JPH10311616A - Cryogenic refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power loss by lubricating and cooling efficiently the inside of bore of a screw compressor for a cryogenic refrigerating machine. SOLUTION: A cryogenic refrigerating machine is constituted of a liquefying means (heat exchangers 3-8, JT valve 9), liquefying a part of gas to be liquefied, which is compressed by a screw compressor 1a which receives a pair of male and female rotors for compressing the gas to be liquefied in the bore thereof, through adiabatic expansion and supplying produced liquefied gas and non- liquefied gas into a cryogenic box 10, a first gas returning passage 12, circulating the non-liquefied gas in the cryogenic box 10 between the engaging teeth of the pair of rotors of the compressor 1a, a second gas returning passage 25, introducing a part of non-liquefied gas from at least either one of the cryogenic box 10 or the first gas returning passage 12 and supplying the same into a low pressure part 26 in a bore excluding a bore high-pressure part (gas compressing chamber), a lubricating oil spraying and supplying means (gas passage 25, oil separator 16, lubricating oil discharging passage 28, choking device 29), which mixes the mist of lubricating oil into the non-liquefied gas in the passage 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to helium, nitrogen,
For cryogenic refrigerators that liquefy low-boiling gas such as oxygen,
In particular, the present invention relates to a cryogenic refrigerator in which the inside of a bore of a compressor is lubricated and cooled with a mixed gas of low-temperature unliquefied gas and lubricating oil spray.

[0002]

2. Description of the Related Art Generally, a cryogenic refrigerator for liquefying a low-boiling gas such as helium, nitrogen, or oxygen is provided with a high-temperature and high-pressure liquefied liquid discharged from a compressor in a cold box kept in a vacuum for heat insulation. The gas is sent through a gas supply passage, pre-cooled by a cooling device of a heat exchanger in a cold box, and then supplied to a Joule-Thomson valve (hereinafter referred to as a JT valve) to partially liquefy the gas. This liquefied gas and the unliquefied gas that has not been liquefied at this stage are supplied to the cryobox, and only the unliquefied gas is returned to the compressor via a gas return passage communicating the cryobox with the suction port of the compressor. And recompressed.

FIG. 2 is a cycle diagram of the cryogenic refrigerator studied by the present inventors. 1 is a compressor, 2 is a cold box, and 3 to 8 are heat exchangers for pre-cooling a liquefied gas. ,
9 is a JT valve, 10 is a cryobox, 11 is a gas supply passage, and 12 is a gas return passage. The compressor 1 is disposed outside the cold box 2 and has a discharge port 1 of the compressor 1.
Gas supply passage 1 that communicates with the cryobox 3
1 is penetrated through one side wall of the cold box 2 and the ceiling of the cryo-box 10 and is inserted deeply near the bottom thereof, and a gas return passage 12 communicating the suction port 14 of the compressor 1 and the cryo-box 10 has a storage space. It is inserted shallowly to a position appropriately separated upward from the liquid surface (liquefied gas).

The heat exchangers 3 to 8 are connected to a gas supply passage 11.
The gas supply passage 11 and the gas supply passage 11 are provided in a multi-stage manner upstream of the JT valve 9 so as to exchange heat with each other.
Between the first heat exchanger 3 and the second heat exchanger 4 of the gas return passage 12 between the second heat exchanger 4 and the third heat exchanger 5 via the first bypass passage 13a, Between the third heat exchanger 5 and the fourth heat exchanger 6 in the gas supply passage 11, between the fourth heat exchanger 6 and the fifth heat exchanger 7 in the gas return passage 12 via the second bypass passage 13 b. A part of the liquefied gas, which has been cooled, is supplied to the gas return passage 12 by expanders 14a and 14b such as expansion turbines which are communicated with each other and are provided in the first bypass passage 13a and the second bypass passage 13b. Has become. Further, an oil separator 16 and a mist separator 17 are sequentially provided in the gas supply passage 11 outside the cold box 2 from the upstream side to the downstream side with an interval therebetween to cool the liquefied gas. The oil cooler 15 is interposed in the lubricating oil collecting passage 28 to cool the lubricating oil.

According to the cryogenic refrigerator, the purified liquefied gas is supplied to each of the heat exchangers 3 to 8 in the cold box 2.
Pre-cooled to a predetermined temperature, for example, about 80 ° K,
After passing through the JT valve 9, the liquefied gas, which has become low in temperature after the precooling, undergoes adiabatic expansion, a part of which becomes liquid, and the remaining part becomes steam of the same temperature.

Incidentally, the JT valve 9 utilizes a cooling effect (Joule-Tamson effect) due to thermal free expansion of the gas when the gas permeates and diffuses through a throttle or a porous body, and a part of the liquefied gas passing therethrough. The liquefaction is performed, and the liquid and the remaining wet steam are supplied to the cryo-box 10. The degree of liquefaction is generally about 5 to 10% of the flow rate. In this liquefaction, the unliquefied gas (wet steam) not liquefied by the JT valve 9 is added to the cryobox 10 together with the liquefied gas.
And only the liquefied gas is retained therein, and the wet steam or the saturated steam flows through the gas return passage 12 through the suction port 1 of the compressor 1.
Inhaled in 4. Therefore, a liquefied gas take-out pipe (not shown) penetrating the cryobox 10 and one side wall of the cold box 2 may be formed, or a low-temperature take-out heat exchanger for exchanging heat with the liquefied gas (see FIG. If not installed), it is possible to take out cryogenic gas using a liquefied gas as a refrigeration source.

[0007]

However, if the entire equipment including the compressor is enlarged in accordance with the recent increase in the consumption of liquefied gas, the rotating and sliding parts of the compressor are lubricated and cooled. There is a problem in that the amount of lubricating fluid used significantly increases, and the resistance increases the power loss. Particularly, as the compressor, as shown in FIGS. 3A and 3B, a pair of bores 18a and 18 communicating with each other along the axial direction.
b, a pair of rotatable male and female rotors 19a and 19b rotatably accommodated with each other, and between the meshing teeth of the pair of rotors 19a and 19b and the respective bores 18a and 1b.
The gas compression chamber 22 is formed by the bore inner surfaces 21a and 21b of the bore 8b, and the bore inner surfaces 21a and 21b and the rotors 19a and 19b are formed.
In order to use the screw compressor 1a configured to inject and supply the lubricating oil between the outer peripheral surface of the tooth b and the seal, the stirring resistance of the rotors 19a and 19b with respect to the lubricating oil O increases to a considerable extent. I will.

An object of the present invention is to efficiently spray-lubricate and cool the inside of a screw compressor as a compression source of a cryogenic refrigerator and reduce power loss caused by lubricating oil stirring resistance.

Japanese Patent Laid-Open Publication No. Sho 60-237183 discloses a related technique for improving lubrication of an oil-lubricated compressor, which includes an oil mist in a flow passage from a discharge port of an oil-cooled compressor body to an oil recovery unit. Is disclosed that supplies a part of a compressed gas containing a gas to a lubrication point of a compressor. However, even if compressed gas can be supplied to a low-pressure part such as a bearing part,
It is difficult to directly supply the compressed gas to the part involved in compression because of the pressure balance, and in the configuration in which part of the compressed gas is returned to the compressor side for lubrication and cooling, the There is also a problem that the discharge capability of the liquid crystal is reduced.

[0010]

The above object is achieved by the following constitution. According to the first aspect of the present invention, a pair of bores communicating with each other along the axial direction and a pair of bores rotatably housed in the bores, respectively, are engaged with each other to compress the liquefied gas introduced between the teeth. Male rotor to be discharged, a screw compressor having a female rotor, and the liquefied gas supplied from the compressor is adiabatically expanded and partially liquefied,
Liquefaction means for supplying the liquefied gas and the unliquefied gas generated by the adiabatic expansion to the cryobox, and the cryobox with respect to a gas compression chamber formed between the meshing teeth of the male rotor and the female rotor of the compressor. A first gas return passage for recirculating the unliquefied gas, and a part of the unliquefied gas taken from at least one of the crybox or the first gas return passage. A second gas return passage for supplying the gas to the gas compression chamber or the other low-pressure portion in the bore, and a lubricating oil spray supply means for mixing lubricating oil into unliquefied gas in the second gas return passage in a spray form And characterized in that:

According to the first aspect of the present invention, a part of the unliquefied gas retained in the crybox is mixed with a lubricant spray by a lubricant spray supply means, and the mixed gas is supplied to a low-pressure bore portion. The lubricating unit cools and lubricates the low-pressure portion in the bore, that is, between the pair of male and female rotors and the bore inner surface, while directly supplying all the liquefied gas discharged from the compressor to the JT valve.

In this case, the supply of the mixed gas of the unliquefied gas and the lubricating oil spray to the low pressure portion in the bore of the compressor is performed by the unliquefied gas from at least one of the cryobox and the second gas return passage. It is preferable to provide a gas pumping means for inhaling gas (wet or saturated vapor retained in the cryobox) and for pumping the gas to the low-pressure portion in the bore.
(Claim 2).

Further, in order to cope with an increase in gas temperature due to the pressurization of the gas pressure feeding means, in the invention according to claim 1 or 2, the temperature of the unliquefied gas is decreased in the second gas return passage. It is preferable to provide a cooling means (claim 3).

In order to generate the mixed gas of the unliquefied gas and the spray of the lubricating oil without using a special pressurizing device,
In the invention according to any one of claims 1 to 3, the lubricating oil spray supply unit separates the lubricating oil from the compressed liquefied gas after compression, before liquefaction, and transfers the lubricating oil to the lubricating oil discharge passage. And a throttle or a nozzle communicating the outlet of the lubricating oil discharge passage and the second gas return passage. The atomization of the lubricating oil is performed by the decompression effect generated by the throttle. Preferably, mixing is performed (claim 4).

Further, in order to perform gas pressure feeding to the second gas return passage by utilizing energy held by the refrigerator, the refrigerator according to any one of claims 2 to 4,
A compressor blower interposed in the second gas return passage for pumping a part of the unliquefied gas remaining in the cryobox to the low-pressure portion in the bore; and a compressor blower after the precooling and before the liquefaction. It is preferable to include an expansion turbine that recovers energy by introducing a part of the liquefied gas, and power transmission means that transmits a rotational driving force of the expansion turbine to the compressor blower.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. However, the same configuration as the configuration already described in the section of the prior art or the same configuration is the same. The reference numerals are used and the detailed description is omitted. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely mere examples. It is only an explanation.

FIG. 1 is a cycle diagram of a cryogenic refrigerator according to one embodiment of the present invention, and FIG. 3 is a sectional view showing a structure of a screw compressor used in the cycle. As shown, a suction port 14 of a screw compressor (hereinafter referred to as a compressor) 1a and a discharge port 13 of the compressor 1a.
Are the first gas return passage 12 and the gas supply passage 1
1 and is connected to the cryo-box 10 so as to recirculate the gas.
The first and sixth heat exchangers 3 to 8 are sequentially provided from upstream to downstream so that heat can be exchanged between the passages 11 and 12 in the gas supply passage 1 and the gas return passage 12.
A JT valve 9 for liquefaction is interposed between the sixth heat exchanger 8 and the cryobox 10 of FIG. 15 is an oil cooler.

The gas supply passage 11 between the first heat exchanger 3 and the second heat exchanger 4 is connected to the second heat exchanger 4 of the gas return passage 12 via the first bypass passage 13a. The gas supply passage 11 communicated with the heat exchanger 5 and between the third heat exchanger 5 and the fourth heat exchanger 6 communicates with the fourth heat exchanger 6 via the second bypass passage 13b. The first and second bypass passages 13 communicate with the fifth heat exchanger 7.
a, an expander 14 such as an expansion turbine interposed between 13b
A part of the liquefied gas whose temperature has been reduced by the adiabatic expansion of the a and b is supplied to the first gas return passage 12.

In the cryogenic refrigerator described above, in order to lubricate and cool the compressor 1a without using a part of the gas to be liquefied immediately after discharge from the compressor 1a, it is necessary to recycle unliquefied gas to the compressor 1a. It is preferable that a part of the gas is used as a cooling gas, and this unliquefied gas is used as a carrier medium for spraying the lubricating oil.

Therefore, in this embodiment, the low pressure portion in the bore of the compressor 1a, that is, the female rotor 19a and the male rotor 19
A second gas return passage 25 is communicated with the bore except for the gas compression chamber 22 (see FIG. 3A) formed between the teeth meshing with each other and the bore inner surfaces 18a and 18b. The portion 26 is configured to be supplied with a part of the unliquefied gas from the first gas return passage 12.

In the middle of the second gas return passage 25, a compressor blower 27 (rotary compressor) is interposed, and the compressor blower 27 causes a part of the unliquefied gas to flow from the first gas return passage 12. Is the low pressure part 2 in the bore
6 to be pumped. In order to drive the compressor blower 27 as a compressor, the second gas supply pipe 34 connects the first heat exchanger 3 and the mist separator 17 in the gas supply passage 11 with each other. An expansion turbine 35 is interposed in the gas supply pipe 34, and the expansion turbine 35 and the compressor blower 27 are connected by a shaft 36 serving as power transmission means. That is, if the expansion turbine 35 is used as the drive source of the compressor blower 35, the thermal energy possessed by the refrigerator can be effectively used, and the equipment and cost can be obtained.

Of course, it is also possible to use a variable capacity turbine for controlling the capacity by adjusting the nozzle throat area as the expansion turbine 35, and to use a sun gear or a planetary gear as shown in FIG. It is also possible to optimally adjust the rotation of the compressor blower 27 using a planetary gear mechanism including a gear, an external gear, an idle gear, and an output gear.

Further, in order to lower the temperature of the unliquefied gas in the second gas return passage 25 and mix the lubricating oil spray with the unliquefied gas, lubricating oil is supplied from the oil recovery device 16 to the second gas return passage 25. The outlet of the lubricating oil recovery passage 28 to be recovered is communicated through a throttle (orifice) 29, and the upstream of the throttle 29 connection portion of the second gas return passage 25 and the downstream of the compressor blower 27, A cooling device, for example, a water heat exchanger 30, for regulating the temperature rise of the unliquefied gas due to the pressurization of the blower 27 is provided.

A first on-off valve 31 is interposed between the throttle 29 connection portion of the second gas return passage 25 and the water exchanger 30, and in the middle of the lubricating oil passage 28. , A second on-off valve 32 is provided. That is, when the compressor 1a is operated, the first on-off valve 31 and the second on-off valve 32 are opened, and the pump 33 of the water heat exchanger 30 is operated to circulate water as a cooling medium. When the closing is completed, the lubricating oil in the lubricating oil discharge passage 28 is atomized by the negative pressure of the unliquefied gas acting on the throttle 29 and is sucked into the second gas return passage 25, and the bore of the compressor 1a is bored. Inner low pressure part 26
Is lubricated with a mixed gas of this lubricating oil spray and unliquefied gas.
All of the liquefied gas cooled and compressed by the compressor 1 is JT
The liquefaction of the valve 9 is provided. As described above, in the cryogenic refrigerator according to the present embodiment, it is possible to lubricate and cool the low-pressure portion 12 in the bore with the mixed gas of the lubricating oil and the unliquefied gas, 1 operation can be performed.

The first opening / closing valve 31 can be used as a flow control valve to adjust the negative pressure to the throttle 29. The gas supply passage 11 and the lubricating oil supply passage 28 are communicated by a passage 38. By using a valve 37 for this, a part of the unliquefied gas (discharge gas) immediately after the mist separator 17 can be used for spraying.

[0026]

As described above, according to the present invention, the following excellent effects are exhibited. (1) The lubricating oil can be lubricated and cooled between the outer peripheral surface of the pair of rotors of the male and female rotors of the screw compressor and the inner surface of the bore by spraying the lubricating oil. Can be provided. (2) Since unliquefied gas (steam staying in the cryobox) is sucked from at least one of the cryobox and the second gas return passage and pumped to the low pressure portion in the bore, at least the bore The low-pressure part can be reliably lubricated and cooled. (3) Since the cooling means for lowering the temperature of the unliquefied gas is provided in the second gas return passage, it is possible to cope with an increase in temperature due to the pressurization of the gas pressure feeding means. (Claim 3). (4) The mixed gas of the unliquefied gas and the spray of the lubricating oil can be generated without using a special power unit. (5) Gas pressure feeding to the second gas return passage can be performed by utilizing energy possessed by the refrigerator (claim 5).

[Brief description of the drawings]

FIG. 1 is a cycle diagram of a cryogenic refrigerator according to the present invention.

FIG. 2 is a cycle diagram of a conventional cryogenic compressor.

FIG. 3 is a cross-sectional view illustrating a structure of a screw compressor.

[Explanation of symbols]

 1a Screw compressor 3-8 Heat exchanger (liquefaction means) 9 JT valve 10 Cryobox 18a, 18b Bore 19a Female rotor 19b Male rotor 12 First gas return passage 16 Oil separator (lubricant spray supply means) 25th Second gas return passage 27 Compressor blower (gas pumping means) 28 Lubricating oil discharge passage (lubricant spray supply means) 29 Throttle (lubricant spray supply means) 30 Water heat exchanger (cooling means) 35 Expansion turbine 36 Shaft (power) Transmission means)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masami Obama 2-13-1, Botan Koto-ku, Tokyo Inside Maekawa Works Co., Ltd. (72) Inventor Masato Noguchi 2-13-1 Botan Koto-ku, Tokyo Stock (72) Inventor Katsumi Fujima 2-13-1, Botan, Koto-ku, Tokyo Inside Maekawa Corporation

Claims (5)

[Claims] A male rotor rotatably accommodated in each of a pair of bores communicating with each other along an axial direction, and rotatably housed in the bores and compressing and discharging the liquefied gas introduced between the teeth. A screw compressor having a female rotor, and adiabatically expanding the liquefied gas supplied from the compressor to partially liquefy the liquefied gas, and supplying the liquefied gas and the unliquefied gas generated by the adiabatic expansion to the cryobox. A first gas return passage for recirculating unliquefied gas in the cryobox to a closed space formed by meshing the bore of the compressor, the female rotor, and the female rotor with each other. And taking in a part of the unliquefied gas from at least one of the crybox or the first gas return passage and transferring it to the gas compression chamber or other A second gas return passage for supplying a low-pressure portion in the bore, and lubricating oil spray supply means for mixing lubricating oil in a spray state with the unliquefied gas in the second gas return passage. Low temperature refrigerator. 2. The cryogenic refrigerator according to claim 1, wherein the second gas return passage sucks an unliquefied gas from the cryobox or the first gas return passage and sends the unliquefied gas to the compressor. A cryogenic refrigerator having a gas pumping means for pumping a gas to a low pressure portion in a bore. 3. The cryogenic refrigerator according to claim 1, wherein cooling means for lowering the temperature of the unliquefied gas is provided in the second gas return passage. The cryogenic refrigerator described. 4. The cryogenic refrigerator according to claim 1, wherein the lubricating oil spray supply unit separates the lubricating oil from the liquefied gas discharged from the compressor after compression and before liquefaction. And an oil separator for discharging the lubricating oil through a lubricating oil discharge passage, and a throttle or a nozzle communicating the outlet of the lubricating oil discharge passage with the second gas return passage. Characterized cryogenic refrigerator. 5. The cryogenic refrigerator according to any one of claims 2 to 4, wherein the gas pumping means stays in the cryobox at a low-pressure portion in the bore provided in the second gas return passage. A compressor blower that pumps a part of the unliquefied gas to be compressed, an expansion turbine that introduces a part of the unliquefied gas before the liquefaction after pre-cooling, and recovers its energy, and a rotational driving force of the expansion turbine to the compressor blower. And a power transmission means for transmitting the power.