Plasma generator cathode inner core with bluff body turbulence cooling structure

Abstract

The invention discloses a plasma generator cathode inner core with a bluff body turbulence cooling structure, and belongs to the technical field of plasma generators. The cathode inner core comprises a bluff body turbulent flow cathode head, an emitter and a cathode seat; the bluff body turbulent flow cathode head is an integrated special-shaped structural body, the bluff body turbulent flow cathode head and the cathode seat are connected together to form a deep cup-shaped structure with one end provided with a circular opening and the other end provided with a horn opening, and the length-diameter ratio of an inner hole of the cathode seat to an inner hole of the connecting end of the bluff body turbulent flow cathode head is 5-15 times; and the emitter is embedded in the center of an inner hole of the bluff body turbulence cathode head. The device is simple in structure, small in size, very low in cost, convenient to replace and maintain, high in plasma temperature and reliable in operation, the working temperature of the cathode inner core can be further reduced, and the service life of the cathode inner core can stably reach more than 1200 hours.

Description

Technical Field

[0001] The present invention relates to the technical field of plasma generators, and in particular to a cathode inner core of a plasma generator with a bluff-body turbulent cooling structure suitable for plasma ignition of pulverized coal boilers. Background Art

[0002] In today's technological field, plasma technology is at the forefront and is developing rapidly. It has been widely penetrated into many industrial fields. For example, in the ignition of pulverized coal, through the energy excitation of plasma, more efficient combustion startup of pulverized coal is realized, improving energy utilization efficiency; in the treatment of hazardous waste and garbage incineration, by virtue of the high-temperature characteristics of plasma, harmful waste and garbage are treated harmlessly and reduced in quantity, effectively solving environmental pollution problems; in the field of steel cutting, using the high energy density of plasma, precise and efficient cutting of steel is achieved, improving processing accuracy and production efficiency; in metal smelting, it promotes the purification and refining of metals and improves metal properties; it also plays a key role in surface spraying and the manufacture of nanomaterials, etc., improving product quality and performance.

[0003] As the core component of the plasma generator, the importance of the cathode is self-evident. On the one hand, it endures harsh conditions such as high temperature and high-energy impact during operation and is a vulnerable part; on the other hand, due to its complex manufacturing process and high material cost, it has become the focus of attention for increasing its lifespan and reducing costs. Under the goal of modern enterprises pursuing cost reduction and efficiency improvement, optimizing the performance of the cathode and reducing its loss cost are crucial.

[0004] Currently, there are some design problems with the cooling structure of the cathode inner core in the prior art. In Patent Publication No. CN107529269A, the water-facing surface of the cathode head only has a conical structure. When the cooling water flows through the conical surface, the water flow state is relatively stable and it is difficult to form a turbulent flow effect. Turbulent flow can enhance the heat transfer coefficient between the fluid and the wall surface and improve the cooling efficiency. This cooling structure that cannot form a turbulent flow effect results in an unsatisfactory cooling effect, making it difficult to meet the cooling performance requirements of the cathode under high-intensity working conditions, and thus affecting the overall performance and service life of the plasma generator. Therefore, developing a cathode inner core structure of a plasma generator that can form a turbulent flow effect and improve the cooling efficiency has important practical significance and market demand. Summary of the Invention

[0005] Technical Problem: The purpose of the present invention is to overcome the deficiencies in the prior art and provide a cathode inner core of a plasma generator with a bluff-body turbulent cooling structure that is simple in structure and good in use effect.

[0006] Technical solution: The inner core of the cathode of a plasma generator with a bluff-body turbulent cooling structure according to the present invention includes a bluff-body turbulent cathode head, an emitter, and a cathode base; the bluff-body turbulent cathode head is an integral special-shaped structure, one side of the outer surface of the bluff-body turbulent cathode head is a cone, and the other side is a cylinder. A hollow inner cylindrical opening with a diameter of Φ1 is opened on the end face of the cone side of the bluff-body turbulent cathode head. A circular arc groove is opened at the bottom of the hollow inner cylindrical opening. There is a raised area inside the circle surrounded by the circular arc groove, and there is a frustum-shaped bluff body with a spherical groove at the top. A plurality of through holes with a diameter of Φ2 that communicate with the inner cylindrical opening of the cone are evenly distributed on the circumference at the junction of the cylinder and the cone. A hollow inner cylindrical opening with a diameter of Φ3 is opened on the end face of the cylinder side. The diameter Φ3 is larger than the diameter Φ1. A frustum with a flat top protrudes from the center of the bottom of the hollow cylindrical opening. A cylindrical blind hole is opened in the center of the frustum. The emitter is embedded in the cylindrical blind hole; the cathode base is a cylindrical tubular body with the same inner and outer diameters as the diameter of the cylinder side of the bluff-body turbulent cathode head. One end of the cylindrical tubular body is a circular opening, and the other end is a flared opening. The circular opening end of the cylindrical tubular body is connected to the circular opening end of the cylinder side end face of the bluff-body turbulent cathode head to form a hollow inner cylindrical deep cup-shaped structure with a flared opening. The ratio of the major axis of the inner hole of the cathode base (3) to the inner hole of the connection end of the bluff-body turbulent cathode head (1) is 5 to 15 times.

[0007] The cone angle a of the cone on one side of the outer surface of the bluff-body turbulent cathode head is 10 to 70°.

[0008] The diameter Φ1 of the hollow inner cylindrical opening on the end face of the cone side of the bluff-body turbulent cathode head is 12 to 20 mm.

[0009] The distance D1 from the end face of the cone side of the bluff-body turbulent cathode head to the end face of the frustum-shaped bluff body with a spherical groove at the top is 3 to 8 mm.

[0010] The distance D from the end face of the cone side of the bluff-body turbulent cathode head to the center of the through holes evenly distributed on the circumference at the junction of the cylinder and the cone is 12 to 15 mm.

[0011] The diameter Φ2 of the circular through holes evenly distributed on the circumference at the junction of the cylinder and the cone of the bluff-body turbulent cathode head is 1 to 5 mm, and the number of circular through holes is 4 to 20.

[0012] The radius SR of the spherical groove on the frustum-shaped bluff body with a spherical groove in the hollow inner cylindrical opening on the cone side of the bluff-body turbulent cathode head is 2 to 6 mm, and the cone angle b of the frustum is 10 to 70°.

[0013] The height D2 of the frustum with a flat top protruding from the hollow inner cylindrical opening on the cylinder side of the bluff-body turbulent cathode head is 3 to 8 mm, and the cone angle c is 20 to 90°.

[0014] The emitter is made of pure silver, pure hafnium, pure tungsten, or an alloy of the three in any proportion, or a new zirconium-titanium-aluminum-scandium alloy; the cathode seat is made of pure silver, pure copper, or an alloy of the two in any proportion.

[0015] The emitter and the bluff-body turbulent cathode head are connected and fixed by brazing or interference fit, and the bluff-body turbulent cathode head and the cathode seat are connected and fixed by welding or threading.

[0016] Beneficial effects: Due to the adoption of the above technical solution and the use of a specially designed bluff body structure, the cooling water flow passing through the water-facing surface at the left end of the cathode head is disturbed, and enters a turbulent state in a very short time, thereby increasing the speed and efficiency of heat transfer, and allowing the heat generated by the emitter to be carried away by the cooling water more quickly through the cathode head, thereby enhancing the cooling effect and increasing the life of the emitter. Computer simulation has shown that the cathode core of the above structure has an excellent cooling effect. It has a simple structure, high plasma temperature, and reliable operation. It can further reduce the operating temperature of the cathode core, and the life of the cathode core can be stably maintained at more than 1,200 hours. Compared with the prior art, the present invention has a novel structure, and utilizes the addition of a bluff body to the water-facing surface of the bluff body turbulent cathode head so that the cooling water around the bluff body produces the following effects:

[0017] 1) Enhanced disturbance: Using a bluff body to disturb the fluid flow, destroy the stability of the boundary layer, and promote a more complete mixing of the low-speed fluid in the boundary layer and the high-speed fluid in the mainstream area. This mixing increases the speed and efficiency of heat transfer, allowing the heat on the bluff body surface to be taken away more quickly, thereby achieving cooling;

[0018] 2) Increase the heat exchange area: The presence of the bluff body increases the contact area between the fluid and the surface of the object. According to the principle of heat transfer, the increase in the heat exchange area is conducive to the transfer of heat. More heat can be transferred from the bluff body to the fluid through the increased contact area and then carried away by the fluid.

[0019] 3) Change the flow field distribution: Blunt body changes the flow field structure of the fluid, forming a complex flow field around the blunt body, such as vortex, wake, etc. These special flow field structures can enhance the disturbance and convection heat transfer capacity of the fluid and improve the cooling effect.

[0020] 4) The present invention has a relatively simple structure, a compact size, and a very low cost, is easy to replace and repair, and has wide practicability and considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a cross-sectional structural schematic diagram of the present invention.

[0022] Figure 2 It is a schematic diagram of the cross-sectional structure of the present invention after being installed on a plasma generator.

[0023] Figure 3 It is a schematic diagram of the internal and external cooling water flow directions in the blunt-body turbulent cathode head structure of the present invention.

[0024] Figure 4 It is a schematic three-dimensional structure diagram of the blunt body side of the blunt-body turbulent cathode head of the present invention.

[0025] In the figure: 1 - blunt-body turbulent cathode head, 2 - emitter, 3 - cathode base. Specific embodiments

[0026] The following further describes an embodiment of the present invention with reference to the accompanying drawings:

[0027] As Figure 1 shown, the plasma generator cathode inner core with a blunt-body turbulent cooling structure of the present invention mainly consists of a blunt-body turbulent cathode head 1, an emitter 2, and a cathode base 3; the blunt-body turbulent cathode head 1 is an integral special-shaped structure; one side of the outer surface of the blunt-body turbulent cathode head 1 is a cone, and the other side is a cylinder. A hollow inner cylindrical opening with a diameter of Φ1 is opened on the end face of the cone side of the blunt-body turbulent cathode head 1. A circular arc groove is opened at the bottom of the hollow inner cylindrical opening. There is a raised area inside the circle surrounded by the circular arc groove, and there is a frustum of a cone with a spherical groove at the top; a plurality of through holes with a diameter of Φ2 that communicate with the inner cylindrical opening of the cone are evenly distributed on the circumference at the junction of the cylinder and the cone. A hollow inner cylindrical opening with a diameter of Φ3 is opened on the end face of the cylinder side, and the diameter Φ3 is greater than the diameter Φ1. A frustum of a cone with a flat top protrudes from the center of the bottom of the hollow cylindrical opening, and a cylindrical blind hole is opened in the center of the frustum of the cone. The emitter 2 is embedded in the cylindrical blind hole; the cathode base 3 is a cylindrical tubular body with the same inner and outer diameters as the diameter of the cylinder side of the blunt-body turbulent cathode head 1. One end of the cylindrical tubular body is a circular opening, and the other end is a flared opening. The circular opening end of the cylindrical tubular body is connected to the circular opening end of the cylinder side end face of the blunt-body turbulent cathode head 1 to form a hollow inner cylindrical deep cup-shaped structure with a flared opening, that is, a complete cathode inner core structure; the ratio of the major axis of the inner hole of the cathode base 3 to the inner hole of the connection end of the blunt-body turbulent cathode head 1 is 5 to 15 times.

[0028] The included angle α of the outer conical surface at the left end of the blunt-body turbulent cathode head 1 ranges from 10° to 70°. The diameter Φ1 of the hollow cylindrical structure at the left end of the blunt-body turbulent cathode head 1 is 12 to 20 mm. The distance D1 from the left end face of the blunt-body turbulent cathode head 1 to the left end face of the frustum with a spherical groove is 3 to 8 mm. The distance D from the left end face of the blunt-body turbulent cathode head 1 to the center of the circular through-holes evenly distributed in the circumference is 12 to 15 mm. The diameter Φ2 of the circular through-holes evenly distributed in the circumference at the left end of the blunt-body turbulent cathode head 1 is 1 to 5 mm, and the number of circular through-holes is 4 to 20. The radius SR of the spherical groove on the frustum with a spherical groove at the left end of the blunt-body turbulent cathode head 1 is 2 to 6 mm, and the included angle β of the frustum is in the range of 10° to 70°. The height D2 of the frustum with a flat top protruding at the right end of the blunt-body turbulent cathode head 1 is 3 to 8 mm, and the included angle γ ranges from 20° to 90°. The material of the emitter 2 is pure silver, pure hafnium, pure tungsten, or an alloy with any proportion of the three, or a new zirconium-titanium-aluminum-scandium alloy, and the optional range of the emitter material is richer than before; the material of the cathode base 3 is pure silver, pure copper, or an alloy with any proportion of the two. The emitter 2 and the blunt-body turbulent cathode head 1 are fixed by brazing or interference fit, and the blunt-body turbulent cathode head 1 and the cathode base 3 are fixed by welding or threaded connection. Compared with the overall structure of the deep-cup cathode inner core before, the split structure is more flexible in use, and the damaged blunt-body turbulent cathode head 1 and cathode base 3 can be replaced separately as needed.

[0029] Specific embodiment: Install the present invention at the axial center position near the front nozzle of the plasma generator, as Figure 2 Figure 3 shown. After the plasma generator starts to work, the air between the anode and cathode is continuously ionized to generate a plasma arc. Electrons are continuously emitted from the emitter 2 of the cathode head 1 and finally land on the inner surface of the anode. Figure 2 The thick black line in it is the flight trajectory of electrons. When a large number of electrons fly concentratedly, it becomes a continuous arc form. Figure 2 Only one arc is shown for easy understanding in the figure, and actually there can be N arcs. The cooling water entering from the central channel of the plasma generator is shunted and refolded by the plasma generator cathode inner core with a blunt-body turbulent cooling structure. When the cooling water reaches the blunt-body turbulent cathode head 1, part of the cooling water enters the hollow cylindrical opening on the conical end face of the blunt-body turbulent cathode head 1, and after passing through the frustum with a spherical groove at the top and the arc-shaped groove, it turns back; a circle of circular through-holes evenly distributed in the circumference near the bottom of the outer conical surface at the left end. Figure 4As shown in the figure, the circular through-hole is perpendicular to and communicates with the hollow cylindrical structure. Part of the cooling water flows out of the blunt-body turbulent cathode head 1 through the circular through-hole and enters the cooling water channel, and continues to flow towards the right side of the cathode base 3; a frustum with a flat top protrudes from the center of the bottom of the cylindrical structure on the outer surface of the right end of the blunt-body turbulent cathode head 1, and a cylindrical emitter 2 is inlaid in the hole at the center of the frustum; the end face of the emitter 2 protrudes. When the compressed air entering the inside of the cathode base 3 reaches the bottom of the frustum, it will return along the surface of the frustum and gather near the end face of the emitter along the axial direction of the frustum, so as to better confine the plasma arc and avoid the arc from eroding the blunt-body turbulent cathode head 1. The cathode base 3 is a tubular body with a circular opening at one end and a flared opening at the other end. The left circular opening end is connected to the right circular opening end of the blunt-body turbulent cathode head 1 to form a complete cathode inner core structure.

[0030] The addition of the blunt body in the present invention makes the cooling water flowing outside the blunt-body turbulent cathode head produce a turbulent effect:

[0031] Microscopic level: In the turbulent state, there are strong random pulsations inside the fluid, and the velocity of the fluid micro-elements changes rapidly and irregularly in all directions. This pulsation greatly enhances the heat conduction and convection between fluid molecules. During the pulsation process, the fluid micro-elements continuously exchange heat with the surrounding fluid and the surface of the object to be cooled, accelerating the heat transfer rate from the object to be cooled to the fluid.

[0032] Macroscopic level: Turbulence can destroy the boundary layer formed between the fluid and the surface of the object to be cooled. The boundary layer is usually a relatively static fluid layer that hinders heat transfer. The strong disturbance of turbulence can make the boundary layer thinner or even completely destroyed, enabling the surface of the high-temperature object to be in more direct contact with the cooling fluid, thereby increasing the heat transfer coefficient and improving the cooling efficiency.

Claims

1. A plasma generator cathode core with a blunt body turbulent cooling structure, characterized in that: It comprises a blunt body turbulent cathode head (1), an emitter (2) and a cathode seat (3); the blunt body turbulent cathode head (1) is an integrated special-shaped structure, one side of the outer surface of the blunt body turbulent cathode head (1) is a cone, and the other side is a column; the blunt body turbulent cathode head (1) has a hollow inner cylindrical opening with a diameter of Φ1 on the end face of the cone side, a circle of arc-shaped grooves is formed at the bottom of the hollow inner cylindrical opening, and a convex inner circle surrounded by the arc-shaped grooves has a frustum blunt body with a spherical groove on the top; a plurality of through holes with a diameter of Φ2 are evenly distributed on the circumference of the connection between the column and the cone, and a hollow inner cylindrical opening with a diameter of Φ3 is formed on the end face of the column side. The diameter Φ3 is larger than the diameter Φ1. A cone with a flat top is protruding from the center of the bottom of the hollow cylindrical mouth. A cylindrical blind hole is opened in the center of the cone. The emitter (2) is embedded in the cylindrical blind hole. The cathode seat (3) is a cylindrical tubular body with the same inner and outer diameters as the diameter of one side of the cylinder of the blunt body turbulent cathode head (1). One end of the cylindrical tubular body is a circular mouth and the other end is a trumpet mouth. The circular mouth of the cylindrical tubular body is connected to the circular mouth end of the side end face of the cylinder of the blunt body turbulent cathode head (1) to form a hollow inner cylindrical deep cup-shaped structure with a trumpet mouth. The aspect ratio of the inner hole of the cathode seat (3) and the inner hole of the connecting end of the blunt body turbulent cathode head (1) is 5 to 15 times.

2. The cathode inner core of a plasma generator with a blunt body turbulent cooling structure according to claim 1, characterized in that: The cone angle a of the cone on one side of the outer surface of the blunt body turbulent cathode head (1) is 10 to 70 degrees.

3. The cathode inner core of a plasma generator with a blunt body turbulent cooling structure according to claim 1, characterized in that: The diameter Φ1 of the hollow inner cylindrical opening of the cone side end surface of the blunt body turbulent flow cathode head (1) is 12-20 mm.

4. The cathode inner core of a plasma generator with a blunt body turbulent cooling structure according to claim 1, characterized in that: The distance D1 from the cone side end surface of the blunt body turbulent cathode head (1) to the frustum blunt body end surface with the top spherical groove is 3-8 mm.

5. The cathode inner core of a plasma generator with a blunt body turbulent cooling structure according to claim 1, characterized in that: The distance D between the cone side end surface of the blunt body turbulent flow cathode head (1) and the center of the through holes uniformly distributed on the circumference at the junction of the column and the cone is 12-15 mm.

6. The cathode inner core of a plasma generator with a blunt body turbulent cooling structure according to claim 1, characterized in that: The diameter Φ2 of the circular through holes evenly distributed around the circumference of the connection between the column and the cone of the blunt body turbulent flow cathode head (1) is 1 to 5 mm, and the number of the circular through holes is 4 to 20.

7. The cathode inner core of a plasma generator with a blunt body turbulent cooling structure according to claim 1, characterized in that: The radius SR of the spherical groove on the frustum bluff body with a spherical groove in the hollow inner cylindrical opening on the cone side of the bluff body turbulent flow cathode head (1) is 2-6 mm, and the cone angle b of the frustum is 10-70°.

8. The cathode inner core of a plasma generator with a blunt body turbulent cooling structure according to claim 1, characterized in that: The height D2 of a flat-topped frustum protruding from the hollow inner cylindrical opening of the cylindrical side of the blunt-body turbulent cathode head (1) is 3 to 8 mm, and the cone angle c is 20 to 90 degrees.

9. The plasma generator cathode inner core with a blunt body turbulent cooling structure according to claim 1, characterized in that: The emitter (2) is made of pure silver, pure hafnium, pure tungsten, or an alloy of the three in any proportion, or a new zirconium-titanium-aluminum-scandium alloy; the cathode seat (3) is made of pure silver, pure copper, or an alloy of the two in any proportion.

10. The plasma generator cathode inner core with a blunt body turbulent cooling structure according to claim 1, characterized in that: The emitter (2) and the blunt-body turbulent cathode head (1) are connected and fixed by brazing or interference fit, and the blunt-body turbulent cathode head (1) and the cathode seat (3) are connected and fixed by welding or threading.

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