Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J49/00—Particle spectrometers or separator tubes
  • H01J49/02—Details
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D33/00—Non-positive-displacement pumps with other than pure rotation, e.g. of oscillating type

Definitions

• the present invention relates to electrostatic gas pumps, and more particularly to methods and apparatuses for producing greater gas flow rates in an electrostatic pump.
• An electrostatic gas pump consists of one or more sharp (corona) and blunt
• neutralizing electrodes An electric field is applied between the two electrodes causing a partial breakdown of the gas, referred to as a corona discharge, near the sharp electrode.
• the discharge produces ions which are attracted to the neutralizing electrode.
• the ions collide with neutral gas molecules creating pressure head and flow similar to that produced by a mechanical fan.
• the flat electrode does not confine the ionization region, so it will arc at a lower voltage and have less pumping power. Finally, the flat electrode does not isolate neighboring electrodes. This necessitates a much larger spacing between electrodes and again decreases the total ion current and pumping power.
• the present invention achieves high gas flow rates through an electrostatic pump having sharp and blunt electrodes with a corona discharge taking place in the gas gap in between the electrodes.
• the invention comprises a specially shaped blunt electrode that is contoured to maintain a constant or approximately constant distance between the sharp (corona) electrode and the neutralizing surface of the blunt electrode.
• the contour provides maximum electric field enhancement at the corona electrode and minimizes the electric field at the blunt electrode. This maximizes the non-arcing operating voltage and increases the maximum power output of the corona discharge.
• the contour also isolates neighboring corona electrodes, preventing their electric fields from interfering with one another and making it possible to increase the density of electrodes which further increases the pumping power of the device.
• FIGs. IA and IB illustrate a contoured blunt electrode for use with a wire-type sharp electrode according to aspects of the invention
• FIGs. 2 and 3 illustrate possible embodiments of an electrostatic pump using a contoured blunt electrode such as that shown in FIG. 1;
• FIGs. 4A to 4C show examples of extruded-type cross sections for a corona electrode that can be used together with a contoured blunt electrode according to aspects of the invention
• FIG. 5 illustrates a configuration of a corona electrode having protruding point-type electrodes that can be used in embodiments of the invention.
• FIG. 6 illustrates an electrostatic pump having a plurality of contoured blunt electrodes respectively paired with a plurality of point-like corona electrodes according to other possible embodiments of the invention.
• the present invention uses a specially shaped blunt electrode having substantial portions of its leading surface located a constant, or near constant, distance from the corona electrode.
• the leading surface comprises the surface that is closest to the corona electrodes, and is the portion of the blunt electrode where the majority of the electric field lines either originate or terminate (depending on the polarity).
• FIGs. IA and IB illustrate certain aspects of the invention in an electrostatic pump having a blunt electrode 102 and corona electrode 104.
• the blunt electrode 102 rather than having a flat shape as in the prior art, has a contoured neutralizing surface 106 facing the corona electrode 104.
• FIG. IB which is taken along sectional line
• surface 106 of blunt electrode 102 facing corona electrode 104 is contoured such that the distance d between a given point on corona electrode 104 is substantially the same at all points on surface 106 of blunt electrode 102 that directly underlie that point. Accordingly, as shown in FIG. IA, for a given length of the corona electrode 104, the contour of the neutralizing surface 106 of the blunt electrode 102 is similar to a portion of the inside of a hollow partial cylinder, the partial cylinder having a height corresponding to the given length.
• the angle ⁇ in FIG. IA when d is substantially the same between all points on surface 106 from a given point on corona electrode 104, can thus be considered as defining the size of an arc with the corona electrode 104 as the center.
• the angle ⁇ can be any value greater than 0° and up to 360°.
• the inventors note that the electric field enhancement at the corona electrode increases as ⁇ increases.
• the isolation between neighboring corona electrodes (not shown) afforded by the contoured blunt electrode also increases as ⁇ increases.
• the present inventors further recognize that as ⁇ is increased beyond 180°, some of the ions begin to be attracted in the upstream direction and exert a detrimental effect on the gas flow.
• FIG. 2 illustrates one example embodiment of an electrostatic gas pump according to aspects of the invention.
• pump 200 employs a series of parallel blunt electrode fins 202 that run perpendicular to the corona electrodes 204.
• each fin 202 has a contoured neutralizing surface facing each of the corona electrodes as described above in connection with FIGs. IA and IB.
• the spacing between the blunt electrode fins 202 define channels 206, and the overall configuration of the provides an array of multiple, parallel electrostatic discharges between the electrodes.
• the channels 206 further allow gas to flow efficiently through the device as a result of the electrostatic pumping action, in the direction illustrated by the large arrows.
• This embodiment also shows an array of corona wires implementing the corona electrodes 204.
• FIG. 3 illustrates another example embodiment of an electrostatic gas pump according to the invention.
• pump 300 includes walls 308 running parallel to direction of the corona electrodes 304 that define separated channels 306 for the flow of gas in between the blunt electrode fins 302 and further between each of their contoured neutralizing surfaces.
• the walls 308 further help to maintain a high electric field concentration over all portions of the corona electrode, particularly in the region between the contoured fins.
• the walls 308 also help to reduce the electric field at the blunt electrode and to provide additional electrical isolation between neighboring corona electrodes 304.
• the above described corona electrodes can be comprised of a thin wire and the blunt electrodes can be comprised of a heat sink fin material such as aluminum.
• the distance d between the corona electrode and blunt electrode surface i.e.
• the electrode gap is about 30 mm
• the corona electrode wire has a diameter of about 0.5 mm
• the voltage applied to the electrode is about 20 kV
• blunt electrode fins have a thickness of about 1 mm.
• the distance d is about 2 mm
• the corona electrode wire has a diameter of about 2 microns
• the voltage is about 1500 V
• the blunt electrode fin has a thickness of about 0.2 mm, and is approximately a semi- cylinder contour (i.e. ⁇ is about 180 degrees).
• the present inventors have recognized that it is desirable to make the electrode gap as small as possible.
• the inventors have demonstrated electrostatic air pumps with gaps from 0.5 to 3 mm and voltages from 1200 to 5000 V. Eventually, the gap can be lowered to 100 ⁇ m with a operating voltage of several hundreds of volts while still maintaining a similar pumping outputs as the larger gaps.
• Corona wire spacing e.g. separation of parallel corona electrodes 204 and 304 is approximately equal to twice the gas gap. As the gap decreases, wire spacing can also decrease.
• FIGs. 4A, 4B and 4C show cross sections of various prismatic shapes of corona electrodes that can be used either singularly as in FIG. 1 or in linear arrays as in FIGs. 2 and 3.
• FIGs. 4A and 4B show elliptical (e.g. circular) and rectangular (e.g. square) shaped cross sections, respectively, of a wire that can be used to implement the corona electrode.
• FIG. 4C shows a knife edge or razor blade cross section of an extruded shape that is used to implement the corona electrode, rather than a wire. It should be apparent that other shapes are possible, such as hexagonal.
• FIG. 5 shows an array of point-type corona electrode configurations, in which the corona electrode is implemented by a supporting member 502 with a plurality of sharp points 504 protruding therefrom.
• the contoured blunt electrode should preferably be a constant or nearly constant distance from the corona region of the sharp electrode, and not necessarily all portions of the electrode.
• FIG. 6 Another possible embodiment involving a plurality of individual point-type corona electrodes is shown in FIG. 6. As shown in FIG.
• an electrostatic gas pump 600 includes contoured blunt electrodes 602 that are configured in sets of four fins that together resemble the inside portion of a hollow sphere facing the respective corona electrode 604. While different in configuration and layout as the pumps in FIGs. 2 and 3, the operating concept is the same as in the wire-type electrodes described earlier.
• the contoured surfaces of the blunt electrodes 602 are a constant or near constant distance from the corona creating region of the point-type corona electrodes 604, except that the overall contour of the blunt electrode is spherical instead of cylindrical as in FIGs. 1-3.
• the contoured electrode described herein by virtue of its geometry, creates the maximum the electric field enhancement at the corona electrode.
• High field enhancement gives this invention many advantageous attributes. First, it results in a lower turn-on voltage for a given gas gap and corona electrode size. Second, since the gas only breaks down where the electric field is high, a high field enhancement confines the ionization region closely to the corona electrode. This makes it more difficult for the corona discharge to transform to an arc as the voltage is increased. Thus, the voltage operating window is larger. Delay of arcing as voltage increases also leads to a higher ion density from a given corona electrode.
• a second major advantage of the contoured electrode is that the electric field lines between the corona electrode and the contoured electrodes are better confined to the region in between the electrodes. The field lines from neighboring electrodes do not interfere. Corona electrodes can be place together more closely and still have the high field enhancement necessary to produce a high quality corona discharge and gas flow. The higher density of electrodes leads to a larger ion current in a given area and results in larger gas flow rates.
• contoured electrode is that with pumps having a plurality of corona electrodes, for example those shown in FIGs. 2 and 3, the spacing between the blunt electrode fins has very little effect on the ion current and pumping power. This gives the designer the freedom to set that spacing such that it optimizes other parameters, such as flow rate, heat transfer and such.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Electron Tubes For Measurement (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Treating Waste Gases (AREA)

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Citations (3)

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• 2008
  • 2008-01-22 WO PCT/US2008/051722 patent/WO2008091905A1/en active Application Filing
  • 2008-01-22 EP EP08728095A patent/EP2126956A1/en not_active Withdrawn
  • 2008-01-22 US US12/017,986 patent/US20080175720A1/en not_active Abandoned
  • 2008-01-22 KR KR1020097017527A patent/KR20090107548A/ko not_active Application Discontinuation
  • 2008-01-22 CN CN200880006317A patent/CN101622687A/zh active Pending
  • 2008-01-22 JP JP2009547386A patent/JP2010517241A/ja active Pending
  • 2008-01-23 TW TW097102574A patent/TW200903558A/zh unknown

Patent Citations (3)

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