Thermoelectric diode cathode assembly heated by external aerobic combustion

Abstract

The invention provides a thermoelectric diode cathode assembly heated through external aerobic combustion. The thermoelectric diode cathode assembly comprises a metal heat conduction cup, a ceramic sealing tube, a heat insulation assembly and a cathode. The outer wall face of the ceramic sealing pipe and the inner wall face of the vertical face sealing ring of the metal heat conduction cup are in vacuum sealing connection through the brazing technology, the cathode is coaxially arranged in the center of an inner side bottom plate of the metal heat conduction cup, and the heat insulation assembly surrounds the cathode, is arranged on the inner side bottom plate of the metal heat conduction cup and is located between the ceramic sealing pipe and the cathode. And the ceramic sealing tube and the cathode are in clearance fit with each other. The structure and the process are optimized, thermal resistance is reduced to improve thermal-electric conversion efficiency, vacuum sealing reliability is guaranteed, electron emission is stabilized, the evaporation amount of a conductive substance on an interelectrode insulator is reduced, the processing difficulty is simplified, the stability of the assembly is remarkably improved, the service life of the assembly is remarkably prolonged, and the application range of the assembly is remarkably widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of machinery, and in particular to a thermoelectric diode cathode assembly heated by external aerobic combustion. BACKGROUND

[0002] The hot cathode of vacuum diode emits electrons to the vacuum space at high temperature, which breaks through the barrier of work function of free electrons in the body (Schoenflies free electron theory), and the electrons emitted by the cathode are collected by the anode and connected to the external circuit to form a port voltage and current, thus completing the conversion of thermal energy to electrical energy.

[0003] The tungsten cathode thermionic generator using vacuum diode for power generation is mainly used in military and aerospace, and has a history of several decades. The cesium ion vapor is used to "neutralize" part of the electrons between the two electrodes of the vacuum diode to increase the output current. A domestic developed thermionic generator has a working temperature of about 1460-1650℃, a current density of 1.7-11.2A / cm 2 , a power density of about 1-7.8W / cm 2 , and a service life of less than 300 hours (Reactor Thermionic Converter, Cao Shengquan et al., Nuclear Science and Engineering 1984 / 9).

[0004] The patent No. Zl-2009-1-0044761.6 relates to a power generation device, in particular to a vacuum thermoelectric diode direct current power generation device with an accelerator for directly converting thermal energy into direct current electrical energy, which is referred to as a thermal energy cell. The basic power generation body of the thermal energy cell is a thermoelectric series structure of a thermoelectric diode and a thermoelectric pile, and the body is combined with a heat source, cooling, electrical control and other components to form a thermal energy cell. The spacing between the two electrodes of the thermoelectric diode is very small, and the waste heat of the thermal energy cell makes the thermoelectric pile work and provides an auxiliary anode voltage for the thermoelectric diode, and the series voltage of the two devices accelerates the electrons in the thermoelectric diode, and the port current increases. The working temperature of the thermal energy cell is lower than that of the thermionic generator, and the performance is higher than that of the thermionic generator. The thermal energy cell can be used for both military and civilian purposes, has the characteristics of simple structure, quietness, high power density, and convenient use, and is suitable for direct current power generation, water, land and air transportation tools and other application scenarios.

[0005] Thermoelectric diode is the core power generation device of thermal energy battery, and cathode assembly is the core component of thermoelectric diode. Cathode is a heat and electric energy conversion device in thermoelectric diode, i.e. an electron source for generating electricity. There are many types of cathodes, and the cathode described in the case mainly refers to a diffusion type barium tungsten hot cathode with tungsten powder and emission salt as the material. The tungsten powder body sintered into a final shape is called tungsten body or tungsten sponge body, which is the support structure of the cathode. The active emission salt containing barium element is the main body of high-temperature electron emission of the cathode, and is filled in the voids of the tungsten body. The case mainly includes tungstate, aluminate and scandate, and each variant formed by adding rare earth elements other than scandium oxide. The two mature processes for preparing the cathode are impregnation type and pressing type.

[0006] For the cathode with a thickness of 1-2 mm, the heating temperature of the scandate cathode bottom is about 900-1050℃, and the heating temperature of the tungstate and aluminate barium tungsten cathode is about 950-1150℃.

[0007] The direct current density that can be extracted by the hot cathode is generally 10A / cm 2 , and the product containing yttrium element exceeds 20A / cm 2 (Patent application publication number: CN 102394208 A).

[0008] The port volt-ampere power density of the scandate barium tungsten hot cathode assembled thermoelectric diode reaches 10W / cm 2 (National pre-research project test and calculation). According to the calculation data, cathode electronics and circuit principle, the thermal energy battery assembled with such a cathode only needs a small anode voltage when the hot state working interelectrode distance is 10-20 microns, and the port volt-ampere power density exceeds 10W / cm 2 , and the battery is completely self-sustaining.

[0009] The scandate cathode barium tungsten diode extracts 5A / cm 2 of current density, and the service life exceeds 15,000 hours; the service life exceeds 9,000 hours when extracting 10A / cm 2 of current density (tested by the Institute of Electronics of the Chinese Academy of Sciences in 1983); the service life exceeds 20,000 hours when extracting 2-3A / cm 2 of small current density, and the service life exceeds 2,000 hours when extracting 4-5A / cm 2 of small current density. The service life of the cathode is not less than 10,000 hours when extracting medium current. Such service life value is higher than or equivalent to the average service life of five electric passenger cars of a city family (about 1-1.5 million hours). The service life of the aluminate barium tungsten cathode is about 3,000-10,000 hours. The service life of the tungstate barium tungsten cathode is slightly lower than that of the aluminate barium tungsten cathode. The service life of the long-life coated cathode coated with a layer of osmium, iridium, osmium ruthenium and other elements on the emission surface of the hot cathode can reach more than 30-50,000 hours.

[0010] Cathode needs to emit electrons at high temperature, the device that produces high temperature is called heat source device. The heat source of thermoelectric diode is widely used, among which, nuclear heat energy, solar concentrated heat energy and oxygen combustion heat energy have bright application prospects. The present application adopts oxygen combustion to generate high temperature, and the device that generates high temperature through oxygen combustion is called combustor. Gas fuel combustor is a micro-scale combustor developed in recent decades, and the minimum flame height and flame diameter can be less than 10 mm, and the technology is mature. After special engineering design, the present application can adopt liquid or solid fuel combustor.

[0011] The cathode of ordinary vacuum electron diode device is usually designed as a cylinder or a flat plate structure coaxial with the anode, and an electric heating device is used to generate high temperature; the cathode of thermionic diode (direct current generator) is usually designed as a cylinder structure coaxial with the anode, and most of them use nuclear heat energy device to generate high temperature. The heat source device of these two devices can work in an oxygen-free condition, and is usually packaged in the vacuum diode tube. In the present application, the combustor works in an oxygen-containing environment, and the heat source device can only be assembled outside the diode tube. In order to conduct the heat generated by oxygen combustion and maintain the vacuum condition of the flat plate thermoelectric diode, in order to realize small inter-electrode distance and maintain long-term inter-electrode insulation, in order to stabilize the output voltage, in order to adapt to different application scenarios, some auxiliary components are needed to form a cathode assembly with the cathode. Compared with ordinary vacuum electronic devices and thermionic generators, the cathode assembly described in the present application has obvious differences in structure.

[0012] The patent number for the invention patent is Zl-2009-1-0044761.6, the embodiment of which Figure 5 A flat plate type floating composite cathode structure is disclosed, the cross section of which is like The upper half is a cathode box, and the lower half is a heat conducting plate. The cathode emitter is assembled in the cathode box 37 made of metal molybdenum by welding. This embodiment itself still has several technical problems to be solved, and there are also some new problems to be solved in using oxygen combustion as the heat source:

[0013] ①The first function of the original heat conducting plate 36 is to transfer the heat generated by the bottom heater to the cathode emitter. In order to be connected as a whole, the composite cathode structure The upper cathode box The cathode is embedded in the cathode box with the metal heat conducting plate needs to be welded once, so there are two welding processes in the connection process of the cathode assembly, and two metal bottom surfaces and two welding layers increase the total thickness, thereby increasing the conduction thermal resistance.

[0014] ②The second function of the original heat-conducting plate 36 is to realize vacuum sealing of the bottom of the diode through brazing of metal-ceramic, and meanwhile, the heating area is considered. For this purpose, the edge section of the metal heat-conducting plate is designed as However, the metal heat-conducting plate The lower edge of the bend at the two ends of the structure is embedded in the vacuum sealing section of the ceramic frame, and it is difficult to dissipate heat, and unless the embedded section is increased or the temperature resistance of the brazing filler metal is very high, vacuum failure is likely to occur. In addition, The forming process is also relatively complex.

[0015] ③The purpose of the original cathode box 37 is to reduce the emission of evaporated particles of the cathode emission salt (containing barium and other metals) from the source. However, the support structure of the cathode emitter is a sintered tungsten powder with rough surface, and if there is no assembly gap, the formed cathode emission tungsten body is completely embedded in the molybdenum cathode box of the structure, which has high process requirements. In addition, the thermal expansion coefficients of tungsten and molybdenum are inconsistent, and the mechanical plasticity of both is low, so the walls of the molybdenum cathode box are prone to deformation and even cracking, causing the leakage of evaporated substances of the cathode emitter.

[0016] ④The original heater 1 does not specify what kind of specific heating device it is, and therefore, there is no design for the flame zone required for aerobic combustion, temperature decay, exhaust gas emission, voltage change caused by changes in combustion heat, high-temperature oxidation resistance measures, and other structures and technologies.

[0017] ⑤The ceramic piece is generally used as an insulating component between the two electrodes, and in order to prevent high-temperature evaporation of the metal and the emission salt body, an electrically conductive film is applied to the surface of the insulating component, which leads to insulation failure. The original scheme sets up an insulating gully groove 114. Although this design has good insulation effect, it has high process difficulty and reduces the mechanical strength of the ceramic component, and cracks may occur under strong vibration, leading to vacuum failure. SUMMARY

[0018] Therefore, the purpose of the present application is to provide a hot electron diode cathode assembly heated by external aerobic combustion, which optimizes the structure and process, reduces the thermal resistance to improve the thermal-electric conversion efficiency, ensures the reliability of vacuum sealing, stabilizes the electron emission, reduces the evaporation amount of conductive substances on the inter-electrode insulator, simplifies the processing difficulty, and significantly improves the stability, life and application range of the assembly.

[0019] The technical scheme adopted by the present application to solve the technical problems is:

[0020] The present application provides a hot electron diode cathode assembly heated by external aerobic combustion, which comprises a metal heat-conducting cup, a ceramic sealing tube, a heat insulation assembly and a cathode.

[0021] The outer wall surface of the ceramic sealing tube is sealed with the inner wall surface of the vertical sealing ring of the metal heat-conducting cup by brazing process to achieve airtight vacuum sealing, the cathode is coaxially arranged in the center of the metal heat-conducting plate inside the metal heat-conducting cup, and the heat insulation assembly is arranged on the metal heat-conducting plate inside the metal heat-conducting cup and located between the ceramic sealing tube and the cathode.

[0022] Preferably, the metal heat-conducting cup comprises a vertical sealing ring and a metal heat-conducting plate, the vertical sealing ring is arranged on the metal heat-conducting plate to form the side wall of the metal heat-conducting cup, the metal heat-conducting plate forms the bottom plate and comprises a cathode heat-conducting area and a temperature attenuation area, the temperature attenuation area is the area of the metal heat-conducting plate after the area of the vertical sealing ring is subtracted from the area of the cathode heat-conducting area, the cathode is welded on the cathode heat-conducting area and coaxial with the cathode heat-conducting area, and the heat insulation assembly is arranged on the temperature attenuation area and close to the inside of the temperature attenuation area.

[0023] Preferably, the heat insulation assembly comprises one primary radiation screen and at least one secondary radiation screen, and both are arranged on the temperature attenuation area, the primary radiation screen is arranged around the cathode, the secondary radiation screen is arranged around the primary radiation screen in a gap fit and is at the same height as the primary radiation screen, the gap L between the primary radiation screen and the cathode is 0.02-0.5mm wide, the gap M between the secondary radiation screen and the primary radiation screen is 0.02-0.5mm wide, and the gap N between the secondary radiation screen and the ceramic sealing tube is 0.05-20mm wide.

[0024] Preferably, the secondary radiation screen is formed by the inner wall of a heat container made of the same material as the cathode heat-conducting area, the heat container is in a ring structure and is welded and fixed on the temperature attenuation area, and the height of the heat container is lower than the thickness of the cathode, the thickness difference between the heat container and the cathode constitutes an exhaust gap, and the width of the exhaust gap is 1 / 10-1 / 4 of the thickness of the cathode.

[0025] Preferably, the metal heat-conducting cup is integrally formed by metal hot die pressing, hot stamping, and precision turning process, or the vertical sealing ring and the bottom metal heat-conducting plate are respectively prepared and then formed by airtight welding, the thickness of the plate is 0.2-2mm, and the outer surface of the metal heat-conducting cup is coated with high-temperature anti-oxidation paint.

[0026] Preferably, the cathode is a diffusion-type barium-tungsten hot cathode, the tungsten body is directly connected to the cathode heat-conducting area by tungsten-molybdenum welding process, and the emission salt of the cathode is any one of scandate, tungstate, aluminate, and a variant formed by adding rare earth elements other than scandium oxide.

[0027] Preferably, the outer bottom of the metal heat-conducting cup is provided with a waste gas guide ring, the inner and outer surfaces of the waste gas guide ring are coated with high-temperature oxidation-resistant paint, the outer surface of the metal heat-conducting plate and the inner surface of the waste gas guide ring form a waste gas guide groove, and the waste gas guide ring can guide the high-temperature waste gas in the flame zone in the waste gas guide groove downward and away from the vertical sealing ring.

[0028] Preferably, the inner guide edge of the waste gas guide ring is arc-shaped or bent, and is connected and fixed to the bottom of the metal heat-conducting cup by welding, and the outer wall of the waste gas guide ring is provided with connecting bolts for fixing the burner.

[0029] Preferably, the distance H between the bottom surface of the ceramic sealing tube and the inner bottom surface of the metal heat-conducting cup is 0.5-10mm, and the bottom surface of the ceramic sealing tube is sprayed with 2-3um of ceramic particle powder.

[0030] Preferably, the brazing process is a metal-ceramic brazing process, and the brazing process uses any one of silver copper, silver, and nickel titanium solder.

[0031] The beneficial effects of the present application are as follows:

[0032] The present application provides a thermoelectric diode cathode assembly heated by external aerobic combustion, which directly welds the cathode tungsten body with the cathode heat-conducting area, omits the traditional cathode box and the secondary welding layer, greatly reduces the thermal resistance, efficiently conducts the combustion heat, and significantly improves the thermal-electric conversion efficiency; the metal heat-conducting cup adopts a one-step forming process of high-temperature pressing and precise machining or a two-step forming process of airtight welding, reduces the risk of bending points and cracks in the machining of hard metals (such as molybdenum), forms a heat gradient with the temperature attenuation area, guides the high-temperature waste gas in the waste gas guide groove away from the sealing part, and further combines the metal-ceramic brazing process and the adaptive solder (such as silver copper solder, silver solder, and nickel titanium solder) to ensure that the temperature of the vacuum sealing part is stable within the safety threshold, effectively guaranteeing the long-term reliability of the airtight vacuum sealing;

[0033] The first and second radiation screens in the heat insulation assembly are matched through the gap, which can not only reflect heat radiation to balance the cathode temperature and reduce the fluctuation of electron emission, but also block the emitted salt particles evaporated by the high-temperature cathode, and the ceramic particle powder sprayed on the bottom of the ceramic sealing tube forms a conductive film, which greatly reduces the evaporation of the material to maintain the insulation between the electrodes; the overall process is simplified, the gap between the radiation screens is replaced by the traditional precise embedded cathode box, and the processing difficulty and deformation risk are reduced.

[0034] Meanwhile, the high-temperature oxidation-resistant paint coated on the outer surface of the metal heat-conducting cup and the inner and outer surfaces of the waste gas guide ring is adapted to the aerobic combustion environment, a variety of emitted salts are selected to adapt to different life requirement scenarios, and the gas, liquid and solid fuel burners are adapted, so as to significantly improve the working stability of the assembly, prolong the service life and broaden the application range. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A perspective view of a thermoelectric diode cathode assembly heated by external aerobic combustion for embodiment 1 of the present invention.

[0036] Figure 2 A top view of a thermoelectric diode cathode assembly heated by external aerobic combustion for embodiment 1 of the present invention.

[0037] Figure 3 A cross-sectional view of a thermoelectric diode cathode assembly heated by external aerobic combustion for embodiment 1 of the present invention.

[0038] Figure 4 A bottom view of a thermoelectric diode cathode assembly heated by external aerobic combustion for the filter of embodiment 1 of the present invention.

[0039] Figure 5 A top view of a thermoelectric diode cathode assembly heated by external aerobic combustion for embodiment 2 of the present invention.

[0040] Figure 6 A cross-sectional view of a thermoelectric diode cathode assembly heated by external aerobic combustion for embodiment 2 of the present invention.

[0041] Figure 7 A perspective view of a thermoelectric diode cathode assembly heated by external aerobic combustion for embodiment 1 of the present invention. Figure 6 An enlarged view of A.

[0042] Figure 8 A bottom view of a thermoelectric diode cathode assembly heated by external aerobic combustion for the filter of embodiment 1 of the present invention.

[0043] In the figure: 1, metal heat-conducting cup; 11, vertical sealing ring; 12, cathode heat-conducting area; 13, temperature attenuation area; 2, ceramic sealing tube; 3, heat insulation assembly; 31, first radiation screen; 32, second radiation screen; 33, heat container; 4, cathode; 5, exhaust gap; 6, exhaust guide ring; 7, connecting bolt.

[0044] It should be noted that the drawings and the written description are not intended to limit the scope of the concept in any way, but are merely to illustrate the concept of the present invention to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present invention.

[0046] Example 1

[0047] like Figures 1-4 As shown, a thermoelectric diode cathode 4 assembly heated by external oxygen combustion includes: a metal heat-conducting cup 1, a ceramic sealing tube 2, a heat insulation component 3, and a cathode 4;

[0048] The outer wall of the ceramic sealing tube 2 and the inner wall of the vertical sealing ring 11 of the metal heat-conducting cup 1 are sealed in an airtight vacuum by brazing. The cathode 4 is coaxially arranged in the center of the inner bottom plate of the metal heat-conducting cup 1. The heat insulation component 3 is arranged around the cathode 4 on the inner bottom plate of the metal heat-conducting cup 1 and is located between the ceramic sealing tube 2 and the cathode 4, and is respectively fitted with the ceramic sealing tube 2 and the cathode 4 with a gap.

[0049] It should be noted that the metal heat-conducting cup 1, as the supporting structure of the entire cathode 4 assembly, has a longitudinal cross-section that is [insert cross-section here]. The shape can be a cylindrical metal heat-conducting cup, or a rectangular or other geometrically shaped cylindrical cup; the outer wall of the ceramic sealing pipe 2 and the inner wall of the vertical sealing ring 11 of the metal heat-conducting cup 1 are brazed to achieve "airtight vacuum sealing", which is to maintain the internal vacuum environment of the thermoelectric diode (vacuum degree not less than 10). -6 The core guarantee of the cathode 4 is to ensure that electron emission and energy conversion are stable under vacuum conditions. The cathode 4, as a heat and electricity energy conversion device, is coaxially set in the center of the inner bottom plate of the metal heat-conducting cup 1 to ensure that the heat generated by combustion in the flame zone is efficiently conducted to the cathode 4. The heat insulation component 3 surrounds the cathode 4 and is located between the ceramic sealing tube 2 and the cathode 4, and is gap-fitted with both. This non-contact design reduces heat conduction from the cathode 4 to the sealing part and reduces heat loss. On the other hand, it can reduce the direct diffusion of emission salt particles (such as barium salt) evaporated at high temperature from the cathode 4 to the inner wall of the ceramic sealing tube 2, and avoid excessive particle deposition to form a conductive film, which would lead to the failure of inter-electrode insulation. The design and material selection of the bottom surface of the metal heat-conducting cup 1 meet the high temperature conditions of 900-1150℃ for electron emission of the diffused barium tungsten cathode.

[0050] The metal heat-conducting cup 1 includes a vertical sealing ring 11 and a metal heat-conducting plate. The vertical sealing ring 11 is disposed on the metal heat-conducting plate to form the sidewall of the metal heat-conducting cup 1. The metal heat-conducting plate forms a bottom plate and includes a cathode heat-conducting area 12 and a temperature attenuation area 13. The temperature attenuation area 13 is the area of ​​the metal heat-conducting plate after deducting the area of ​​the cathode heat-conducting area 12 from the area enclosed by the vertical sealing ring 11. The cathode 4 is welded to the cathode heat-conducting area 12 and is coaxial with it. The heat insulation component 3 is disposed on the temperature attenuation area 13 and close to the inner side of the temperature attenuation area 13.

[0051] It needs to be explained that the function of the cathode heat conduction area 12 is to transfer heat from the combustion flame area to the cathode 4, and the cathode 4 is directly welded on the cathode heat conduction area 12, compared with the original "cathode 4-cathode 4 box-heat conduction plate" secondary welding structure, the intermediate thermal resistance is reduced, and the heat energy conduction efficiency is improved; The heat gradient of the temperature attenuation area 13 makes the high temperature (about 900-1050℃ for scandate cathode, about 950-1150℃ for tungstate and aluminate cathode) gradually attenuate from the cathode heat conduction area 12 to the vertical sealing ring 11. In order to ensure that the sealing part temperature is lower than the safety threshold of vacuum sealing of brazing filler metal (such as silver copper solder ≤300℃), the width of the temperature attenuation area 13 can be adjusted. For 1050℃ temperature, silver copper solder and nickel titanium solder are selected, and the minimum width is 2-3 cm and 1-1.5 cm respectively. If the outer wall of the vertical sealing ring (11) is cooled, the size can be greatly reduced; the metal heat conduction cup (1) can be integrally formed by mature hot molding, hot stamping and precision turning process, or the vertical sealing ring (11) and the bottom metal heat conduction plate are prepared separately, and then formed by airtight welding. Compared with the original structure, the bending point is reduced, and the crack risk in the forming process is also greatly reduced.

[0052] As Figure 3 shown, the heat insulation assembly 3 includes one primary radiation screen 31 and at least one secondary radiation screen 32, and the width K is 0.1-0.5 mm. The primary radiation screen 31 surrounds the cathode 4 and is arranged inside the temperature attenuation area 13 of the metal heat conduction plate, and the gap L between the primary radiation screen 31 and the cathode 4 is 0.02-0.5 mm. The secondary radiation screen 32 surrounds the primary radiation screen 31 and is also arranged inside the temperature attenuation area 13 of the metal heat conduction plate, and is the same height as the primary radiation screen 31. The gap M between the primary radiation screen 31 and the secondary radiation screen 32 is 0.02-0.5 mm. The gap N between the secondary radiation screen 32 and the ceramic sealing pipe 2 is the remaining amount after deducting the total width of the heat insulation assembly (3) and the gap from the width of the temperature attenuation area 13. For 1050℃ temperature, silver copper solder and nickel titanium solder, the gap N between the secondary radiation screen 32 and the ceramic sealing pipe 2 can be set to 10-30 mm, and the N size can be reduced when the outer wall of the vertical sealing ring 11 is cooled.

[0053] It should be noted that the width of the first radiation screen 31 is strictly controlled to be 0.1-0.5 mm, which not only ensures the effective area of radiation heat exchange, but also avoids the redundancy of heat capacity due to excessive width. The gap L between the first radiation screen 31 and the cathode 4 is 0.02-0.5 mm. According to the principle of molecular free path, most of the emitted salt particles from the cathode 4 at a high temperature of 900-1150℃ will be deposited inside the first radiation screen 31 due to collision, and part of them will return to the cathode 4 through thermal motion, thereby reducing the amount of particle leakage from the source. The gap M between the first radiation screen 31 and the second radiation screen 32 is also 0.02-0.5 mm. In addition to secondary radiation heat exchange, it further blocks escaping particles. At the same time, due to vacuum insulation, the heat conduction of the cathode 4 to the outside is reduced (the thermal resistance is increased by about 30%), and the temperature difference between the center and the edge of the cathode 4 is reduced by about 10-30℃, which improves the problem of uneven electron emission of the original cathode 4. This design replaces the traditional cathode 4 box structure, which not only reduces the risk of deformation due to the difference in thermal expansion coefficient between tungsten and molybdenum, but also improves the temperature uniformity of the cathode 4 and stabilizes the electron emission by precise gap control and radiation screen layout, thereby prolonging the insulation life of the ceramic sealing tube 2 and simplifying the process difficulty.

[0054] The metal heat-conducting cup 1 is integrally formed by metal molybdenum, has a thickness of 0.2-2 mm, and the outer surface of the metal heat-conducting cup 1 is coated with high-temperature oxidation-resistant paint.

[0055] It should be noted that the metal heat-conducting cup 1 uses metal molybdenum as the preferred material. Molybdenum is chosen because it has a high melting point (2620℃), excellent thermal conductivity (138 W / (m·K)), and high-temperature stability, can withstand the working temperature of the cathode 900-1150℃, and has a similar thermal expansion coefficient (molybdenum is about 5.1×10 -6 / ℃, tungsten is about 4.5×10 -6 / ℃) to that of tungsten (cathode 4 support structure), reducing structural stress at high temperatures; and is integrally formed by a process such as hot die pressing or hot stamping. Compared with the traditional splicing or welding process, the one-piece forming reduces the bending points and welding seams of molybdenum as a hard metal (poor mechanical plasticity) during processing, reduces the risk of cracks due to stress concentration, and simplifies the complex forming steps of the traditional "U" shaped structure, thereby improving the structural integrity and process feasibility of the assembly; molybdenum is easily oxidized to form molybdenum trioxide (which reduces thermal conductivity and causes surface peeling) in an oxygen environment above 300℃, while the paint forms a dense protective layer to block the oxidation reaction, allowing the molybdenum component to maintain stable thermal conductivity and structural integrity during long-term high-temperature operation, and adapt to the external oxygen combustion working environment.

[0056] The cathode 4 is a diffusion-type barium tungsten thermal cathode 4, and its tungsten body is directly connected to the cathode heat-conducting region 12 by a tungsten-molybdenum welding process. The emission salt of the cathode 4 is any one of scandium, tungstate, aluminate, and their respective variants formed by adding rare earth elements other than scandium oxide.

[0057] It should be noted that cathode 4 is a diffusion-type barium-tungsten thermocathode 4. Its core structure consists of a tungsten body (tungsten sponge) formed by sintering tungsten powder and emission salts filling the voids in the tungsten body. As the core electron source of the thermoelectric diode, it can achieve stable electron emission at high temperatures, with a maximum DC density of 10-15 A / cm³. 2 Suitable for 5-10W / cm 2 The cathode 4 tungsten body and cathode heat-conducting area 12 are directly connected by tungsten-molybdenum welding process. Compared with the existing secondary welding structure of "cathode 4-cathode box-heat-conducting plate", the thermal resistance of the intermediate welding layer and the bottom surface of the cathode 4 box is reduced (heat loss is reduced by about 30%), ensuring that the heat generated by the burner is efficiently transferred to the cathode 4, accurately meeting the operating temperature requirements of scandate cathode 900~1050℃ and tungstate / aluminate cathode 950~1150℃, and improving the thermoelectric conversion efficiency. The selection of emission salts covers scandate, tungstate, aluminate, and their variants formed by adding rare earth elements other than scandium oxide: scandate emission salts are suitable for long-life scenarios (drawing 2-3A / cm). 2 With a lifespan exceeding 20,000 hours under current conditions, tungstate and aluminate are suitable for short- to medium-term operating needs (aluminate lifespan 3,000-10,000 hours), while rare earth variants further enhance electron emission stability through optimized surface activity. This diverse selection allows the components to be adapted to different application scenarios, from family passenger vehicles (lifespan comparable to the entire vehicle) to short-term high-power devices, expanding the applicability of thermoelectric diodes.

[0058] like Figure 4 As shown, an exhaust gas guide ring 6 is provided on the outer bottom of the metal heat-conducting cup 1. The inner and outer surfaces of the exhaust gas guide ring 6 are coated with high-temperature anti-oxidation coating. The outer side of the metal heat-conducting plate and the inner side of the exhaust gas guide ring 6 surround each other to form an exhaust gas guide groove. The exhaust gas guide ring 6 can guide the high-temperature exhaust gas in the flame zone of the exhaust gas guide groove downward and away from the vertical sealing ring 11.

[0059] It should be noted that the metal thickness of the prepared waste flow guide ring is about 0.1-1 mm, which can be punched, molded, or cut, spliced, and butt welded; through the directional guiding effect of the waste gas flow guide groove, the high-temperature waste gas (temperature close to the center temperature of the flame zone) generated by the burner flame zone is guided downward and away from the vertical sealing ring 11; in the existing structure, the high-temperature waste gas is easy to directly impact or surround the sealing part, causing the temperature of the vertical sealing ring 11 to rise, which may exceed the safe threshold of the brazing filler metal (such as silver-copper solder ≤300℃) to cause vacuum sealing failure; and the design guides the waste gas away from the sealing part through the flow guide groove (which can be connected to a waste heat utilization device), reducing the heat radiation and heat conduction of the waste gas to the sealing ring body, and further reducing the temperature of the sealing part with the temperature attenuation area 13 design to ensure the long-term stability of the brazing layer.

[0060] The inner side of the waste gas flow guide ring 6 is a bending structure, and is connected and fixed with the bottom of the metal heat conduction cup 1 by welding, and the outer side wall of the waste gas flow guide ring 6 is provided with a connecting bolt 7 for fixing the burner.

[0061] It should be noted that the cross section of the inner side of the waste gas flow guide ring 6 is a bending structure, which is easier to process than an arc (such as by punching forming), reduces the manufacturing difficulty, and can adapt to a more compact installation space, enhancing the assembly compatibility with different types of burners and widening the application scenarios of the assembly; and the directivity of the high-temperature waste gas is more direct, which can accurately guide the high-temperature waste gas generated by combustion along the preset path and away from the vertical sealing ring 11 of the metal heat conduction cup 1, reducing the heat radiation and heat conduction of the waste gas to the sealing part. With the temperature attenuation area 13 of the metal heat conduction cup 1, the temperature of the brazing part can be more stably controlled within the safety threshold, avoiding vacuum sealing failure caused by overheating, and protecting the internal vacuum environment (vacuum degree not less than 10 -6 The outer side wall of the waste gas flow guide ring 6 is provided with a connecting bolt 7 for stable assembly with the burner, and the bolt positioning ensures that the burner flame zone is coaxial with the cathode 4 and the cathode heat conduction area 12 (coaxiality error ≤0.1 mm), so that the heat is uniformly transmitted to the cathode heat conduction area 12; and the bolt connection can adapt to the position fine adjustment requirement of the burner, enhance the assembly stability of the assembly and the heat source device, and provide synergistic protection for the efficient utilization of external aerobic combustion heat and the protection of the sealing part.

[0062] The distance H between the lower end bottom surface of the ceramic sealing tube 2 and the inner bottom surface of the metal heat conduction cup 1 is 0.5-10 mm, and the bottom surface of the ceramic sealing tube 2 is sprayed with 2-3 μm of ceramic particle powder.

[0063] It should be noted that the distance H between the bottom surface of the ceramic sealing tube 2 and the inner bottom surface of the metal heat-conducting cup 1 is limited to 0.5-10 mm, which has three functions: on the one hand, the solder between the outer wall surface of the ceramic sealing tube (2) and the inner wall surface of the vertical sealing ring (11) of the metal heat-conducting cup (1) is as far as possible from the high temperature of the bottom surface of the metal heat-conducting cup (1), so as to reduce the evaporation of the solder, which can be regarded as the continuation of the temperature attenuation zone (13); on the other hand, if the bottom surface of the ceramic sealing tube 2 does not form a continuous conductive film, the ceramic sealing tube (2) between the two electrodes is insulating, so that the ceramic particle powder with an average particle size of 2-3 μm is sprayed on the bottom surface of the ceramic sealing tube 2 to reduce the interconnection probability of the "island effect", and the rough surface cooperates with the heat insulation assembly 3 to further block the deposition of evaporated particles and form a conductive film, thereby greatly reducing the risk of forming a conductive film and improving the insulation life of the cathode assembly, so as to ensure long-term stable operation; on the third hand, the bottom surface of the ceramic sealing tube (2) is not connected with the inner bottom surface of the metal heat-conducting cup (1), so as to avoid the deformation (positive pressure) caused by the different thermal expansions of the two materials.

[0064] The brazing process is a metal-ceramic brazing process, and the brazing solder is any one of silver copper, silver, and nickel titanium solder.

[0065] It should be noted that the metal-ceramic brazing process is the core process for realizing the "airtight vacuum sealing" between the outer wall surface of the ceramic sealing tube 2 and the inner wall surface of the vertical sealing ring 11 of the metal heat-conducting cup 1, and the core goal is to ensure that the internal environment of the thermoelectric diode is maintained at a high vacuum environment of not less than 10 -6 The solder is selected from any one of silver copper solder, silver solder, and nickel titanium solder, and the specific selection is based on the temperature control requirement of the sealing part: the melting point of silver copper solder is about 780℃, the melting point of silver solder is about 960℃, and the melting point of nickel titanium solder is about 1200℃; and the vacuum sealing part needs to be controlled at about 1 / 3 of the melting point of the solder as a safety temperature (such as silver copper solder safety temperature ≤300℃), which cooperates with the temperature attenuation zone 13, the waste gas guide groove, etc. of the metal heat-conducting cup 1, the high melting point solder, the waste gas guide groove design, the cathode 4, and the internal radiation heat shunting (heat flow unit: watt) technology of the heat insulation assembly (3), so as to shorten the size of the temperature attenuation zone (13) under the condition of ensuring the safety temperature and improve the specific power of the thermoelectric diode.

[0066] The working principle and preparation process of the power generation thermoelectric diode cathode 4 assembly heated by external aerobic combustion in the embodiment are as follows:

[0067] This embodiment provides a thermoelectric diode cathode 4 assembly heated by external aerobic combustion. Heat generated by the external burner is transferred to the cathode 4 via the cathode heat conduction area 12 of the metal heat conduction cup 1, causing the cathode 4 to excite electrons at high temperature, completing the energy conversion from heat to electricity. The metal heat conduction cup 1 serves as a support structure, with its cathode heat conduction area 12 directly connected to the cathode 4, reducing intermediate obstacles to heat transfer and ensuring efficient heat delivery to the cathode 4. The temperature attenuation zone 13, through structural design, forms a heat gradient, causing the high temperature to gradually decrease from the cathode heat conduction area 12 towards the vertical sealing ring 11, preventing damage to the sealing area due to overheating. Simultaneously, the exhaust gas guide ring 6 on the outside of the metal heat conduction cup 1 and the cathode heat conduction area 12 form an exhaust gas guide channel, guiding the high-temperature exhaust gas generated by combustion away from the vertical sealing ring. The direction of 11 further reduces the thermal impact on the sealing part, and together with the temperature attenuation zone 13, it ensures the stability of the airtight vacuum seal formed by brazing the ceramic sealing tube 2 and the vertical sealing ring 11, maintaining the vacuum environment inside the component. The inner guide edge of the exhaust gas guide ring 6 adopts a bent structure, which is easier to form by stamping than the arc shape, reducing the processing difficulty. In the heat insulation component 3, the primary radiation screen 31 surrounds the cathode 4, and balances the temperature of each area of ​​the cathode 4 by reflecting the thermal radiation of the cathode 4, ensuring uniform electron emission, while blocking the emission salt particles evaporated by the cathode 4 at high temperature. The secondary radiation screen 32 surrounds the primary radiation screen 31, further intercepting the escaped particles and preventing them from diffusing to the ceramic sealing tube 2. With the special treatment at the bottom of the ceramic sealing tube 2, it avoids the particle deposition to form a conductive film that affects the inter-electrode insulation.

[0068] In use, following traditional processes, the blank of the ceramic sealing tube 2 is prepared using ceramic powder (such as alumina 99) and then sintered.

[0069] The metal heat-conducting cup 1 is made of metal sheet, preferably molybdenum, with a thickness of 0.2-2 mm depending on the application. Molybdenum is a hard metal with poor mechanical plasticity and ductility at room temperature, making it prone to internal cracks or dark lines during machining, leading to scrap. Mechanical plasticity and ductility are also related to the purity of molybdenum and the thickness of the sheet; higher purity and thinner sheet result in better plasticity and ductility. Therefore, molybdenum needs to be heated during machining. For 0.9999% pure molybdenum sheets, 50-60°C (close to room temperature) is sufficient; for other purities, the temperature needs to be increased to approximately 100-600°C. After the molybdenum sheet is cut to the designed dimensions, it is preheated in an electric resistance furnace before being placed in a pressing mold. Alternatively, it can be preheated in a mold using high-frequency induction heating. The heating element is integrally formed by stamping or molding, or the vertical sealing ring 11 and the bottom metal heat-conducting plate are separately prepared and then formed by airtight welding.

[0070] In the heat insulation assembly 3, the first radiation screen 31 surrounds the cathode 4, and the second radiation screen 32 surrounds the first radiation screen 31, both of which have different circular ring diameters, the same height, and the same radiation screen width K of 0.1-0.5 mm; the radiation screen height is lower than the thickness of the cathode 4, and the thickness difference between the radiation screen and the cathode 4 forms an exhaust gap 5, the width of the exhaust gap 5 is 1 / 10-1 / 4 of the thickness of the cathode 4; a molybdenum strip with a thickness of K and the same material is tightly wound on a cylindrical assembly mold with a corresponding diameter, and the two ends are welded together, and the inner side of the workpiece needs to be finely ground and polished after being taken out. The workpieces of the heat insulation assembly 3 are respectively and accurately positioned on the coaxial workstations corresponding to the temperature attenuation area 13 on the bottom surface of the metal heat conduction cup 1, and then they are respectively and accurately connected with the bottom surface of the metal heat conduction cup 1 through metal welding; the process difficulty of the heat insulation assembly 3 is lower than that of the original precise embedding process of the cathode box, and it is suitable for batch production requirements.

[0071] The exhaust gas guide ring 6 is arranged outside the temperature attenuation area 13 on the bottom surface of the metal heat conduction cup 1, and a connecting bolt 7 for fixing the burner is arranged on the outer side wall of the exhaust gas guide ring 6; the inner side guide edge of the exhaust gas guide ring 6 is in a bending structure, and the bending point of the cross section can be two or multiple; the metal for preparing the exhaust gas guide ring is preferably the same material as the metal heat conduction cup 1, and the thickness is about 0.1-1 mm; since the exhaust gas guide ring 6 has relatively low air tightness requirements, it can be punched or molded, and can also be cut, spliced and butt welded; the punching or molding process has lower requirements for the mold precision, is more easily formed by punching, and has lower manufacturing difficulty than the arc-shaped guide edge exhaust gas guide ring; the screw hole position of the connecting bolt 7 is punched out; the exhaust gas guide ring 6 is accurately positioned on the coaxial workstations corresponding to the outside of the temperature attenuation area 13 on the bottom surface of the metal heat conduction cup 1, and then the two are connected into one through metal welding.

[0072] The semi-finished product assembled by the metal heat conduction cup 1, the heat insulation assembly 3, and the exhaust gas guide ring 6 is placed in a hydrogen furnace for heat treatment to eliminate internal stress generated by machining and welding.

[0073] The ceramic and metal airtight vacuum sealing is a mature process in vacuum electronic industry, generally divided into three steps: the outer side of the ceramic sealing tube 2 corresponding to the vacuum sealing part is subjected to metalization treatment (for example, activated molybdenum-manganese method), the outer wall surface of the ceramic sealing tube 2 is coated with pre-configured activated metal paste, then nickel plating is performed after sintering in a hydrogen furnace, at this time, a surface metal layer has been formed, and the ceramic-metal welding is converted into metal-metal welding; the ceramic sealing tube 2 with the outer wall surface metallized is slowly pressed into the inner wall surface of the vertical sealing ring 11 of the metal heat-conducting cup 1, the gap is generally not more than 80 microns, the assembled workpiece is placed into a heating furnace (hydrogen welding furnace, resistance welding furnace, high-frequency induction welding furnace) with specific gas protection, the brazing filler metal is placed at a proper position on the gap, and through high-temperature heating, the brazing filler metal is melted into a fluid and infiltrates into the gap to complete the brazing; after the brazing filler metal is cooled, the airtight vacuum sealing between the outer wall surface of the ceramic sealing tube 2 and the inner wall surface of the vertical sealing ring 11 of the metal heat-conducting cup 1 is finally formed.

[0074] The cathode 4 is prepared through immersion or pressing process, then the welding surface of the cathode 4 and the cathode heat-conducting area 12 is subjected to fine turning or fine grinding treatment, and is flattened and polished to ensure the flatness and cleanliness of the welding surface, then the cathode 4 and the two smooth surfaces of the cathode heat-conducting area 12 on the inner side of the bottom surface of the metal heat-conducting cup 1 are overlapped and placed into a welding assembly mold, after the edge welding is positioned by using a laser beam or an electron beam, the tungsten-molybdenum area welding is finally completed through resistance welding, high-frequency induction welding and other processes. This process directly welds the cathode 4 on the inner side of the cathode heat-conducting area 12, reduces the thermal resistance and improves the heat energy utilization efficiency of the cathode 4. In the assembly mold, the tungsten body of the prepared cathode 4 is embedded into the inner ring of the first radiation screen 31, the uniformity of the gap of the inner ring of the first radiation screen 31 is adjusted, and the first radiation screen 31 is accurately positioned on the central axis position on the inner side of the cathode heat-conducting area 12, the gap between the cathode 4 and the bottom surface of the metal heat-conducting cup 1 is compressed through the mold, and finally the cathode 4 is integrated with the metal heat-conducting cup 1 through tungsten-molybdenum welding;

[0075] The outer surface of the metal heat-conducting cup 1 of the formed cathode assembly and the inner and outer surfaces of the waste gas flow guide ring 6 are coated with high-temperature oxidation-resistant paint to adapt to the oxygen combustion environment;

[0076] After the above assembly is completed, the cathode 4 assembly is assembled into a thermoelectric diode and is additionally provided with a thermoelectric pile and a cooling device, the thermoelectric diode is fixed with the burner through the connecting bolts 7 on the outer side wall of the waste gas flow guide ring 6, the flame area of the burner is kept coaxial with the cathode 4 and the cathode heat-conducting area 12 to ensure uniform heat transfer, the burner is started, the heat generated by the flame is transmitted to the cathode 4 through the cathode heat-conducting area 12, the electrons emitted by the cathode 4 at high temperature are received by the anode, the port voltage is formed, and thus the thermoelectric conversion is realized and the electric power is output.

[0077] Example 2

[0078] As Figures 5-8As shown, on the basis of Embodiment One, the independent secondary radiation screen 32 is removed and the inner side wall of the heat container 33 is used instead of the secondary radiation screen 32; due to the influence of multiple factors such as fuel mixing ratio and fuel transmission, slight changes in combustion heat will cause changes in the temperature of the cathode 4, and further cause fluctuations in the emission current of the cathode 7, the heat container 33 added in this example can further expand the heat capacity of the cathode assembly, which is conducive to maintaining temperature stability and reducing current fluctuations; the heat container 33 surrounds the primary radiation screen 31, has a ring structure and is coaxial with the cathode 4 and the primary radiation screen 31, and a gap of 0.02-0.5 mm is reserved between the heat container 33 and the primary radiation screen 31 to form a nested layout of “cathode 4-primary radiation screen 31-heat container 33”; this layout continues the blocking function of the evaporated particles of the secondary radiation screen 32, and the inner side of the heat container 33 can replace the heat radiation function of the secondary radiation screen 32; the height of the heat container 33 is lower than the thickness of the cathode 4, and the thickness difference between the heat container 33 and the cathode 4 constitutes the exhaust gap 5, which provides a channel for discharging gases such as electrode-adsorbed gases during vacuumization, and the width of the exhaust gap 5 is 1 / 10-1 / 4 of the thickness of the cathode 4; at the same time, the narrow gap 5 size can reduce the probability of evaporation of particles from the side wall of the cathode 4; the gap N between the heat container 33 and the ceramic sealing tube 2 is obtained by deducting the total width of the heat insulation assembly 3, the different wall thicknesses of the ceramic sealing tube 2 and the relatively wide size tolerance of the ceramic sealing tube 2 after sintering, which can reach ±0.1 mm, and N=0.5-1 cm can be selected; the material of the heat container 33 and the bottom surface of the metal heat-conducting cup 1 is the same, preferably molybdenum plate, to ensure that the thermal expansion coefficients of the two are consistent to avoid stress cracks caused by the difference in material at the working temperature of 900-1150℃ of the high-temperature cathode 4.

[0079] The molybdenum plate with a designed thickness is fixed on the work station, and the heat container 33 ring body is cut, for example, laser cutting to remove burrs and polish both sides; the heat container 33 ring body is precisely positioned at the corresponding coaxial position on the inner side of the bottom of the metal heat-conducting cup 1, pressed and subjected to molybdenum-molybdenum metal welding to connect the two into one; when the metal heat-conducting cup 1 is prepared by fine turning process, the heat container 33 ring body can also be integrally formed with the metal heat-conducting cup 1; the integrally formed process is more difficult, but the heat conduction is better than that of the two-body formed piece.

[0080] As shown in Figure 6 and Figure 8 , the inner side flow guiding edge of the exhaust gas flow guiding ring 6 is arc-shaped, and it needs to be noted that the inner side flow guiding edge of the exhaust gas flow guiding ring 6 is arc-shaped, compared with the bent inner surface of the exhaust gas flow guiding ring, the arc-shaped flow guiding edge reduces the gas flow resistance through the smooth curved surface, and the temperature distribution of the inner surface is uniform and is not easy to appear obvious ablation points; the material and process of the arc-shaped flow guiding edge exhaust gas flow guiding ring 6 are generally similar to those of the bent flow guiding edge, and the forming mold and processing precision are different.

[0081] The two embodiments of the heat insulation assembly 3, which reduce the function of the evaporation material leakage close to the original cathode box, and the process difficulty is lower than the precise embedding process of the original cathode box, and is suitable for batch production requirements. Compared with example one, the heat container 33 is arranged in example two, the heat capacity of the cathode assembly is improved, so the weight of the cathode assembly is higher than that of example one, and the weight specific power is slightly lower, but the port voltage and current are more stable, and a better technical foundation is laid for later electric control energy saving.

[0082] Finally, it should be noted that: the above only for the preferred embodiments of the present application, only for the description of the technical solutions of the present application, and not for limiting the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, are included in the protection scope of the present application.

[0083] In the description of the present application, it should be understood that the terms "upper", "lower", "upper end", "lower end", "upper surface", "lower surface" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the present application.

[0084] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connecting", "setting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

Claims

1. A thermoelectric diode cathode assembly heated by external oxy-fuel combustion, comprising: The components are: a metal heat-conducting cup (1), a ceramic sealing pipe (2), a heat insulation assembly (3), and a cathode (4); characterized in that: The outer wall of the ceramic sealing tube (2) and the inner wall of the vertical sealing ring (11) of the metal heat-conducting cup (1) are sealed in an airtight vacuum by brazing. The cathode (4) is coaxially arranged in the center of the metal heat-conducting plate inside the metal heat-conducting cup (1). The heat insulation component (3) is arranged around the cathode (4) on the inner metal heat-conducting plate of the metal heat-conducting cup (1) and is located between the ceramic sealing tube (2) and the cathode (4), and is respectively fitted with the ceramic sealing tube (2) and the cathode (4) with a gap.

2. The thermoelectric diode cathode assembly heated by external oxygen combustion as described in claim 1, characterized in that: The metal heat-conducting cup (1) includes a vertical sealing ring (11) and a metal heat-conducting plate. The vertical sealing ring (11) is disposed on the metal heat-conducting plate to form the side wall of the metal heat-conducting cup (1). The metal heat-conducting plate forms a bottom plate and includes a cathode heat-conducting area (12) and a temperature attenuation area (13). The temperature attenuation area (13) is the area of ​​the metal heat-conducting plate after deducting the area of ​​the cathode heat-conducting area (12) from the area enclosed by the vertical sealing ring (11). The cathode (4) is welded to the cathode heat-conducting area (12) and coaxial with it. The heat insulation component (3) is disposed on the temperature attenuation area (13) and close to the inner side of the temperature attenuation area (13).

3. The thermoelectric diode cathode assembly heated by external aerobic combustion as described in claim 2, characterized in that: The heat insulation component (3) includes a primary radiation screen (31) and at least one secondary radiation screen (32), both of which are disposed on the temperature attenuation zone (13). The primary radiation screen (31) is disposed around the cathode (4), and the secondary radiation screen (32) is disposed around the primary radiation screen (31) with a gap fit and is at the same height as the primary radiation screen (31). The gap L between the primary radiation screen (31) and the cathode (4) is 0.02 to 0.5 mm wide, the gap M between the primary radiation screen (31) and the secondary radiation screen (32) is 0.02 to 0.5 mm wide, and the gap N between the secondary radiation screen (32) and the ceramic sealing pipe (2) is 0.05 to 20 mm wide.

4. The thermoelectric diode cathode assembly heated by external oxygen combustion as described in claim 3, characterized in that: The secondary radiation screen (32) is formed on the inner wall of a heat container (33) made of the same material as the cathode heat conduction zone (12). The heat container (33) has an annular structure and is welded and fixed on the temperature attenuation zone (13). Its height is lower than the thickness of the cathode (4). The thickness difference between the heat container (33) and the cathode (4) constitutes an exhaust gap (5). The width of the exhaust gap (5) is 1 / 10 to 1 / 4 of the thickness of the cathode (4).

5. A thermoelectric diode cathode assembly heated by external aerobic combustion as described in claim 2, characterized in that: The metal heat-conducting cup (1) is integrally formed by metal hot molding, hot stamping and precision machining process, or the vertical sealing ring (11) and the bottom metal heat-conducting plate are prepared separately and then formed by airtight welding. The plate thickness is 0.2-2mm, and the outer surface of the metal heat-conducting cup (1) is coated with high temperature anti-oxidation coating.

6. A thermoelectric diode cathode assembly heated by external aerobic combustion as described in claim 2, characterized in that: The cathode (4) is a diffusion-type barium tungsten hot cathode (4), and its tungsten body is directly connected to the cathode heat-conducting area (12) by a tungsten-molybdenum welding process. The emission salt of the cathode (4) is any one of scandium, tungstate, aluminate and their respective variants formed by adding rare earth elements other than scandium oxide.

7. A thermoelectric diode cathode assembly heated by external aerobic combustion as described in claim 2, characterized in that: The outer bottom of the metal heat-conducting cup (1) is provided with a waste gas guide ring (6). The inner and outer surfaces of the waste gas guide ring (6) are coated with high-temperature anti-oxidation coating. The outer side of the metal heat-conducting plate and the inner side of the waste gas guide ring (6) surround each other to form a waste gas guide groove. The waste gas guide ring (6) can guide the high-temperature waste gas in the flame zone of the waste gas guide groove downward and away from the vertical sealing ring (11).

8. A thermoelectric diode cathode assembly heated by external oxygen combustion as described in claim 7, characterized in that: The inner guide edge of the exhaust gas guide ring (6) is an arc or bent structure and is fixed to the bottom of the metal heat-conducting cup (1) by welding. The outer wall of the exhaust gas guide ring (6) is provided with connecting bolts (7) for fixing to the burner.

9. A thermoelectric diode cathode assembly heated by external aerobic combustion as described in claim 1, characterized in that: The distance H between the bottom surface of the ceramic sealing tube (2) and the inner bottom surface of the metal heat-conducting cup (1) is 0.5-10mm, and the bottom surface of the ceramic sealing tube (2) is coated with ceramic particles of 2-3μm.

10. A thermoelectric diode cathode assembly heated by external aerobic combustion as described in claim 1, characterized in that: The brazing process is a metal-ceramic brazing process, and the brazing process uses any one of silver-copper, silver, or nickel-titanium solder.

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