JPH0794928B2 - Cryogenic refrigerator and operation control method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cryogenic refrigerator, and more particularly to a cryogenic refrigerator having a supercritical expansion turbine and an operation control method thereof.

[Conventional technology]

In the conventional liquefaction refrigeration system, for example, a helium liquefaction refrigeration system, in the lowest temperature part, there are many devices that enthalpy-expand high-pressure helium gas by an expansion valve to liquefy a part of the helium gas. However, the isenthalpic expansion by the expansion valve is relatively inefficient, so the isenthalpic expansion is performed up to the critical pressure by the expansion turbine, and after the critical pressure, the isenthalpic expansion is performed by the expansion valve to liquefy a part of the helium gas. Has been.

Note that, as a device related to this kind of device, for example,
JP-A-59-134460, JP-A-60-164182 and the like are listed.

[Problems to be Solved by the Invention]

The above-mentioned conventional technology is designed to prevent the liquefaction of helium gas in the expansion turbine and to prevent the liquefied helium from impacting the rotor blade that is rotating at high speed and damaging the blade. There was a problem in that the entire device had to be stopped when the expansion turbine was stopped, because no consideration was given to the efficient operation of the device.

A first object of the present invention is to provide a cryogenic refrigeration system and an operation control method thereof that can continue efficient operation without stopping the system even when the expansion turbine is at rest.

A second object of the present invention is to provide a cryogenic refrigeration system capable of performing stable operation of the expansion turbine and an operation control method thereof.

[Means for Solving the Problems]

In order to achieve the above first and second objects, in a cryogenic refrigeration system having an expansion turbine on the upstream side of an expansion valve, valves are provided on the inlet and outlet sides of the expansion turbine, and on the upstream side of the inlet side valve. A bypass flow path that communicates with the downstream side of the valve on the outlet side is provided, and a valve is provided in the bypass flow path to expand all or part of the refrigerant gas supplied to the expansion turbine through the valve of the bypass line. This is the method of supplying to the valve.

Further, in order to achieve the second object with higher accuracy, in a method of operating a cryogenic refrigeration system having an expansion turbine upstream of an expansion valve, the refrigerant flow rate of the expansion turbine is adjusted by the pressure and temperature on the expansion turbine outlet side. It is something that is done.

[Action]

During operation of the expansion turbine, the valve on the inlet / outlet side of the expansion turbine is opened to send the refrigerated gas to the expansion valve via the expansion turbine to improve the cold generation efficiency, but the refrigerant gas is liquefied in the expansion turbine. In this case, the valve of the bypass line is opened and a part of the refrigerant gas is sent to the expansion valve through the bypass line. This reduces the flow rate to the expansion turbine side, lowers the turbine speed, reduces the amount of cold generation, and prevents liquefaction of the refrigerant in the expansion turbine.
Stable operation can be performed.When the expansion turbine is at rest, the valve on the inlet / outlet side of the expansion turbine is closed to stop the supply of the refrigerant gas to the expansion turbine, and the valve on the bypass line is opened to prevent the refrigerant gas from flowing. Send all to expansion valve. As a result, the refrigerant gas adiabatically expands in the expansion valve to generate cold, so that the operation can be continued without stopping the device even if the expansion turbine is stopped, and the bypass line valve can be used as an expansion valve. For example, the two-stage expansion enables efficient operation.

Furthermore, by adjusting the refrigerant flow rate of the expansion turbine according to the pressure and temperature on the outlet side of the expansion turbine, when the pressure or temperature approaches the critical point, the flow rate of the expansion turbine can be reduced to reduce the amount of cold generation, and liquefaction in the expansion turbine can be reduced. Can be prevented and stable operation can be performed.

〔Example〕

 An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows the configuration of a cryogenic refrigerator, for example, a helium refrigerator. The high-pressure gas pipe 2 connected to the outlet side of the compressor 20 includes a high temperature side of the first heat exchanger 21, a high temperature side of the second heat exchanger 22, a high temperature side of the third heat exchanger 23, and a fourth heat exchange. The hot side of the vessel 24 and the hot side inlet of the fifth heat exchanger 11 are connected in series. The high temperature side intermediate part outlet of the fifth heat exchanger 11 and the helium gas inlet of the supercritical expansion turbine 5 are the turbine inlet pipe 3
Connected by. The helium gas outlet of the supercritical expansion turbine 5 and the high temperature side intermediate inlet of the fifth heat exchanger 11 are connected by a turbine outlet pipe 6, and the high temperature side outlet of the fifth heat exchanger 11 and the inlet of the refrigeration load 10 are joules. It is connected to the JT inlet pipe 8 through the Thomson expansion valve 9. Further, the turbine inlet pipe 3 and the turbine outlet pipe 6 are connected via a bypass passage 13. Refrigerating load 10 outlet, 5th heat exchanger
11 low temperature side, 4th heat exchanger 24 low temperature side, 3rd heat exchanger 23
, The low temperature side of the second heat exchanger 22, the low temperature side of the first heat exchanger 21, and the inlet side of the compressor 20 are connected in series by a low pressure gas pipe 12. Furthermore, the first heat exchanger 21 and the second
A branch pipe 27 is connected to the high-pressure gas pipe 2 connecting the heat exchanger 22, and the branch pipe 27 is connected to the first expansion turbine 25, the second high temperature side of the third heat exchanger 23, and the second expansion turbine. 26 are connected in series, and are joined and connected to the low-pressure gas pipe 12 that connects the fifth heat exchanger 11 and the fourth heat exchanger 24.

An inlet valve 4 is provided on the inlet side of the supercritical expansion turbine 5 of the turbine inlet pipe 3, and an outlet valve 7 is provided on the turbine 5 outlet side of the turbine outlet pipe 6. In addition, the second Joule-Thomson expansion valve 14 (hereinafter,
"Called the second JT valve") is provided. Further, a pressure detector 17 and a temperature detector 18 are attached to the turbine outlet pipe 6, and the signals thereof are sent to a controller 19. The controller 19 can adjust the valve opening degree of the second JT valve 14 by judging from the signal. Further, the controller 19 can control the opening / closing of the inlet valve 14, the outlet valve 7 and the second JT valve 14, respectively.

Although not shown, in this case, the other devices except the compressor 20 and the controller 19 are housed in a vacuum-insulated space.

The helium gas compressed to, for example, 16 atm and 300 ° K (normal temperature) by the compressor 20 by the apparatus configured as described above is pre-cooled through the first to fourth heat exchangers 21 to 24. , High pressure and low temperature helium gas (eg 16atm, 10 °
K) and enters the high temperature side of the fifth heat exchanger 11. Fifth
The helium gas flowing into the high temperature side of the heat exchanger 11 flows into the turbine inlet pipe 3 from the high temperature side intermediate outlet of the heat exchanger 11. In the normal operation state, the second JT valve 14 is closed and the inlet valve 4 and the outlet valve 7 are open. Turbine inlet piping 3
The helium gas that has flowed into the tank is adjusted to an appropriate pressure by the inlet valve 4 and enters the supercritical expansion turbine 5, where it undergoes adiabatic expansion and its temperature and pressure drop. The medium-pressure helium gas (for example, 4 atm, 6 ° K) whose temperature and pressure have dropped is passed through the outlet valve 7 and the turbine outlet pipe 6 and returned to the high pressure side of the fifth heat exchanger 11 to cool the helium gas on the low temperature side. Replace it and the temperature will drop further. The helium gas having the lowered temperature passes through the Joule-Thomson expansion valve 9 to undergo isenthalpic expansion (for example,
Liquefaction is performed at 1.2atm, 4.4 ° K). The liquefied helium is vaporized while passing through the refrigeration load 10 and passes through the low-pressure gas pipe 12, the fifth heat exchanger 11 and the fourth to first heat exchangers 24 to 21 on the low temperature side, but on the high temperature side. It exchanges heat with the flowing helium gas, returns to the compressor 20, and repeats circulation. Since the supercritical expansion turbine 5 performs isentropic expansion that is more efficient than the Joule-Thomson expansion valve 9, the helium is liquefied more efficiently than the conventional device that liquefies helium only with the Joule-Thomson expansion valve.

On the other hand, due to the outlet pressure of the supercritical expansion turbine, the critical pressure Pc (=
2.27atm) and the outlet temperature is the critical temperature Tc (= 5.2 °)
If it becomes smaller than K), helium gas may partially liquefy in the rotor of the supercritical expansion turbine, causing fluctuations in the turbine outlet pressure, preventing normal turbine rotation, or causing turbine failure. Therefore, the outlet pressure P ₂ is measured by the pressure detector 17 provided in the outlet pipe 6 of the supercritical expansion turbine 5, and the controller 19 calculates the temperature T = f (P ₂ ) at which the helium gas is liquefied. Moreover, the outlet temperature T ₂ of the supercritical expansion turbine 5 can be known from the signal of the temperature detector 18 provided in the outlet pipe 6 of the turbine. Therefore, when the outlet temperature T ₂ is lower than the liquefaction temperature T, the helium gas is liquefied. In this case, the controller 19
A signal for opening the 2JT valve 14 by an appropriate amount is sent to the second JT valve. In this case, the opening of the turbine inlet valve 4 is the same, but the second JT valve 14
By opening, the flow rate of gas flowing to the supercritical expansion turbine 5 decreases, the rotational speed of the turbine decreases, and the amount of cold generation of the supercritical expansion turbine 5 decreases. Therefore, the outlet temperature of the supercritical expansion turbine 5 rises. It is possible to prevent liquefaction of helium gas in the supercritical expansion turbine 5 by opening the second JT valve 14 until the outlet temperature T ₂ becomes higher than the liquefaction temperature T.

Further, even if the supercritical expansion turbine 5 fails, if the turbine inlet valve 4 and the turbine outlet valve 7 are closed, the helium is isolated by the circulating piping systems 4 and 7. It can be repaired and replaced, and the trouble of replacing helium in the entire system for repair can be saved. Further, if the second JT valve 14 is opened at the same expansion ratio as that of the supercritical expansion turbine 5, for example, the helium gas will flow through the bypass pipe 13, the JT valve 9, and the refrigeration load 10. Therefore, if the refrigeration load 10 can be appropriately reduced compared to the steady state, the liquefaction of helium gas can be efficiently continued by performing JT expansion in two stages (compared to JT expansion in one stage).

As described above, according to this embodiment, even if the helium gas is liquefied in the supercritical expansion turbine 5, it has an effect of easily preventing the liquefaction of the helium gas and prevents the failure of the supercritical expansion turbine. effective. Further, even if the supercritical expansion turbine fails, there is an effect that the liquefaction of helium can be continued, the reliability of the refrigerating apparatus is improved, and the maintenance of the refrigerator is facilitated.
Also at this time, there is an effect that the two-stage expansion by the JT valve enables efficient operation.

In the present embodiment, the refrigerating load 10 is a condenser for recondensing the liquid helium vaporized by the superconducting magnet 15 in the liquid helium tank 16, but it is not limited to this.

Further, although the valve provided in the bypass pipe 13 is a JT valve, it may be a normal valve (hereinafter referred to as “bypass valve”). In this case, when liquefying helium gas in the supercritical expansion turbine 5, the controller 19 is adjusted to open (normally closed) the same as described above.
In this case also, the opening of the turbine inlet valve 4 is the same,
By opening the bypass valve, the flow rate of gas flowing to the supercritical expansion turbine 5 is reduced, the rotational speed of the turbine is reduced, and the amount of cold generation of the turbine is reduced. Therefore, the outlet temperature of the turbine rises and liquefaction of helium gas is prevented.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this figure, the same reference numerals as those in FIG. 1 indicate the same members, and the description thereof will be omitted. The frame 1 indicated by the one-dot chain line in the figure is
The range of the frame 1 indicated by the one-dot chain line in FIG. 1 is shown, and the inside is omitted. The difference between this figure and Figure 1 is that
The point is that the controller 19 controls the turbine outlet valve 7 by the signals of the pressure detector 17 and the temperature detector 18. Although not shown, the controller 19 can control opening / closing of the turbine inlet valve 4, the turbine outlet valve 7, and the second JT valve 14.

In the above configuration, when the helium gas is liquefied in the supercritical expansion turbine 5, the controller 19 adjusts the outlet valve 7 of the turbine to be closed. That is, the outlet pressure P ₂ is measured by the pressure detector 17 provided in the outlet pipe 6 of the supercritical expansion turbine 5, and the controller 19 calculates the temperature T = f (P ₂ ) at which the helium gas is liquefied. Further, the turbine outlet temperature T ₂ is detected by a signal from a temperature detector 18 provided in the turbine outlet pipe 6. The outlet temperature T ₂ is the liquefaction temperature T
If smaller, helium gas is liquefied, and in this case, the controller 19 sends a signal in the direction of reducing the opening of the outlet valve 7 of the turbine. As a result, the turbine outlet pressure P ₂ rises. When the output pressure P ₂ rises, the liquefaction temperature of helium gas rises. Therefore, the outlet temperature T ₂ is the liquefaction temperature T
Until it becomes larger, the outlet valve 7 of the supercritical expansion turbine 5
Liquefying the helium gas in the turbine can be prevented by appropriately squeezing.

Further, by closing the inlet valve 4 and the outlet valve 7 and opening the second JIT valve 14 by the controller 19, the operation can be continued even if the supercritical expansion turbine 5 is disconnected as in the case of the one embodiment.

As described above, according to the present embodiment, even when the helium gas is liquefied in the supercritical expansion turbine as in the case of the one embodiment, there is an effect of easily preventing the liquefaction of the helium gas, and the reliability of the refrigeration system is improved. It has the effects of improving the property and preventing the failure of the supercritical expansion turbine. Further, even if the supercritical expansion turbine fails, there is an effect that the liquefying operation of helium can be efficiently continued.

Next, a third embodiment of the present invention will be described with reference to FIG.

In this figure, the same reference numerals as those in FIG. 1 indicate the same members, and the description thereof will be omitted. The frame 1 shown by the one-dot chain line in this figure is the same as that described in FIG. The difference between this drawing and FIG. 1 is that the controller 19 controls the turbine inlet valve 4 by the signals of the pressure detector 17 and the temperature detector 18. Although not shown, the controller 17 can control opening / closing of the turbine inlet valve 4, the turbine outlet valve 7, and the second JT valve 14.

In the above configuration, when the helium gas is liquefied in the supercritical expansion turbine 5, the controller 19 adjusts the opening of the turbine inlet valve 4 to be closed. That is, the controller 19 calculates the temperature T = f (P ₂ ) at which the helium gas is liquefied from the pressure signal P ₂ of the pressure detector 17 of the outlet pressure. In addition, the temperature from the temperature detector 18 causes the turbine outlet temperature to change.
Detect T ₂ . When the outlet temperature T ₂ is lower than the liquefaction temperature T, the turbine inlet valve 4 is closed until the outlet temperature T ₂ becomes higher than the liquefaction temperature T. By restricting the inlet valve 4 of the turbine, the gas flow rate to the supercritical expansion turbine 5 is reduced, the rotational speed of the turbine is reduced, and the amount of cold generation of the turbine is reduced. As a result, the outlet temperature of the supercritical expansion turbine 5 rises, and the turbine outlet temperature rises above the critical temperature (T _c = 5.2 ° K) at which helium is liquefied. Here, if the design temperature T ₂ of the supercritical expansion turbine 5 is set in the controller 19, the inlet valve 4 can be adjusted to control the outlet temperature T ₂ to approach the design temperature T _d .

Further, by closing the inlet valve 4 and the outlet valve 7 and opening the second JT valve 14 by the controller 19, the operation can be continued even if the supercritical expansion turbine 5 is disconnected as in the case of the one embodiment.

As described above, according to this embodiment, by controlling the inlet valve, it is possible to easily prevent the liquefaction of helium gas in the supercritical expansion turbine as in the case of the above-mentioned embodiment, and the turbine outlet temperature can be easily adjusted. It also has the effect of controlling the design temperature. Further, there is an effect that the liquefaction operation of helium can be efficiently continued even when the turbine fails.

In these first to third embodiments, the inlet valve 4, the outlet valve 7 or the second JT valve 14 near the supercritical expansion turbine 5 are adjusted to prevent liquefaction in the supercritical expansion turbine 5. However, as shown in FIG. 4, a part of the room temperature / high pressure helium gas from the upstream side of the fifth heat exchanger 11, for example, the discharge side of the compressor 20, is branched off, and is superposed via the valve 28. The valve is connected to the inlet of the critical expansion turbine 5 by the controller 19 by the valve 28.
May be controlled. In this case, when the liquefaction is about to occur, the valve 20 is controlled so as to be opened, and the high temperature helium gas is supplied to the supercritical expansion turbine 5 to make the outlet temperature T ₂ higher than the liquefaction temperature T.

Further, as shown in FIG. 5, the refrigerator inlet valve 29 provided on the discharge side of the compressor 20 may be controlled by the controller 19. In this case, liquefied by controlling the direction to narrow the refrigerator inlet valve 29 if unlikely, by reducing cold emission under supercritical expansion turbine 5 by subtracting the flow rate of the whole refrigerator, outlet temperature T ₂ Is higher than the liquefaction temperature T.

〔The invention's effect〕

According to the present invention, even when liquefaction is about to occur in the supercritical expansion turbine, the outlet pressure of the turbine can be increased or the amount of cold generation of the turbine can be reduced,
Liquefaction in the turbine can be prevented, and the expansion turbine can be operated stably.

Further, there is an effect that even when the supercritical expansion turbine is stopped, efficient operation can be continued through the bypass circuit without stopping the refrigerator.

[Brief description of drawings]

FIG. 1 is a system diagram showing a cryogenic refrigerating apparatus which is an embodiment of the present invention, and FIGS. 2 to 5 are system diagrams showing other embodiments of the present invention. 4 …… Inlet valve, 5 …… Supercritical expansion turbine, 7 …… Outlet valve, 13 …… Bypass piping, 14 …… Second JT valve, 17 …… Pressure detector, 18 …… Temperature detector, 19 …… Controller, 28 ... valve,
29 …… Refrigerator inlet valve

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kazuo Okamoto Kazuo Okamoto 794, Higashi-Toyoi, Kudamatsu City, Yamaguchi Prefecture Stock company Hitachi Kasado Plant (72) Inventor Kozo Matsumoto 794, Higashi-Toyoi, Shimomatsu City, Yamaguchi Prefecture Hitachi, Ltd. Kasado Factory (56) References Japanese Patent Laid-Open No. 1-155755 (JP, A)

Claims (6)

[Claims] 1. A cryogenic refrigeration system having an expansion turbine upstream of an expansion valve, wherein valves are provided on the inlet and outlet sides of the expansion turbine, and the upstream side of the inlet side valve and the downstream side of the outlet side valve. A cryogenic refrigerating device, characterized in that a bypass flow path communicating with the side is provided and a valve is provided in the bypass flow path. 2. The cryogenic refrigerating apparatus according to claim 1, wherein the valve provided in the bypass passage is an expansion valve. 3. The cryogenic refrigerating apparatus according to claim 1,
A pressure detector and a temperature detector are provided on the outlet side of the expansion turbine, and the expansion valve, the bypass passage valve, the outlet side valve, and the inlet side valve are received by receiving signals from the both detectors. Alternatively, the cryogenic refrigeration system is provided with control means for controlling any of the valves on the upstream side of the valves on the inlet side. 4. The cryogenic refrigerating apparatus according to claim 1,
A means for supplying a refrigerant gas having a relatively high temperature upstream of the valve on the inlet side to the expansion turbine is provided, and a pressure detector and a temperature detector are provided on the outlet side of the expansion turbine. A cryogenic refrigerating apparatus comprising a control means for controlling a supply amount of the means by receiving a signal from the refrigerator. 5. A method for operating a cryogenic refrigeration system having an expansion turbine upstream of an expansion valve, wherein a valve is provided in a line bypassing the expansion turbine so that all or one of refrigerant gas supplied to the expansion turbine is supplied. Is supplied to the expansion valve via the valve, the operation control method of the cryogenic refrigeration system. 6. A method for operating a cryogenic refrigeration system having an expansion turbine upstream of an expansion valve, wherein valves are provided on the inlet and outlet sides of the expansion turbine, and valves on the upstream side and the outlet side of the inlet side valve are provided. A bypass flow path including a valve, which communicates with the downstream side of the expansion turbine, a pressure detector and a temperature detector are provided on the outlet side of the expansion turbine, and the expansion valve receives the signals from both detectors, A method for controlling operation of a cryogenic refrigerating apparatus, comprising controlling any one of a bypass flow path valve, the outlet side valve, the inlet side valve, and a valve upstream of the inlet side valve.