Vortex arc generator and method of controlling the length of the arc

• US 5,374,802 A
• Filed: 12/31/1992
• Issued: 12/20/1994
• Est. Priority Date: 12/31/1992
• Status: Expired due to Fees

• Current Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Sampath, Sanjay, Scheithauer, Michael J., Vanderpool, Jack E., Dorfman, Leonid P.
• Primary Examiner(s): Paschall, Mark H.
• Application Number:
  US07/999,623
• Time in Patent Office: 719 Days
• Field of Search: 219/121.59, 219/121.5, 219/121.51, 219/121.52, 219/75, 219/121.48, 219/121.36, 313/231.21, 313/231.31, 313/231.41, 313/231.51
• US Class Current: 219/121.52
• CPC Class Codes: H05H 1/34 Details, e.g. electrodes, nozzles
• CPC Class Codes: H05H 1/3405 Arrangements for stabilising or constricting the arc, e.g. by an additional gas flow
• CPC Class Codes: H05H 1/3431 Coaxial cylindrical electrodes
• CPC Class Codes: H05H 1/3468 Vortex generators

Abstract

A DC plasma arc generator and method of operation to reduce erosion of the internal parts. The arc generator includes a generally cylindrical anode and a generally cylindrical interelectrode having critical dimensions and spacing to allow introduction of vortical gas flows and stabilization of the primary arc thereby, reducing degradation and erosion of the generator.

Claims

1. A DC plasma arc generator comprising:

a generally cylindrical anode and a generally cylindrical interelectrode, each being coaxial with the other, said anode and said interelectrode each having distal and proximal ends, said distal end of said interelectrode being spaced from said proximal end of said anode by a predetermined distance, the inner diameter of said anode being greater than the inner diameter of said interelectrode, said interelectrode being electrically insulated from said anode prior to arc ignition;

a cathode disposed adjacent said proximal end of said interelectrode and electrically insulated therefrom;

means to introduce tangentially a vortex-generating gas adjacent said proximal end of said interelectrode;

means to introduce tangentially a second stream of a vortex-generating gas in the space between said distal end of said interelectrode and said proximal end of said anode;

means forming an arc-generating locality in said space between said distal end of said interelectrode and said proximal end of said anode;

means for establishing two arcs, a first arc between said cathode and said distal end of said interelectrode and a second arc in said arc-generating locality.

2. The arc generator according to claim 1 wherein a power supply is connected solely between said cathode and said anode.

3. The arc generator of claim 1 wherein said means forming said arc-generating locality is a pair of opposing flanges, one flange being disposed at said distal end of said interelectrode and the other flange being disposed at said proximal end of said anode, said flanges being arranged in a face-to-face relationship with each other.

4. The arc generator of claim 1 wherein the inner diameter of said anode is 1.1 to 1.5 times greater than the inner diameter of said interelectrode.

5. The arc generator of claim 1 wherein said predetermined distance is between 0.03 and 0.15 times the length of said anode.

6. The arc generator of claim 1 wherein the length of said anode is 0.5 to 4 times its diameter.

7. The arc generator of claim 1 wherein the length of said interelectrode is 3 to 10 times its diameter.

8. A DC plasma arc generator comprising:

a generally cylindrical anode and a generally cylindrical interelectrode, each being coaxial with the other, said anode and said interelectrode each having distal and proximal ends, said distal end of said interelectrode being spaced from said proximal end of said anode by 0.03 to 0.15 times the length of said interelectrode, the length of said interelectrode being 3 to 10 times its inner diameter, the inner diameter of said anode being 1.1 to 1.5 times the inner diameter of said interelectrode, the length of said anode being 0.5 to 4 times its inner diameter, said interelectrode being insulated from said anode prior to arc ignition;

a cathode adjacent said proximal end of said interelectrode and electrically insulated therefrom;

means to introduce tangentially a first stream of a vortex-generating gas adjacent said proximal end of said interelectrode;

means to introduce tangentially a second stream of a vortex-generating gas in space between said distal end of said interelectrode and said proximal end of said anode;

means forming an arc-generating locality in said space between said distal end of said interelectrode and said proximal end of said anode;

means for establishing two arcs, a first one between said cathode and said distal end of said interelectrode and a second arc in said arc-generating locality.

9. A method of controlling the arc length in a vortex-stabilized DC plasma arc generator, the steps comprising:

establishing a first vortical flow of an ionizable gas in a first cylindrical chamber, said chamber having a proximal and a distal end, said first vortical flow being adjacent a cathode disposed adjacent said proximal end of said first chamber, said cathode being electrically insulated from said first chamber;

establishing a second vortical flow of an ionizable gas in a second cylindrical chamber, said second chamber having a proximal and a distal end, the diameter of said second chamber being greater than the diameter of said first chamber, whereby the diameter of said first vortical flow suddenly expands upon entry of said first vertical flow into said second chamber, said proximal end of said second chamber being spaced from said distal end of said first chamber, the space between said first and second chambers serving as the source for establishing said second vortical flow of gas, said chambers being electrically insulated from each other prior to arc ignition, said proximal end of said second chamber and said distal end of said first chamber each having flanges extending from their perimeters and being disposed in a face-to-face relationship, said first chamber being electrically insulated from said second chamber prior to arc ignition;

imposing a potential between said cathode and said second chamber and establishing a first arc between said cathode and said distal end of said first chamber and simultaneously establishing a second arc between said flanges, said first vortical flow of gas forcing said first arc to revolve around the axis of said first chamber to stabilize said first arc, said second arc ionizing said second flow of gas and forcing a finger from said first arc to revolve around said distal end of said first chamber whereby degradation and erosion of said first chamber due to the attachment of said finger is reduced.

10. The method according to claim 9 wherein the diameter of said vortical flow in the second chamber is 1.1 to 1.5 times greater than the diameter of said vortical flow in the first chamber.

11. A method of operating a DC plasma arc generator having a cathode, a generally cylindrical anode and a generally cylindrical interelectrode, said anode and said interelectrode being coaxial with each other, said anode and said interelectrode each having distal and proximal ends, said cathode being disposed adjacent said proximal end of said interelectrode, said distal end of said interelectrode being spaced from said proximal end of said anode by 0.03 to 0.15 times the length of said anode, the length of said interelectrode being 3 to 10 times greater than its inner diameter, the inner diameter of said anode being 1.1 to 1.5 times greater than the inner diameter of said interelectrode, said anode having a length that is 0.5 to 4 times its diameter, said cathode, said interelectrode and said anode being electrically insulated from each other prior to arc ignition, said method comprising:

introducing tangentially a first stream of a vortex-generating gas adjacent said proximal end of said interelectrode to establish a vortical flow of said gas;

introducing tangentially a second stream of a vortex-generating gas into the space between said distal end of said interelectrode and said proximal end of said anode, said second stream intersecting said first stream;

imposing a potential between said cathode and said anode and forming a first arc between said cathode and said distal end of said interelectrode and a second arc in the space between said interelectrode and said anode, said first stream of gas forcing said first arc to revolve about the axis of said interelectrode, said first arc forming a finger which revolves about said distal end of said interelectrode, said second arc ionizing the gas of the second stream and forcing said finger of said first arc to remain attached to said distal end of said interelectrode.