, and high-tension bus-bar 39 picks out through hole 28 through high-tension bus-bar pallet and high-tension bus-bar passage 27 picks out outside nozzle body 15, and is connected with adjustable high voltage D. C 37 cathode output end.Because when corona discharge, the discharge inception voltage of negative corona discharge is low and breakdown voltage is high, so needle electrode 17 is connected with power cathode, adjustable high voltage D. C 37 cathode output end to be connected with workpiece power-up device 38 also ground connection by high-tension bus-bar 39.

Because workpiece area is comparatively large, needle electrode 17 and the structure of its formation for plate.Thus define extremely uneven electric field (condition of corona discharge).What the spraying of this electrostatic corona adopted is multipole needle-discharging, because each pole needle tip relative distance is comparatively large so do not affect mutual discharge inception voltage, but corona discharge occurs for they can increase electronics between electrode and workpiece and ion concentration dramatically simultaneously, thus the charged efficiency of droplet can be increased, and after their electric field compound, electric field force suffered by droplet also strengthens, and is more conducive to the directed movement of droplet.Because the adjustable voltage scope of adjustable high voltage D. C 37 is between 2KV to 120KV.Because in working condition, pd > 26.66kpacm(p is the ambient pressure of operating mode, d is needle plate electrode spacing) so we use streamer theory analysis and do not use the inferior theory of soup.

When add at needle electrode 17 two ends higher but do not reach the voltage punctured time, if the electric field near electrode surface (internal field) is very strong, then the gas medium of ate electrode can be produced corona discharge phenomenon by partial breakdown.Here the air pressure of gas is about 10 ⁵pa.When the radius of curvature of electrode is very little, because the field intensity near it is high especially, be easy to corona discharge occurs.

In severe non-uniform electric field, air gap complete breakdown before, can there is corona discharge in ate electrode, produce lazuline halation.This special halation is that the discharge process of electrode surface ionized region causes.Molecule in ionized region, under ionizing the effect of factor (as light source) and electric field outside, creates and excites, ionizes, form a large amount of electron avalanches.Also reversible process---the compound exciting and ionize is produced at the same time.In recombination process, can light radiation be produced, thus define halation.Here it is corona.The current strength of corona discharge depends on applied voltage, electrode shape, anode-cathode distance, gas property and density etc.

When two interelectrode potential differences increase gradually by zero, the non-self-maintained discharge that initial generation is noiseless, electric current is at this moment very faint, and its size determines a f residual ionization; When voltage is increased to certain numerical value V _s, time, corona discharge there occurs.This voltage V _s, be called the late threshold voltage of discharge inception voltage or corona discharge, the unexpected increase of its magnitude numerical value mountain electricity electrode current is (from about 10 ^-14to 10 ^-6a) and the appearance of the aura dim at the electrode place that radius of curvature is less characterized.

The computing formula of threshold values field intensity is:

(E _r) _s＝E ₀mδ[1+K/(δr) ^1/2] （1）

(E in formula _r) _sfor threshold values field, E ₀=3100kV/m (the spark field intensity in the uniform field that this value is equivalent to aerial discharge gap under standard state when being lcm), m is a coefficient (0.6<m<l) describing conductive surface state, and δ is the relative density of air: δ=2.94X10 ^-3p/ (273+T) (P, in units of Pa, works as P=101325Pa, during T=25 DEG C, and δ=1), K=3.08X10-2m ^1/2, r is the radius of electrode tip.

For different curvature electrode as plate electrode, computing formula is:

${\left(E_r\right)}_s=E_0(1+\frac{K}{{(r/2)}^{1/2}})---\left(2\right)$

Here E ₀identical with formula (1) with the numerical value of K, m and δ is 1.Above formula to the little negative electrode of radius of curvature or anode all applicable.

The calculating of threshold voltage:

(3) paraboloidal pin-plane clearance, the radius on pin top is r, and clearance distance is d, then along axle center, gap from the electric-field intensity of pin top χ distance be:

$\mathrm{Ex}=\frac{2V}{(r+2x)\ln [(r+2d)/r]}---\left(3\right)$

Threshold voltage is:

V _s＝(E _r) _s(r/2)ln[(r+2d)/r] （4）

For grinding machine processing operating mode, suppose that the tip radius of needle electrode 17 is 0.5mm, die opening is that the effect of 20-30cm(electric field force when distance is greater than 30cm falls into a decline).Calculating discharge inception voltage scope according to formula (4) is 15.2848-16.2064KV.

When after generation corona discharge, increase potential difference if continue, then current strength will increase, and size and the brightness thereof of luminescent layer also increase simultaneously.When applied voltage higher than threshold voltage a lot of time, corona discharge can change spark discharge-scintillant into and puncture.

Make nozzle angle remain on 30 ° when carrying out grinding, when nozzle and workpiece distance are 20cm, known nozzle and workpiece minimum range are 20sin30 °=10cm(nozzle and workpiece vertical range).When working environment air pressure p is 10 ⁵during the air of pa, table look-up known when d is 10cm spark breakdown voltage be 265KV, when d is 20cm, spark breakdown voltage is 510KV.Its spark breakdown voltage visible is very high.

Electrostatic drop atomization mechanism:

Electrostatic atomization is that electrostatic force overcomes surface tension of liquid, thus causes liquid crushing to be the phenomenon of mist droplet.Due to corona discharge effect, under " surface action ", make drip gauge wear a large amount of same sex electric charges, add liquid surface activity, surface molecules is produced and aligns significantly, reduce surface tension.When droplet size is constant, along with quantities of charge increases, surface tension can reduce gradually.When capillary size is not enough to constraint liquid, liquid just can be broken for fine mist under the liquid surface disturbances that causes of repulsive interaction between surperficial same sex electric charge and external force.

Between drop and gas around, have higher relative velocity, then the division of drop is controlled by Pneumatic pressure, surface tension and viscous force.For the liquid that viscosity is lower, the fragmentation of drop determines primarily of Pneumatic pressure and surface tension.Pneumatic pressure suffered by large drop is 0.5 ρ _gΔ V ², wherein ρ _gbe gas density, Δ V is gas-liquid relative velocity.But obstruction drop deforms fragmentation by the cohesive force that surface tension produces, and cohesive force can be expressed as 4 σ/D, σ is the intrinsic surface tension of liquid, and D is initial drop diameter.

When liquid-drop diameter reduces, cohesive force strengthens, and when the tension that cohesive force and Pneumatic pressure cause balances, drop keeps stable, if both can not cancel each other, drop will be out of shape even broken.The cohesive force that the tension produced according to the aerodynamic force acted on drop and surface tension produce balances this principle, can draw a dimensionless number:

$\mathrm{We}=\frac{{\mathrm{\&rho;}}_g{\mathrm{\&Delta;V}}^{2}D}{\mathrm{\&sigma;}}=8---\left(5\right)$

Thus known when Weber number is greater than 8, drop, by force unbalance, deforms.The maximum steady state liquid-drop diameter corresponding with Δ V can be obtained in addition according to (5):

$D_{\max }=\frac{8\mathrm{\&sigma;}}{{\mathrm{\&Delta;V}}^2{\mathrm{\&rho;}}_g}---\left(6\right)$

Charged droplet is under the effect of Coulomb repulsion, and surface tension dies down, and the surface tension value after dying down is:

${\mathrm{\&sigma;}}^{\&prime;}=\mathrm{\&sigma;}-\frac{q^2}{64{\mathrm{\&pi;}}^2{\mathrm{\&epsiv;r}}^3}---\left(7\right)$

Wherein r is droplet radius, and q is the carrying capacity of drop, and ε is surrounding air dielectric constant.Obviously can find out when carried charge q increases from formula, surface tension just declines, it can thus be appreciated that drop surface charge contributes to atomization.

Now the We of charged droplet can be expressed as:

$\mathrm{We}=\frac{{\mathrm{\&rho;}}_g{\mathrm{\&Delta;V}}^{2}D}{\mathrm{\&sigma;}-\frac{q^2}{64{\mathrm{\&pi;}}^2{\mathrm{\&epsiv;r}}^3}}=\frac{{128\mathrm{\&pi;}}^2{\mathrm{\&epsiv;R}}^4{\mathrm{\&rho;}}_g{\mathrm{\&Delta;V}}^2}{{64\mathrm{\&pi;}}^2\mathrm{\&epsiv;}{R}^3\mathrm{\&sigma;}-q^2}---\left(8\right)$

From (8), in high velocity air, there is close relationship the fragmentation of charged droplet and gas-liquid relative velocity, gas-liquid physical parameter and field of charging.In addition, if drop reaches stable state in the gas flow, on lotus after electrostatic, We number increases, and surface tension of liquid reduces, and is not enough to resisting pneumatic pressure, drop by deforming further, broken, so when gas-liquid parameter is identical, on lotus, after electrostatic, mist droplet particle size is less.This just reaches the object of refinement droplet particle, and the electric charge that drop surface is identical simultaneously, can ensure that the distribution of drop is more even.

The charging mechanism of drop:

When there is negative polarity corona discharge at the tip of needle electrode 17, a large amount of ions can produced in corona zone, cation can move to electrode cathode and electrical counteract occur, and anion and electrons anode move, enter drift region, at drift region and droplet collision, be attached on drop, make drop become electric charge carrier, bring the electric charge identical with polarity of electrode.

The carrying capacity computing formula of droplet corona charging is as follows:

$q=f[1+2\frac{k-1}{k+2}]{4\mathrm{\&pi;\&epsiv;}}_0{\mathrm{Er}}^2---\left(9\right)$

In formula (9) $f=\frac{\frac{\mathrm{NeKi}}{{4\mathrm{\&epsiv;}}_0}t}{\frac{\mathrm{NeKi}}{{4\mathrm{\&epsiv;}}_0}t+1}---\left(10\right)$

Q---droplet carrying capacity, C;

K---droplet dielectric constant;

ε ₀---dielectric constant of air, is about 8.85 × 10 ^-12, c ²/ nm ²;

The electric-field intensity that E---corona discharge is formed, V/m;

R---droplet radius, μm;

N---charged ions concentration, population/m ²;

E---electron charge, 1.6 × 10 ^-19, C;

Ki---charged ions mobility, m ²/ (Vs);

T---charging holdup time, s.

From the droplet of nozzle ejection, to workpiece accelerated motion under the effect of aerodynamic force and electric field force, its speed is greatly between 50m/s to 70m/s.Nozzle is 20cm to 30cm to the distance of workpiece, so run duration is between 0.0029s to 0.006s.But the charged required time of droplet is only 10 ^-7s to 10 ^-6s, can ensure from the mist of oil of nozzle ejection fully charged before arrival workpiece.

When the droplet of nozzle ejection is by after charged, displacement under the effect of electric field force, what make its maximum is covered in surface of the work.In charged process, because nanoparticle surface is larger, surface polarity is stronger, after charged, its charge-mass ratio is larger than the charge-mass ratio of droplet, so nano particle is tending towards more early arriving workpiece, cover oil film lower floor, the exchange capability of heat that can better utilize it desirable like this.In electrostatic field, there is " electrostatic is encircled " effect, therefore when droplet and nano particle are more easily enter into workpiece to have certain roughness depression in the surface place to workpiece motion s, thus expand relative area coverage, better lubrication and heat exchange effect can be played.

Can find out according to Fig. 7, adjustable high voltage D. C 37 is made up of self-maintained circuit, power amplification circuit, high-frequency impulse stepup transformer, voltage doubling rectifing circuit, direct-flow voltage regulation unit V1 and direct-flow voltage regulation unit V2 and constant current automatic control circuit.Its operation principle is input termination AC power, and direct-flow voltage regulation unit V1 and direct-flow voltage regulation unit V2 provides DC voltage.Direct-flow voltage regulation unit V1 is as the operating voltage of self-maintained circuit.Direct-flow voltage regulation unit V2 is the main energy sources of power transfer, high-frequency impulse stepup transformer obtains high-pressure electrostatic through voltage doubling rectifing circuit rectification, main pulse signal is obtained by self-maintained circuit, after power amplification circuit amplifies, under the boosting of high-frequency impulse stepup transformer, final output high-voltage signal, through voltage doubling rectifing circuit thus export high direct voltage.

The feature of this power supply to produce higher electrostatic high-pressure, and supply current is small, is generally no more than 500 μ A.Constant current automatic control circuit samples the electrostatic operating current of voltage doubling rectifing circuit automatically, when constant current, when workload normally strengthens, can not cause the rising of operating current.When outer load exceedes permission electric current, self-maintained circuit stops shake, and high pressure is cut off, the safety of this characteristic to operating personnel is reliable, once close to or touch high-pressure side, the shock current caused is very faint, block High voltage output, so can not be in peril of one's life simultaneously.

Claims (8)

1. a nano-fluid electrostatic atomization controllable jet micro lubricating grinding system, it is characterized in that, it comprises grinding system, grinding system is provided with corona charging nozzle, the nozzle body of corona charging nozzle is connected with liquid-supplying system, air supply system, the high-magnitude DC electrostatic generator of nozzle body bottom is connected with the negative pole of adjustable high voltage D. C, and the positive pole of adjustable high voltage D. C is connected with workpiece power-up device, and workpiece power-up device is attached to the not finished surface of workpiece; Grinding nanometer fluid liquid sends into corona charging nozzle by liquid-supplying system, compressed air is sent into corona charging nozzle by air supply system simultaneously, grinding nanometer fluid liquid by compressed air drive export ejection atomization from nozzle body while by high-magnitude DC electrostatic generator charged be controllable jet, the grinding area being distributed to processing work controlled under the effect of electric field force and aerodynamic force;

Described workpiece power-up device comprises workpiece power-up device insulation shell, foundary weight, permanent magnet, holddown spring; Permanent magnet is arranged on workpiece power-up device insulation shell periphery; In the middle part of workpiece power-up device insulation shell, have opening, foundary weight stretches out workpiece power-up device insulation shell from one end and is set with holddown spring; Foundary weight has split pin slot, and for insertion opening pin, foundary weight is connected with the positive pole of adjustable high voltage D. C;

Described liquid-supplying system is connected with nozzle body by nano-fluid conveying coiled pipe, and air supply system is connected with nozzle body by Compressed Gas conveying coiled pipe.

2. nano-fluid electrostatic atomization controllable jet micro lubricating grinding system as claimed in claim 1, it is characterized in that, described high-magnitude DC electrostatic generator comprises the electrode tray being arranged on corona charging nozzle bottom, electrode tray is made up of insulating materials, along the multiple electrode slot of its circumference array, needle electrode is arranged in electrode slot; In electrode tray central diameter, place has wiring duct, installation high-voltage electric wire in it, and on electrode tray, has a high-tension bus-bar pallet pick out through hole, and each needle electrode is all connected with high-tension bus-bar, and high-tension bus-bar is connected with adjustable high voltage D. C negative pole; Electrode tray bottom is positioning threads ring, and positioning threads adopts ceramic material to make, and with the external screw thread coordinated with corona charging nozzle, positions electrode tray.

3. nano-fluid electrostatic atomization controllable jet micro lubricating grinding system as claimed in claim 1, it is characterized in that, described adjustable high voltage D. C comprises transformer, primary is connected with AC power, two secondary lines are respectively as direct-flow voltage regulation unit V1 and direct-flow voltage regulation unit V2, direct-flow voltage regulation unit V1 is connected with self-maintained circuit, self-maintained circuit and power amplification circuit, high-frequency impulse stepup transformer and voltage doubling rectifing circuit, constant current automatic control circuit connects, constant current automatic control circuit is connected with direct-flow voltage regulation unit V2, direct-flow voltage regulation unit V2 is connected with power amplification unit, the adjustable voltage scope of adjustable high voltage D. C is between 2KV to 120KV, direct-flow voltage regulation unit V1 is as the operating voltage of self-maintained circuit, direct-flow voltage regulation unit V2 is the main energy sources of power transfer, pulse signal is obtained by self-maintained circuit, after power amplification circuit amplifies, under the boosting of high-frequency impulse stepup transformer, final output high-voltage signal, through voltage doubling rectifing circuit thus export high direct voltage, constant current automatic control circuit samples the electrostatic operating current of voltage doubling rectifing circuit automatically, when constant current, when workload normally strengthens, can not cause the rising of operating current, when outer load exceedes permission electric current, self-maintained circuit stops shake, and high pressure is cut off.

4. nano-fluid electrostatic atomization controllable jet micro lubricating grinding system as claimed in claim 2, it is characterized in that, the grinding nanometer fluid liquid of atomization is charged in the drift region of needle electrode corona discharge and the electron collision of drift, controlledly under electric field force, aerodynamic force and Action of Gravity Field after droplets sprays to surface of the work.

5. nano-fluid electrostatic atomization controllable jet micro lubricating grinding system as claimed in claim 2, is characterized in that, be interference fit, clamp needle electrode by the elastic deformation force of insulating materials between described needle electrode and electrode slot.

6. the nano-fluid electrostatic atomization controllable jet micro lubricating grinding system as described in claim 2 or 5, it is characterized in that, the discharge tip radius of described needle electrode is 0.5mm, and die opening is 20-30cm, and discharge inception voltage scope is 15.2848-16.2064KV.

7. nano-fluid electrostatic atomization controllable jet micro lubricating grinding system as claimed in claim 1, it is characterized in that, the nozzle angle of described nozzle body remains on 30 ° to 45 °, and nozzle body outlet is 20-30cm with the jet length of workpiece.

8. nano-fluid electrostatic atomization controllable jet micro lubricating grinding system as claimed in claim 1, it is characterized in that, the carrying capacity computing formula of droplet corona charging is as follows:

$q=f[1+2\frac{k-1}{k+2}]{4\mathrm{\&pi;\&epsiv;}}_0{\mathrm{Er}}^2$

In formula $f=\frac{\frac{\mathrm{NeKi}}{{4\mathrm{\&epsiv;}}_0}t}{\frac{\mathrm{NeKi}}{{4\mathrm{\&epsiv;}}_0}t+1}$

Q---droplet carrying capacity, C;

K---droplet dielectric constant;

ε ₀---dielectric constant of air is 8.85 × 10 ^-12, c ²/ nm ²;

The electric-field intensity that E---corona discharge is formed, V/m;

R---droplet radius, μm;

N---charged ions concentration, population/m ²;

E---electron charge, 1.6 × 10 ^-19, C;

Ki---charged ions mobility, m ²/ (Vs);

T---charging holdup time, s.