CN102903399A - Multistage differential vacuum pumping system for pellet charging propulsive gas in nuclear fusion - Google Patents

Abstract

The invention belongs to the technical field of nuclear fusion feeding, and in particular relates to a multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propellant gas. The purpose is to limit the amount of propellant gas entering the vacuum chamber of the main engine, reduce the propellant gas entering the discharge vacuum chamber after the projectile is injected, and reduce the resistance of the flying projectile at the same time. The multi-stage differential vacuum pumping system is divided into two stages, the primary pumping system is directly connected to the accelerator barrel (2), and the primary pumping system passes through the restrictor tubes (5, 9) in the support tube 1 (7). ) is connected to the secondary air extraction system. The invention has the advantages of adopting the design of a two-stage air pumping system, high pumping efficiency and vacuum degree of pumping to meet the experimental requirements. The pumping system has a good seal to prevent the leakage of external air; it can effectively pump out a large amount of propelling gas after the projectile is launched, and does not affect the flight of the projectile; the system has a simple structure and is easy to operate.

Description

Nuclear fusion projectile feeding propellant gas multi-stage differential vacuum pumping system

technical field

The invention belongs to the technical field of nuclear fusion feeding, and in particular relates to the extraction technology of propellant gas during the feeding process of projectiles in the nuclear fusion field.

Background technique

In the field of fusion, projectile feeding has been widely used. Pneumatic propulsion is often used to accelerate projectiles. The propellant gas generally uses high-pressure high-purity helium. In order to reduce the propellant gas entering the discharge vacuum chamber, it is necessary to design a vacuum pumping system to Restrict and evacuate propellant gases.

The present invention is aimed at reducing the propelling gas after the projectile is injected in the fusion.

Contents of the invention

The purpose of the present invention is to provide a vacuum pumping system for the projectile injector and limit the amount of propelling gas entering the vacuum chamber of the main engine, so as to reduce the propelling gas entering the discharge vacuum chamber after projectile injection and reduce the resistance of flying projectiles.

The present invention is realized in this way: a multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propellant gas, wherein,

The multi-stage differential vacuum pumping system is divided into two stages, the primary pumping system is directly connected to the accelerator barrel, and the primary pumping system is connected to the second stage through the vacuum restrictor tube 2 and the vacuum restrictor tube 3 in the support tube 1. stage pumping system, the support tube 1 fixes the vacuum restrictor tube 2 and the vacuum restrictor tube 3;

The first-stage air extraction system sets the vacuum restrictor 1 and the vacuum restrictor 2 sequentially on the flight trajectory of the projectile. There is a gap between the two for the escape of the propelling gas. The outer periphery of the tube 2 is provided with a sealed expansion chamber 1, and the outside of the diffusion chamber 1 is connected to the large diffusion chamber through pipelines, and the large diffusion chamber is also connected to the exhaust unit 1. Finally, the vacuum restrictor tube 2 and the vacuum restrictor tube A fast electromagnetic gate valve is installed between 3;

The primary air extraction system is connected to the secondary air extraction system through the vacuum current limiting tube 2 and the vacuum current limiting tube 3 in the support tube 1. The restrictor tube 4 has a gap between the two, which is used to promote the escape of gas. A sealed expansion chamber 2 is arranged on the periphery of the vacuum restrictor tube 3 and the vacuum restrictor tube 4. The outside of the diffusion chamber 2 is in contact with the pumping chamber. The gas unit 2 is connected; finally, the vacuum restrictor tube 4 is fixed in the support tube 2.

A multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propellant gas as described above, wherein,

The inner diameter of the vacuum restrictor is d=2-6mm, the inner wall of the restrictor is electrostatically polished, the port is made into a trumpet shape, and the gap between the restrictor and the restrictor is 50mm; the fast The electromagnetic gate valve is closed within 20ms after the high-speed projectile enters the current limiting pipe 1 through the current limiting pipe 1. The diffusion chamber 1, the diffusion chamber 2, and the large diffusion chamber are diffusion chambers with volumes of 0.1m ³ , 0.1m ³ , and 0.5m ³ respectively , vacuum restrictor 1, vacuum restrictor 2, vacuum restrictor 3 are respectively L1: 0.5m, d ₁ : 2mm; L2: 2.5m, d ₂ : 3mm; L3: 1.5m, d ₃ : 6mm, L indicates length and d indicates diameter.

A multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propulsion gas as described above, wherein, the main pump of pumping unit 1 adopts a compound molecular pump, and the front stage uses a Roots pump; the main pump of pumping unit 2 adopts a compound molecular pump. Pump, the front stage adopts rotary vane vacuum pump.

A multi-stage differential vacuum pumping system for fueling nuclear fusion projectiles as described above, wherein, the pumping unit 1, the main pump adopts Zhongkeyi FF-250 compound molecular pump, pumping speed: 2000L/S, the front stage Nanguang ZJP-70 Roots pump is adopted, pumping speed: 70L/S; the main pump of the air extraction unit 2 adopts Zhongkeyi FF-200 compound molecular pump, pumping speed: 1300L/S, the front stage adopts Zhongkeyi RVP-18 rotary Vane vacuum pump, pumping speed: 18L/S.

The advantages of the present invention are:

The design of the two-stage pumping system improves the pumping efficiency and vacuum degree.

1. There is a good seal to prevent the leakage of external air;

2. It can effectively extract a large amount of propellant gas without affecting the flight of the projectile;

3. The system structure is simple and easy to operate.

Description of drawings

Fig. 1 is a schematic structural diagram of a multi-stage differential vacuum pumping system for fueling nuclear fusion projectiles according to the present invention.

Among them: 1. Projectile injector; 2. Accelerating gun barrel; 3. Diffusion chamber 1; 4. Vacuum current limiting tube 1; 5. Vacuum current limiting tube 2; 6. Fast electromagnetic gate valve; 7. Support tube 1; 8. Diffusion chamber 2; 9. Limiting pipe 3; 10. Support pipe 2; 11. Manual flapper valve 1; 12. Large diffusion chamber; 13. Manual flapper valve 2; 14. Air extraction unit 1; 15. Air extraction Unit 2; 16. Manual flapper valve 3; 17. Limiting tube 4.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

As shown in Figure 1, since the projectile injector adopts the method of aerodynamically accelerating projectiles, each projectile fired will generate propellant gas. If multiple projectiles are fired continuously, a large amount of propellant gas will be generated. If a large amount of propellant gas is not effectively extracted in time, The propellant gas will enter the discharge main vacuum chamber, which will affect the plasma discharge test. In order to avoid a large amount of propellant gas entering the discharge vacuum chamber and affecting the discharge, I provide an effective multi-stage differential vacuum pumping system method.

The present invention is specifically a set of multi-stage differential vacuum pumping system installed between the projectile injector 1 and the discharge vacuum chamber. The projectile injector 1 launches the projectile, shoots out through the accelerated gun barrel 2, and passes through the multi-stage differential vacuum pumping system. The system enters the discharge vacuum chamber, and the present invention extracts the propellant gas during the flight of the projectile.

The multi-stage differential vacuum pumping system is divided into two stages, the primary pumping system is directly connected to the accelerator barrel 2, and the primary pumping system passes through the vacuum restrictor tube 2 and the vacuum restrictor tube 3 ( 5, 9) Connect the secondary air extraction system, and the support tube 1 (7) fixes the vacuum restrictor tube 2 and the vacuum restrictor tube 3 (5, 9);

The first-stage air extraction system sets the vacuum restrictor 1 (4) and the vacuum restrictor 2 (5) sequentially on the flight trajectory of the projectile. There is a gap between the two for the escape of the propellant gas. The periphery of the tube 1 (4) and the vacuum restrictor tube 2 (5) is provided with a sealed expansion chamber 1 (3), and the outside of the diffusion chamber 1 (3) is connected to the large diffusion chamber 12 through a pipeline, and the large diffusion chamber 12 It is connected with the air extraction unit 1 (14), and a manual slide valve 2 (13) is installed between the large diffusion chamber 12 and the air extraction unit 1 (14); finally, between the vacuum flow limiting tube 2 (5) and the vacuum flow limiting A fast electromagnetic gate valve (6) is installed between the pipes 3 (9).

The primary air extraction system is connected to the secondary air extraction system through the vacuum restrictor tube 2 and the vacuum restrictor tube 3 (5, 9) in the support tube 1 (7), and the secondary air extraction system is sequentially arranged on the flight trajectory of the projectile. Vacuum current limiting tube 3 (9), vacuum current limiting tube 4 (17) are set, there is a gap between the two, used to promote the escape of gas, between vacuum current limiting tube 3 (9) and vacuum current limiting tube 4 ( 17) is provided with a sealed expansion chamber 2 (8) on the periphery, and the outside of the diffusion chamber 2 (8) is connected to the air extraction unit 2 (15). Between the diffusion chamber 2 (8) and the air extraction unit 2 (15) A manual gate valve 3 (16) is installed; finally, the vacuum restrictor tube 4 (17) is fixed in the support tube 2 (10), and a manual gate valve 1 (11) is installed on the support tube 2 (10) .

The multi-stage differential vacuum pumping system reasonably selects the components of the system according to the size of the propellant gas load, and finally obtains the optimal design and equipment selection.

Taking the propellant gas load of each projectile fired by the pneumatic projectile injector in our hospital <5Pa·m ³ /shot, and continuously launching 40 projectiles as an example, the rationality and practicability of this method are briefly explained.

1. The overall structure of the system

Install each component on the support frame in sequence. The restrictor tubes (4, 5, 9) are installed in the support tubes (7, 10) and are kept concentric and level with the projectile accelerating barrel (2).

The current limiting tube not only limits the flow, but also can restrict the flying position of the projectile and guide the projectile. Among them, the inner diameter of the vacuum current limiting tube is d=2~6mm, the inner wall of the current limiting tube is electrostatically polished, and the port is made into a trumpet shape. It is beneficial for projectiles not to be easily broken in the flow-limiting tube, and it is also beneficial for projectiles to enter the lower-level flow-limiting tube. The distance between the flow-limiting tube and the flow-limiting tube is 50mm, which is to release a large amount of propulsive gas in each diffusion chamber. The use of the fast electromagnetic turn valve is increased in order to better reduce the propellant gas entering the next-stage diffusion chamber. A fast electromagnetic turn valve is installed between the diffusion chamber 1 (3) and the diffusion chamber 2 (8). After the projectile enters the flow-limiting pipe 2 (5) through the flow-limiting pipe 1 (4), the fast electromagnetic turn valve is closed within 20 ms, which can also effectively reduce the entry of propellant gas into the next-stage diffusion chamber. For the convenience of recording vacuum data, the system is equipped with an automatic vacuum acquisition system, which can effectively monitor and record vacuum changes. The specific structure of the multi-stage differential vacuum pumping system is shown in Figure 1.

2, the type selection of air extraction unit (14,15). Air extraction unit 1 (14), the main pump adopts Zhongkeyi FF-250 compound molecular pump (pumping speed: 2000L/S), and the front stage adopts Nanguang ZJP-70 Roots pump (pumping speed: 70L/S); The main pump of gas unit 2 (15) adopts Zhongkeyi FF-200 compound molecular pump (pumping speed: 1300L/S), and the front stage adopts Zhongkeyi RVP-18 rotary vane vacuum pump (pumping speed: 18L/S). The use of compound molecular pump as the main pump mainly considers the improvement of pumping speed and compression ratio in the high pressure area, which greatly shortens the recovery time of the working vacuum limit after repeated inflation of the application system and equipment, and the speed is faster than that of the turbo molecular pump, so in a short time A greater pumping speed will be obtained in the interior, and the pumping speed obtained by using such a combination method should be greatly increased.

3. According to the pipeline conductance calculation formula (known technology), it can be seen that under different flow conditions, the gas is only related to the length, diameter and average pressure in the pipe. Therefore, according to the required pressure of each diffusion chamber, determine the diffusion chamber ( 3, 8, 12) Diffusion chambers with volumes of 0.1m ³ , 0.1m ³ , and 0.5m ³ respectively, the vacuum restrictors (4, 5, 9) are L1: 0.5m, d ₁ : 2mm; L2: 2.5 m, d ₂ : 3 mm; L3: 1.5 m, d ₃ : 6 mm.

4. Calculation of vacuum degree

4.1 Conductance of restrictor tube 2(5)

According to the propulsion gas load <5Pa·m ³ /shot, 40 grains are launched continuously, and the maximum propellant gas volume Q ₀ is 200Pa.m ³ . After the propelling gas ejected from the accelerating gun barrel enters the restrictor tube 1 (4), the propelling gas diffuses in a conical shape in the diffusion chamber 1 (3). tube connection, so a large amount of propellant gas diffuses in the diffusion chamber 1 (3) and the large diffusion chamber 12, and a small amount of propellant gas enters the diffusion chamber 2 (8) through the restrictor tube 2 (5), so it can be approximately considered that the propellant gas is filled instantly Diffusion chamber 1 (3) and large diffusion chamber 12, P _1max is the maximum pressure achievable. P _1max is calculated by the following formula:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

After calculation: P _1max = 340 (Pa), because the pressure difference between the two ends of the restrictor tube 2 (5) is relatively large P ₁ >>P ₂ , so the average pressure of the restrictor tube 2 (5)

according to $P_1{d}_1=170\&times;3\&times;{10}^{-3}=0.51\mathrm{Pa}.m,$ because $0.02\mathrm{Pa}.m<{\stackrel{\&OverBar;}{P}}_1{d}_1<0.67\mathrm{Pa}.m,$ It can be judged that the gas is in a viscous-molecular flow state at this time. Since L1/d ₁ =2.5/3×10 ^-3 =833>>20, the conductance of the restrictor tube 2(5) can be calculated by the following formula:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="u"\; filenames="HDA0000079834440000011.png"\; state="\{\{state\}\}">u</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 128</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}}{\mathrm{<span\; class="notranslate">\; \&eta;L</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 6</span>}}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;RT</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}}\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; RT</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}}{\mathrm{<span\; class="notranslate">\; \&eta;</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1.24</span>}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; RT</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}}{\mathrm{<span\; class="notranslate">\; \&eta;</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

为限流管内的平均压强(170Pa)；L为限流管2(5)的长度(2.5m)；M为气体摩尔质量(4×10^-3kg/mol)；T为气体温度(300K)；R为摩尔气体质量(8.314J/K·mol)。In the formula, d is the diameter of restrictor tube 2(5) (3×10 ^-2 m); η is the viscosity coefficient of helium (1.96×10 ^-5 Ns/m ² );

is the average pressure in the restrictor tube (170Pa); L is the length of the restrictor tube 2 (5) (2.5m); M is the gas molar mass (4×10 ^-3 kg/mol); T is the gas temperature (300K) ; R is the molar gas mass (8.314J/K·mol).

Calculated: U ₁ =9.8×10 ^-6 m ³ /s

3.2 Pressure in diffusion chamber 2(8)

The gas volume Q ₂ of a small amount of propellant gas entering the diffusion chamber 2 ( 8 ) through the restrictor tube 2 ( 5 ) is calculated by the following formula.

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Q"\; filenames="HDA0000079834440000011.png"\; state="\{\{state\}\}">Q</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

为限流管5平均压强；U₁为限流管5的流导。In the formula, _Q2 enters the gas volume of the diffusion chamber 2 (8);

is the average pressure of the restrictor tube 5; U ₁ is the conductance of the restrictor tube 5.

Calculated: Q ₂ =1.7×10 ^-3 (Pa.m ³ /s)

Diffusion chamber 2 (8) is equipped with Zhongkeyi FF-200 compound molecular pump, pumping speed: 1300L/s, based on the effective pumping speed of 1m ³ /s, the vacuum of the vacuum chamber can reach 1.7×10 ^-3 (Pa), It can meet the requirements of HL-2A discharge experiment.

Claims (4)

1. A multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propellant gas, characterized in that: The multi-stage differential vacuum pumping system is divided into two stages, the primary pumping system is directly connected to the accelerator barrel (2), and the primary pumping system passes through the vacuum restrictor tube 2 and the vacuum in the support tube 1 (7). The restrictor tube 3 (5, 9) is connected to the secondary pumping system, and the support tube 1 (7) fixes the vacuum restrictor tube 2 and the vacuum restrictor tube 3 (5, 9); The first-stage air extraction system sets the vacuum restrictor 1 (4) and the vacuum restrictor 2 (5) sequentially on the flight trajectory of the projectile. There is a gap between the two for the escape of the propellant gas. The periphery of the tube 1 (4) and the vacuum restrictor tube 2 (5) is provided with a sealed expansion chamber 1 (3), and the outside of the diffusion chamber 1 (3) is connected to the large diffusion chamber (12) through a pipeline, and the large diffusion chamber (12) is also connected with the air extraction unit 1 (14), and finally, the vacuum restrictor 2 (5) and the vacuum restrictor 3 (9) are fixed in the support pipe 1 (7), and at the same time, the vacuum restrictor 2 A fast electromagnetic gate valve (6) is installed between the vacuum restrictor tube 3 (5, 9); The primary air extraction system is connected to the secondary air extraction system through the vacuum restrictor tube 2 and the vacuum restrictor tube 3 (5, 9) in the support tube 1 (7), and the secondary air extraction system is sequentially arranged on the flight trajectory of the projectile. Vacuum current limiting tube 3 (9), vacuum current limiting tube 4 (17) are set, there is a gap between the two, used to promote the escape of gas, between vacuum current limiting tube 3 (9) and vacuum current limiting tube 4 ( 17) is provided with a sealed expansion chamber 2 (8) on the periphery, and the outside of the diffusion chamber 2 (8) is connected to the air extraction unit 2 (15); finally, the vacuum restrictor tube 4 (17) is fixed on the support pipe 2 ( 10) Inside. 2. A multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propellant gas as claimed in claim 1, characterized in that: The inner diameter of the vacuum restrictor is d=2-6mm, the inner wall of the restrictor is electrostatically polished, the port is made into a trumpet shape, and the gap between the restrictor and the restrictor is 50mm; the fast The electromagnetic gate valve (6) closes within 20ms after the high-speed projectile enters the current limiting tube 2 (5) through the current limiting tube 1 (4), and the diffusion chamber 1, the diffusion chamber 2, and the large diffusion chamber (3, 8, 12) are volumes Respectively 0.1m3, 0.1m3, 0.5m3 diffusion chamber, vacuum restrictor tube 1, vacuum restrictor tube 2, vacuum restrictor tube 3 (4, 5, 9) are respectively L1: 0.5m, d ₁ : 2mm; L2: 2.5m, d ₂ : 3mm; L3: 1.5m, d ₃ : 6mm, L means length, d means diameter. 3. A multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propellant gas as claimed in claim 2, characterized in that: the pumping unit 1 (14), the main pump adopts a compound molecular pump, and the front stage adopts a Roots pump ; The main pump of the air extraction unit 2 (15) adopts a compound molecular pump, and the front stage adopts a rotary vane vacuum pump. 4. A multi-stage differential vacuum pumping system for nuclear fusion projectile feeding propellant gas as claimed in claim 3, characterized in that: the pumping unit 1 (14), the main pump adopts Zhongkeyi FF-250 compound molecular pump , Pumping speed: 2000L/S, Nanguang ZJP-70 Roots pump is used in the front stage, pumping speed: 70L/S; the main pump of the air extraction unit 2 (15) adopts Zhongkeyi FF-200 compound molecular pump, pumping speed: 1300L /S, the front stage adopts Zhongkeyi RVP-18 rotary vane vacuum pump, pumping speed: 18L/S.

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