WO2005030397A1

WO2005030397A1 - Electrostatic precipitator for diesel blow-by

Info

Publication number: WO2005030397A1
Application number: PCT/US2004/030628
Authority: WO
Inventors: Benjamin Y. H. Liu
Original assignee: Msp Corporation
Priority date: 2003-09-23
Filing date: 2004-09-20
Publication date: 2005-04-07
Also published as: US7267711B2; US20050061152A1

Abstract

A compact electrostatic precipitator (50) is designed specifically for use in connection with eliminating particles from crankcase emissions of a Diesel engine (55). Such emissions may carry solid soot particles as well as suspended oil droplets. The electrostatic precipitator (50) has an electrode housing (52) in which a high voltage electrode (66) is mounted, and the emissions from the crankcase of a Diesel engine (55) are passed across the electrode (66) to an outlet (56) . A high voltage power supply (80) is mounted in a separate housing (70), and the output of the high voltage power supply (80) is connected to the electrode (66) only when the electrode housing (52) and the power supply housing (70) are properly mated, to thereby disable the high voltage connection to the electrode (66) when the power supply housing (70) is removed.

Description

ELECTROSTATIC PRECIPITATOR FOR DIESEL BLOW-BY BACKGROUND OF THE INVENTION The present invention relates to an Electrostatic Precipitator that is particularly adapted for use in connection with diesel engines for removing particulate matter from crankcase gases prior to venting the gases to the atmosphere or returning the gases into the intake manifold for exhaust gas recirculation. More particularly, the present invention relates to certain improvements in the high voltage power supply to make it more suitable for Diesel blowby gas filtration. The invention also relates to mounting the high voltage power supply in a separate housing that can be completely separated from the precipitator electrode and electrode housing in a manner that minimizes the likelihood of a continued high voltage charge on the electrode as the power source housing is removed from the electrode housing. US-A- 6221136 describes a compact, high efficiency electrostatic precipitator for collection of aerosols containing suspended droplets and particles in a gas. As the dirty gas containing suspended droplets and other forms of particulate matter is passed through the precipitator the droplets and other forms of particulate matter are charged by the corona ions generated by a high voltage electrical discharge from a fine wire. Some of the particles may also carry a natural electrical charge as a result of the particle formation process in the Diesel engine combustion chamber and the blowby gas in the crankcase. The applied high voltage then causes the charged droplets and particles to migrate toward an adjacent grounded surface where they are collected, and the droplets and particulates are allowed to drain off by gravity to a sump. The electrostatic precipitator section disclosed in US-A-6221136 is suited for use with a Diesel engine to remove suspended droplets and particles from a blowby gas. The blowby gas has its origin in the high temperature, high-pressure combustion gas formed inside the combustion chambers of the Diesel engine. Some of this high-temperature, high-pressure gas can leak past the piston rings of the Diesel engine to the crankcase. This gas contains, both unburned Diesel soot as well as lubricating oil droplets formed as the blowby gas flows past the piston rings, where it encounters and atomizes the lubricating oil film to form droplets. The blowby gas thus contains both lubricating oil droplets as well as unburned Diesel soot . In the past, the blowby gas usually was vented to the atmosphere directly. Concerns about air pollution from motor vehicles in general, and from the Diesel-powered vehicles in particular, have led to regulations that would require particulate emissions from Diesel engines to be greatly reduced. The electrostatic precipitator described in U.S. Patent 6,221,136 has a small size, highly efficient droplet and particle collection, and low pressure drop created by the blowby gas as it flows through the device for droplet and particle removal. In addition, the electrostatic precipitator collects not only the suspended oil droplets in the blowby gas, but also the dry, solid Diesel soot. The dry soot particles normally would cling to the surface on which they are collected. However, in the presence of oil drops in the blowby gas from a Diesel engine, a thin film of oil is formed on the collecting surface. The soot particles are thus collected onto this liquid thin film and are carried away as the oil film drains off from the collecting surface by gravity, thus returning both the oil and Diesel soot into the crankcase of the engine. As a result, the collecting surface in the electrostatic precipitator can remain relatively clean over long periods, thus insuring the reliable operation of the device over a long lifetime. The operation of the electrostatic precipitator is dependent upon a power source to provide a high-voltage DC power to the high voltage electrode in the electrostatic precipitator. The DC high voltage needed may range up to 20,000 volts or more. The presence of this high voltage must be addressed in order to avoid accidentally having a person come in contact with the high voltage. The high voltage DC power source may also cause arcing and the emission of electromagnetic waves that can interfere with the engine control computer and other sensitive electronic circuitry nearby. For these reasons, the design of the high voltage power supply and its coupling to the electrostatic precipitator in Diesel blowby applications are both very important . SUMMARY OF THE INVENTION The present invention relates to an electrostatic precipitator construction which utilizes a separate high voltage DC power supply in a power supply housing that can be assembled onto an electrode housing or body used for the precipitator to form a complete electrostatic precipitator unit. In one aspect of the invention, the power supply is capable of being coupled to the precipitator housing using a high voltage connection made so that when the power supply housing is in place on the electrostatic precipitator housing there is an electrical connection to the high voltage power supply. The high voltage connection is opened when the high voltage power source housing is removed so the electrode is no longer carrying power. The lower precipitator housing has a dirty gas inlet and a clean gas outlet. The power supply circuitry is designed to provide the needed D.C. voltage to the precipitator electrode, but the connection and mounting of the power supply housing of the present invention disconnects the high voltage source from the electrode if the power supply housing is removed from the precipitator or electrode housing. The high voltage source is again connected to the electrode when the power supply housing is installed on the electrode housing. In another aspect of the invention, problems with electromagnetic interference (EMI) are minimized by providing suitable shielding, and eliminating any gaps or crevices between the power supply housing and the precipitator electrode housing. The high frequency EMI disturbances may be carried from the high voltage output side of the high voltage power supply circuit to the low voltage input side of the circuitry, and carried by the low voltage input wires outside the power supply housing, where they can radiate electromagnetic waves. As a further aspect of the invention, circuitry is provided to shunt the high frequency signals generated by any arcing that might occur to ground. The shunt circuitry permits the DC input voltage to pass through essentially unimpeded, but will reduce the high frequency emissions carried on the input lines which are generated in or transmitted through the high voltage electronic power supply circuitry. Such shunt circuitry can include high pass filters, for example, or other circuits that will shunt high frequency noise to ground, but will block the DC input voltage from being directly connected to ground . Also, current limiting circuits or circuit components are provided on the output of the high voltage transformer or converter circuit so that if arcing does occur, the current is controlled and limited. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross sectional view of the prior art device shown in Figure 14 of prior art US-A-6221136; Figure 2 is a schematic representation of the high voltage power supply housing shown joining an electrostatic precipitator electrode body, and illustrating a typical electrical coupling used for the high voltage connection; Figure 3 is a schematic block diagram of a typical high voltage power supply used in the precipitator shown in Figure 2 ; Figure 4 is a schematic exploded view of the electrostatic precipitator of Figure 2; Figure 5 is a schematic representation of a modified switch for input power connections; Figure 6 is a schematic representation of a further modified form of switch for the input power; and Figure 7 is a modified high voltage power supply for the precipitator of Figures 2 and 4. DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS Figure 1 is a vertical cross-sectional view of a prior art compact electrostatic precipitator 10. A conductive sleeve or housing 12 forms a passage for fluid, with an inlet connection 13 for receiving an aerosol, and an outlet connection 14. Conductive sleeve 12 is also a collector electrode. A flow passageway is defined by a plurality of openings 15 in a housing plate 16 that is supported on a sleeve 16A, which is positioned at the upper end of the conductive sleeve 12, and is supported on a cap plate 17. An insulated main electrode support 18 is supported on the cap plate 17 in a suitable manner with an insulator block that includes cartridge heaters 19. The cartridge heaters are mounted in a heat conducting jacket 20. The jacket 20 distributes the heat uniformly to its outer surface and keeps the insulator support surface hot and clean to avoid contamination by vapor condensation and particle deposition . A power connection line 22 can be passed out through a central opening of a cap 23. As shown, a power supply 24 which provides the high voltage for the discharge electrode can be potted in the cap 23, and the connector line or rod 26 can be within the precipitator and does not have to extend through the cap. The line 22 can be relatively low voltage, for example, a 24 -volt supply could be provided. The heaters 19 also would be connected generally to a 12 or 24 volt supply. The electrode support 18 has an interior passageway in which the high voltage connection rod or line 26 extends, and a thin electrode connector wire 27 extends for connection directly to the electrode wire 28 that, as shown, is helically wrapped around the insulating electrode support 18. The electrode wire 28 is shown larger than actual size and is a thin wire. Various other ways of supporting the thin electrode wire on a solid support and the spacing between the wire segments on the electrode and the distance between the wires and the grounded cylinder are discussed in U.S. Patent # 6,221,136. The aerosol flow comes into the sleeve collector electrode 12 as shown by the arrow 30, and the aerosol flows up and around the passageway 31 between the high-voltage electrode wire 28 and the collector electrode 12, which is the outer metal sleeve housing. The collector electrode 12 is a solid (imperforate) member that can either be stainless steel, for example, or could be a conducting plastic. As the flow passes through the space between the electrode wire 28 and the interior of collector electrode sleeve 12, the particles are charged by the corona ions produced by the wire electrode 28. Some of these particles are precipitated onto the collector electrode sleeve 12 in this region. The remaining particles are carried by the gas to the upper part of the assembly in the space between a thin metal sleeve 34 on the outside of support 18, and the collector electrode sleeve 12. The sleeve 34 is connected to the high voltage source. The remaining particles are precipitated onto the collector electrode sleeve 12 by virtue of the high voltage on the electrode 28. The flow then goes up through the openings 15, and out through the outlet 14, as shown. In Figure 2, an electrostatic precipitator shown generally at 50 has a lower electrically conductive electrode housing or sleeve body 52 that has an internal precipitator electrode 66 mounted thereon. Precipitator electrode 66 is similar in construction shown in the prior art device of Figure 1. The electrode housing 52 forms a gas flow path and has a dirty gas inlet 54 that is connected to the crankcase of a Diesel engine 55. A clean gas outlet 56 from the electrode housing 52 discharges to a suitable location, such as back to the air intake of the diesel engine, or to a filter and then to the atmosphere . The electrode housing 52 is made of a conductive material, and is connected to ground through line 58 so that it is grounded. The electrode housing 52 includes a peripheral flange 62 around the periphery that extends outwardly laterally and encircles the electrode housing 52. In addition, the precipitator electrode 66 has an internal connecting prong or pin 64 connected thereto on the interior of the electrode housing 52. The precipitator electrode 66 comprises an insulating support and a fine, helically wound wire, constructed generally as shown in Figure 1. Pin 64 is mounted on an insulating block 68 so that the pin 64 is insulated from the electrode housing 52, which is grounded. The pin 64 protrudes upwardly beyond the plane 96 of the top of flange 62. A high voltage power supply housing 70 is made of a conductive material, and has a lower flange 72 that encircles a cylindrical wall 74 of the housing 70 and mates with the flange 62. Suitable fasteners can be used for joining the flanges 62 and 72 together, and if desired, a thin conductive gasket can be placed between the flanges. The high voltage power supply circuit or transformer indicated generally at 80 is known circuitry and is represented as a block. The circuitry is shown in greater detail in Figure 3. The power supply circuit 80 changes a low voltage input to the 15 to 20,000 volts or more needed at the precipitator electrode 66. The high voltage circuitry output line 81 is connected to a connector 82 that has an interior receptacle or jack that slidably fits over the outward extending portion of the pin 64 to make the high voltage connection to the precipitator electrode on the interior of the lower electrode housing 52. This connector 82 is also shown in Figure 3, where the power supply housing 70 is shown positioned above the electrode housing 52. A low voltage input line 84 leads from a low voltage input power supply 86 such as a 12 or 24 volt battery. Line 84 extends through an insulator 88 to the interior of the power supply, housing 70. The line 84 is connected to the high voltage power supply circuitry through a magnetically actuated, normally open proximity switch 90. The switch 90 is in a housing 92 that is positioned to be directly above a magnet 94 that is supported in a suitable manner on the electrode housing 52 close to the plane 96 of the flange 62 or, in other words, close to the interface plane between the flanges 62 and 72. The output side of the switch 90 is connected to a line 98 that connects to the input side of the high voltage conversion or transformer circuitry 80. The voltage is boosted to the 15,000 to 20,000 volt or higher range by the circuitry 80 using known circuitry for producing high DC voltage outputs. The components for the high voltage power supply circuit are illustrated in block diagram form in Figure 3. The entire interior chamber of power supply housing 70 is filled with an insulating potting compound 87 to pot the circuit components in place. The high voltage generating circuit is shown at 80A. It is desired to reduce the likelihood of high frequency electromagnetic interference (EMI) being carried back through the lines 98 and 84. If the EMI is carried on lines 98 and 84 outside the shielding of the metal power supply housing 70, the EMI could cause interference with critical components such as computers on a vehicle. A circuit 100 is connected with a line 102 to the line 98, and to the ground with a line 104. The circuit 100 includes known components to shunt the high frequency electromagnetic interference signals to ground, and thus prevent radiation of such high frequency signals from the lead in wire 84 in a manner that may interfere with vehicle operation or the like. The low voltage DC signal to the input of the high voltage generating circuitry 80A is not shunted to ground. It also is of importance to limit the current that can be generated from the high voltage power supply and in particular from the output of the high voltage generating circuit 80A in the event that there is an arc generated from the high voltage generating circuit 80A to ground, which can damage the connectors, the circuitry, or the like. A high current flows through the arc. The physical damage to the connectors, circuitry or electrodes will shorten the life of the device. Current limiting circuitry 106 is provided on the output line of the high voltage generating circuit 80A. The circuitry 106 is known and can be either an active circuit or a passive circuit. For example, a passive circuit could be a high value resistor limiting the current flow from the high voltage generating circuit 80A in the event of an arc. Active current limiting circuitry is well knownin current limiting devices and can be used on the output line of the high voltage generating circuit 80A. In Figure 4, the position of the power supply housing 70 relative to the electrode housing 52 is such that the magnetic switch 90 is spaced from the magnet 94 sufficiently so that the switch is open, to illustrate that when the flanges 62 and 72 are separated the input switch for the high voltage power supply 80 remains open. When the flanges 62 and 72 are seated, there is a magnetic field that will close the switch 90 in the line 84 to the high voltage generating circuitry 80A in the high voltage power supply 80. The normally open proximity switch ensures that when the power supply housing 70 and the electrode housing 52 are separated, the switch 90 will open, so that the high voltage generating circuitry 80A is no longer energized. Contact with the connector 82 when it is carrying the high voltage is unlikely. The connector 82, pin 64 and the electrode 66 in Figure 2 will be completely disconnected from the high voltage power supply when housings 52 and 70 are separated. Figure 5 shows a portion of the power supply housing 70 with a mechanically actuated switch 110 in the input power line mounted on the housing 70. Switch 110 can be a normally open micro switch. The switch 110 has an actuator button 112, and is engaged by a switch actuator 114 on the electrode housing 52. When the flanges 62 and 72 are mated, the actuator 114 will strike the button 112 and close the switch 110 so that the input power circuit to the high voltage power supply is closed. An additional type of switch for the input power line is shown in Figure 6, where a photosensitive electric switch 118 is provided in the input power line. When the input line 84 is connected to a power supply such as a 12 volt battery, an LED 122 will light. A jumper 120 connects line 84 to switch 118. LED 122 will shine into the photosensitive switch 118 to keep the internal switch open, but when a light obstructing blade 124 mounted on the electrode housing 52 is in position, that is, when the flanges 62 and 72 are mated, the blade 124 will interrupt the light from LED source 122 and cause the photosensitive switch 118 to close, thereby closing the circuitry to the high voltage power supply circuit. The feature of having the high voltage power supply in a separate housing 72 that is easily separated from the high voltage electrode in electrode housing 50 along a dividing plane can be accomplished with other types of mating portions of the housing, such as a telescoping rim on the power supply housing that could either go inside or outside the rim of the electrode housing 52 for the electrostatic precipitator electrode 66. The connection between the high voltage transformer circuit and the electrostatic precipitator electrode is such that when the power supply housing 70 is seated, there is a connection from the high voltage power supply 80 to the electrostatic precipitator electrode 66. The direction of movement for seating and separating the power supply housing 70 from the electrode housing 52 is preferably linear. The linear movement simplifies coupling and uncoupling the connectors. The housings 52 and 70 are not threaded together. The connection from the high voltage power supply 80 to the electrode 66 can be accomplished with the linearly interfitting connector 82 and pin 64, such as that shown, or can be accomplished with clips and other types of mating connectors where two connector parts mate together linearly to create an electrical connection. Likewise, as pointed out above, the proximity switch 90, which shown is a magnetic switch on the input side of the high voltage power supply, can be replaced with other types of proximity detector switches that will complete a circuit to the input side of the high voltage power supply 80 only when the two housings, one for the power supply, and the other for the electrostatic precipitator electrode, are properly seated. Figure 7 illustrates a modified connection that keeps the entire housing 70A for the high voltage power supply separate from the electrode housing 52A, but yet has a connection for insuring that the high voltage power is applied to an output connector only when there is a connection of the components to the electrode. In Figure 7, a high voltage power supply housing indicated at 70A is essentially the same as that shown before, except that the interior is enclosed with a lower wall 130, which has an outlet opening 132 through which the lines 82 and 98 pass. The lines are for connection to a proximity control switch 134. The control switch 134 is mounted in a separate metal housing or plug 136, and this plug is connected to a modified precipitator housing 52A. The housing 52A is the same as that shown at 52, except it has an upper wall 136 that is made of metal that encloses the electrostatic precipitator. High voltage line 81 also passes through the opening 132, as does a ground line 138. The ground line is part of the system for providing the high frequency signal shunt. The housing 52A is connected to a ground line 58A. A shielded cable represented at 140, has an outer high frequency emission shield, and is provided with an adequate number of conductors to carry the lines 82, 98, 81 and 138. One end of the cable 140 is connected with a suitable connector 142 to a mating connector on the housing 70A, and also has a connector 144 at its opposite end that is connected to a connector 146A the plug 136. The shielded cable 140 may have its conductors directly wired to the corresponding lines in the plug 136, which are numbered the same. The switch 134, again, is a normally open switch such as that shown at 90, and it is magnetically actuated with a magnet 94A in the housing 52A. The plug 136 has a connector socket 82A that connects to a pin 64A as was shown in Figure 2. It can be seen therefore that the high voltage power supply can be completely shielded by the housing 70A, and shielding can continue through a connecting cable 140 to a plug 136 that would connect up the high voltage socket 82A and the pin 64A. The proximity switch 134 that is shown operated with the magnet 94A, will be such that it will be open to disconnect power to the input of circuit 80 in housing 70A if the plug 136 is removed from the housing 52A. The connector 82A will no longer be at the high voltage. The plug 136 can be filled with potting compound 146, and held in place with suitable fasteners. Also, it can be seen that the chamber in the housing 70A is filled with an insulated potting compound 87A as well. The high voltage power supply 80 carries the same number, inasmuch as it is exactly the same as that shown in Figure 2. The advantage of having shielded sources, and the EMI reducing and current limiting circuitries mounted in a shielded housing, carried along a shielded cable to a plug that has the proximity switch 134 for interrupting power when the plug 136 is disconnected, are available with a separate power supply housing. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A high voltage power supply for an electrostatic precipitator for Diesel blowby filtration, said high voltage power supply having low voltage input connections for an external low- voltage source, and generating an output of a substantially higher yoltage, the power supply including circuitry to limit output current in the event of an arc, and including circuitry to reduce emission of electromagnetic radiation that can interfere with sensitive electronic equipment nearby.

2. The high voltage power supply of claim 1, combined with an electrostatic precipitator having a high voltage electrode connected to receive the higher voltage output of the high voltage power supply.

3. The high voltage power supply of ^' either of claims 1 or 2 further comprising shielding surrounding the electrostatic precipitator and the high voltage power supply.

4. The high voltage power supply of claim 3, wherein said shielding comprises a housing.

5. The high voltage power supply of claim 1 further comprising a switch to interrupt the low voltage input connections to prevent high voltage from being generated by the high voltage power supply as an output upon occurrence of selected events.

6. The high voltage power supply of any one of the previous claims combined with a separate electrostatic precipitator having a high voltage electrode connected with a separable connector to receive the higher voltage output, wherein said switch to interrupt the low voltage input connections comprises a normally open switch placed in a low voltage input line to the high voltage power supply, and an actuator on the electrostatic precipitator for causing said normally open switch to close when the actuator is near said normally open switch.

7. The combination of claim 6, wherein there are first and second separate shielded housings which when brought together form a completely shielded unit for the combination, the first housing mounting the high voltage electrode and said actuator, said first housing having a fitting for receiving incoming gas carrying particulate matter, and an outlet connection for carrying gas that has passed by the high voltage electrode of the electrostatic precipitator, said second housing mounting the high voltage power supply, a separable connector between the high voltage electrode and an output of the high voltage power supply such that when the two housings are brought together, the high voltage electrode and the separable connector become connected, and said actuator in the first housing is brought near the normally open switch in the second housing, causing the switch to close to provide low voltage input power to the high voltage power supply to generate high voltage for the high voltage electrode.

8. The combination of claim 7, wherein said normally open switch is a normally open magnetic switch and the actuator is a magnet.

9. The combination of claim 7, wherein said normally open switch is a normally open push button mechanical switch and the actuating element is a solid surface that comes in contact with the push button of the mechanical switch thereby depressing the push button and causing the mechanical switch to be closed.

10. The combination of claim 7, wherein said normally open switch is a normally open optical switch that includes a light source projecting a light beam, a light-sensing means and a switch that closes upon sensing a change in light intensity by the light sensor, and wherein the actuator is a device to cause the light intensity reaching the light sensor to change when the device is brought near the light beam.

11. An electrostatic precipitator having a high voltage precipitator electrode, and a high voltage power supply for converting an input voltage on a low voltage input line to a substantially higher output voltage at an output thereof, a first housing for housing the high voltage precipitator electrode, said first housing having an inlet for receiving incoming gas carrying particulate matter, and having an outlet for carrying gas that has passed by the high voltage precipitator electrode, and a second separate housing for housing the high voltage power supply, the first and second housings being separable and having mating supports to hold the housings together with the output of the high voltage power supply connected to the high voltage precipitator electrode, a switch on the low voltage input line to the high voltage power supply in the second housing, said switch being normally open and cioseable to connect the low voltage input line to the high voltage power supply, and a switch actuator on the first housing operable to close the switch when the second housing and the first housing are positioned together on the mating supports .

12. The electrostatic precipitator of claim 11, including a first portion of an electrode connector for the output of the high voltage power supply and a second portion of an electric connector that mates with and electrically connects to the first portion when the first and second housings are positioned together on the mating supports.