Stirling cryocooler service life monitoring equipment and method

Abstract

The invention relates to a Stirling cryocooler service life monitoring device and method, and relates to the technical field of Stirling cryocoolers. Comprising the steps that 1, the gas condition in a compressor in an initial state is monitored, and a pressure value curve a of gas total pressure and a partial pressure value curve b of working medium gas are obtained; the pressure value curve a and the pressure value curve b are the same curve A; 2, the gas condition in the compressor in the working state is monitored, and a pressure value curve a'of the gas total pressure and a pressure value curve b 'of the gas partial pressure of the working medium gas are obtained; and 3, comparing the pressure value curve a'in the step 2 with the pressure value curve b ', comparing with the pressure value curve A obtained in the step 1, and judging the leakage and pollution conditions of the working medium gas in the compressor. By comparing the pressure value curve of the total pressure of the gas with the pressure value curve of the partial pressure of the working medium gas, the performance condition of the Stirling cryocooler is monitored, and an operator can conveniently carry out targeted maintenance on the Stirling cryocooler.

Description

Technical Field

[0001] The present invention relates to the technical field of Stirling refrigerators, and in particular to a Stirling refrigerator life monitoring device and method. Background Art

[0002] The high reciprocating motion between the piston and cylinder of the Stirling refrigerator causes severe wear between the piston and cylinder, and the non-volatile substances in the Stirling refrigerator and the impurities generated by friction can cause the performance of the Stirling refrigerator to deteriorate, thus causing the failure of the Stirling refrigerator. The failure of the Stirling refrigerator will cause the infrared detector chip that it cools to be in a high temperature state (relative to 80K), which will cause imaging degradation or even damage the detector.

[0003] The main reasons for the failure of a Stirling refrigerator at the end of its life are leakage of the working fluid and contamination of the working fluid. There are three sealing structures in the Stirling refrigerator, namely the motor surface, the compressor sealing surface and the expansion seal cover. Stirling refrigerators generally use gases with smaller molecules as working fluids, which will bring certain challenges to the sealing work. In particular, the large temperature difference in the storage environment of the Stirling refrigerator and the long working time may cause leakage of the working fluid gas in the Stirling refrigerator. The adhesives used in the parts inside the Stirling refrigerator, the surfaces of the metal parts, and the grease used in the bearings will have slow outgassing, and the residual air will pollute the purity of the working fluid gas, resulting in a decrease in the performance of the Stirling refrigerator.

[0004] In the prior art, a pressure sensor is usually used to measure the internal pressure of the Stirling refrigerator. The accuracy is not high, and it is impossible to judge whether it is caused by leakage of working gas or contamination. It is not convenient to make targeted adjustments to the Stirling refrigerator later. Therefore, a Stirling refrigerator life monitoring device and method are proposed. Summary of the invention

[0005] The present invention provides a Stirling refrigerator life monitoring device and method, which are used to monitor the leakage and pollution status of working gas inside the Stirling refrigerator, so as to judge the performance of the Stirling refrigerator and avoid serious consequences caused by sudden failure of the Stirling refrigerator.

[0006] The present invention provides a Stirling refrigerator life monitoring method, comprising the following steps:

[0007] Step 1: monitor the gas condition in the compressor at the initial state, and obtain a pressure value curve a of the total gas pressure and a pressure value curve b of the gas partial pressure of the working gas;

[0008] The pressure value curve a and the pressure value curve b are the same curve A.

[0009] Step 2: monitor the gas condition in the compressor in the working state, and obtain a pressure value curve a' of the total pressure of the gas and a pressure value curve b' of the partial pressure of the working gas;

[0010] Step 3: Compare the pressure value curve a' in step 2 with the pressure value curve b', and compare with the pressure value curve A obtained in step 1 to determine the leakage and contamination status of the working gas in the compressor.

[0011] In one embodiment, in step 2, the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of the curve B are equal to the curve A, then the internal airtightness of the Stirling refrigerator is good.

[0012] In one embodiment, in step 2, the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of the curve B are smaller than those of the curve A, then the internal working fluid gas of the Stirling refrigerator is leaking.

[0013] In one embodiment, in step 2, the pressure value curve a' is curve B, the pressure value curve b' is curve C, the amplitude and peak value of the pressure wave of curve B are both smaller than those of curve A, and the amplitude and peak value of the pressure wave of curve C are both smaller than those of curve B, then the internal working fluid gas of the Stirling refrigerator is contaminated.

[0014] In one embodiment, the pressure amplitude of curve A is 0.2 MPa and the peak value is 1.8 MPa.

[0015] In one embodiment, the pressure wave amplitude of the curve B ranges from 0.14 to 0.2 MPa, and the peak value ranges from 1.3 to 1.8 MPa.

[0016] In one embodiment, the warning value of the peak difference between the curve B and the curve A is 0.5 MPa.

[0017] In one embodiment, the warning value of the peak difference between the curve B and the curve C is 0.4 MPa.

[0018] The present invention provides a Stirling refrigerator life monitoring device comprising: a first pressure sensor and a second pressure sensor, wherein the probe of the first pressure sensor and the probe of the second pressure sensor are respectively connected to the inside of the compressor of the Stirling refrigerator through a connecting hole on the compressor end cover of the Stirling refrigerator.

[0019] In one embodiment, a polymer membrane is provided at the probe of the second pressure sensor, and the polymer membrane is used to pass working gas molecules and block other gas molecules, so as to facilitate the second pressure sensor to measure the partial pressure of the working gas.

[0020] Compared with the prior art, the advantage of the present invention is that by comparing the pressure value curve of the total gas pressure with the pressure value curve of the partial pressure of the working fluid gas, it is possible to quickly and accurately determine whether the failure of the Stirling refrigerator is caused by leakage or contamination of the working fluid gas, thereby monitoring the performance of the Stirling refrigerator, making it convenient for operators to promptly respond to the failure of the Stirling refrigerator under the condition of working fluid gas leakage or contamination, and to perform targeted maintenance on the Stirling refrigerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Hereinafter, the present invention will be described in more detail based on embodiments and with reference to the accompanying drawings.

[0022] Figure 1 is a schematic diagram of the positions of the pressure sensor and the Stirling refrigerator of the present invention;

[0023] Figure 2 is a cross-sectional schematic diagram of the installation of the pressure sensor of the present invention;

[0024] Figure 3 is a schematic diagram of a pressure value curve of the pressure sensor of the present invention;

[0025] Reference numerals:

[0026] 1. Compressor; 2. First pressure sensor; 3. Second pressure sensor; 4. Polymer membrane. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings.

[0028] The present invention discloses a Stirling refrigerator life monitoring method, comprising the following steps:

[0029] Step 1: Monitor the gas situation in the compressor at the initial state, and obtain the pressure value curve a of the total gas pressure and the pressure value curve b of the gas partial pressure of the working gas. The internal pressure of the compressor can be detected by the first pressure sensor 2 and the second pressure sensor 3 connected to the inside of the compressor, and the pressure value curve a and the pressure value curve b are obtained respectively. At this time, the pressure value curves obtained by the two pressure sensors are equal, both of which are curve A.

[0030] When the Stirling refrigerator is in the initial state, the pressure value curves generated by the first pressure sensor 2 and the second pressure sensor 3 are the same, both are curve A. The pressure amplitude of curve A is 0.2MPa and the peak value is 1.8MPa. This data is used as a standard indicator for subsequent evaluation of whether the Stirling refrigerator has working gas leakage and contamination.

[0031] In this embodiment, the working fluid gas of the Stirling refrigerator is preferably helium. In order to measure the helium partial pressure when the internal helium of the compressor is contaminated, the second pressure sensor 3 can also be a piezoelectric pressure sensor, a capacitive pressure sensor, and a piezoresistive pressure sensor.

[0032] Step 2: Monitor the gas conditions in the compressor under working conditions, obtain the pressure value curve a' of the total gas pressure and the pressure value curve b' of the gas partial pressure of the working gas, that is, use the first pressure sensor 2 to measure the pressure value curve a', and the second pressure sensor 3 to measure the pressure value curve b'.

[0033] Step 3: Compare the pressure value curve a' in step 2 with the pressure value curve b', and compare with the pressure value curve A obtained in step 1 to determine the leakage and contamination status of the working gas in the compressor.

[0034] In step 3, if the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of curve B are equal to those of curve A, the internal airtightness of the Stirling refrigerator is good.

[0035] Example 1

[0036] In step 3, the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of curve B are smaller than those of curve A, such as Figure 3 As shown, the pressure wave amplitude range of curve B should be 0.14~0.2MPa, and the peak range should be 1.3~1.8MPa. When the pressure wave amplitude and peak value of curve B are out of range, that is, the peak difference between curve B and curve A exceeds the warning value of 0.5MPa, it is judged that the working fluid gas in the Stirling refrigerator is leaking.

[0037] However, at this time, the pressure amplitude of curve B is 0.18MPa, and the peak value is 1.58MPa, which means that the internal helium of the Stirling refrigerator is leaking. The difference between the peak values ​​of curve B and curve A is 0.22MPa, so although the helium inside the Stirling refrigerator is leaking, it has not reached the warning value of 0.5MPa, and has not completely affected the refrigeration effect of the Stirling refrigerator. The Stirling refrigerator can be temporarily replaced.

[0038] Since the Stirling refrigerator is still in a state of internal helium leakage, the sealing surface of the Stirling refrigerator can be checked. If there are discontinuities such as pits, wear, or radial or penetrating scratches, repairs can be carried out to improve the sealing effect of the Stirling refrigerator.

[0039] Example 2

[0040] In step 3, the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of the same curve B are smaller than those of curve A. At this time, the pressure wave amplitude of curve B is 0.14MPa and the peak value is 1.3MPa, indicating that the internal helium of the Stirling refrigerator is leaking.

[0041] The difference between the peak values ​​of curve B and curve A is 0.5 MPa, so the helium leak inside the Stirling refrigerator affects the refrigeration effect of the Stirling refrigerator, and the Stirling refrigerator needs to be replaced.

[0042] Example 3

[0043] In step 3, the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of the same curve B are smaller than those of curve A. At this time, the pressure wave amplitude of curve B is 0.14MPa and the peak value is 1.2MPa, indicating that the internal helium of the Stirling refrigerator is leaking.

[0044] At this time, the difference between the peak values ​​of curve B and curve A is 0.6MPa, which has exceeded the warning value of 0.5MPa. Therefore, the helium inside the Stirling refrigerator is leaking, affecting the refrigeration effect of the Stirling refrigerator, and the Stirling refrigerator needs to be replaced. For the Stirling refrigerator that has been replaced, the sealing of the Stirling refrigerator can be repaired, such as replacing the sealing ring, etc., to ensure that the sealing ring or sealing wire and the sealing surface are smooth and free of impurities.

[0045] Example 4

[0046] In a mixed gas, the pressure formed when a certain component occupies the same volume as the mixed gas at the same temperature is the gas partial pressure of the gas, and the partial pressure of the gas is less than the total pressure of the mixed gas.

[0047] In the present invention, the mechanical parts inside the Stirling refrigerator cavity will absorb gas for a long time and then release gas, the grease in the bearings will evaporate, and the air present in the inflation is all impurity gas. After the Stirling refrigerator has been working for a long time, the impurity gas will enter the working gas and pollute the working gas.

[0048] In step 3, when the pressure value curve a' is curve B, the pressure value curve b' is curve C, and the amplitude and peak value of the pressure wave of curve B are both smaller than those of curve A, and the amplitude and peak value of the pressure wave of curve C are both smaller than those of curve B, Figure 3As shown, when the peak value difference between curve B and curve C exceeds the warning value 0.4MPa, it is determined that the working gas in the Stirling refrigerator is contaminated.

[0049] At this time, the pressure wave amplitude of curve B is 0.18MPa, the peak value is 1.58MPa, and the pressure wave amplitude of curve C is 0.17MPa, the peak value is 1.47MPa, which means that the internal working fluid gas of the Stirling refrigerator is contaminated.

[0050] However, the difference between the peak values ​​of curve B and curve C is 0.11MPa. Therefore, although the helium inside the Stirling refrigerator is contaminated, it has not reached the warning value of 0.4MPa and has not completely affected the refrigeration effect of the Stirling refrigerator. The Stirling refrigerator can be temporarily replaced, but it needs to be repaired in time to extend the service life of the Stirling refrigerator. When repairing a Stirling refrigerator with contaminated helium, the Stirling refrigerator can be baked at high temperature to remove the pollutants accumulated inside, and high-purity nitrogen can be filled multiple times in a high-temperature baking environment to replace and remove the air and pollutants in the Stirling refrigerator.

[0051] Example 5

[0052] In step 3, the pressure value curve a' is curve B, the pressure value curve b' is curve C, and the amplitude and peak value of the pressure wave of curve B are smaller than those of curve A, and the amplitude and peak value of the pressure wave of curve C are smaller than those of curve B. At this time, if the pressure wave amplitude of curve B is 0.16MPa and the peak value is 1.42MPa, and the pressure wave amplitude of curve C is 0.14MPa and the peak value is 1.02MPa, then the internal working fluid gas of the Stirling refrigerator is contaminated.

[0053] The difference between the peak values ​​of curve B and curve C is 0.4 MPa, and the warning value between curve B and curve C is 0.4 MPa. In order to prevent the refrigeration capacity of the Stirling refrigerator from being unable to meet the temperature requirements of the infrared detector in the future, the Stirling refrigerator needs to be replaced.

[0054] Example 6

[0055] In step 3, the pressure value curve a' is curve B, the pressure value curve b' is curve C, and the amplitude and peak value of the pressure wave of curve B are smaller than those of curve A, and the amplitude and peak value of the pressure wave of curve C are smaller than those of curve B. At this time, if the pressure wave amplitude of curve B is 0.18MPa and the peak value is 1.58MPa, and the pressure wave amplitude of curve C is 0.16MPa and the peak value is 1.09MPa, the internal helium gas of the Stirling refrigerator is contaminated.

[0056] However, the difference between the peak values ​​of curve B and curve C is 0.49MPa, which exceeds the warning value of 0.4MPa between curve B and curve C. The cooling capacity of the Stirling refrigerator can no longer meet the temperature requirements of the infrared detector, and the Stirling refrigerator needs to be replaced. Similarly, since the Stirling refrigerator is detected because the internal helium is contaminated, the replaced Stirling refrigerator can be repaired in a targeted manner according to this situation.

[0057] The present invention provides a Stirling refrigerator life monitoring device, comprising: a first pressure sensor 2 and a second pressure sensor 3, wherein the probe of the first pressure sensor 2 and the probe of the second pressure sensor 3 are respectively connected to the inside of the compressor 1 of the Stirling refrigerator through a connecting hole on the end cover of the compressor 1 of the Stirling refrigerator, such as Figure 1 As shown. The first pressure sensor 2 and the second pressure sensor 3 are electrically connected to the amplifier, and the amplifier is electrically connected to the oscilloscope, and the data is read and stored through the oscilloscope. The present invention is provided with at least two pressure sensors, and more pressure sensors can be added to improve the measurement accuracy.

[0058] The first pressure sensor 2 and the second pressure sensor 3 are both miniature high-frequency pressure sensors. In this embodiment, the Kunshan Shuangqiao GY506 miniature low-pressure sensor is preferred. The probe of the second pressure sensor 3 is provided with a polymer film 4, such as Figure 2 As shown, the polymer membrane 4 is used to pass the working gas molecules and block other gas molecules, so as to facilitate the second pressure sensor 3 to measure the partial pressure of the working gas.

[0059] The first pressure sensor 2 and the second pressure sensor 3 can be connected and installed with the end cover of the compressor 1 of the Stirling refrigerator in a threaded connection manner.

[0060] The working gas in the present invention can be selected according to the specific refrigeration requirements and operating conditions, and nitrogen or hydrogen can be used. The polymer membrane 4 set at the probe of the second pressure sensor 3 also needs to be adjusted according to the actual working gas selection to ensure that the working gas molecules can pass through the polymer membrane 4 and prevent other impurity gas molecules from passing through the polymer membrane 4. In the embodiment of the present invention, helium is preferably used as the working gas because it has the advantages of low inertial mass, stable physical properties and low leakage rate. Therefore, the polymer membrane 4 at the probe of the second pressure sensor 3 should also be selected to be a polymer membrane 4 that can pass helium molecules and prevent other gas molecules from passing through.

[0061] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A Stirling refrigerator life monitoring method, characterized in that: The following steps are involved: Step 1: monitor the gas condition in the compressor at the initial state, and obtain a pressure value curve a of the total gas pressure and a pressure value curve b of the gas partial pressure of the working gas; Wherein, the pressure value curve a and the pressure value curve b are the same curve A; Step 2: monitor the gas condition in the compressor in the working state, and obtain a pressure value curve a' of the total pressure of the gas and a pressure value curve b' of the partial pressure of the working gas; Step 3: Compare the pressure value curve a' in step 2 with the pressure value curve b', and compare with the pressure value curve A obtained in step 1 to determine the leakage and contamination status of the working gas in the compressor.

2. The Stirling refrigerator life monitoring method according to claim 1, characterized in that: In step 2, the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of the curve B are equal to the curve A, then the internal air tightness of the Stirling refrigerator is good.

3. The Stirling refrigerator life monitoring method according to claim 2, characterized in that: In step 2, if the pressure value curve a' and the pressure value curve b' are the same curve B, and the amplitude and peak value of the pressure wave of the curve B are smaller than those of the curve A, the internal working fluid gas of the Stirling refrigerator is leaking.

4. The Stirling refrigerator life monitoring method according to claim 1, characterized in that: In step 2, the pressure value curve a' is curve B, the pressure value curve b' is curve C, the amplitude and peak value of the pressure wave of curve B are both smaller than those of curve A, and the amplitude and peak value of the pressure wave of curve C are both smaller than those of curve B, then the internal working fluid gas of the Stirling refrigerator is contaminated.

5. The Stirling refrigerator life monitoring method according to claim 1, characterized in that: The pressure wave amplitude of the curve A is 0.2 MPa, and the peak value is 1.8 MPa.

6. The Stirling refrigerator life monitoring method according to claim 3, characterized in that: The pressure wave amplitude of the curve B ranges from 0.14 to 0.2 MPa, and the peak value ranges from 1.3 to 1.8 MPa.

7. The Stirling refrigerator life monitoring method according to claim 3, characterized in that: The warning value of the peak difference between the curve B and the curve A is 0.5 MPa.

8. The Stirling refrigerator life monitoring method according to claim 4, characterized in that: The warning value of the peak difference between the curve B and the curve C is 0.4 MPa.

9. A Stirling refrigerator life monitoring device, used to implement the monitoring method according to any one of claims 1 to 8, characterized in that: include: a first pressure sensor and a second pressure sensor, Wherein, the probe of the first pressure sensor and the probe of the second pressure sensor are respectively connected to the inside of the compressor of the Stirling refrigerator through the connecting holes on the compressor end cover of the Stirling refrigerator.

10. The Stirling refrigerator life monitoring device according to claim 9, characterized in that: A polymer membrane is provided at the probe of the second pressure sensor, and the polymer membrane is used to pass working gas molecules and block other gas molecules, so as to facilitate the second pressure sensor to measure the partial pressure of the working gas.

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