Electrostatic filter having insulated electrodes
In various aspects of the invention, electrostatic filters having insulated electrodes are described. In such embodiments, care is taken to prevent the accumulation of opposing charges on the insulation, which, over time, would serve to significantly degrade the strength of the electrostatic field created in the dielectric, and thus reduce the performance of the electrostatic filter. A variety of mechanisms are described for mitigating the opposing charge buildup problem.
1. An electrostatic filter suitable for collecting aerosol particulates carried in a fluid stream passing through the electrostatic filter, the electrostatic filter comprising: a first porous electrode wherein the first electrode has a core formed from a conductive material, an insulation layer that electrically insulates the core, and a charge distribution conductor that is isolated from the core by the insulation layer;
a second porous electrode spaced apart from the first electrode;
a porous dielectric positioned between the first and second electrodes and arranged such that in operation the fluid steam passes through the electrodes and the dielectric; and
a charge source in communication with the conductor whereby in operation a first potential having a first polarity may be applied to the first porous electrode and the charge source at least periodically applies charges having the same polarity as the first electrode to the conductor in order to help neutralize opposing charges that seek to accumulate on the insulation layer of the first electrode.
2. An electrostatic filter as recited in claim 1 further comprising an ion source that serves as the charge source, the ion source having the same polarity as the first electrode and being in communication with the conductor on the first electrode, wherein the ion source is configured to neutralizing opposing charges that seek to accumulate on the insulation layer of the first electrode during operation of the electrostatic filter.
3. An electrostatic filter as recited in claim 1 wherein the second electrode includes a second core and a second insulation layer that electrically insulates the second core.
4. An electrostatic filter as recited in claim 3 wherein the second electrode further includes a second charge distribution conductor that is isolated from the second core by the second insulation layer.
5. An electrostatic filter as recited in claim 4 further comprising a second charge source in communication with the second conductor; and whereby in operation a second potential having a second polarity may be applied to the second porous electrode and the charge source at least periodically applies charges having the same polarity as the second electrode to the second conductor in order to help neutralize opposing charges that seek to accumulate on the second insulation layer.
6. An electrostatic filter as recited in claim 3 wherein different insulators are used on the first and second electrodes.
7. An electrostatic filter as recited in claim 1 wherein the second electrode includes a second core and a promiscuous second insulation layer that electrically insulates the second core against shorting in normal operational conditions, but allows opposing charges that seek to accumulate on the second electrode to migrate through the insulation to the second core.
8. An electrostatic filter as recited in claim 1 wherein the second insulation layer is a paint material.
9. An electrostatic filter as recited in claim 1 comprising a plurality of sequentially arranged first and second electrodes, each adjacent pair of first and second electrodes having a dielectric interposed between the adjacent electrode pair.
10. An electrostatic filter comprising:
a first insulated electrode having a core and a promiscuous insulation layer;
a second insulated electrode spaced apart from the first electrode; and
a dielectric positioned between the first and second electrodes and arranged such that in operation the fluid steam passes through the electrodes and the dielectric wherein the promiscuous insulation layer is arranged to electrically insulate the first electrode against shorting in normal operational conditions, but allows opposing charges that seek to accumulate on the first electrode during operation to migrate through the insulation layer to the core such that during operation, opposing charges do not accumulate sufficiently on the first electrode to significantly degrade a field induced in the dielectric by the first and second electrodes.
11. An electrostatic filter as recited in claim 10 wherein the second insulated electrode has a second core and a second promiscuous insulation layer and the second promiscuous insulation layer is arranged to electrically insulate the second electrode against shorting in normal operational conditions, but allows opposing charges that seek to accumulate on the second electrode during operation to migrate through the second insulation layer to the second core such that during operation, opposing charges do not accumulate sufficiently on the second electrode to significantly degrade the field induced in the dielectric by the first and second electrodes.