Plasma torch with a lateral injector
View Patent ↗The invention relates to a plasma torch, comprising: a plasma generator comprising a cathode extending along an axis X and an anode ( 24 ), the cathode and the anode being arranged so as to be capable of generating, in a chamber ( 26 ), an electric arc between the anode and the cathode due to an electrical voltage, the plasma generator also comprising a plasmagen gas injection device ( 30 ) comprising an injection pipe ( 72 ) leading, along an injection axis (I i ), to an injection opening ( 74 ) in the chamber; a means for injecting a material to be discharged into a plasma flow generated by said plasma generator, the plasma torch being characterized in that: the relationship R″ between: the radial distance (y i ) of said injection opening, defined as the minimum distance between the axis X and the center of said injection orifice; the largest transverse size (D C ) of the cathode in the region of the chamber downstream from the position P AC , wherein P AC denotes the axial position of maximum radial mutual encroachment of the anode and the cathode, is less than 2.5; and the projection of the injection axis (I i ) into a transverse plane passing through the center of the injection orifice of said injection conduit forms an angle β less than 45° with a radius extending into said transverse plane and passing through the axis X and through the center of said injection orifice.
1. A plasma torch comprising:
a plasma generator having:
a cathode extending along an axis X,
an anode, and
a chamber, the cathode and the anode being placed so as to be able to generate an electric arc in the chamber when voltage is applied between the anode and the cathode; and
an injection device for injecting a plasmagen gas, the injection device comprising an injection duct opening, along an injection axis (I i ), via an injection orifice, into the chamber;
means for injecting a material to be sprayed into a plasma flux generated by said plasma generator;
wherein,
a ratio R″ between:
a radial distance (y i ) of said injection orifice, defined as a minimum distance between the axis X and a center of said injection orifice; and
a largest transverse dimension (D C ) of the cathode in a region of the chamber downstream of an axial position p AC , p AC denoting the axial position of minimum radial distance between the anode and cathode,
is smaller than 2.5, and
a projection of the injection axis (I i ) in a transverse plane passing through the center of the injection orifice of said injection duct defines an angle β smaller than 45° with a radius lying in said transverse plane and passing through the axis X and through the center of said injection orifice.
2. The plasma torch according to claim 1 , in which the projection of the injection axis (I i ) in a radial plane passing through the center of the injection orifice of said injection duct makes an angle α, with the axis X, larger than 10° and smaller than 70°.
3. The plasma torch according to claim 1 , in which said angle β is larger than 5°.
4. The plasma torch according to claim 1 , in which:
the angle α is larger than 20° and smaller than 60°; and/or
the angle β is smaller than 30°.
5. The plasma torch according to claim 1 , in which, among a set of injection orifices of said injection device, said injection orifice is that or one of those having a furthest downstream axial position (p i ).
6. The plasma torch according to claim 1 , in which a radial distance (y i ) of said injection orifice is shorter than 27 mm and longer than 6 mm.
7. The plasma torch according to claim 1 , in which the injection device is placed upstream of the position p AC of minimum radial distance between the anode and cathode.
8. The plasma torch according to claim 1 , in which the cathode comprises a frustoconical portion and in which said injection orifice is placed in a transverse plane cutting said frustoconical portion.
9. The plasma torch according to claim 5 , in which the cathode comprises a frustoconical portion and all of the injection orifices are placed in one or more transverse planes cutting said frustoconical portion.
10. The plasma torch according to claim 8 , in which said transverse plane or planes are placed at a distance from a base of said frustoconical portion lying between 30% and 90% of the length of said frustoconical portion.
11. The plasma torch according to claim 1 , in which an axial distance x″ separating the axial position p AC from an axial position (P A ) of the furthest downstream point of the anode is longer than 30 mm.
12. The plasma torch according to claim 11 , in which the axial distance x″ separating the axial position p AC from the axial position (p A ) of the furthest downstream point of the anode is shorter than 60 mm.
13. The plasma torch according to claim 1 , in which the ratio R between:
an axial distance x between the axial position p AC of minimum radial distance between the anode and cathode and an axial position (p i ) of said injection orifice; and
a largest transverse dimension (D C ) of the cathode in a region of the chamber downstream of the axial position p AC , is smaller than 3.2.
14. The plasma torch according to claim 13 , in which the axial distance x is longer than 5 mm and shorter than 25 mm.
15. The plasma torch according to claim 1 claims, in which a ratio R′ between:
an axial distance x′ separating an axial position p C of a downstream end of the cathode and an axial position (p i ) of said injection orifice; and
the largest transverse dimension (D C ) of the cathode in the region of the chamber downstream of the axial position p AC of minimum radial distance between the anode and cathode, is smaller than 3.5.
16. The plasma torch according to claim 15 , in which the axial distance x′ is longer than 9 mm and shorter than 30 mm.
17. The plasma torch according to claim 1 , in which a ratio R′″ between a minimum radial distance y AC between the anode and the cathode in the axial position p AC and the largest transverse dimension (D C ) of the cathode in the region of the chamber downstream of the axial position p AC of minimum radial distance between the anode and cathode is smaller than 1.25.
18. The plasma torch according to claim 1 , in which the injection device comprises a plurality of injection orifices, at least one of conditions on ratios R, R′, and R″, and on distances x, x′, x″ and y i , being true whichever injection orifice is considered.
19. The plasma torch according to claim 1 , comprising a single cathode and/or a single anode.
20. The plasma torch according to claim 1 , in which the cathode, in the form of a rod of axis X, comprises in succession, coaxially, from upstream to downstream, a frustoconical portion of decreasing diameter, a cylindrical portion of circular cross section and a conical portion having a rounded apex.