JP2008291781A - Refrigeration device for helium liquefaction, and compressor unit for helium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve performance and elongate service life, while suppressing increase in cost, simplifying and facilitating capacity controllability of a compressor, in a refrigeration device for helium liquefaction. <P>SOLUTION: The air-cooled compressor unit for helium of the refrigeration device for helium liquefaction comprises: a low-stage compressor unit 1100 having a low-stage compressor 100 increasing pressure of helium gas from low pressure to intermediate pressure; and a high-stage compressor unit 1200 having a high-stage compressor 200 increasing pressure of the helium gas from intermediate pressure to high pressure. A stroke capacity of the low-stage compressor 100 is set to be the same as a cylinder capacity of the high-stage compressor 200, an electric motor for inverter is commonly used for the low-stage compressor 100 and the high-stage compressor 200, and drive control of the low-stage compressor 100 and the high-stage compressor 200 is performed by using a single inverter 900 at the same revolution speed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a helium liquefaction refrigeration apparatus and a helium compressor unit, and is particularly suitable for a helium liquefaction refrigeration apparatus and a helium compressor unit including a low stage compressor and a high stage compressor.

  As for the conventional helium liquefaction refrigeration apparatus, for example, there is one disclosed in FIGS. 15 and 18 of Japanese Patent Laid-Open No. 3-271582 (Patent Document 1). This helium liquefaction refrigeration apparatus includes a compressor unit that uses helium gas as a working gas, a load-side refrigerator, these pipes, and an inverter that controls the helium scroll compressor. The compressor unit includes one helium scroll compressor, an oil injection circuit having an oil cooler, and a gas cooler that cools the helium gas discharged from the helium scroll compressor. The helium scroll compressor includes a fixed scroll and an orbiting scroll having a scroll tooth profile with a scroll wrap portion having a set volume ratio of 3.4 to 4.5, and has a high pressure and low pressure ratio. The pressure ratio is configured to be around 20.

JP-A-3-271583

The oil cooler and gas cooler in the helium liquefaction refrigeration apparatus are generally water-cooled, but now they are shifting to an air-cooled system that does not require water. For this reason, the temperature of the whole apparatus becomes high, and accordingly, the discharge side pressure Pd2 increases to around 2.5 MpaG (25 kg / cm ² G), and the ratio between the discharge side pressure Pd2 and the suction side pressure Ps1 of the compressor The operating pressure ratio is required to be 24 to 26 operating pressure ratio conditions of a higher pressure ratio than the conventional 18 to 20 or so. In a conventional compressor, there is a problem of performance degradation, that is, a large reduction in volumetric efficiency and an increase in compressor power when attempting to achieve with a single compressor. In particular, the significant reduction in volumetric efficiency leads to a problem that the Joule Thomson valve and the amount of liquefied helium flowing down from the valve are reduced, and the cooling effect on the superconducting magnet in the helium vessel is impaired.

  An object of the present invention is to provide a helium liquefaction refrigeration apparatus and a helium compressor unit that can achieve high performance and long life while suppressing cost increase and simplifying and facilitating compressor capacity controllability. There is to get.

  In order to achieve the above object, a first aspect of the present invention is a helium liquefaction refrigeration apparatus comprising an air-cooled helium compressor unit using helium gas as a working gas and a load-side refrigerator. The helium compressor unit includes a low-stage compressor unit having a low-stage compressor that boosts helium gas from a low pressure to an intermediate pressure, and helium gas compressed to an intermediate pressure by the low-stage compressor. A high-stage compressor unit having a high-stage compressor that boosts the pressure to the same, and the load-side refrigerator includes a helium gas precooling refrigerator, a Joule-Thompson valve, and a helium container for storing liquefied helium flowing down from the valve, The stroke volume of the low stage compressor and the process volume of the high stage compressor are set to be the same, and the inverter motors of the low stage compressor and the high stage compressor are set to be the same. Is to drive control at the same rotational speed of the low-stage compressor and the high stage compressor at one inverter.

A more preferable specific configuration example in the first aspect of the present invention is as follows.
(1) It has the same scroll tooth profile shape where the set volume ratio of the scroll wrap part of the said low stage compressor and the said high stage compressor is 2.1-2.4.
(2) The operating pressure ratio of the low stage compressor is set to 9 to 11 and the operating pressure ratio of the high stage compressor is set to 2.3 to 2.8. A certain high pressure ratio should be 24 to 26.
(3) A check valve is provided on the discharge side of the low-stage compressor.
(4) A check valve is provided on the discharge side of the low-stage compressor and on the low-stage compressor side of the pipe from the helium gas precooling refrigerator to the high-stage compressor, and the low-stage compressor discharge And a bypass pipe for bypassing from the low-stage compressor side to the suction side of the low-stage compressor from the check valve, and a pressure reducing valve means having a flow rate adjusting function in the middle of the bypass pipe.

  The second aspect of the present invention provides a low-stage compressor unit having a low-stage compressor that uses helium gas as a working gas and raises the helium gas from a low pressure to an intermediate pressure, A high-stage compressor unit having a high-stage compressor that raises the helium gas compressed to a high pressure from an intermediate pressure to a high pressure, and stores a helium gas precooling refrigerator, a Joule-Thomson valve, and liquefied helium flowing down from the valve In an air-cooled helium compressor unit that supplies helium gas to a load-side refrigerator composed of a helium container, the stroke volume of the low-stage compressor and the process volume of the high-stage compressor are set to be the same, and The inverter motors of the low-stage compressor and the high-stage compressor are set to be the same, and the low-stage compressor and the high-stage compressor are driven and controlled at the same rotational speed by a single inverter. A.

A more preferable specific configuration example in the second aspect of the present invention is as follows.
(1) The set volume ratios of the scroll wrap portions of the low stage compressor and the high stage compressor have the same scroll tooth profile shape of 2.1 to 2.4, and the operating pressure ratio of the low stage compressor is 9 to 11 and the operating pressure ratio of the high stage compressor is set to 2.3 to 2.8, and the high pressure ratio that is the pressure ratio between the high pressure and the low pressure is set to 24 to 26. A check valve is provided on the discharge side of the compressor and on the lower stage compressor side than the pipe from the helium gas precooling refrigerator to the higher stage compressor, and on the discharge side of the lower stage compressor and the check A bypass pipe for bypassing from the lower stage compressor side to the suction side of the lower stage compressor than the valve is provided, and a pressure reducing valve means having a flow rate adjusting function is provided in the middle of the bypass pipe.

  According to the present invention, a low-stage compressor for increasing the pressure of helium gas from a low pressure to an intermediate pressure and a high-stage compressor for increasing the pressure of the helium gas from an intermediate pressure to a high pressure are provided. Since it is set to the same volume, the operating pressure ratio of each compressor can be set to about half the pressure ratio of the conventional machine, and volume efficiency can be improved by reducing internal leakage between the compression chambers. At the same time, each compressor can be manufactured at the same cost because it can be manufactured in the same way. Furthermore, by setting the same process volume as each compressor, the same motor can be used for the inverter built-in inverter, and the number of revolutions of two compressors can be controlled simultaneously by one inverter. Thus, the ability controllability of both compressors is simple and easy, and when the refrigeration load is small, the operating frequency can be lowered and a significant energy saving can be achieved.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. The same reference numerals in the drawings of the respective embodiments indicate the same or equivalent.
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.

  The overall configuration and function of the helium liquefaction refrigeration apparatus 50 of this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing an overall configuration of a helium liquefaction refrigeration apparatus 50 according to this embodiment, and FIG. 2 is a diagram showing a configuration of a compressor unit 258 according to this embodiment.

  As shown in FIG. 1, the helium liquefaction refrigeration apparatus 50 includes an air-cooled helium compressor unit 258 that uses helium gas as a working gas and a load-side refrigerator 259.

  The compressor unit 258 includes a low-stage compressor unit 1100 having a low-stage compressor 100 (see FIG. 2) that boosts helium gas from a low pressure to an intermediate pressure, and helium gas compressed to an intermediate pressure by the low-stage compressor 100. And a high-stage compressor unit 1200 having a high-stage compressor 200 (see FIG. 2) for increasing the pressure from an intermediate pressure to a high pressure.

  The load side refrigerator 259 includes helium gas precooling refrigerators 300 and 400, a Joule Thomson valve 260, and a helium container 500 that stores liquefied helium flowing down from the Joule Thomson valve 260.

  The pipes connecting between the compressor unit 258 and the equipment constituting the load side refrigerator 259 are a low pressure pipe 600 extending from the helium vessel 500 to the low stage compressor 100, and a low stage compressor unit 1100 to the high stage compressor unit. Intermediate pressure pipes 650, 820, 860, 830, 700 from 1200 and precooling refrigerators 300, 400 to high stage compressor unit 1200, and precooling refrigerators 300, 400 and joules from high stage compressor unit 1200 It consists of a high-pressure pipe 773 leading to the Thomson valve.

  The low stage compressor 100 and the high stage compressor 200 are installed in series, and the stroke volume Vth and the set volume ratio Vr of the low stage compressor 100 and the stroke volume Vth and the set volume ratio Vr of the high stage compressor 200 are set. Are the same.

  The refrigerators 300 and 400 are connected between an intermediate pressure pipe 700 that is a suction side pipe of the high-stage compressor unit 1200 and a high pressure pipe 750 that is a discharge side pipe. The helium vessel 500 is connected between a low pressure pipe 600 and a high pressure pipe 750 that are suction side pipes of the low-stage compressor unit 1100. Reference numeral 780 denotes a joining point of the outflow side pipe 820 of the refrigerator 300 and the outflow side pipe 860 of the refrigerator 400 to the pipe 830. Reference numeral 832 denotes a joining point of the intermediate pressure gas pipe 650 and the pipe 830 which are discharge side pipes of the low stage compressor unit 1100 to the intermediate pressure pipe 700. Reference numeral 760 denotes a branch point from the pipe 750 to the inflow side pipe 800 of the refrigerator 300 and the inflow side pipe 756 of the refrigerator 400 and the helium container 500. Reference numeral 770 denotes a branch point from the pipe 756 to the inflow side pipe 850 of the refrigerator 400 and the inflow side pipe 773 of the helium container 500.

By adopting such a configuration, for example, when a scroll wrap shape having a stroke volume Vth = 150 CC / rev is applied, the flow rate of helium gas circulating through the low-stage compressor 100 at an operating frequency of 75 Hz is Gs = 30 Nm ³ / h. Thus, the flow rate of helium gas circulating through the high-stage compressor 200 is Gh = 300 Nm ³ / h. The flow rate / capacity ratio is set so that Gh / Gs = 10. In an example using a conventional single compressor, when a helium gas flow rate Gs ₁ = 15 Nm ³ / h is secured, a high ratio of Gh / Gs ₁ = 20 is obtained. In the present embodiment, the same product with a stroke volume of the high-stage compressor 200, for example, Vth = 150 CC / rev, is applied to the low-stage compressor 100, thereby reducing the flow rate ratio, The difference in power load can be reduced. Further, the load on the high stage compressor 200 can be reduced. As a result, as shown in FIG. 10 to be described later, energy saving can be achieved as the entire apparatus.

  As shown in FIG. 2, the low-stage compressor unit 1100 includes the low-stage compressor 100, the oil cooler 33, the throttle unit 271, the cooler 651, and the oil separation unit 652 as main components. The high-stage compressor unit 1200 includes the high-stage compressor 200, the oil cooler 333, the throttle unit 2711, the cooler 753, and the oil separation unit 754 as main components.

  The inverter 900 may be installed outside the compressor unit 258 or may be installed inside the compressor unit 258. The two compressors 100 and 200 are driven by a single inverter 900, and the rotational speed can be controlled at the same operating frequency. The same helium compressor and the inverter motors 3a and 3b accommodated in the same helium compressor are the same, and the inverter control function (operating frequency, secondary voltage relationship, etc.) can be unified.

  In the present embodiment, as described above, in the refrigeration apparatus 50 for helium liquefaction, both the low-stage compressor 100 that boosts from the low pressure Ps1 to the intermediate pressure Pd1 and the high-stage compressor 200 that boosts from the intermediate pressure Pd1 to the high pressure Pd2 are used. The stroke volume Vth of the compressor is set to the same value of, for example, 150 CC / rev.

  The helium gas discharged from the low-stage compressor 100 passes through the air-cooled cooler 651 and the oil separator 652, and reaches the suction pipe 700 of the high-stage compressor 200. Further, the helium gas discharged from the compressor 200 has a high discharge pressure. Pd2 is reached from the discharge pipe 20 to the air-cooled cooler 752. The helium gas from the cooler 752 moves to the external refrigerators 300 and 400 and the helium container 500 via an oil separator 753 and an adsorber (oil adsorber) 754.

  Next, the helium gas is appropriately adiabatic and expanded in the helium refrigerators 300 and 400, and then returns to the high-stage compressor 200 as suction gas in the pipes 820, 830 and 860 again. Further, helium gas from the helium vessel 500 returns to the low-stage compressor 100 as suction gas through the pipe 600. Both compressors 100 and 200 are driven by one inverter 900. Thereby, the rotation speed of the two compressors 100 and 200 is set to be the same, and there is an effect that the capacity control of the refrigeration load can be performed in a well-balanced manner. Even if the load on the refrigerator side changes, the flow rate ratio of Gh / Gs can always be set to be the same. Thus, in this embodiment, two compressors with different operating pressure conditions are connected by one inverter. It is characterized by simultaneous operation. Reference numeral 980 denotes a power supply, and reference numeral 390 (390a, 390b) denotes a power supply line.

  Next, the configuration and function of the low-stage compressor unit 1100 will be described with reference to FIGS. 3 to 9. FIG. 3 is a diagram showing a low-stage compressor unit 1100 in the present embodiment. FIG. 3 shows an example in which an oil-lubricated hermetic scroll compressor having a vertical structure is used as the low-stage compressor 100, and a portion of the low-stage compressor 100 is shown in a vertical cross section. 4 is a plan view of the fixed scroll 5 of the low stage compressor 100 of FIG. 3, FIG. 5 is a longitudinal sectional view of the fixed scroll 5 of FIG. 4, and FIG. 6 is a plane of the orbiting scroll 6 of the low stage compressor 100 of FIG. 7 is a longitudinal sectional view of the orbiting scroll 6 of FIG. 6, FIG. 8 is a front view of the low stage compressor 100 or the high stage compressor 200, and FIG. 9 is a plan view of FIG. The configuration and functions described below for the low-stage compressor unit 1100 are basically the same as those for the high-stage compressor unit 1200, and thus redundant description is omitted.

  As shown in FIG. 3, in the low-stage compressor unit 1100, the working gas is helium gas, and an oil injection pipe 31 for cooling the working helium gas passes through the lid cap 2 a of the sealed container 1 and the fixed scroll 5. Is connected to an oil injection port 22 provided in the end plate portion 5a. The opening portion of the oil injection port 22 is opened facing the tooth tip surface of the wrap 6 b of the orbiting scroll 6. In the hermetic container 1, the scroll compressor part 250 is accommodated on the upper side, and the electric motor part 3 is accommodated on the lower side. The electric motor unit 3 is composed of an inverter electric motor, and has a characteristic that the rotation speed can be varied from 30 Hz to 100 Hz as an operating frequency. The sealed container 1 is partitioned into a discharge chamber 1a and an electric motor chamber 1b with a frame 7 in between. The scroll compressor section 250 forms a compression chamber (sealed space) 8 by meshing the fixed scroll 5 and the orbiting scroll 6 with each other.

  As shown in FIGS. 4 and 5, the fixed scroll 5 is composed of a disc-shaped end plate 5a and a wrap 5b which stands upright on the disc and is formed in an involute curve or a curve approximate thereto. The outlet 10 is provided with suction ports 15 (15a, 15b) on the outer periphery.

  As shown in FIGS. 6 and 7, the orbiting scroll 6 includes a disc-shaped end plate 6a, a wrap 6b that stands upright and is formed in the same shape as the wrap 5b of the fixed scroll 5, and an anti-wrap surface of the end plate. And a boss portion 6c formed on the surface.

  Returning to FIG. 3, a main bearing 40 that is a bearing portion is provided at the center of the frame 7, the rotating shaft 14 is supported on the main bearing 40, and an eccentric shaft 14 a is provided at the tip of the rotating shaft 14. The eccentric shaft 14a is inserted into the boss portion 6c so as to be capable of turning. The fixed scroll 5 is fixed to the frame 7 by a plurality of bolts 81. The orbiting scroll 6 is supported on the frame 7 by an Oldham mechanism 38 including an Oldham ring and an Oldham key, and is configured to perform a revolving motion without rotating with respect to the fixed scroll 5. The rotating shaft 14 is integrally provided with an electric motor shaft 14b extending in a direction opposite to the compressor portion 250, and the electric motor portion 3 is directly connected to the electric motor shaft 14b.

  A suction pipe 17 is connected to the suction port 15 of the fixed scroll 5 through the sealed container 1. The discharge chamber 1a in which the discharge port 10 is opened communicates with the electric motor chamber 1b through passages 18a and 18b. The electric motor chamber 1b communicates with a discharge pipe 20 that penetrates the casing 2b at the center of the sealed container. Further, the motor chamber 1b1 on the upper side of the motor 3 has a gap 25 (25b, 25C) between the motor stator 3a and the side wall of the casing 2b and a gap 26 between the motor stator 3a and the motor rotor 3b. It communicates with the lower motor chamber 1b2.

  An O-ring 53 that seals the high pressure portion and the low pressure portion is provided between the suction pipe 17 and the fixed scroll 5. A check valve 13 is provided in the suction pipe 17. The check valve 13 is provided to prevent reverse rotation of the rotating shaft 14 when the compressor is stopped and to prevent the lubricating oil in the sealed container 1 from flowing out to the low pressure side.

  A space 36 (hereinafter referred to as a back pressure chamber) surrounded by the scroll compressor section 250 and the frame 7 is formed on the back surface of the end plate 6 a of the orbiting scroll 6. An intermediate pressure Pb1 between the suction pressure Ps1 and the discharge-side pressure Pd1 is introduced into the back pressure chamber 36 through the pores 6e and 6f (see FIG. 6) formed in the end plate 6a of the orbiting scroll 6. Thereby, the axially applied force for pressing the orbiting scroll 6 against the fixed scroll 5 is given.

  The lubricating oil 23 is stored at the bottom of the sealed container 1. The lubricating oil 23 is sucked into the oil suction pipe 27 by the differential pressure between the high pressure Pd1 in the sealed container 1 and the intermediate pressure Pb1 in the back pressure chamber 36, and then the oil in the oil supply hole 14c of the rotary shaft 14 is absorbed. The oil is supplied to the flow, the slewing bearing 32, the main bearing 40 and the auxiliary bearing 39. Oil supplied to the slewing bearing 32 and the main bearing 40 is injected into the compression chamber 8 of the scroll wrap through the holes 6e and 6f through the back pressure chamber 36, mixed with the compressed gas, and discharged to the discharge chamber 1a together with the discharge gas. Is done. In addition, since the oil supply differential pressure to the cylindrical roller main bearing 40 of the main bearing is ensured, the cooling action of the bearing 40 is promoted, and the cylindrical roller is combined with the effect of reducing the bearing load accompanying the performance improvement of the helium compressor. The life of the main bearing 40 can be greatly extended. Further, the oil supply to the bearing portions 32, 40, 39 is ensured, and the reliability of the compressor can be improved. An oil take-out pipe 30 for taking out the lubricating oil 23 at the bottom is provided at the bottom of the sealed container 1. An oil injection pipe 31 for injecting oil into the compression chamber 8 in the middle of compression of the scroll compressor section 250 is provided in the lid cap section 2 a of the sealed container 1.

  With the above configuration, when the motor shaft 14 b directly connected to the motor rotor 3 b rotates and the eccentric shaft 14 a rotates eccentrically, the orbiting scroll 6 performs a orbiting motion via the orbiting bearing 32. By this turning motion, the compression chamber 8 gradually moves to the center and the volume decreases. The working gas enters the suction chamber 5f from the suction pipe 17 through the suction port 15 (15a, 15b), and is mixed with the oil that has passed through the bearings and the narrow holes 6d, 6e and the oil that has been injected from the oil injection port 22. Compressed in the compression chamber 8 and discharged from the discharge port 10 to the discharge chamber 1a.

  The discharged mixture of working gas and oil flows into the motor chamber 1b through the passages 18a and 18b. The solid arrows in FIG. 3 indicate the flow of the working gas, and the broken arrows indicate the flow of the oil. The working gas and oil that have flowed into the motor chamber 1b in a large space from the narrow passages 18a and 18b have their flow rates rapidly reduced and the flow direction changed, so that most of the oil contained in the working gas is separated. The working gas flows out from the discharge pipe 20, and the oil falls downward and stays at the bottom of the sealed container 1.

  The lubricating oil 23 stored at the bottom of the sealed container 1 is caused by the pressure difference between the pressure in the sealed container 1 (discharge pressure Pd1) and the pressure in the compression chamber 8 (pressure below the discharge pressure Pd1). The oil flows into the oil take-out pipe 30 from the inflow portion 30a. The oil that has flowed into the oil take-out pipe 30 reaches the air-cooled oil cooler 33 through the external oil pipe 36a, where it is appropriately cooled, and then compressed through the oil injection pipes 36b and 31 and the oil injection port 22. It is injected into the chamber 8. Reference numeral 271 denotes an oil flow control valve. The oil injected into the compression chamber 8 in this manner plays a role of cooling the working gas and lubricating the sliding portion such as the scroll wrap tip in the compression chamber 8.

  The scroll compressors 100 and 200 include a fixed scroll 5 and a swivel that are meshed with each other and have the same scroll tooth shape with a set volume ratio Vr of 2.1 to 2.4 of the scroll wrap portion shown in the following formula (1). A scroll 6 is provided.

Vr = (2λ1−4π + α) / (2λs + 2π + α) (1)
Here, λ1: end angle of wrap winding (involute extension angle), λS: wrap winding start angle (involute extension angle), π: circumference ratio, α: turning radius εth and ratio of basic circle radius a of scroll wrap (= Εth / a).

  The set volume ratio Vr is a value obtained by dividing the stroke volume Vth that is the maximum suction volume by the volume Vd of the innermost chamber immediately before the discharge stroke of the compression chamber 8. In particular, among these, as the most effective scroll compressor, the set volume ratio Vr of the scroll wrap portion is set to a scroll tooth profile shape of 2.3 in common to both the compressors 100 and 200. As a specific scroll wrap shape, as shown in FIG. 6, the position 6m of the ramp terminal portion (tip portion) is the wrap winding start angle λ1, and the position of 6p at the center portion (tip portion) of the wrap is the above wrap winding. The starting angle is λS.

  In FIG. 6, 65 is an involute curve, and point a is the starting point (λS). A curve 67 connecting the d point and the c point is an inner arc curve, and a tip portion connects the a point and the c point with a smooth arc curve 66. A curve 68 outside the point d is an involute curve. The tooth gap dimension (Dt dimension in FIG. 6) is given by the following equation (2).

Dt = 2 × εth + t (2)
In the case of the scroll scroll wrap shape example of Vr = 2.3 specifications, the wrap winding start angle (point a) is approximately λs = 2.0 rad. The points f and g are the points at the end of the wrap winding. The angle is the position of the point f, for example, the involute extension angle λ1 = 19.3 rad. A curved line 69 has an arc shape and smoothly connects the points f and g.

  Next, the compressor input will be described with reference to FIG. FIG. 10 is a characteristic diagram of the compressor input with respect to the intermediate pressure Pd1 and the intermediate pressure ratio Pd1 / Ps1 in the present embodiment.

In the two helium scroll compressor units equipped with an air-cooled cooler, the high-pressure pressure is, for example, Pd2 = 2.4 MpaG (about 24 kg / cm ² G) as described above. From FIG. 10, in terms of the input pressure of the compressor under the pressure conditions of the helium liquefaction refrigeration apparatus, for example, Ps1 = 0.01 MpaG (about 0.1 kg / cm2G), Pd2 = 2.4 MpaG (about 24 kg / cm2G). The optimum range of the intermediate pressure Pd1 is 0.8 MpaG to 1.0 MpaG. The pressure ratio is mainly Pd1 / Ps1 = 9 to 11 as the operating pressure ratio of the low-stage compressor 100 that increases the pressure from the low pressure Ps1 to the intermediate pressure Pd1. On the other hand, the operating pressure ratio of the high-stage compressor 200 that increases the pressure from the intermediate pressure Pd1 to the high pressure Pd2 is Pd2 / Pd1 = 2.3 to 2.8. The input value of the scroll compressor 100 for helium serving as a low-stage compressor is W1 = about 5.8 kW at a stroke volume of 150 CC / rev and an operating frequency of 65 Hz. In addition, the input value of the helium scroll compressor 200 as a high-stage compressor is W2 = about 16.5 kW at a stroke volume of 150 CC / rev and an operating frequency of 65 Hz. The input ratio W2 / W1 = 270 to 280% and the input of the high-stage compressor 200 becomes high.

  For this reason, in order to reduce the input of the entire apparatus, it is possible to set the scroll wrap shape of the high-stage compressor to a set volume ratio Vr = 2.1 to 2.4 that is high in energy saving to meet the low pressure ratio condition. desirable. If the volume ratio Vr of the scroll wrap shape deviates from 2.1 to 2.4, the input of the entire apparatus tends to increase as shown in FIG. 10, and high performance cannot be realized. By setting the operating pressure ratio condition of this embodiment, it is possible to achieve a high pressure ratio of 24 to 26, which is a pressure ratio between high pressure and low pressure, and to provide a device with high energy saving performance. Among them, it is practically advantageous in terms of performance to set the scroll wrap-shaped set volume ratio Vr = 2.3.

  Next, the helium gas flow rate will be described with reference to FIGS. 11 and 12.

  FIG. 11 is a characteristic diagram showing the relationship between the intermediate pressure Pd1 and the helium gas flow rates Gs and Gh of the low-stage compressor 100 and the high-stage compressor 200 in the present embodiment. In addition, although the characteristic of the helium gas flow rate Gs of the rotary type compressor is illustrated for comparison by a one-dot broken line, a scroll compressor having a small internal leakage is advantageous as is apparent from this.

  As shown in FIG. 11, by setting the intermediate pressure Pd1 high, the helium gas flow rate Gh of the high-stage compressor 200 increases, while the helium gas flow rate Gs of the low-stage compressor 100 gradually decreases.

The refrigerator 300 is an example of an N ₂ gas shield plate refrigerator or a He gas pre-cooling refrigerator built in the container wall, and the cooling temperature is 20K level. On the other hand, the refrigerator 400 is an example of a refrigerator for cooling a superconducting magnet, and the cooling temperature is 4K level. When the refrigeration load of both 300 and 400 has a necessary capacity of 280 Nm ³ / h at an operation frequency of 75 Hz and an intermediate pressure of Pd1 = 0.8 MpaG, the intermediate pressure is set high to Pd1 = 0.85 MpaG. The capacity can be increased from point a to point b. Accordingly, the capability can be secured (point a) even if the operating frequency is lowered from 75 Hz to 65 Hz.

  These actions will be described with reference to FIG. FIG. 12 is a characteristic diagram showing the relationship between the helium gas flow rates Gh and Gs with respect to the operating frequency in the present embodiment. In FIG. 12, the value of the intermediate pressure Pd1 is shown as a parameter, and the capabilities of the intermediate pressure Pd1 = 0.7 MPaG condition and the Pd1 = 0.85 MPaG condition are compared and shown.

  The state change from point A to point B is as follows: the stroke volume Vth of the high stage compressor 200 is the same at 150 CC / rev, the intermediate pressure Pd1 is increased from 0.7 MPaG to 0.85 MPaG, and the operating frequency is increased from 75 Hz to 65 Hz. The case where it falls is shown. The state change from the point C to the point D increases the stroke volume Vth of the low-stage compressor 100 from 100 CC / rev to 150 CC / rev and increases the intermediate pressure Pd1 from 0.7 MPaG to 0.85 MPaG. The case where the frequency is reduced from 75 Hz to 65 Hz is shown. By increasing the intermediate pressure Pd1 to an appropriate range in this way, even if the operating frequency is lowered, the same ability can be secured with the deduction point A in the state of point B, and the ability is increased with point C in the state of point D. it can. The whole compressor input at the point B (point D) relative to the whole compressor input at the point A (point C) is 5 due to the effect of reducing the rotational speed of the compressors 100 and 200, as shown in FIG. % Reduction effect. In addition, when the operating state is changed from the point C to the state of the point D, a surplus capacity of the low-stage compressor 100 is generated. This is indicated by the symbol ΔG in FIG. This surplus refrigeration capacity is provided to the refrigeration load at the initial stage of startup which becomes higher than the normal refrigeration load, and the pull-down operation time can be shortened.

  In the present embodiment, the maximum refrigeration capacity at points E and F can be operated by increasing the operating state from point B (point D) to the conventional operating frequency (75 Hz). In the case where the conventional capacity is sufficient, 65 Hz / 75 Hz = 86%, and an effect that the stroke volume Vth is reduced by about 14% and the compressor can be reduced in size can be obtained.

  As described above, when the intermediate pressure Pd1 is set to an appropriate value, the Gs flow rate that can improve the input reduction effect of the compressor, the input reduction of the entire helium device, and the cooling effect of the entire liquid helium vessel by the operation at a lower operating frequency. From the viewpoint of ensuring the above, it is desirable to set the intermediate pressure Pd1 from 0.8 MpaG to 0.95 MpaG. Since the operating frequency of both the compressors 100 and 200 can be lowered, there is an effect that the life of the rolling bearing of the main bearing portion can be greatly extended.

  Next, a control method when the compressors 100 and 200 are driven by the inverter 900 from the stopped state will be described with reference to FIG. FIG. 13 shows changes in the helium gas flow rates Gs and Gh with respect to the operating frequency of the low-stage compressor 100 and the high-stage compressor 200 in the present embodiment.

  When the compressors 110 and 200 are driven by the inverter 900 from the stopped state, the frequency is not controlled according to the refrigeration load from the beginning, but first the temperature of each part of the compressors 110 and 200 is increased to some extent inside the compressor. In order to spread the lubricating oil, it is sufficient in terms of compressor reliability that the 60 Hz operation is forcibly continued for about 20 to 40 minutes in the initial stage of startup. In the inverter drive, first, the operation pattern in which the warm-up operation is performed is used. Thereafter, capacity control and frequency control are performed according to the refrigeration load. Points (a) to (f) in FIG. 13 indicate the helium gas flow rate at each frequency. As described above, Gh / Gs at each frequency is set to be around 10.

As described above, according to the present embodiment, the following operational effects can be achieved.
(1) The two compressors 100 and 200 are arranged in series in the helium liquefaction refrigeration apparatus 50, and the low-stage compressor 100 that boosts from low pressure to intermediate pressure, and the high-stage compressor 200 that boosts from intermediate pressure to high pressure. These two compressors 100 and 200 have the same stroke volume, so that the operating pressure ratio can be set to about half that of the conventional machine. The effect of improving volumetric efficiency by reducing internal leakage and the effect of cooling the superconducting coil in the liquid helium container can be improved. Further, by installing and using the two compressors 100 and 200 in the same manner, productivity can be improved, and the manufacturing cost of the compressor unit 258 and the compressors 100 and 200 can be reduced.
(2) By arranging the same compressors 100 and 200 and also using the same built-in inverter motor, the number of revolutions of the two compressors 100 and 200 can be simultaneously controlled by one inverter 900. The capacity controllability of both compressors 100 and 200 is simple and easy. In addition, when the refrigeration load is small, the operating frequency can be lowered and significant energy saving can be achieved. In addition, the life of the rolling bearing and, in turn, the life of the helium compressors 100 and 200 can be increased by inverter control.
(3) By setting the intermediate pressure within the optimum range, the high-stage compressor 200 can be reduced in size and energy can be saved, and the reliability can be greatly improved in connection with the item (2).
(4) The optimum setting of the intermediate pressure maximizes the load reduction effect that is input to the high-stage compressor 200. As a result, the entire apparatus is highly efficient and reliable with respect to the high pressure ratio. A helium liquefaction refrigeration apparatus can be provided.
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 14 is a diagram showing an overall configuration of a helium liquefaction refrigeration apparatus according to a second embodiment of the present invention. The second embodiment is different from the first embodiment in the points described below, and the other points are basically the same as those in the first embodiment, and thus redundant description is omitted.

  In the second embodiment, the discharge pipe 660 of the low-stage compressor 100 for increasing the pressure from the low pressure Ps1 to the intermediate pressure Pd1 is provided with a check valve means, and the suction pipe flow path 600 is provided with an electric valve means 610 such as an electromagnetic valve. It is a thing. This is because when the compressors 100 and 200 are stopped after the operation of the refrigeration cycle, the entire refrigeration cycle is balanced to one pressure, and the valve means 660, 610 is provided.

  For example, when the compressor stops under the pressure conditions of Ps1 = 0.1 kg / cm2G, Pd1 = 9.0 kg / cm2G, Pd2 = 24 kg / cm2G, the balance pressure PB is a relatively high pressure of 16 to 20 kg / cm2G. May be a level. When the two compressors 100 and 200 are restarted from the high balance pressure, the discharge pressure Pd1 of the low-stage compressor 100 becomes smaller than the balance pressure PB, and a reverse flow from the pipe 700 to the pipe 650 occurs. As a result, the load torque at the start of the low-stage compressor 100 increases, and the compressor input increases accordingly. In order to solve this problem, in this embodiment, the discharge pipe 660 is provided with a check valve means 660, and the suction pipe flow path 600 is provided with an electric valve means 610 such as an electromagnetic valve.

Note that even if the motor-operated valve means 610 of the suction pipe flow path 600 is omitted, the object of the present invention is not hindered. Further, only for the low-stage compressor 100, a reed valve type check valve means (not shown) may be attached to the upper portion of the discharge hole 10 of the compressor 100.
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 15 is a diagram showing an overall configuration of a helium liquefaction refrigeration apparatus according to a third embodiment of the present invention. The third embodiment is different from the second embodiment in the following points, and the other points are basically the same as those in the second embodiment, and thus redundant description is omitted.

  In the third embodiment, a pipe 645 that bypasses from the discharge pipe 650 side to the suction pipe 600 side of the low-stage compressor 100 that boosts from the low pressure Ps1 to the intermediate pressure Pd1 is provided, and a flow rate adjusting function is provided in the middle of the bypass pipe 645. The pressure reducing valve means 666 having the above is provided. A part of the excess helium gas flow rate Gs may be bypassed. The bypass pipe 645 includes a branch point 644 on the downstream side of the check valve means 660 provided in the discharge pipe 660 and a branch point 648 on the upstream side of the electric valve means 610 provided in the middle of the suction pipe flow path 600. It constitutes.

It is a figure which shows the whole structure of the freezing apparatus for helium liquefaction of 1st Embodiment. It is a figure which shows the structure of the compressor unit of FIG. It is a figure which shows the low stage compressor unit in 1st Embodiment of this invention. It is a top view of the fixed scroll of the low stage compressor of FIG. It is a longitudinal cross-sectional view of the fixed scroll of FIG. It is a top view of the turning scroll of the low stage compressor of FIG. It is a longitudinal cross-sectional view of the turning scroll of FIG. It is a front view of the low stage compressor or high stage compressor of 1st Embodiment. It is a top view of FIG. It is a characteristic figure of the compressor input to the intermediate pressure and intermediate pressure ratio in a 1st embodiment. It is a characteristic view of the helium gas flow rate to the intermediate pressure and the operating frequency in the first embodiment. It is a characteristic view which shows the relationship of the helium gas flow volume with respect to the operating frequency in this embodiment. It is a figure explaining the control method in this embodiment at the time of driving a compressor with an inverter from a stop state. It is a figure which shows the whole structure of the freezing apparatus for helium liquefaction of 2nd Embodiment of this invention. It is a figure which shows the whole structure of the freezing apparatus for helium liquefaction of 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Sealed container, 1a ... Discharge chamber, 1b ... Electric motor chamber, 3 ... Electric motor part, 3a ... Electric motor stator, 3b ... Electric motor rotor, 5 ... Fixed scroll, 5a ... Fixed scroll end plate, 5b ... Wrap, 5f ... Inhalation chamber, 6 ... Orbiting scroll, 6a ... Orbiting scroll end plate, 6b ... Wrap, 6c ... Boss part, 6p ... Orbiting scroll central tip, 7 ... Frame, 8 ... Compression chamber, 10 ... Discharge port, 13 ... Check valve, 14 ... Rotating shaft, 14a ... eccentric shaft, 14b ... motor shaft, 15 ... suction port, 17 ... suction pipe, 18a, 18b ... passage, 20 ... discharge pipe, 22 ... port, 23 ... lubricating oil, 27 ... oil suction pipe, DESCRIPTION OF SYMBOLS 30 ... Oil extraction pipe | tube, 30a ... Inflow part, 31 ... Oil injection pipe | tube, 32 ... Slewing bearing, 33 ... Oil cooler, 36 ... Oil piping, 38 ... Oldham mechanism, 39 ... Bearing part (auxiliary bearing), 40 ... Bearing (Main bearing 50 ... Refrigeration system for helium liquefaction, 53 ... O-ring, 250 ... Compressor unit, 258 ... Air-cooled helium compressor unit, 259 ... Load side refrigerator, 260 ... Joule-Thompson valve, 271 ... Throttle unit, 300, 400 ... refrigerator, 500 ... helium container, 600 ... suction pipe, 651 ... gas and oil cooler, 652 ... oil separation means, 700 ... suction pipe, 752 ... gas and oil cooler, 753 ... oil separation means, 754 ... Adsorber (oil adsorber), 900 ... Inverter, 1100, 1200 ... Compressor unit.

Claims (7)

In a refrigeration system for liquefaction of helium comprising an air-cooled helium compressor unit using a helium gas as a working gas and a load side refrigerator,
The air-cooled helium compressor unit includes a low-stage compressor unit having a low-stage compressor that boosts helium gas from a low pressure to an intermediate pressure, and helium gas compressed to an intermediate pressure by the low-stage compressor. With a high-stage compressor unit having a high-stage compressor that boosts from high pressure to high pressure,
The load side refrigerator includes a helium gas precooling refrigerator, a Joule Thomson valve, and a helium container for storing liquefied helium flowing down from the valve,
The stroke volume of the low stage compressor and the process volume of the high stage compressor are set to be the same, and the inverter motors of the low stage compressor and the high stage compressor are set to be the same, and the low stage compression is set. The helium liquefaction refrigeration apparatus, wherein the motor and the high-stage compressor are driven and controlled at the same rotational speed by a single inverter.   2. The refrigeration apparatus for liquefaction of helium according to claim 1, wherein the low volume compressor and the high volume compressor have the same scroll tooth profile with a set volume ratio of 2.1 to 2.4 of the scroll wrap portion. .   In Claim 2, the operating pressure ratio of the low stage compressor is set to 9 to 11 and the operating pressure ratio of the high stage compressor is set to 2.3 to 2.8, so that the pressure between the high pressure and the low pressure is set. A helium liquefaction refrigeration apparatus characterized in that a high pressure ratio as a ratio is 24 to 26.   4. The refrigeration apparatus for helium liquefaction according to claim 3, wherein a check valve is provided on the discharge side of the low stage compressor.   The low-stage compressor according to claim 3, further comprising a check valve on a discharge side of the low-stage compressor and on a low-stage compressor side of a pipe from the helium gas precooling refrigerator to the high-stage compressor. A bypass pipe that bypasses from the low-stage compressor side to the suction side of the low-stage compressor from the check valve, and a pressure reducing valve means that has a flow rate adjusting function in the middle of the bypass pipe. A refrigeration system for liquefaction of helium. A low-stage compressor unit having a low-stage compressor that uses helium gas as a working gas and raises the helium gas from a low pressure to an intermediate pressure, and the helium gas compressed to an intermediate pressure by the low-stage compressor from the intermediate pressure. A high-stage compressor unit having a high-stage compressor for increasing the pressure to a high pressure, helium gas precooling refrigerator, Joule Thomson valve, and helium container for storing liquefied helium flowing down from the valve, helium in the load-side refrigerator In the air-cooled helium compressor unit that supplies gas,
The stroke volume of the low stage compressor and the process volume of the high stage compressor are set to be the same, and the inverter motors of the low stage compressor and the high stage compressor are set to be the same, and the low stage compression is set. The air-cooled helium compressor unit, wherein the compressor and the high-stage compressor are driven and controlled at the same rotational speed by a single inverter.   The operation pressure of the low-stage compressor according to claim 6, wherein the low-stage compressor and the high-stage compressor have the same scroll tooth profile with a set volume ratio of 2.1 to 2.4 of the scroll wrap portion. The ratio is set to 9 to 11 and the operating pressure ratio of the high-stage compressor is set to 2.3 to 2.8, and the high pressure ratio that is the pressure ratio between the high pressure and the low pressure is set to 24 to 26, A check valve is provided on the discharge side of the low-stage compressor and on the low-stage compressor side of the pipe from the helium gas precooling refrigerator to the high-stage compressor, and on the discharge side of the low-stage compressor and the An air-cooled type comprising a bypass pipe for bypassing from a low-stage compressor side to a suction side of the low-stage compressor from a check valve, and having a pressure reducing valve means having a flow rate adjusting function in the middle of the bypass pipe Helium compressor unit.

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