JP2009500160A - Electrostatic atomizer - Google Patents

Abstract

The present invention relates to an electrostatic fluid atomizing device having a fluid inlet (2) and a fluid channel (3) for guiding fluid to a wall (6) in which an orifice (100) is formed (see FIG. 1). The fluid exiting the orifice (100) is atomized into droplets corresponding to the first group of large droplets (12) and the second group of small droplets (13). The two charging electrodes (4, 6) charge the fluid passing through the flow path (3). The droplet separator (200) applies electrical force to the droplets to deflect the small droplets (13) without deflecting the large droplets (12) from the droplets (201) of the atomizer. It has a separator electrode (16) that is collected by a droplet collector (15).
[Selection] Figure 1

Description

  The present invention is very important that the droplets are consistently sized, i.e. their diameters fall within a selected diameter range, despite the need for high flow rates, especially drying, coating, And an electrostatic atomizer having a wide variety of applications in the field of mixing.

The closest known prior art is the international application PCT / GB2004 / 000458 according to the applicant's own prior application. This prior published patent application discloses the use of a multi-orifice atomizer with a main charging electrode straddling an array of orifices. With a constant flow rate, such an electrostatic atomizer produces two sets of distinctly different diameter droplets. Due to the physics of droplet formation, each pair of large droplets is separated by a small droplet. For example, small droplets can have a diameter between 20 and 80 microns, while large droplets can have a diameter between 150 and 350 microns. Because of such diameter differences, small droplets have a much lower specific charge while having a much lower mass than large droplets. In many applications, it is desirable to obtain fluid droplets that are consistently sized, i.e., within a selected diameter range, thus requiring an electrostatic atomizer that acts to separate large droplets from small droplets. is there.
International Application PCT / GB2004 / 000458 (International Publication WO 2004/071670 A1)

  In the first aspect, the present invention relates to a fluid inlet, a first group of droplets having the same diameter, and a second group of liquids having the same diameter and smaller diameter than the first group of droplets. One or more orifices that discharge an atomized form of fluid that includes at least a droplet; a fluid flow path that connects the fluid inlet to the orifice; and at least for applying a charge to the fluid that passes through the fluid flow path An electrostatic fluid atomizer comprising two charging electrodes, wherein the second group of electrostatic fluid atomizers are grounded or charged and continue to exit the first group of large droplets from the droplet outlet of the atomizer. An electrostatic atomizer comprising a fluid droplet separator downstream of an orifice, having a separator electrode that applies an electrical force to the droplet that deflects a small droplet to an atomizer droplet collector provide.

  This configuration is advantageous because it allows the electrostatic fluid atomizer to output only fluid droplets with a diameter that falls within the selected range.

  The droplet collector can comprise a hygroscopic wall or a porous wall. The walls are cylindrical and can be located around the droplets as they exit the orifice. A fluid droplet connector can be connected to the fluid return line. If the droplet collector includes a cylindrical wall surrounding the droplet exiting the orifice, the fluid return line can easily be avoided from intersecting the orifice path.

  The fluid return line returns the collected droplets to the fluid input. This configuration maximizes the efficiency of the electrostatic atomizer. There is no waste or minimal waste.

  The orifice can include a number of orifices in close proximity to one substantially flat surface of a charging electrode straddling the number of orifices. This configuration achieves the ideal combination of atomization that diffuses evenly across multiple orifices and efficient collection of the second group of droplets.

  The orifice can be tilted to produce a convergent or divergent stream of atomized droplets. In certain applications, generating a directed stream can improve collection by the droplet collector as compared to the use of parallel linear orifices.

  The orifice is preferably provided in the orifice wall, and the droplet collector can then be provided with a plurality of portions of the orifice wall that project downstream from between the orifices. This not only allows for improved collection of small droplets within the central portion of the orifice array, but also allows for excellent collection of small droplets from the outer portion of the fluid ejection. Become.

  The separator electrode of the fluid droplet separator can be electrically connected to one of the charging electrodes.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an electrostatic atomizer 1 having a fluid inlet 2. The fluid flow path 3 connects the fluid inlet 3 to an array 100 of multiple orifices provided in the orifice wall 6. The fluid passing through the flow path 3 is charged by a pair of charging electrodes including an electrode 4 and an orifice wall 5. It can be seen in the figure that the high voltage source 18 is connected to apply a charge of the first polarity to the charging electrode 4 and to apply a charge of the opposite polarity to the wall 6. The electrode 4 has a tip 5 that is substantially flat and straddles an array 100 of multiple orifices. A fluid, which can be any type of chargeable fluid, is pumped by the pump 7 to the fluid inlet. Prior to pumping, the fluid is filtered by filter 8.

  Upon exiting the orifice 6, the fluid is atomized and initially forms so-called “ligament” jets 9, 10, and 11, immediately thereafter, substantially two sets of droplets of different sizes, ie It breaks down into a first group containing droplets such as droplet 12 (a relatively large droplet) and a second group containing droplets such as droplet 13 (a relatively small droplet). Each small droplet necessarily has a lower mass and a much higher specific charge than a large droplet.

  In the atomizing device 1, a set of small diameter droplets (for example 12) is replaced with a set of large diameter droplets (for example 13) so that only the large diameter droplets leave from the fluid outlet 201 of the atomization device. A fluid droplet separator 200 is provided for separating from the fluid. Separator 200 has a cylindrical wall 16 that encloses the droplets exiting from orifice 100. Wall 16 functions as a separator electrode and is appropriately charged or grounded to attract droplets. In the figure, wall 16 is connected to a high voltage source and is charged to the same polarity as wall 6. Small droplets are attracted more than large droplets. Thus, the small droplets deflect toward the wall 16 while the large droplets remain largely undeflected and exit from the fluid outlet 201. Separator 200 has a layer 14 of porous hygroscopic material located radially inward from wall 16. The wall 16 has a downstream portion that extends around the downstream end of the porous layer 14, and the wall 16 extends radially inward to form a fluid flow path 15 at the downstream end of the layer 14.

  The collected fluid is drawn out from the flow path 15 by the scavenging pump 17. The scavenging pump 17 draws the fluid from the droplet collector 100 and relays the fluid to the accumulator tank 101. The fluid from tank 101 is then filtered and pumped back to fluid inlet 2.

  The voltage applied to the charging electrodes 4, 6 and the wall 16 (which functions as a separator electrode), and the size of the orifice 100 are dependent on the characteristics of the fluid used, the selected flow rate, and the desired output droplet size. Can be adjusted according to.

  In the embodiment of FIG. 1, the wall 6 is provided with a number of straight parallel orifices 100. An alternative geometric arrangement of orifices is shown in FIGS. 2a and 2b. FIG. 2a shows a divergent array of orifices 110 that provide a divergent stream of droplets. FIG. 2b shows a converging array of orifices 111 that provide a converging stream of droplets. The use of the orifices 110, 111 of FIG. 3a or 3b may be suitable for certain fluids.

  FIG. 3 shows an electrostatic atomizer 19 according to the second embodiment. This embodiment shares many components in common with the first embodiment of FIG. 1, and the same reference numerals are assigned to the same components. The atomizing device has two charging electrodes 26, 27. They are both connected to the high voltage source 18, a first polarity voltage is applied to the electrode 26, and a second opposite polarity voltage is applied to the electrode formed by the orifice wall 27. Orifice wall 27 has a number of orifices provided with reference numerals 20, 21, 22, 23. The fluid passing through the orifices 20, 21, 22, 23 is atomized to form two sets of droplets, one set of small diameter droplets and one set of large diameter droplets. All droplets move into the droplet separator 24. The droplet separator 24 has an outer wall 25 that is charged or grounded to attract and collect small droplets from the outer jets 28, 29. In the figure, it can be seen that the separator wall 25 is connected to the high voltage source 18 and charged to the same polarity as the orifice wall 27. The droplet separator 24 also has a central collection rod 30 that is charged or grounded to attract and collect the droplets of the central streams 31 and 32. In the figure, the electrode 30 is electrically connected to the charging electrode 27 and is charged to the same polarity. The outer wall 25 and the rod 30 are provided with a hygroscopic layer. There is a layer 34 for the wall 25 and a layer 35 for the rod 30. The scavenging pump 33 is provided for extracting the fluid collected by the rod 27 through the pipe 36 and transferring it to the accumulator tank 101. The tube 36 penetrates through a central passage provided through the electrode 26.

  The lowermost surface of the charging electrode 26 is provided with a rough surface facing the orifices 20, 21, 22, 23, for example by providing a facet element in a diamond coating or the like to improve the charging of the fluid ( As described in the applicant's own previous patent application PCT / GB2004 / 000458). Only the portion of the surface facing the orifices 20, 21, 22, 23 need be roughened / coated.

  The present invention also envisages the use of several spaced rods of the same type as the large multi-orifice array rod 30 to minimize the occurrence of small droplets being ejected from the atomizer. The rods extend downward (i.e. downstream) from the orifice wall 27 and are spaced from each other and extend from the portion of the wall 27 located between the orifices in the wall 27.

  FIG. 4 shows a further embodiment of an electrostatic atomizer 39 having the same components with the same reference numbers as FIG. Similar to the embodiment of FIG. 1, it is an array of multiple orifices 42, 43, 44, 45 in an orifice wall 46 that also functions as an input fluid line 40, a charging electrode 41, a second charging electrode, and charged or grounded A drop separator 47 with an outer cylindrical drop collector wall 48. As shown, the collector wall 48 is connected to the high voltage source 18 and is charged to the same polarity as the orifice wall 46. In addition, a central rod 50 is placed in the spray channel 49 of the separator 47 and the rod 50 is appropriately charged so as to repel small charged droplets in the direction of the wall 48 where they are collected. The top of the rod 50 is separated from the orifice wall 46 by an insulator 51. The rod 50 is electrically connected to the charging electrode 41 by a connector 52. On the flat bottom surface of the electrode 41, facet elements are provided only in regions facing the orifices 42, 43, 44, 45.

FIG. 1 is a partial cross-sectional perspective view of a first embodiment of an electrostatic fluid atomizer according to the present invention, schematically showing components external to the atomizer. 2a and 2b show alternative geometric arrangements of orifices of the atomizer of FIG. 1 (or the atomizer of FIGS. 3 and 4). FIG. 3 is a cross-sectional view of a second embodiment of an electrostatic fluid atomizer according to the present invention, schematically showing again the external components of the atomizer. FIG. 4 is a diagram showing a third embodiment of the electrostatic fluid atomizer according to the present invention, schematically showing the external components of the atomizer once more.

Claims (17)

A fluid inlet;
A first group of droplets of similar diameter and a fluid in an atomized form containing at least a second group of droplets of the same size and smaller than the first group of droplets. One or more orifices to
A fluid flow path connecting the fluid inlet to the orifice;
An electrostatic atomizer comprising: at least two charged electrodes for applying a charge to a fluid passing through a fluid flow path;
An electric force is applied to the droplets that is grounded or charged and deflects the small droplets of the second group to the droplet collector while continuing to eject the large droplets of the first group from the droplet outlet of the atomizer. An electrostatic atomizer comprising a fluid droplet separator having a first separator electrode extending downstream of an orifice.   The electrostatic atomizer of claim 1, wherein the droplet collector includes a hygroscopic layer.   The electrostatic atomizer according to claim 1 or 2, wherein the first separator electrode applies a suction electric force that attracts the fluid droplet to move toward the first separator electrode.   The electrostatic atomizer according to any one of claims 1 to 3, wherein the first separator electrode is a cylindrical wall disposed around the orifice and extending downward.   A second separator electrode that extends parallel to and spaced from the cylindrical wall and that is grounded or charged to apply an attractive electrical force to the droplet is provided, and the atomizer is attracted by the second separator electrode The electrostatic atomizer of Claim 4 which has a 2nd fluid droplet collector which collects a droplet.   The second fluid droplet collector is connected to the fluid return path via a conduit passing through the passage formed in the charging electrode, and the fluid return path passes the fluid collected by the droplet collector to the fluid inlet. The electrostatic atomizer of Claim 5 made to recirculate | reflux.   A plurality of fluids, wherein an orifice is provided in the orifice wall, and wherein the fluid droplet separator is spaced from each other and extends from a location between the orifices of the orifice wall and extends downstream from the orifice wall The electrostatic atomizer as described in any one of Claims 1 thru | or 6 containing a collector.   9. The electrostatic atomizer of claim 8, wherein each fluid collector is individually associated with a separator electrode that is charged to draw fluid droplets to the fluid collector.   The electrostatic atomizer according to claim 7 or 8, wherein the orifice wall functions as a charging electrode.   A second separator electrode spaced apart from the first separator electrode and charged with a voltage of a polarity different from that of the first separator electrode, wherein the liquid droplets are liquid from the second electrode; The electrostatic atomizer of Claim 3 which applies the repulsive electric force repelled in the direction of a droplet collector to a fluid droplet.   The electrostatic atomizer as described in any one of Claim 1 thru | or 6 or 10 with which the orifice was provided in the orifice wall which functions also as one of the charging electrodes.   The electrostatic atomizer according to claim 1, further comprising a fluid return path for returning the fluid collected by the droplet collector to the fluid inlet.   The electrostatic atomization according to any one of claims 1 to 12, wherein the atomizer incorporates a large number of orifices in close proximity to a substantially flat surface of a charging electrode straddling the large number of orifices. apparatus.   14. An electrostatic atomizer as claimed in any one of the preceding claims, comprising an orifice inclined to produce a converging stream of droplets.   14. An electrostatic atomizer as claimed in any one of the preceding claims comprising an orifice inclined to produce a divergent stream of droplets.   The electrostatic atomizer according to claim 1, wherein a first separator electrode is electrically connected to one of the charging electrodes.   The electrostatic atomizer of any one of claims 5, 6, 7, or 10, wherein a second separator electrode is electrically connected to one of the charged electrodes.

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