Waste heat utilization ejector of coupled plasma generator

Abstract

The invention belongs to the technical field of electric heating, and particularly relates to a waste heat utilization ejector coupled with a plasma generator, the waste heat utilization ejector comprises the plasma generator, a nozzle and a Laval pipe structure, the rear end of the nozzle is provided with a working fluid inlet, and the Laval pipe structure sequentially comprises a receiving chamber, a mixing chamber, a throat pipe structure and a diffuser from back to front. A front end opening of the diffuser is a mixed fluid outlet, the nozzle is located in the receiving chamber, an anode structure of the plasma generator penetrates through the rear end of the receiving chamber and is communicated with an inner cavity of the nozzle through a working fluid inlet, a driving fluid inlet is formed in the side face of the receiving chamber, and a front end opening of the nozzle faces the throat pipe structure. The diffuser is conical, and the size of the mixed fluid outlet is larger than that of the rear end inlet of the diffuser. According to the invention, the waste heat utilization efficiency can be improved while the heating area of the plasma is obviously increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric heating, and particularly relates to a waste heat utilization ejector coupled with a plasma generator. Background Art

[0002] Arc thermal plasma has the advantages of high energy efficiency and the ability to select the properties of working fluid gases. It is an ideal heat source for green high-temperature chemistry and has been widely used in industries with long reaction times (above seconds), such as metallurgy. Due to its unique advantages, people hope to expand the application of arc thermal plasma in fast / high-temperature chemical engineering to form new green chemical processes. High-temperature / fast chemical process reactions have short reaction times (in the millisecond range) and require a large heating area to meet industrial-scale production. The highly concentrated energy and small volume of arc plasma restrict the development of plasma green chemical processes. Increasing the heating area of arc plasma is of great significance for expanding the large-scale industrial application of arc plasma. Existing research (such as the technical solutions disclosed in patent documents with publication numbers CN219058794U and CN111479376A) has tried to increase the heating area of arc plasma by optimizing the structure of the arc plasma generator, applying an external magnetic field, etc., but the expected effect has not been achieved. Summary of the Invention

[0003] The purpose of the present invention is to provide a waste heat utilization ejector coupled with a plasma generator, which is used to solve the technical problems in the prior art that the plasma jet length of arc plasma is short and it is difficult to significantly increase the length and the range of the high-temperature plasma flame.

[0004] The waste heat utilization ejector coupled with a plasma generator includes a plasma generator, a nozzle, and a Laval tube structure. A working fluid inlet is provided at the rear end of the nozzle. The Laval tube structure includes an acceptance chamber, a mixing chamber, a throat structure, and a diffuser in sequence from the rear to the front. The front opening of the diffuser is the mixed fluid outlet. The nozzle is located in the acceptance chamber. The anode structure of the plasma generator passes through the rear end of the acceptance chamber and communicates with the inner cavity of the nozzle through the working fluid inlet. An entrainment fluid inlet is provided on the side of the acceptance chamber. The front end opening of the nozzle faces the throat structure. The diffuser is conical and the size of the mixed fluid outlet is larger than the rear end inlet of the diffuser.

[0005] Preferably, the nozzle has a front section that contracts from large to small towards the middle and a rear section that expands from small to large outwards.

[0006] Preferably, there is a contraction section between the rear end of the Laval tube structure and the throat structure, and the length of the contraction section is not less than 10 times the diameter of the throat.

[0007] Preferably, the inside of the contraction section corresponds to the mixing chamber, and the inside between the contraction section and the rear end of the Laval tube structure is the receiving chamber. When the low-pressure and high-speed plasma passes through the receiving chamber, a negative pressure is formed in the receiving chamber to suck in the entrained fluid.

[0008] Preferably, the diameter of the throat structure is more than 5 times the outlet diameter of the nozzle.

[0009] Preferably, the section between the front opening of the Laval tube structure and the throat structure is the expansion section, which is the diffuser 5. The expansion section is made of high-temperature resistant material or protected by water cooling.

[0010] Preferably, the expansion angle of the expansion section is less than 12°.

[0011] Preferably, the entrained fluid is low-temperature waste heat gas.

[0012] Preferably, the plasma generator is combined with a high-pressure gas supply system, and the gas supply pressure ≥ 0.3 Mpa.

[0013] The advantages of the present invention are as follows: The ejector provided by the present invention meets the requirement of the process to generate a larger volume heating area under high-temperature conditions, is expected to meet industrial-scale production, and has direct economic and energy-saving benefits. The flame length of a conventional plasma torch is about 200 - 300 mm, while the technology using the above-mentioned ejector can make the injection length of the plasma flame reach more than 1 meter. Using low-temperature waste heat gas as the entrained fluid can not only significantly increase the heating area of the plasma, but also increase the waste heat utilization efficiency, reduce energy waste in plasma heating, and utilize energy more efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic structural diagram of a waste heat utilization ejector coupled with a plasma generator in the present invention.

[0015] The reference numerals in the drawings include: 1 plasma generator, 2 nozzle, 3 receiving chamber, 4 mixing chamber, 5 diffuser, 6 working fluid inlet, 7 entrained fluid inlet, 8 mixed fluid outlet, 9 throat structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] The following further describes in detail the specific embodiments of the present invention with reference to the drawings through the description of the embodiments, so as to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0017] As Figure 1As shown in the figure, the present invention provides a waste heat utilization ejector for a coupled plasma generator, which includes a plasma generator 1, a nozzle 2 and a Laval tube structure. A working fluid inlet 6 is provided at the rear end of the nozzle 2. The Laval tube structure sequentially includes a receiving chamber 3, a mixing chamber 4, a throat structure 9 and a diffuser 5 from back to front. The front end opening of the diffuser 5 is a mixed fluid outlet 8. The nozzle 2 is located in the receiving chamber 3. The anode structure of the plasma generator 1 passes through the rear end of the receiving chamber 3 and communicates with the inner cavity of the nozzle 2 through the working fluid inlet 6. An ejector fluid inlet 7 is provided on the side of the receiving chamber 3. The front end opening of the nozzle 2 faces the throat structure 9. The diffuser 5 is conical and the size of the mixed fluid outlet 8 is larger than the rear end inlet of the diffuser 5.

[0018] The nozzle 2 has a front section that contracts from large to small towards the middle and a rear section that expands from small to large outwards. This structure of the nozzle 2 converts the high-temperature and high-pressure plasma jet (i.e., the working fluid) output from the plasma generator 1 into a supersonic and low-pressure plasma jet. The nozzle 2 ejects the low-pressure and high-speed plasma jet, and the average gas temperature of the plasma jet is ≥3500 °C.

[0019] There is a contraction section between the rear end of the Laval tube structure and the throat structure 9, and the length of the contraction section is not less than 10 times the throat diameter. Through the longer length of the contraction section, this ejector can provide sufficient mixing time for the plasma and the low-temperature waste heat. The inside of the contraction section corresponds to the mixing chamber 4, and the part from the contraction section to the rear end of the Laval tube structure is the receiving chamber 3. When the low-pressure and high-speed plasma passes through the receiving chamber 3, a negative pressure is formed in the receiving chamber 3 to suck in the ejector fluid. The diameter of the throat structure 9 is more than 5 times the outlet diameter of the nozzle 2. This can effectively offset the possible thermal choking phenomenon at the outlet of the throat structure 9.

[0020] The section between the front end opening of the Laval tube structure and the throat structure 9 is an expansion section, and the expansion section is the diffuser 5. It is made of a high-temperature resistant material (high-temperature resistant performance ≥1500 °C) or is protected by water cooling. This can prevent the expansion section and the front end opening from being deformed by heat and ensure the growth effect of the plasma flame. At the same time, the expansion angle of the expansion section is less than the angle threshold, and the angle threshold is 12°. This can avoid the reduction of the ejector jet length due to the separation of the shock wave boundary layer of the plasma flame.

[0021] The plasma generator 1 includes an arc ignition device, an embedded tubular electrode, a working fluid inlet, and a plasma jet outlet. The plasma generator jet outlet is communicated with the working fluid inlet 6. Inside the plasma generator 1, a cathode and an anode are provided. The arc ignition device is used to generate an arc between the cathode and the anode and provide a constant current between the cathode and the anode. The working fluid forms a plasma jet between the cathode and the anode and enters the nozzle 2 through the working fluid inlet 6. The plasma generator 1 is combined with a high-pressure gas supply system, and the gas supply pressure is ≥ 0.3 Mpa. The working fluid uses a working gas such as air, nitrogen, or hydrogen. The output direction of the working gas is arranged along the direction of the plasma generator jet outlet to generate a plasma jet with a high enthalpy value.

[0022] The working process of the embodiment of the present invention includes: First, input the working gas into the working gas inlet of the plasma generator 1. After setting the flow rate, the arc ignition device is used to ignite the arc to generate a plasma jet. The high-temperature and high-pressure plasma jet output by the plasma generator 1 enters the nozzle 2 through the working fluid inlet 6. In the nozzle 2, the high-temperature and high-pressure plasma jet continues to accelerate, and the final state is a supersonic and low-pressure plasma jet. The supersonic and low-pressure plasma jet ejected from the nozzle 2 creates a partial low-pressure area through the receiving chamber 3, and the entrained fluid enters the receiving chamber 3 through the entrained fluid inlet 7. In some embodiments, the entrained fluid is the exhausted working fluid after heating and recycling or other low-temperature waste heat gases.

[0023] The mixing chamber 4 mixes the working fluid and the entrained fluid. Since in the jet direction, the mixing chamber contracts from large to small towards the middle, the two fluids generate a strong shearing effect under the action of the pressure difference, and the two continuously carry out mass and energy transfer, and the mixing degree gradually tends to be uniform. After passing through the throat structure 9, the mixed fluid enters the diffuser 5. The diffuser 5 expands from small to large in the jet direction, the flow area of the mixed fluid continuously increases, the velocity of the mixed fluid decreases while the pressure increases, and part of the kinetic energy is re-converted into pressure potential energy and heat energy to meet the requirements of the heating process. Subsequently, the mixed fluid is discharged through the mixed fluid outlet 8.

[0024] Through the structure of the nozzle 2, the flow rate of the plasma jet in the receiving chamber 3 is increased in this solution. At the same time, low-temperature waste heat gas is inhaled through the entrainment effect, increasing the gas volume. The contraction mixing is achieved through the mixing chamber with the Laval tube structure, and then the speed is reduced and the pressure is increased through the diffuser. While the volume of the injected gas is increased, a higher pressure is provided, effectively increasing the injection length of the mixed fluid, thereby greatly increasing the injection length and heating area of the plasma jet. Thus, the injector provided by the present invention meets the requirement of the process to generate a larger volume heating area under high-temperature conditions, is expected to meet the industrial-scale production, and has direct economic and energy-saving benefits. The flame length of a conventional plasma torch is about 200 - 300 mm, while the technology using the above injector can make the injection length of the plasma flame reach more than 1 meter.

[0025] The present invention has been described exemplarily above in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the inventive concept and technical solution of the present invention, or the inventive concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A waste heat utilization ejector coupled with a plasma generator, characterized in that: It includes a plasma generator, a nozzle and a Laval tube structure. A working fluid inlet is provided at the rear end of the nozzle. The Laval tube structure successively includes a receiving chamber, a mixing chamber, a throat structure and a diffuser from the rear to the front. The front end opening of the diffuser is the mixed fluid outlet. The nozzle is located in the receiving chamber. The anode structure of the plasma generator passes through the rear end of the receiving chamber and communicates with the inner cavity of the nozzle through the working fluid inlet. An ejector fluid inlet is provided on the side of the receiving chamber. The front end opening of the nozzle faces the throat structure. The diffuser is conical and the size of the mixed fluid outlet is larger than the rear end inlet of the diffuser.

2. The waste heat utilization ejector of a coupled plasma generator according to claim 1, characterized in that: The nozzle has a front section that contracts from large to small towards the middle and a rear section that expands from small to large outwards.

3. The waste heat utilization ejector of a coupled plasma generator according to claim 2, wherein: There is a contraction section between the rear end of the Laval tube structure and the throat structure, and the length of the contraction section is not less than 10 times the diameter of the throat.

4. The waste heat utilization ejector of a coupled plasma generator according to claim 3, characterized in that: The inside of the contraction section corresponds to the mixing chamber, and the inside between the contraction section and the rear end of the Laval tube structure is the receiving chamber. When the low-pressure and high-speed plasma passes through the receiving chamber, a negative pressure is formed in the receiving chamber to suck in the ejector fluid.

5. The waste heat utilization ejector of a coupled plasma generator according to claim 4, characterized in that: The diameter of the throat structure is more than 5 times the outlet diameter of the nozzle.

6. The waste heat utilization injector of a coupled plasma generator according to claim 5, characterized in that: The section between the front end opening of the Laval tube structure and the throat structure is an expansion section, and the expansion section is the diffuser 5. The expansion section is made of a high-temperature resistant material or protected by water cooling.

7. The waste heat utilization ejector of a coupled plasma generator according to claim 6, characterized in that: The expansion angle of the expansion section is less than 12°.

8. The waste heat utilization ejector of a coupled plasma generator according to claim 7, characterized in that: The ejector fluid is a low-temperature waste heat gas.

9. The waste heat utilization ejector of a coupled plasma generator according to claim 8, characterized in that: The plasma generator is combined with a high-pressure gas supply system, and the gas supply pressure ≥ 0.3 Mpa.

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