CN103216966B - Free piston type pulse tube refrigerator - Google Patents

Abstract

The invention discloses a free-piston pulse tube refrigerator, which includes at least one refrigeration unit, and the refrigeration unit includes a sequentially connected compression device, a regenerator, a cold-end heat exchanger, a pulse tube, and a heat exchanger at the hot end of the pulse tube. A free piston system is built in the vessel, the free piston system includes a free piston and a spring, the free piston fits with the vessel and is connected to the heat exchanger at the hot end of the vessel through the spring. In the present invention, a free piston system is placed in the pulse tube, and the free piston in the pulse tube can not only replace the gas piston in the pulse tube refrigerator to recover the expansion work of the gas to improve the intrinsic efficiency of the pulse tube refrigerator, but also realize Phase adjustment, thus eliminating the relatively complex phase adjustment mechanism such as inertial tube and gas storage, making the structure of the refrigerator more compact.

Description

A free piston pulse tube refrigerator

technical field

The invention relates to a pulse tube refrigerator, in particular to a free piston type pulse tube refrigerator.

Background technique

The pulse tube refrigerator was proposed by Gifford and Longsworth in 1964. It has no moving parts at the cold end and has the potential advantages of high reliability and long life. After nearly half a century of development, the pulse tube refrigerator has been widely used in Aerospace, low-temperature superconductivity and other fields. According to different driving sources, pulse tube refrigerators are mainly divided into G-M pulse tube refrigerators (also called low-frequency pulse tube refrigerators) and Stirling pulse tube refrigerators (also called high-frequency pulse tube refrigerators); G-M pulse tube refrigerators are composed of The G-M refrigerator is driven by the compressor, and its operating frequency is generally 1 to 2 Hz. The Stirling pulse tube refrigerator is driven by a linear compressor, and its operating frequency is generally 30 Hz.

Although pulse tube refrigerators have been widely used in ground and space fields, their low intrinsic efficiency limits their further applications. Theoretical analysis indicates that because the pulse tube refrigerator cannot recover the expansion work in the pulse tube, this part of the expansion work is dissipated in the form of heat at the hot end of the pulse tube, resulting in the intrinsic efficiency of the pulse tube refrigerator (the temperature of the low-temperature heat source/ The temperature zone of the high temperature heat source) is less than the efficiency of the Stirling refrigerator (Carnot efficiency). At present, there is a huge demand for low-temperature refrigerators in the superconducting field. The analysis report of the US Department of Energy pointed out that in order to meet the cooling requirements of future high-temperature superconducting equipment, the efficiency of refrigerators should be higher than 0.1 (80K).

The Chinese patent with the notification number CN100485828C discloses a cooling device for high-temperature superconducting devices, including a cold head of a refrigerator and a cooling plate. The flexible connection coupler at the lead end is connected to the flexible connection coupler at the end of the refrigerator through a flexible cooling strip, the cooling rod is connected to the cooling sheet, and the cooling sheet is sandwiched between the high-temperature superconducting magnet windings to conduct cooling. The rod is placed on the periphery of the high-temperature superconducting magnet assembly, and the upper and lower conductive cold end plates are respectively located on the upper and lower surfaces of the high-temperature superconducting device assembly. This cooling device is suitable for cooling high-temperature superconducting devices, but not suitable for pulse tube refrigerators. The efficiency of current pulse-tube refrigerators is generally lower than 0.1 (80K), which cannot meet the high-efficiency refrigeration technology requirements for cooling high-temperature superconducting devices. At the same time, the efficiency of pulse tube refrigerators is extremely low at deep low temperatures, especially in temperatures below 10K, making further improvement of efficiency a hot and difficult point in the research of pulse tube refrigerators.

Airgel is a solid-like substance with a porous structure, and its density is extremely small. The density of the lightest airgel in the world is only 0.16 mg/cubic centimeter, and it has very good elasticity. It returns to its original shape when compressed to 20%, and has good thermal insulation performance.

Contents of the invention

The invention provides a free-piston pulse tube refrigerator. A free piston system is arranged in the pulse tube so that the free-piston pulse tube refrigerator can recover the expansion work in the pulse tube, thereby improving its intrinsic efficiency to ideal Carnot High efficiency and compact structure to meet the high-efficiency cooling requirements of high-temperature superconducting devices.

A free-piston pulse tube refrigerator includes at least one refrigeration unit, the refrigeration unit includes a compression device, a regenerator, a cold-end heat exchanger, a pulse tube, and a pulse-tube hot-end heat exchanger connected in sequence, the A free piston system is built in the vessel, and the free piston system includes a free piston and a spring, and the free piston fits with the vessel gap and is connected with the heat exchanger at the hot end of the vessel through the spring.

The free piston and spring can be connected by detachable mechanical or chemical glue.

The free piston in the pulse tube can not only replace the gas piston in the pulse tube refrigerator, but also realize the phase adjustment, thus eliminating the complicated phase adjustment mechanism such as the inertial tube and the gas bank, and making the structure of the refrigerator more compact.

In order to increase the theoretical efficiency of the pulse tube refrigerator to the Carnot efficiency. Preferably, there is one refrigerating unit, the compression device is a low-frequency compressor unit, and the low-frequency compressor unit includes a compressor, an after-stage cooler, a compressor low-pressure control valve, and a compressor high-pressure control valve that are sequentially connected to form a circuit. The pipeline between the low-pressure control valve and the high-pressure control valve of the compressor is connected to the regenerator.

The specific connection mode of the above-mentioned free-piston pulse tube refrigerator is: the compressor and the after-stage cooler, the low-pressure control valve and the high-pressure control valve are sequentially connected to form a circuit, and the pipeline between the low-pressure control valve of the compressor and the high-pressure control valve of the compressor It is connected with the regenerator, the cold end heat exchanger, the pulse tube and the hot end heat exchanger of the pulse tube in sequence, the free piston is placed in the pulse tube and fits with the gap of the pulse tube, and the free piston is connected to the hot end heat exchanger of the pulse tube through a spring connected.

The regenerator is the core component of the pulse tube refrigerator. Reducing the loss of the regenerator has a decisive impact on improving the performance of the pulse tube refrigerator, and the two-way air intake can effectively reduce the gas flow through the regenerator, thereby reducing regenerator losses, thereby improving the performance of the pulse tube refrigerator.

More preferably, the heat exchanger at the hot end of the pulse tube is also connected with a two-way intake valve, one end of the two-way intake valve communicates with the heat exchanger at the hot end of the pulse tube, and the other end of the two-way intake valve communicates with the regenerator and Piping communication between low frequency compressor units.

The specific connection mode of the above-mentioned free-piston pulse tube refrigerator is as follows: the low-frequency compressor unit includes a compressor, an after-stage cooler, a compressor low-pressure control valve, and a compressor high-pressure control valve that are sequentially connected to form a circuit, and the compressor low-pressure control valve of the low-frequency compressor unit The pipeline between the control valve and the high-pressure control valve of the compressor is connected with the regenerator, the cold-end heat exchanger, the pulse tube and the hot-end heat exchanger of the pulse tube in sequence. The free piston is placed in the pulse tube and connected to the pulse tube by a spring. The hot end heat exchanger is connected; one end of the two-way air intake valve is in communication with the pulse tube hot end heat exchanger, and the other end of the two-way air intake valve is in communication with the pipeline between the regenerator and the low-frequency compressor unit.

As mentioned in the background technology, the efficiency of the low-frequency compressor unit is low due to the presence of resistance components such as high and low-pressure switching valves, while the high-frequency pulse tube refrigerator uses a valveless linear compressor and drives the linear compressor. The high efficiency of the linear motor makes the high-frequency pulse tube refrigerator have the potential to work efficiently.

More preferably, the compression device is a linear compressor.

The specific connection mode of the above-mentioned free-piston pulse tube refrigerator is: the linear compressor is connected with the regenerator, the cold-end heat exchanger, the pulse tube, and the pulse-tube hot-end heat exchanger in sequence, and the free piston is placed in the pulse tube. Connected to the pulse tube hot end heat exchanger.

In order to obtain a lower refrigeration temperature and obtain higher refrigeration performance at a lower refrigeration temperature, the structure of a multistage pulse tube refrigerator can be adopted, and at least one pulse tube of the multistage pulse tube refrigerator is arranged with a A free piston system with a free piston and a spring is used to recover the expansion work in the pulse tube, thereby improving the intrinsic efficiency of the pulse tube refrigerator.

Considering the special mechanical properties and thermophysical properties of airgel, as a preference, the free piston of any free-piston pulse tube refrigerator is composed of an airgel column.

The length of the airgel column is 1/3-1/2 of the length of the vessel, so that it can effectively isolate the heat exchange between the gas in the high-temperature section and the low-temperature section, as well as the gas and the vessel while recovering the expansion work in the vessel. The shuttling loss between the tube walls improves the performance of the pulse tube refrigerator.

The shape of the airgel column is cylindrical.

Arrange a free piston made of aerogel that can move freely in the pulse tube of the above-mentioned free piston type pulse tube refrigerator, and use the good thermal insulation performance of aerogel to effectively reduce the shuttling loss and gas in the pulse tube. Heat conduction loss, thereby further improving the efficiency of the free-piston pulse tube refrigerator. At the same time, the free piston made of airgel can store the compression work of the gas in the free piston through deformation during the compression stage, and release the compression work stored in the free piston during the expansion stage, thereby realizing the expansion work in the vessel. recovery, and then realize the improvement of the intrinsic refrigeration performance of the pulse tube refrigerator, so as to meet the current urgent demand for high-efficiency pulse tube refrigerators.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

(1) The free-piston pulse tube refrigerator replaces the gas piston in the pulse tube refrigerator by setting a free piston in the pulse tube refrigerator, so as to realize the recovery of the expansion work in the pulse tube refrigerator, and then realize the pulse tube refrigerator itself. Improvement of refrigeration performance is required to meet the current demand for high-efficiency pulse tube refrigerators.

(2) Compared with the current passive phase-modulating pulse tube refrigerator, the free-piston pulse tube refrigerator can recover the expansion work in the pulse tube, and at the same time has a compact structure; Compared with this free-piston pulse tube refrigerator, the structure is simple.

(3) The airgel column with good thermal insulation performance is made into the free piston of the pulse tube refrigerator, which can effectively reduce the shuttle loss in the pulse tube and the heat conduction loss of the gas, thereby further improving the efficiency of the pulse tube refrigerator.

Description of drawings

Fig. 1 is a schematic structural view of an embodiment of a free-piston pulse tube refrigerator of the present invention;

Fig. 2 is a structural schematic diagram of another embodiment of the free-piston pulse tube refrigerator of the present invention;

Fig. 3 is a schematic structural view of another embodiment of the free-piston pulse tube refrigerator of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following is merely illustrative and does not limit the scope of the present invention.

Example 1

As shown in Figure 1, a free-piston pulse tube refrigerator includes a compressor C, an aftercooler AC, a compressor low-pressure control valve LV and a compressor high-pressure control valve HV, a regenerator RG, and a cold-end heat exchanger HX2, pulse tube PT, free piston FP, spring S, and pulse tube hot end heat exchanger HX3.

The connection relationship of the above-mentioned components is as follows: compressor C, after-stage cooler AC, compressor high-pressure control valve HV and compressor low-pressure control valve LV are sequentially connected in series to form a circulation loop of the low-frequency compressor unit; the inlet of the regenerator RG is connected to the compressor The pipeline between the high pressure control valve HV of the compressor and the low pressure control valve LV of the compressor is connected; the outlet of the regenerator RG is connected with the cold end heat exchanger HX2, the pulse tube PT and the pulse tube hot end heat exchanger HX3 through the pipeline in turn ; The free piston FP is placed in the vessel PT and fits with the vessel PT clearance, its inner diameter is slightly smaller than the inner diameter of the vessel PT, and its length can be selected as 1/3-1/2 of the vessel length according to the simulation calculation results. The piston FP is connected with the hot end heat exchanger HX3 of the pulse tube through a spring S.

Example 2

Utilize the airgel column to form the free piston in embodiment 1, other structures are the same as embodiment 1, the specific structure of the piston type pulse tube refrigerator of this embodiment is: comprise compressor C, after-stage cooler AC, compressor Low pressure control valve LV and compressor high pressure control valve HV, regenerator RG, cold end heat exchanger HX2, pulse tube PT, free piston FP, spring S and pulse tube hot end heat exchanger HX3.

Compressor C, after-stage cooler AC, compressor high pressure control valve HV and compressor low pressure control valve LV are sequentially connected in series to form a circulation loop of low frequency compressor unit; the inlet of regenerator RG is connected with compressor high pressure control valve HV and compressor The pipeline between the low pressure control valve LV is connected; the outlet of the regenerator RG is connected with the cold end heat exchanger HX2, the pulse tube PT and the pulse tube hot end heat exchanger HX3 through the pipeline in turn; The free piston FP is placed in the vessel PT and fits with the vessel PT. Its inner diameter is slightly smaller than the inner diameter of the vessel PT, and its length can be selected as 1/3-1/2 of the vessel length according to the simulation calculation results. The free piston FP formed by the gel column is connected with the hot end heat exchanger HX3 of the pulse tube through the spring S.

The operation process of the piston pulse tube refrigerator in this embodiment is as follows:

In the initial stage, the compressor low-pressure regulating valve LV and compressor high-pressure regulating valve HV are both closed, the gas is compressed by the compressor C and becomes a high-temperature and high-pressure gas, and the high-temperature and high-pressure gas flows through the after-stage cooler AC and then cools down to room temperature. When the gas pressure is higher than the set value, the high-pressure regulator valve HV of the compressor is opened, and the high-pressure room temperature gas flows out from the high-pressure valve HV of the compressor, passes through the regenerator RG and exchanges heat with the packing in it, and the temperature drops into subsequent related components. The high-pressure gas in the pulse tube PT compresses the free piston FP, and the gas compression work is stored in the free piston FP, so that the whole system is in a high-pressure state, then the high-pressure regulating valve HV of the compressor is closed, and the low-pressure regulating valve LV of the compressor is opened. The gas passes through the pulse tube PT, the free piston FP, and the regenerator RG, and finally returns to the compressor C through the compressor low-pressure regulating valve LV. The free piston FP releases the compression work stored in the high-pressure stage in the low-pressure stage, thus A cycle is completed. During the cycle, there is a temperature difference between the gas entering and leaving the cold end heat exchanger HX2, thereby generating a refrigeration effect, and the cooling capacity is taken from the cold end heat exchanger HX2 to cool various equipment and devices that need to be cooled.

Example 3

As shown in Figure 2, a free-piston pulse tube refrigerator includes a compressor C, an aftercooler AC, a compressor low-pressure control valve LV and a compressor high-pressure control valve HV, a regenerator RG, and a cold-end heat exchanger HX2, pulse tube PT, free piston FP, spring S, pulse tube hot end heat exchanger HX3 and bidirectional intake valve O. The free piston FP is composed of an airgel column, which is cylindrical, with an inner diameter slightly smaller than that of the vessel PT, and its length can be selected as 1/3-1/2 of the vessel length according to the simulation calculation results.

The connection relationship of the above-mentioned components is as follows: compressor C, after-stage cooler AC, compressor high-pressure control valve HV and compressor low-pressure control valve LV are sequentially connected in series to form a circulation loop of the low-frequency compressor unit; the inlet of the regenerator RG is connected to the compressor The pipeline between the high pressure control valve HV of the compressor and the low pressure control valve LV of the compressor is connected; the outlet of the regenerator RG is connected with the cold end heat exchanger HX2, the pulse tube PT and the pulse tube hot end heat exchanger HX3 through the pipeline in turn ; The free piston FP is placed in the pulse tube PT and is in clearance fit with the pulse tube PT. The free piston FP is connected to the heat exchanger HX3 at the hot end of the pulse tube through a spring S; one end of the two-way intake valve O is connected to the regenerator RG and the low-frequency compressor unit The pipeline between them is connected, and the other end of the two-way inlet valve O is connected with the heat exchanger HX3 at the hot end of the pulse tube.

The operation process of the free-piston pulse tube refrigerator of the present embodiment is as follows:

In the initial stage, the compressor low-pressure regulating valve LV and compressor high-pressure regulating valve HV are both closed, the gas is compressed by the compressor C and becomes a high-temperature and high-pressure gas, and the high-temperature and high-pressure gas flows through the after-stage cooler AC and then cools down to room temperature. When the gas pressure is higher than the set value, the high-pressure regulating valve HV of the compressor is opened, and the high-pressure room temperature gas flows out from the high-pressure valve HV of the compressor and is divided into two streams. One stream passes through the regenerator RG and exchanges heat with the packing therein. The high-pressure gas in the pulse tube PT compresses the free piston FP to store the compression work of the gas in the free piston FP, and the other gas passes through the hot end heat exchanger HX3 of the pulse tube from the two-way intake valve O Into the pulse tube PT, so that the whole system is in a high pressure state, then the high pressure regulating valve HV of the compressor is closed, the low pressure regulating valve LV of the compressor is opened, and the gas is divided into two streams at the heat exchanger HX3 at the hot end of the pulse tube, and one stream flows from the two-way The intake valve O returns to the compressor C through the compressor low-pressure regulating valve LV, and the other flow passes through the pulse tube PT, the free piston FP, and the regenerator RG in turn, and finally returns to the compressor C through the compressor low-pressure regulating valve LV, and the free piston FP releases the compression work stored in the high-pressure stage in the low-pressure stage, thereby completing a cycle. During the cycle, there is a temperature difference between the gas entering and leaving the cold-end heat exchanger HX2, which produces a refrigeration effect, and the cooling capacity changes from The cold end heat exchanger HX2 is taken out to cool various equipment and devices that need to be cooled.

Example 4

As shown in Figure 3, a free-piston pulse tube refrigerator includes a linear compressor C', a regenerator hot-end heat exchanger HX1, a regenerator RG, a cold-end heat exchanger HX2, a pulse tube PT, and a free piston FP, spring S and pulse tube hot end heat exchanger HX3. The free piston FP is composed of an airgel column, the airgel column is cylindrical, its inner diameter is slightly smaller than the inner diameter of the vessel PT, and its length can be selected as 1/3-1/2 of the vessel length according to the simulation calculation results .

The connection relationship of the above components is as follows: the linear compressor C' is sequentially connected with the regenerator hot-end heat exchanger HX1, regenerator RG, cold-end heat exchanger HX2, pulse tube PT, and pulse tube hot-end heat exchanger HX3, The free piston FP is placed in the pulse tube PT and is in clearance fit with the pulse tube PT. The free piston FP is connected with the heat exchanger HX3 at the hot end of the pulse tube through a spring S.

The operation process of the free-piston pulse tube refrigerator of this embodiment is:

In the high-pressure stage, the high-temperature and high-pressure gas compressed by the linear compressor C' flows through the heat exchanger HX1 at the hot end of the regenerator and is cooled to room temperature, and then exchanges heat with the regenerative filler in the regenerator RG, the temperature drops, and then It flows through the cold end heat exchanger HX2, the pulse tube PT, the free piston FP and the hot end heat exchanger HX3 of the pulse tube in sequence. The high-pressure gas in the pulse tube PT compresses the free piston FP and stores the compression work of the gas in the free piston FP. After entering the low-pressure cycle, the gas returns to the linear compressor C' through the free piston FP, the pulse tube PT, the cold-end heat exchanger HX2, and the regenerator RG to complete a cycle from the hot-end heat exchanger HX3 of the pulse tube. During the circulation process, there is a temperature difference between the gas entering and leaving the cold end heat exchanger HX2, thereby generating a refrigeration effect at the cold end heat exchanger HX2, and the cold energy is taken out from the cold end heat exchanger HX2 to cool various equipment and devices that need to be cooled. device.

Claims (7)

1. a free-piston type vascular refrigerator, comprise at least one refrigeration unit, described refrigeration unit comprises the compression set, regenerator, cool end heat exchanger, vascular and the vascular hot-side heat exchanger that connect successively, it is characterized in that, described vascular is built-in with a free-piston system, described free-piston system comprises free-piston and spring, and described free-piston and vascular space are joined merga pass spring and be connected with vascular hot-side heat exchanger.

2. free-piston type vascular refrigerator according to claim 1, it is characterized in that, described refrigeration unit is one, described compression set is low-frequency compression unit, low-frequency compression unit comprises the compressor, level aftercooler, compressor low-pressure control valve and the compressor high pressure control valve that are in turn connected to form loop, be provided with one between compressor low-pressure control valve and compressor high pressure control valve and extend pipeline, described extension pipeline and the pipeline connection between compressor low-pressure control valve and compressor high pressure control valve, described regenerator is arranged on this extension pipeline.

3. free-piston type vascular refrigerator according to claim 2, it is characterized in that, described vascular hot-side heat exchanger is also connected with a bidirection air intake valve, described bidirection air intake valve one end is communicated with vascular hot-side heat exchanger, the bidirection air intake valve other end and the extension pipeline connection between regenerator and low-frequency compression unit.

4. free-piston type vascular refrigerator according to claim 1, is characterized in that, described compression set is Linearkompressor.

5., according to described free-piston type vascular refrigerator arbitrary in claim 1-4, it is characterized in that, the length of described free-piston is the 1/3-1/2 of vessel length.

6., according to described free-piston type vascular refrigerator arbitrary in claim 1-4, it is characterized in that, described free-piston is made up of aeroge post.

7. free-piston type vascular refrigerator according to claim 5, is characterized in that, described free-piston is made up of aeroge post.