Low temperature screw extruder

Abstract

This invention discloses a cryogenic screw extruder, belonging to the field of nuclear fusion projectile injection technology. The vacuum cylinder of this invention has an extension tube, an extrusion chamber, and a six-way assembly arranged sequentially from top to bottom. A servo motor drives the extrusion screw to rotate via a magnetic transmission assembly. The working gas enters the vacuum cylinder through a working gas inlet pipe and condenses into liquid under the action of a liquefier. The liquid working gas automatically flows into the extrusion chamber and solidifies there. Under the action of the extrusion screw, the working gas is extruded from the conical nozzle in the form of solid ice columns. This invention avoids the leakage risks of working gases such as deuterium and tritium caused by dynamic seals, improves the quality of ice column formation, and reduces the demand for liquid helium.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fusion projectile injection technology, specifically relating to a cryogenic screw extruder. Background Technology

[0002] During the operation of a controlled nuclear fusion device, the plasma needs to be continuously fed. Solid pellet injection is a technique that involves condensing fusion fuel gases such as deuterium and tritium into solid pellets, which are then injected into the plasma at high speed. It offers advantages such as deep particle injection and high feeding efficiency, making it a crucial method for core feeding in fusion devices. When using solid pellet injection to feed the plasma, the gaseous fusion fuel must first be solidified into a shape under cryogenic conditions to prepare for subsequent pellet injection.

[0003] Cryogenic screw extrusion is an effective method for solidifying gaseous fuels, enabling the continuous production of cryogenic solid pellets and allowing for long-pulse continuous pellet injection. However, existing cryogenic screw extruders rely on dynamic seals, such as mechanical seals, to transmit the rotation of the servo motor to the extrusion screw. Furthermore, the sealing materials in contact with working gases like deuterium and tritium contain rubber, which fails to meet the tritium compatibility requirements of future fusion reactors. Additionally, the extrusion chamber and nozzle of existing cryogenic screw extruders are generally separate components, resulting in poor cold energy transfer between them. This leads to poor-quality extruded ice pellets, which are prone to breakage, thus compromising the continuous and stable production of ice pellets. Moreover, for future fusion reactors, due to their larger size, the required pellet size is also relatively large. This increases the flow rate of the cooling medium needed to condense fusion fuel gases like deuterium and tritium, significantly increasing the construction cost of the cryogenic system. Therefore, to meet the feeding requirements of future fusion reactor pellet injection, ensure the stable operation of the pellet system, and reduce the construction cost of cryogenic systems, it is imperative to upgrade existing cryogenic screw extruders. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A cryogenic screw extruder includes: a servo motor, a motor bracket, an outer magnetic rotor, an isolation cover, an inner magnetic rotor, a bearing, an extension tube, a liquid helium inlet tube, an extrusion chamber, a six-way assembly, an inlet pipe, an outlet tube, a waste pipe, an extrusion screw, a helium vapor return pipe, a working gas inlet pipe, a liquefier, a liquid helium flow regulating valve, a vacuum cylinder, and a cooling screen.

[0006] The servo motor is fixed above the motor bracket, which is fixed to the outer side of the upper end of the vacuum cylinder. The outer magnetic rotor is connected to the output shaft of the servo motor and is located below the motor bracket. The isolation cover is fixed to the outer side of the upper end of the vacuum cylinder and is located below the outer magnetic rotor. An inner magnetic rotor is set inside the isolation cover. A bearing is fixed in the center hole at the upper end of the vacuum cylinder below the inner magnetic rotor. A pressing screw passing through the center of the bearing is also fixed below the inner magnetic rotor.

[0007] An extension tube, a compression chamber, and a six-way assembly are arranged sequentially from top to bottom inside the vacuum cylinder; a cold shield is installed inside the vacuum cylinder; the upper end of the extension tube is fixed to the inner side of the upper end of the vacuum cylinder, and the lower end is connected to the working gas inlet tube;

[0008] The working gas inlet pipe enters the vacuum cylinder from the top of the vacuum cylinder, passes through the cold shield and liquefaction device, and is connected to the bottom of the extension pipe.

[0009] The liquid helium inlet pipe enters the vacuum cylinder from the top, passes through the cold screen, and connects to the lower inlet of the shell-and-tube heat exchanger wrapped around the periphery of the extrusion chamber; the upper outlet of the shell-and-tube heat exchanger is connected to the helium vapor return pipe; the helium vapor return pipe passes through the liquefier and the liquid helium flow regulating valve from bottom to top, and finally exits from the top of the vacuum cylinder.

[0010] The lower end of the extrusion chamber is aligned with the six-way assembly; the upper end of the extrusion screw is connected to the inner magnetic rotor, and the extrusion screw is inserted into the bearing, extension tube and extrusion chamber from top to bottom in sequence.

[0011] The left and right sides of the six-way assembly are connected to the air intake pipe and the exhaust pipe, respectively, and observation windows are provided on the front and rear sides; the lower end of the six-way assembly is connected to the waste pipe.

[0012] The present invention has the following beneficial effects:

[0013] First, the present invention is equipped with a magnetic power assembly including an outer magnetic rotor, an inner magnetic rotor and an isolation cover, which transmits the rotation of the servo motor to the extrusion screw, avoiding the risk of leakage of working gases such as deuterium and tritium caused by dynamic sealing; at the same time, all the sealing rings in contact with working gases such as deuterium and tritium are made of metal materials, thereby meeting the tritium compatibility requirements of future fusion reactors.

[0014] Secondly, the present invention sets the extrusion chamber to be made of a material with high thermal conductivity and has a conical nozzle at the lower end. The entire extrusion chamber and nozzle are an integral structure, which facilitates direct temperature control of the nozzle and thus improves the quality of icicle forming.

[0015] Third, this invention utilizes refluxed helium vapor to pre-cool working gases such as deuterium and tritium, reducing the demand for liquid helium and lowering the construction cost of cryogenic systems. Attached Figure Description

[0016] Figure 1This is a schematic diagram of the structure of the low-temperature screw extruder of the present invention, wherein: 1-servo motor, 2-motor bracket, 3-outer magnetic rotor, 4-isolation cover, 5-inner magnetic rotor, 6-first sealing ring, 7-second sealing ring, 8-bearing, 9-extension tube, 10-third sealing ring, 11-liquid helium inlet pipe, 12-extrusion chamber, 13-first heating rod, 14-shell heat exchanger, 15-second heating rod, 16-fourth sealing ring, 17-six-way assembly, 18-inlet valve, 19-electromagnetic coil, 20-inlet pipe, 21-cutter, 22-observation window. 23-Fifth sealing ring, 24-Pressure ring, 25-Sixth sealing ring, 26-First vacuum pumping unit, 27-Waste pipe, 28-Solid ice column, 29-Emission tube, 30-Conical nozzle, 31-Second low-temperature sensor, 32-Extrusion screw, 33-Helium vapor return pipe, 34-First low-temperature sensor, 35-Working gas inlet pipe, 36-Liquefier, 37-Third heating rod, 38-Third low-temperature sensor, 39-Liquid helium flow regulating valve, 40-Second vacuum pumping unit, 41-Vacuum cylinder, 42-Cold shield. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0018] The low-temperature screw extruder of the present invention, such as Figure 1 As shown, it includes: servo motor 1, motor bracket 2, outer magnetic rotor 3, isolation cover 4, inner magnetic rotor 5, bearing 8, extension tube 9, liquid helium inlet pipe 11, extrusion chamber 12, six-way assembly 17, air inlet pipe 20, launch tube 29, waste pipe 27, extrusion screw 32, helium vapor return pipe 33, working gas inlet pipe 35, liquefier 36, liquid helium flow regulating valve 39, vacuum cylinder 41 and cold shield 42.

[0019] Servo motor 1 is fixed above motor bracket 2, motor bracket 2 is fixed on the outer side of the upper end of vacuum cylinder 41, outer magnetic rotor 3 is connected to the output shaft of servo motor 1 and located below motor bracket 2, isolation cover 4 is also fixed on the outer side of the upper end of vacuum cylinder 41 and located below outer magnetic rotor 3, a first sealing ring 6 is installed between isolation cover 4 and vacuum cylinder 41; inner magnetic rotor 5 is set inside isolation cover 4, bearing 8 is set below inner magnetic rotor 5, bearing 8 is fixed in the center hole at the upper end of vacuum cylinder 41, and extrusion screw 32 is also set below inner magnetic rotor 5, passing through the center of bearing 8 and fixed below inner magnetic rotor 5.

[0020] Inside the vacuum cylinder 41, from top to bottom, are arranged an extension tube 9, a compression chamber 12, and a six-way assembly 17. A second sealing ring 7 is installed between the upper end of the extension tube 9 and the inner side of the upper end of the vacuum cylinder 41; a third sealing ring 10 is installed between the lower end of the extension tube 9 and the upper end of the compression chamber 12; and a fourth sealing ring 16 is installed between the lower end of the compression chamber 12 and the upper end of the six-way assembly 17. A liquefier 36 is installed inside the vacuum cylinder 41, with its installation height higher than the lower end of the extension tube 9. To achieve good heat preservation, a cold shield 42 is installed inside the vacuum cylinder 41. The lower end of the extension tube 9, the liquefier 36, the compression chamber 12, the six-way assembly 17, and the upper end of the waste pipe 27 (the lower end of the six-way assembly 17 is connected to the waste pipe 27) are located inside the cold shield 42.

[0021] The lower end of the six-way assembly 17 is connected to the waste pipe 27, and a fifth sealing ring 23 is installed between the six-way assembly 17 and the waste pipe 27. The waste pipe 27 extends out from the lower end of the vacuum cylinder 41, and a pressure ring 24 and a sixth sealing ring 25 are installed on the outer side of the lower end of the vacuum cylinder 41 between the pressure ring 24 and the outer side of the lower end of the vacuum cylinder 41. The waste pipe 27 and the vacuum cylinder 41 are sealed by the pressure ring 24 pressing the sixth sealing ring 25.

[0022] Liquid helium inlet pipe 11 enters the vacuum cylinder 41 from the upper end, passes through the cold screen 42 and connects to the lower inlet of the shell-and-tube heat exchanger 14; the upper outlet of the shell-and-tube heat exchanger 14 is connected to the helium vapor return pipe 33; the helium vapor return pipe 33 passes through the liquefier 36 and the liquid helium flow regulating valve 39 from bottom to top, and finally exits from the upper end of the vacuum cylinder 41.

[0023] The working gas inlet pipe 35 enters the vacuum cylinder 41 from the upper end of the vacuum cylinder 41, passes through the cold screen 42 and the liquefier 36, and is connected to the small hole on the flange at the lower end of the extension pipe 9.

[0024] The liquid helium inlet pipe 11, the helium vapor return pipe 33, the working gas inlet pipe 35, and the vacuum cylinder 41 are sealed and fixed by sealing welds, respectively.

[0025] Liquid helium enters the vacuum cylinder 41 and the cold shield 42 through the liquid helium inlet pipe 11, and flows sequentially through the shell-and-tube heat exchanger 14, the liquefier 36 and the liquid helium flow regulating valve 39, where it exchanges heat with the working gas at the shell-and-tube heat exchanger 14 and the liquefier 36.

[0026] The working gas enters the vacuum cylinder 41 and the cooling screen 42 through the working gas inlet pipe 35, and condenses into liquid under the action of the liquefaction device 36; the liquid working gas automatically flows into the extrusion chamber 12 and solidifies in the extrusion chamber 12; under the action of the extrusion screw 32 set in the extrusion chamber 12, the solidified working gas is squeezed out from the conical nozzle 30 in the form of solid ice column.

[0027] The extension tube 9 is made of a material with low thermal conductivity (such as stainless steel). Its upper end is fixed to the inner side of the upper end of the vacuum cylinder 41, and a small hole is opened on the flange at the lower end for connecting the working gas inlet tube 35.

[0028] A conical nozzle 30 is located at the lower end of the extrusion chamber 12. The outlet of the conical nozzle 30 is aligned with the six-way assembly 17. The entire extrusion chamber 12 and the conical nozzle 30 are integrated into one structure, facilitating direct temperature control of the nozzle and thus improving the quality of the icicle forming. A first heating rod 13 and a first low-temperature sensor 34 are installed at the upper end of the extrusion chamber 12, and a second heating rod 15 and a second low-temperature sensor 31 are installed at the lower end of the extrusion chamber 12 to control the temperature of the extrusion chamber 12. A sleeve heat exchanger 14 is wound around the periphery of the extrusion chamber 12 and is fixed to the periphery of the extrusion chamber 12 by brazing. Both the extrusion chamber 12 and the sleeve heat exchanger 14 are made of a material with high thermal conductivity (such as copper).

[0029] The extrusion screw 32 is made of a material with low thermal conductivity (such as stainless steel). Its upper end is connected to the inner magnetic rotor 5. The extrusion screw 32 is inserted into the bearing 8, the extension tube 9, and the extrusion chamber 12 from top to bottom. The outer circumferential surface of the extrusion screw 32 in the extrusion chamber 12 is threaded, while other positions may not have threads. The lower end of the extrusion screw 32 that is adapted to the conical nozzle 30 is tapered. The central axes of the extrusion screw 32, the bearing 8, the extension tube 9, the extrusion chamber 12, the six-way assembly 17, and the waste pipe 27 coincide with each other.

[0030] The six-way assembly 17 is made of a material with low thermal conductivity (such as stainless steel). The left and right sides are connected to the air inlet pipe 20 and the launch pipe 29, respectively. The left and right sides are also connected to the air inlet pipe 20 and the launch pipe 29, respectively. The front and rear sides are also provided with observation windows 22 to observe the state of the solid ice column 28 that is squeezed out from the conical nozzle 30 and enters the six-way assembly 17.

[0031] The intake pipe 20 is connected to the intake valve 18 outside the vacuum cylinder 41. It penetrates directly into the vacuum cylinder 41 from the left, where a cutter 21 is installed. An electromagnetic coil 19 is fitted around the cutter 21, and the pipe further penetrates into the six-way assembly 17 from the left. The launch tube 29 penetrates directly into the vacuum cylinder 41 from the right, and further penetrates into the six-way assembly 17 from the right. The central axes of the intake pipe 20 and the launch tube 29 coincide. A gap is left between the right end of the intake pipe 20 and the left end of the launch tube 29 within the six-way assembly 17, allowing the solid ice column 28 to pass vertically from top to bottom. When the electromagnetic coil 19 is energized, it drives the cutter 21 to move linearly, thereby cutting the solid ice column 28 into individual projectiles and pushing the projectiles into the launch tube 29.

[0032] The outer diameter of the waste pipe 27 is uneven, with the largest outer diameter at the interface with the lower flange of the vacuum cylinder 41. The first vacuum pumping unit 26 is connected to the waste pipe 27 and is used to remove waste ice and waste gas.

[0033] The liquefier 36 is made of a material with high thermal conductivity (such as copper), and is equipped with a third heating rod 37 and a third low-temperature temperature sensor 38 for controlling the temperature of the liquefier 36.

[0034] The second vacuum pumping unit 40 is connected to the vacuum cylinder 41 and is used to evacuate the vacuum cylinder 41, thereby providing an insulated environment for the components inside the vacuum cylinder 41.

[0035] The first sealing ring 6, the second sealing ring 7, the third sealing ring 10, the fourth sealing ring 16, and the fifth sealing ring 23 are all made of soft metal (such as indium); the sixth sealing ring 25 is made of rubber.

[0036] When the low-temperature screw extruder of the present invention is in operation, the following steps must be followed:

[0037] Step 1: Start the first vacuum pumping unit 26 and the second vacuum pumping unit 40 to evacuate the vacuum cylinder 41 and the extrusion chamber 12 respectively.

[0038] Step 2: Introduce liquid helium into the liquid helium inlet pipe 11 to cool the extrusion chamber 12 and the liquefier 36;

[0039] Step 3: Introduce working gas into working gas inlet pipe 35. The working gas is liquefied and solidified in liquefier 36 and extrusion chamber 12, respectively.

[0040] Step 4: Turn on the servo motor 1 to drive the extrusion screw 32 to rotate and extrude solid ice column 28;

[0041] Step 5: Solid ice column 28 enters six-way assembly 17. Electromagnetic coil 19 drives cutter 21 to move in air inlet pipe 20, cutting solid ice column 28 into projectiles and pushing the projectiles into launch tube 29. At the same time, air inlet valve 18 opens (about 20 milliseconds) and then closes quickly. Propellant gas accelerates the projectiles, causing the projectiles to be launched from the right end of launch tube 29.

[0042] Step 6: Excess waste ice and propulsion gas enter the waste pipe 27 and are removed by the first vacuum pump unit 26.

[0043] The above description is merely an embodiment of the present invention and does not limit the scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the protection scope of the present invention.

[0044] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A cryogenic screw extruder, characterized in that include: Servo motor, motor bracket, external magnetic rotor, isolation cover, internal magnetic rotor, bearing, extension tube, liquid helium inlet pipe, extrusion chamber, six-way assembly, air inlet pipe, launch tube, waste pipe, extrusion screw, helium vapor return pipe, working gas inlet pipe, liquefier, liquid helium flow regulating valve, vacuum cylinder and cooling screen; The servo motor is fixed above the motor bracket, which is fixed to the outer side of the upper end of the vacuum cylinder. The outer magnetic rotor is connected to the output shaft of the servo motor and is located below the motor bracket. The isolation cover is fixed to the outer side of the upper end of the vacuum cylinder and is located below the outer magnetic rotor. An inner magnetic rotor is set inside the isolation cover. A bearing is fixed in the center hole at the upper end of the vacuum cylinder below the inner magnetic rotor. A pressing screw passing through the center of the bearing is also fixed below the inner magnetic rotor. An extension tube, a compression chamber, and a six-way assembly are arranged sequentially from top to bottom inside the vacuum cylinder; a cold shield is installed inside the vacuum cylinder; the upper end of the extension tube is fixed to the inner side of the upper end of the vacuum cylinder, and the lower end is connected to the working gas inlet tube; The working gas inlet pipe enters the vacuum cylinder from the top of the vacuum cylinder, passes through the cold shield and liquefaction device, and is connected to the bottom of the extension pipe. The liquid helium inlet pipe enters the vacuum cylinder from the top, passes through the cold screen, and connects to the lower inlet of the shell-and-tube heat exchanger wrapped around the periphery of the extrusion chamber; the upper outlet of the shell-and-tube heat exchanger is connected to the helium vapor return pipe; the helium vapor return pipe passes through the liquefier and the liquid helium flow regulating valve from bottom to top, and finally exits from the top of the vacuum cylinder. The lower end of the extrusion chamber is aligned with the six-way assembly; the upper end of the extrusion screw is connected to the inner magnetic rotor, and the extrusion screw is inserted into the bearing, extension tube and extrusion chamber from top to bottom in sequence. The left and right sides of the six-way assembly are connected to the air intake pipe and the exhaust pipe, respectively, and observation windows are provided on the front and rear sides; the lower end of the six-way assembly is connected to the waste pipe.

2. Cryogenic screw extruder according to claim 1, characterized in that The lower end of the extension tube, the liquefier, the extrusion chamber, the six-way assembly, and the upper end of the waste tube are located inside the cold shield.

3. Cryogenic screw extruder according to claim 1, characterized in that A first sealing ring is installed between the isolation cover and the vacuum cylinder; a second sealing ring is installed between the upper end of the extension tube and the inner side of the upper end of the vacuum cylinder; a third sealing ring is installed between the lower end of the extension tube and the upper end of the extrusion chamber; a fourth sealing ring is installed between the lower end of the extrusion chamber and the upper end of the six-way assembly; and a fifth sealing ring is installed between the six-way assembly and the waste pipe. A pressure ring and a sixth sealing ring are installed on the outer side of the lower end of the vacuum cylinder and between the pressure ring and the outer side of the lower end of the vacuum cylinder.

4. Cryogenic screw extruder according to claim 3, characterized in that The first, second, third, fourth, and fifth sealing rings are all made of soft metal; the sixth sealing ring is made of rubber.

5. Cryogenic screw extruder according to claim 1, characterized in that The liquefier is installed at a height higher than the lower end of the extension pipe.

6. Cryogenic screw extruder according to claim 1, characterized in that The liquid helium inlet pipe, helium vapor return pipe, working gas inlet pipe, and vacuum cylinder are sealed and fixed by sealing welds.

7. Cryogenic screw extruder according to claim 1, characterized in that The extension tube is made of a material with low thermal conductivity. Its upper end is fixed to the inner side of the upper end of the vacuum cylinder, and a small hole is opened on the flange at the lower end for connecting the working gas inlet tube.

8. Cryogenic screw extruder according to claim 1, characterized in that A conical nozzle is located at the lower end of the extrusion chamber, with its outlet aligned with the six-way assembly. The entire extrusion chamber and the conical nozzle are integrated into one structure, facilitating direct temperature control of the nozzle and thus improving the quality of the icicle forming. A first heating rod and a first low-temperature sensor are installed at the upper end of the extrusion chamber, while a second heating rod and a second low-temperature sensor are installed at the lower end to control the temperature of the extrusion chamber. A sleeve heat exchanger is wound around the periphery of the extrusion chamber and is fixed to the periphery of the extrusion chamber by brazing. Both the extrusion chamber and the sleeve heat exchanger are made of materials with high thermal conductivity.

9. Cryogenic screw extruder according to claim 1, characterized in that The extrusion screw is made of a material with low thermal conductivity and has threads on the outer circumferential surface of the extrusion chamber. The lower end, which is adapted to the tapered nozzle, is tapered. The central axes of the extrusion screw, bearing, extension tube, extrusion chamber, six-way assembly, and waste tube coincide.

10. Cryogenic screw extruder according to claim 1, characterized in that The intake pipe is connected to the intake valve outside the vacuum cylinder. It enters the vacuum cylinder directly from the left side, where a cutter is installed. An electromagnetic coil is fitted on the outside, and the pipe further enters the six-way assembly from the left side. The launch tube enters the vacuum cylinder directly from the right side and further enters the six-way assembly from the right side. The central axes of the intake pipe and the launch tube coincide. Inside the six-way assembly, there is a gap between the right end of the intake pipe and the left end of the launch tube, allowing the solid ice column to pass vertically from top to bottom. When the electromagnetic coil is energized, it drives the cutter to move in a straight line, thereby cutting the solid ice column into individual projectiles and pushing the projectiles into the launch tube.

11. Cryogenic screw extruder according to claim 1, characterized in that The waste pipe extends from the bottom of the vacuum cylinder, and its outer diameter is uneven, with the largest outer diameter at the flange at the bottom of the vacuum cylinder.

12. Cryogenic screw extruder according to claim 1, characterized in that The first vacuum pump unit is connected to the waste pipe; the second vacuum pump unit is connected to the vacuum cylinder.

13. Cryogenic screw extruder according to claim 1, characterized in that The liquefier is made of a material with high thermal conductivity, and is equipped with a third heating rod and a third low-temperature sensor to control the temperature of the liquefier.

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