JPH02263063A - Supercryogenic refrigerating machine - Google Patents

Abstract

PURPOSE:To shorten the time for the cooling down to a specified level of supercryogenic temperature by providing a means for altering the opening of a nozzle passageway in area and b increasing by mans of this means the opening of the nozzle passageway in area when the temperature of the actuating fluid is high. CONSTITUTION:When the operation is started with actuating fluid at a high temperature, that is, at room temperature, a valve 36 is actuated to open the first nozzle passageway 33a in a first nozzle 33 so that the actuating fluid is ejected into a first nozzle opening 29 also from the first nozzle passageway 33a. Although the high temperature makes the flow of the actuating fluid larger in valume than at a supercryogenic temperature level, the actuating fluid is given a passage with an increased area, since it passes through both the first nozzle passageway 33a and a second nozzle passageway 34a. This increase in area of the passage makes it possible, even at the start-up, to pass the actuating fluid at the same mass flow rate (m1) a at a supercryogenic temperature level while the expansion-pressure ratio is held smaller than the critical expansion-pressure ratio. As a result, a considerable cut can be achieved in the time for the cooling from the room temperature to a supercryogenic point.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a cryogenic refrigeration system with a turboexpander.

(Prior Art) Conventionally, cryogenic refrigeration equipment having a turbo expander is known. This cryogenic refrigeration equipment uses a radiator to absorb the heat of a working fluid with extremely low content, such as helium, compressed by a compressor.The working fluid that has passed through the radiator is then expanded by a turbo expander, and the expanded working fluid absorbs heat. The frozen food will be taken out at the freezer removal section.

The turbo expander used in this cryogenic refrigeration equipment is
It includes a housing having a turbine hole, and a turbine supported in the turbine hole of the housing via a turbine shaft. The turbine shaft is supported in the thrust direction via a thrust bearing.

The high-pressure working fluid compressed by the compressor and heat removed by the radiator is injected from the inlet side to the turbine, causing the turbine to rotate and expanding the working fluid.

Here, if the absolute force on the inlet side of the working fluid in the turbo expander is pa, the absolute pressure inside the housing is pb, and the absolute pressure on the expansion side, that is, the outlet side, of the working fluid is PC, then pa>pb > pC. When the expansion pressure ratio (Pa/Pc) increases, the thrust acting on the turbine shaft that supports the turbine becomes too large, exceeding the load capacity of the thrust bearing that supports the turbine shaft in its thrust direction, and the turbine The rotation of the shaft becomes irregular. In conventional turbo expanders, the expansion pressure ratio (r=Pa/P
c) is called the critical expansion pressure ratio (rcr).

(Problem to be Solved by the Invention) In the turbo expander as described above, the relationship between the mass flow rate supplied to the turbo expander and the expansion pressure ratio (r=Pa/PC) is shown in FIG. . The characteristic line x1 in FIG. 4 shows the case when the temperature of the working fluid reaches an extremely low temperature.
The characteristic line X2 in FIG. 4 shows the case where the temperature of the working fluid is room temperature. As shown by the characteristic line x1 in FIG. 4, when the mass flow rate is m1, the expansion pressure ratio when the cryogenic temperature is reached is rl. This expansion pressure ratio (rl) is set smaller than the above-mentioned limit expansion pressure ratio (rcr). The reason is that the expansion pressure ratio is the critical expansion pressure ratio (
rcr), as described above, the thrust acting on the turbine shaft increases excessively, and the rotation of the turbine and the turbine shaft is inhibited.

By the way, when the cryogenic refrigeration system starts operating, the temperature of the working fluid is high and close to room temperature.

Here, the volume of the working fluid basically increases in proportion to the value of the absolute temperature, so even if the mass flow is the same 1 ml, the volumetric flow rate of the working fluid at the start of operation increases significantly compared to when the temperature reaches a low temperature. .

Here, the size of the expansion pressure ratio obtained with the turbo expander is:
It increases as the volumetric flow rate of the working fluid supplied to the turbo expander increases. Therefore, as shown by the characteristic line X2 in FIG. 4, when a mass flow rate m1 is supplied to the turbo expander at room temperature, the expansion pressure ratio (Pa/Pc) becomes r2,
The critical expansion pressure ratio (rcr) is exceeded, and the thrust acting on the turbine shaft supporting the turbine becomes large, exceeding the load capacity of the thrust bearing, and the smoothness of rotation of the turbine is impaired.

Therefore, in the turbo expander used in conventional cryogenic refrigeration equipment, at the start of operation when the working fluid is high temperature, the fourth
As is clear from the characteristic line ×2 in the figure, the mass flow rate is reduced from ml to m2, the expansion pressure ratio is set to r2-, and as the temperature of the working fluid decreases and approaches cryogenic temperature, the mass flow rate of the working fluid is reduced to m2. We plan to increase the amount from ml to ml.

In this way, in conventional cryogenic refrigeration equipment, the mass flow rate of the working fluid supplied to the turbo expander must be reduced from ml to m2 at the start of operation, so a cool-down process is required to cool the fluid to a predetermined cryogenic temperature range. There is a problem that takes a very long time.

The present invention was developed in view of the above-mentioned problems, and it is an object of the present invention to provide a cryogenic refrigeration system that is advantageous in shortening the time required for cooling down to a predetermined cryogenic temperature range.

[Structure of the Invention] (Means for Solving the Problems) The cryogenic refrigeration apparatus of the present invention includes a compressor that compresses a cryogenic working fluid, a radiator that takes heat from the working fluid compressed by the compressor, It is composed of a turbo expander that expands the working fluid that has passed through the radiator, and a refrigeration take-out section that takes out the frozen working fluid that has been expanded by the turbo expander as it absorbs heat. , a rotatable turbine disposed in a turbine hole of the housing;
It consists of a nozzle passage disposed in the housing that injects working fluid to the turbine to rotate the turbine, and a variable opening area member that changes the opening area of the nozzle passage, and when the temperature of the working fluid is high, the variable opening area member This feature is characterized in that the opening area of the nozzle passage is increased.

The variable opening area member may be any member that allows the opening area of the nozzle passage to be varied, and its structure can be appropriately selected as necessary. For example, an appropriate number of nozzle passages may be formed, and an opening/closing valve or opening/closing wing may be provided as a variable opening area member for opening and closing at least one of the nozzle passages.

Note that the turbo expander may be either an impulse type or a reaction type.

(Operation) When the temperature of the working fluid is high, the opening area variable member increases the opening area of the nozzle passage, increasing the flow path area of the working fluid.

(Embodiments) (1) First Embodiment A first embodiment of the cryogenic refrigeration apparatus of the present invention will be described below.

First, the overall structure of the cryogenic refrigeration system will be explained, and then the main structure, the turbo expander, will be explained.

This cryogenic refrigeration system uses a reverse Preyton cycle as shown in Fig. 1, and includes a turbo compressor 10 that compresses a cryogenic working fluid, and a a radiator 11 that takes the heat, a counterflow heat exchanger 12, a turbo expander 13 that expands the working fluid that has passed through the radiator 11, and a refrigeration extractor that takes out the frozen working fluid that is expanded by the turbo expander 13 as it absorbs heat. 14, a cooled object 15 located close to the frozen extraction section 14, and a flow path 16 connecting these.

This cryogenic refrigeration equipment is filled with helium, neon, nitrogen gas, etc. as a working fluid. When the cryogenic refrigeration system is operated, the working fluid is compressed by the turbo compressor 10 connected to a motor (not shown), flows into the radiator 11, and is operated by the cooling fluid (water, air, etc.) flowing through the flow path 17. The heat of compression of the fluid is removed. The working fluid then enters the counterflow heat exchanger 12 and is cooled by the returning working fluid before entering the turboexpander 13 . Since the pressure energy and velocity energy of the working fluid are absorbed by the turbo expander 13, the working fluid expands while absorbing heat, and its temperature decreases. In other words, a freezing effect is generated.

The working fluid that has generated the freezing effect flows into the frozen extraction section 14 and cools the object 15 to be cooled. The working fluid then enters the counterflow heat exchanger 12 to cool the working fluid entering the turbo expander 13 and turbo compression returns to 10. This cycle is repeated and the object to be cooled 15 reaches an extremely low temperature (
It is usually cooled to -170'C to -269°C.

Next, the configuration of main parts will be explained with reference to FIGS. 2 to 4. That is, the turbo expander 1 for cryogenic refrigeration equipment of this embodiment
3 is an impulse type turbo expander 13, as shown in FIG. It is formed of a second housing part 22 and a third housing part 23 connected to the first housing part 21. In the housing 20, a circular turbine hole 26 is formed in a part of a side wall forming a bearing chamber 25, and an expansion chamber 27 connected to the frozen extraction section 14 is formed. As shown in FIG. 3, a ring body 28 is disposed in the housing 20, and a spiral first nozzle hole 29 is formed at one end of the ring body 28.
A spiral second nozzle hole 3 is provided at the other end of the ring body 28.
0 is formed.

Furthermore, as shown in FIG. 3, a first nozzle 33 and a second nozzle 34 are arranged in parallel along the circumferential direction of the housing 20 at positions facing each other. The first nozzle 33 and the second nozzle 34 supply the working fluid that has passed through the heat exchanger 12 of the reverse Preyton cycle described above.

Here, the first nozzle 33 forms a first nozzle passage 33a with a predetermined opening area, and the second nozzle 34 forms a second nozzle passage 34a with a predetermined opening area. The tip 33b of the first nozzle 33 is arranged to face the first nozzle hole 29. The tip 34b of the second nozzle 34 is arranged to face the second nozzle hole 30. As shown in FIG. 2, the first nozzle 33 is provided with an opening/closing valve 36 as a variable opening area member that opens and closes the first nozzle passage 33a.

Furthermore, a turbine 37 is rotatably disposed in the turbine hole 26 of the housing 20 with a small gap between the turbine hole 26 and the wall surface that partitions the turbine hole 26 . As shown in FIG. 3, a large number of impeller portions 37a are formed in the turbine 37 at predetermined intervals in the circumferential direction thereof.

Furthermore, as shown in FIG. 2, a turbine 37 is held at one end of this turbine shaft 38. The turbine shaft 38 is held by a hydrodynamic gas bearing 39.

This hydrodynamic gas bearing 39 is a tilting pad type hydrodynamic gas bearing, and is attached to a stem 4 fixed to the housing 20.
It is held by 0. Further, a flange portion 38a is formed in the midsection of the turbine shaft 38 in a radially outward direction, and the seventh rank portion 38a is supported facing the gas thrust bearing 42. The gas' thrust bearing 42 is a spiral group type hydrodynamic gas bearing. The gas thrust bearing 42 supports the flange portion 38a of the turbine shaft 38 in the thrust direction.
Supported by a gas film of approximately 0 μm. Gas thrust bearing 42
The load capacity of the turbine shaft 38 is set small in order to reduce loss during high-speed rotation of the turbine shaft 38 and to be suitable for high-speed rotation. This gas thrust bearing 42 is held by a gimbal ring 44 via a pivot 43, and this gimbal ring 44 is further held by a stem 46 via a pivot 45.

Moreover, this turbine shaft 38 has a synchronous generator 48 installed in its midsection.
The rotor 49 is a part of the rotor 49. A magnet is embedded in the rotor 49. Further, there is a stator 50 fixed by the housing 20 in the bearing chamber 25 so as to face the rotor 49, and the stator 50 and the rotor 49 work together to perform synchronous power generation 48.

The operation of the above-mentioned turbo expander 13 will be explained. First, for convenience of explanation, a description will be given of the time when the extremely low temperature is reached. That is, when the cryogenic temperature is reached, the on-off valve 36 is closed and the first nozzle passage 33a is closed, so that the high-pressure cryogenic working fluid that has passed through the turbo compression 1110 of the reverse Preyton cycle is as shown in FIG. It flows into the second nozzle hole 30 via the second nozzle passage 34a of the second nozzle 34 and the chamber 20a. As a result, the pressure energy of the cryogenic working fluid is converted into velocity energy and the turbine 3
7 and rotates the turbine 37 together with the turbine shaft 3B. Thereafter, the working fluid flows out into the expansion chamber 27, as is clear from FIG. Here, the turbine shaft 38 is supported by a hydrodynamic gas bearing 39 with a gas film of about 10 μm.

Further, in the turbo expander] 3 according to this embodiment, the kinetic energy of the working fluid is absorbed by the synchronous generator 48 formed by the rotor 49 and the stator 50. The rotational speed of this turbine shaft 38 reaches from 0.5 rpm to several hundreds of thousands of rpm when the temperature reaches an extremely low temperature.

Here, the absolute pressure at the working fluid inlet, that is, the second nozzle passage 34a is Pa, the absolute pressure in the bearing chamber 25 is Pb, the pressure in the expansion chamber 27 is pc, and the outer diameter of the turbine 37 is Dt. Assuming that the inner diameter of the outlet to the expansion chamber 27 is [)0, a thrust (FO) acts on the turbine shaft 38 in its axial direction. This thrust (Fq) is the second
Acts in the direction of the arrow in the figure.

The thrust (PCI) is considered to be expressed as the following equation.

FCl-(π/4>Dt2・Pb-((yr/4) (Dt2-DO2)-Pa0(
π/4)Do2・Pc) However, pa>Pb>PC, Dt>[)0 In this embodiment, as described above, the load capacity of the gas thrust bearing 42 is set to reduce the loss when the turbine shaft 38 rotates at high speed. This is set to a small value. Therefore, the expansion pressure ratio (
When r=Pa/Pc) becomes, for example, 2 or more, the thrust (Fg) becomes larger than the load capacity of the gas thrust bearing 42, as explained in the prior art section, and the 7th rank portion 38a of the turbine shaft 38 becomes gas thrust This results in solid contact with the bearing 42.

In this embodiment, at the start of operation when the temperature of the working fluid is high, that is, room temperature, the opening/closing valve 36 is opened to open the first nozzle passage 33a of the first nozzle 33, and the first nozzle passage 33a is also connected to the first nozzle. A working fluid is ejected into the hole 29. Therefore, since the working fluid is at a high temperature, the volumetric flow rate is increased compared to when it reaches the cryogenic temperature, but the working fluid passes through both the first nozzle passage 33a and the second nozzle passage 34a, so the flow path Area increases. When the flow path area increases in this way, even if a predetermined mass flow rate m1 flows, the expansion pressure ratio becomes r3, which is smaller than the critical expansion pressure ratio rcr, as shown by the characteristic line X3 in FIG. .

As described above, in this embodiment, at the start of operation when the temperature of the working fluid is high near room temperature and the volumetric flow rate of the working fluid increases, the flow path area of the working fluid can be increased by opening the on-off valve 36. Therefore, even at the start of operation, it is possible to flow the same mass flow rate m1 as when the cryogenic temperature is reached, while suppressing the expansion pressure ratio (r) to a value lower than the limit expansion pressure ratio (rcr). Therefore, compared to conventional methods, the cool-down time from room temperature to extremely low temperature can be significantly shortened. For example, what used to be 8 hours will now be 2 hours.

It is conceivable to remove the on-off valve 36 and use the first nozzle passage 33a and the second nozzle passage 34a not only at the start of operation but also when the cryogenic temperature is reached, but this would reduce the volumetric flow rate. However, there is a problem in that the flow path area is too large, the pressure ratio becomes too small when the cryogenic temperature is reached, and the refrigerating efficiency of the entire cryogenic refrigeration apparatus is significantly reduced. In this embodiment, when the extremely low temperature is reached, the on-off valve 36 is closed and the flow path area is set to the required value, so this problem does not occur.

The opening/closing valve 36 may be opened and closed automatically by the control unit using a magnet or the like, or may be opened and closed manually. Furthermore, in addition to the configuration of the embodiment described above, the housing 20 includes a pressure sensor that detects the pressure Pa in the second nozzle passage 34a, a pressure sensor that detects the pressure pb in the bearing chamber 25, and a pressure sensor that detects the pressure pc in the expansion chamber 27. A pressure sensor can also be provided. It is also possible to adopt a configuration in which the control section automatically controls the opening operation of the on-off valve 36 according to the values of the absolute pressures pa, pb, and pc measured by the respective pressure sensors.

(2) Other Embodiments A turbo expansion system [60] according to another embodiment of the present invention is shown in FIGS. 5 to 7. The turbo expansion IJ 60 according to the embodiment shown in FIGS. 5 to 7 is of a reaction type, and includes a housing 61, a turbine 62, a spiral outer first nozzle passage 63, and a spiral inner first nozzle passage. It is formed of two nozzle passages 64 and a scroll wall 65 that partitions the first nozzle passage 63 and the second nozzle passage 64. The first nozzle passage 63 and the second nozzle passage 64 are connected to the housing 20
are arranged in parallel in the radial direction. FIG. 7 shows a boat 63a of the first nozzle passage 63 and a boat 64a of the second nozzle passage 64. Boat 63a of first nozzle passage 63
can be opened and closed by an opening/closing valve 66 as a variable opening area member.

In this embodiment, when the cryogenic temperature is reached, the on-off valve 66
is closed, therefore the port 63 of the first nozzle passage 63
Since a is closed, the working fluid passes only through the inner second nozzle passage 64 in a spiral manner. The pressure energy of the working fluid is then converted into velocity energy and blown to the turbine 62.

Therefore, the turbine 62 rotates together with the turbine shaft 38, and as a result, the working fluid expands while absorbing heat, and the temperature of the working fluid decreases due to the heat absorption, causing refrigeration. As in the previous embodiment, the pressure and velocity energy of the working fluid is then absorbed by the generator in the enclosure.

Also in the second embodiment, when the cryogenic temperature is reached, the mass flow im1
The working fluid passes through the second nozzle passage 64 to the turbine 62 .
However, at the start of operation when the temperature of the working fluid is high, that is, room temperature, the opening/closing valve 66 is operated to open the port 63a of the first nozzle passage 63, thereby increasing the flow passage area.

Therefore, at the start of operation when the temperature of the working fluid is high,
Since the working fluid passes through both the first nozzle passage 63 and the second nozzle passage 64, the flow passage area increases approximately twice as compared to when the cryogenic temperature is reached.

When the flow path area increases in this way, as shown by the characteristic line It becomes smaller than the pressure ratio rCr. Therefore, similarly to the first embodiment described above, the thrust acting on the turbine shaft 38 can be suppressed, and stable rotation of the turbine 62 and the turbine shaft 38 can be maintained.

As described above, in the second embodiment, even at room temperature, the predetermined mass flow ff1ml can flow without hindrance to the rotation of the turbine 62, just as when reaching a cryogenic temperature. Cooldown time can be significantly reduced.

In addition, in each of the above embodiments, two nozzle passages, the first nozzle passage and the second nozzle passage, are arranged in parallel, but the invention is not limited to this, and three or more nozzle passages can be arranged in parallel in the circumferential direction or radial direction of the housing. However, at least one of the nozzle passages may be provided with an on-off valve.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings; for example, the compressor is not limited to a turbo compressor, but may be a piston type compressor, and can be implemented with appropriate modifications as necessary. It is possible.

[Effects of the Invention] In the cryogenic refrigeration system of the present invention, when supplying working fluid to the turbo expander, at the start of operation when the volumetric flow rate increases even if the mass flow rate is the same, the flow rate in the nozzle passage is controlled by the variable opening area member. Road area can be increased. Therefore, it is possible to flow the same mass flow rate as when the temperature reaches a low temperature while suppressing the expansion pressure ratio of the turbo expander to be lower than the value of the critical expansion pressure ratio. Therefore, the cool-down time from room temperature to extremely low temperature can be significantly shortened.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention, FIG. 1 is a schematic configuration diagram showing the entire cryogenic refrigeration equipment, FIG. 2 is a sectional view of a turbo expander, and FIG. The figure is from ■-■ in Figure 2.
The arrow view along the line, FIG. 4, is a graph showing the relationship between mass flow rate and expansion pressure ratio. 5 to 7 show other embodiments of the present invention, FIG. 5 is a sectional view of the turbo expander of this embodiment, and FIG. 6 is a sectional view of the turbo expander of this embodiment.
7 is a sectional view taken along the line Vl-Vl in the figure, and FIG. 7 is a plan view of the boat. In the figure, 10 is a compressor, 11 is a radiator, 13 is a turbo expander, 14 is a frozen extractor, 20 is a housing, 33a is a first nozzle passage, 34a is a second nozzle passage, 36 is an on-off valve (opening area (variable member), 37 is a turbine, and 38 is a turbine shaft. Figure 1 Patent applicant Aisin Seiki Co., Ltd.

Claims (1)

[Claims] (1) A compressor that compresses a working fluid for cryogenic use, a radiator that takes heat from the working fluid compressed by the compressor, a turbo expander that expands the working fluid that has passed through the radiator, and a turbo expander that expands the working fluid that has passed through the radiator. The turbo expander includes a housing having a turbine hole;
a rotatable turbine disposed in a turbine hole of the housing; a nozzle passage disposed in the housing for injecting working fluid to the turbine to rotate the turbine; and a variable opening area for making the opening area of the nozzle passage variable. 1. A cryogenic refrigeration system comprising: a member, wherein the opening area of the nozzle passage is increased by the variable opening area member when the temperature of the working fluid is high.