CN104654648A - Multistage Stirling type pulse tube refrigerator - Google Patents

Abstract

The invention relates to a multi-stage stepped piston type pulse tube refrigerator, which includes a compressor, an n-stage cold head and an n-stage stepped moving piston system, wherein, n is an integer greater than 1, and the cold head includes a cooler, a regenerator, Cooling heat exchanger and pulse tube, the cooling heat exchanger in the nth stage cold head is used as the nth stage cold output end, the compression chamber of the compressor is connected with the cooler in the cold head, and the n stage step push piston system The working chambers of the pushing pistons are respectively connected to the pulse tubes, and the back working chambers of the pushing pistons of the n-stage stepped moving piston system communicate with the compression chamber of the compressor. An adjustment chamber is connected between the piston working chambers. Compared with the prior art, the present invention can make the gas flow and pressure at the cold end of the pulse tube work at an optimal phase angle by adjusting the volume of the adjustment cavity, while taking into account the distribution of input work at all levels, and the expansion work can be recovered , the theoretical efficiency is the same as that of the Carnot machine.

Description

A multi-stage Stirling-type pulse tube refrigerator

technical field

The invention relates to a pulse tube refrigerator, in particular to a multistage Stirling type pulse tube refrigerator.

Background technique

The Stirling-type pulse tube refrigerator has no moving parts at low temperatures, and its compressor can be suspended by a linear motor and a leaf spring, so that the compressor has a long life and high efficiency. In the 77K refrigeration temperature range, among the existing small cryogenic refrigerators, the Stirling pulse tube refrigerator has the highest lifespan and the highest efficiency. In order to obtain low temperature, such as 20-4K refrigeration temperature, a multi-stage pulse tube refrigerator is necessary. At present, the two-stage Stirling-type pulse tube refrigerator has been put into practical use in the 35K temperature range. In the 20K temperature zone, it is difficult to lower the temperature and improve the efficiency. 20K is the liquid hydrogen temperature zone, which has very important uses, such as hydrogen liquefaction, cryogenic pumps, etc.

There is a phase shifter at the hot end of the pulse tube of the pulse tube refrigerator. Its function is to make the flow and pressure of the gas at the cold end of the pulse tube have an optimal phase angle, so that the efficiency of the regenerator is the highest, and the efficiency of the refrigerator is improved. Highest. In the existing multi-stage pulse tube refrigerators, the phase shifter is generally a two-way inlet type or an inertial tube type, and its effect is not good at lower temperatures, and the flow and pressure of the gas at the cold end of the pulse tube cannot be operated at the optimum level. good phase angle. At lower temperatures, phase shifters are very important, which is why the development of Stirling-type pulse tube refrigerators with refrigeration temperatures below 20K is progressing slowly. In the step-moving piston type multi-stage pulse tube refrigerator, a step-moving piston is used as a phase shifter, and the step-moving piston working chambers formed by the step-moving pistons are respectively connected to the hot ends of the pulse tubes of each level. Each step pushes the working chamber of the piston to recover the expansion work, and the theoretical efficiency is the same as the Carnot efficiency. Thus appears to be an optimal phase shifter. However, the disadvantage is that the ratio of the scavenging volume of the working chamber of each step-moving piston formed by the step-moving piston determines the input work of the compressor to each stage. For different purposes, the cooling temperature and cooling capacity of each stage are design values. The refrigerating capacity is related to the input work, so the ratio of the scavenging volume of the working chamber of each step-moving piston is basically determined by the refrigerating capacity. Since the working temperature of each stage of the pulse tube is different, the scavenging volume required for phase modulation has an optimal value. Therefore, the existing stepped piston type phase shifter cannot give consideration to both phase modulation and input work distribution at the same time.

Contents of the invention

The object of the present invention is to provide a multi-stage Stirling type pulse tube refrigerator in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A multi-stage stepped piston type pulse tube refrigerator includes a compressor, an n-stage cold head and an n-stage stepped moving piston system, wherein n is an integer greater than 1, and the cold head is composed of a cooler, a regenerator, and a cooling capacity exchange Heater, pulse tube, pulse tube hot end gas homogenizer and pulse tube connecting pipe are connected. The cold heat exchanger in the nth stage cold head is used as the nth stage cold output end. The compression of the compressor The cavity is connected to the cooler in the cold head through a connecting pipe, and the moving piston working chamber of the n-level stepped moving piston system is respectively connected to the vessel through the connecting pipe of the vessel, and the moving piston of the n-level stepped moving piston system The back working chamber communicates with the compression chamber of the compressor, and an adjustment chamber is connected between the vessel in at least one stage of the cold head and the working chamber of the push piston connected thereto.

The volume of the compression chamber changes periodically, so that the gas pressure basically changes in a sine wave. The gas reciprocates between the compression chamber, the cold heads of all levels and the working chamber of the push piston, and the flow velocity basically shows a sine wave. By adjusting the volume of the chamber , so that the phase difference between the gas flow at the cold end of the pulse tube and the pressure change reaches an optimal value.

The n-level cold heads are pre-cooled or coupled.

When the n-level cold heads are connected in a pre-cooling type, the n-th level cold head contains n regenerators, n-1 pre-cooling heat exchangers, a cooling heat exchanger, a pulse tube, and a pulse tube heat exchanger. end gas homogenizer and a pulse tube connecting pipe, the regenerator and pre-cooling heat exchanger are alternately connected between the cooler and the cooling heat exchanger, the cooling heat exchanger, the pulse tube, and the pulse tube heat exchanger The end gas homogenizer and the pulse tube connecting pipe are connected in sequence, and the pre-cooling heat exchanger is connected with the cooling heat exchanger of the same level through a thermal bridge; the compression chamber of the compressor is respectively connected with the cold head of each stage The coolers are connected by connecting pipes.

When the n-stage cold heads are coupled, the compression chamber of the compressor is connected to the cooler in the first-stage cold head through a connecting pipe, and the regenerator in the first-stage cold head is connected to the second-stage cold head. The regenerator in the head is connected, the regenerator in the second-stage cold head is connected with the regenerator in the third-stage cold head, until the regenerator in the n-1th cold head is connected to the n-th cold head The regenerator in the head is connected.

Further, there is an adjustment chamber connected between the vessel in the n-1 stage cold head and the working chamber of the step-moving piston connected to it.

Furthermore, an adjustment chamber is connected between the vessel in each stage of the cold head and the working chamber of the step-moving piston connected to it.

The adjustment chamber is the dead volume of the working chamber of the push piston which is equivalent to the volume of the adjustment chamber.

The adjustment chamber is a connecting pipe corresponding to the volume of the adjustment chamber.

Preferably, n=2 or 3.

Compared with the prior art, the multi-stage Stirling-type pulse tube refrigerator of the present invention can make the flow and pressure of the gas at the cold end of the pulse tube work at an optimal phase angle by adjusting the volume of the adjustment chamber, while taking into account the The distribution of input work, and the expansion work can be recovered, and the theoretical efficiency is the same as that of the Carnot machine.

Description of drawings

Fig. 1 is the structural representation of embodiment 1;

Fig. 2 is the structural representation of embodiment 2;

Fig. 3 is the structural representation of embodiment 3;

FIG. 4 is a schematic structural view of Embodiment 4.

In the figure, 1a is a three-stage pre-cooling cold head, 1b is a two-stage pre-cooling cold head, 1c is a three-stage coupled cold head, 1d is a two-stage coupled cold head, 11 is a first-stage cold head, 101 is the first-stage connecting pipe, 102 is the first-stage cooler, 103 is the first-stage regenerator, 111 is the first-stage cooling heat exchanger, 112 is the first-stage pulse pipe, and 113 is the first-stage pulse pipe Hot-end gas homogenizer, 114 is the first-stage vessel connecting pipe, 115 is the first-stage adjustment cavity, 12 is the second-stage cold head, 12b is the second-stage coupling cold head, 13 is the third-stage cold head, 13b is the third-stage coupling cold head, 201 is the second-stage connecting pipe, 202 is the second-stage cooler, 203 is the second-stage first regenerator, 204 is the second-stage pre-cooling heat exchanger, and 205 is the second 206 is the second heat regenerator of the second stage, 211 is the second-stage cold heat exchanger, 212 is the second-stage pulse tube, 213 is the gas homogenizer at the hot end of the second-stage pulse tube, and 214 is the second-stage heat exchanger. Two-stage pulse tube connecting pipe, 215 is the second-stage regulating chamber, 221 is the second-stage cold connecting pipe, 222 is the second-stage second regenerator gas homogenizer, 301 is the third-stage connecting pipe, 302 is the third-stage 303 is the first regenerator of the third stage, 304 is the first pre-cooling heat exchanger of the third stage, 305 is the first heat bridge of the third stage, 306 is the second regenerator of the third stage, 307 308 is the second heat bridge of the third stage, 309 is the third regenerator of the third stage, 311 is the third-stage cooling heat exchanger, and 312 is the third stage Vessel, 313 is the hot end gas homogenizer of the third-stage vessel, 314 is the connecting pipe of the third-stage vessel, 315 is the third-stage regulating chamber, 321 is the third-stage cold connecting pipe, and 322 is the third-stage third-stage Regenerator gas homogenizer, 4a is a three-stage step push piston system, 4b is a two-step step push piston system, 41 is the first working chamber of the push piston, 42 is the second work chamber of the push piston, and 43 is the third work of the push piston chamber, 44 is the working chamber on the back of the push piston, 45 is the air storage space of the push piston, 461 is a three-step step push piston, 462 is a three-step step cylinder, 461b is a two-step step push piston, 462b is a two-step step cylinder, and 463 is a Push the piston rod, 464 is the back cover, 465 is the leaf spring, 466 is the air storage of the push piston, 47 is the connecting pipe of the back working chamber of the push piston, 5 is the compressor, 51 is the compression chamber, 521 is the compression piston, 522 is the compression cylinder , 53 is a linear motor, and 54 is a compressor connecting pipe.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

The structure of the three-stage piston pre-cooling pulse tube refrigerator is shown in Figure 1, which includes a three-stage step moving piston system 4a, a compressor 5 and a three-stage pre-cooling cold head 1a.

The three-stage pre-cooling cold head 1 a includes a first-stage cold head 11 , a first-stage cold head 12 and a third-stage cold head 13 .

The first-stage cold head 11 is composed of a first-stage connecting pipe 101, a first-stage cooler 102, a first-stage regenerator 103, a first-stage cooling heat exchanger 111, a first-stage pulse pipe 112, a first-stage pulse The gas homogenizer 113 at the hot end of the tube and the first-stage vessel connecting pipe 114 are connected accordingly, and the first-stage vessel connecting pipe 114 has a first-stage adjustment chamber 115 on it. Gas can flow back and forth between the various components.

The second-stage cold head 12 is composed of a second-stage connecting pipe 201, a second-stage cooler 202, a second-stage first regenerator 203, a second-stage pre-cooling heat exchanger 204, and a second-stage second regenerator 206. , the second-stage cooling heat exchanger 211, the second-stage pulse tube 212, the second-stage pulse tube hot-end gas homogenizer 213, and the second-stage pulse tube connecting pipe 214 are connected in sequence, and the second-stage pulse tube is connected The tube 214 is connected with a second-stage adjustment cavity 215 . Gas can flow back and forth between the various components.

The third-stage cold head 13 is composed of a third-stage connecting pipe 301, a third-stage cooler 302, a third-stage first heat regenerator 303, a third-stage first pre-cooling heat exchanger 304, and a third-stage second heat exchanger. device 306, third-stage second pre-cooling heat exchanger 307, third-stage third regenerator 309, third-stage cooling heat exchanger 311, third-stage pulse tube 312, third-stage pulse tube hot end gas The homogenizer 313 and the third-stage vascular connection pipe 314 are connected in sequence, and the third-stage vascular connection pipe 314 is connected with a third-stage adjustment cavity 315 . Gas can flow back and forth between the various components.

The first-stage refrigeration temperature is generally 80K, and the cooling capacity is output from the first-stage cooling heat exchanger 111; the second-stage refrigeration temperature is generally 20K, and the cooling capacity is output from the second-stage cooling heat exchanger 211; The temperature is generally at 4K, and the cooling capacity is output from the cooling capacity heat exchanger 311 .

The right end of the vessel is at room temperature and is customarily called the hot end, and the left end is at low temperature and is customarily called the cold end. The left end of the regenerator has a high temperature and is called the hot end, and the right end has a low temperature, which is customarily called the cold end.

The second-stage heat bridge 205 and the third-stage first heat bridge 305 connect the second-stage pre-cooling heat exchanger 204, the third-stage first pre-cooling heat exchanger 304 and the first-stage cooling heat exchanger 111 together , the third-stage second heat bridge 308 connects the third-stage second pre-cooling heat exchanger 307 and the second-stage cooling heat exchanger 211 together. In this way, the cooling capacity of the first-stage cooling heat exchanger 111 can precool the second-stage first heat regenerator 203 and the third-stage first heat regenerator 303, so that the leakage heat from the hot end leaks to the first stage, and Not second level. The cooling capacity of the second-stage cooling heat exchanger 211 can pre-cool the third-stage second regenerator 304, so that the heat leakage from the hot end leaks to the second stage instead of the third stage. Like this, the cooling capacity of the second stage and the third stage is just larger.

Thermal bridges and heat exchangers are made of materials with good thermal conductivity, such as copper, while regenerators and pulse tubes are made of materials with poor thermal conductivity, such as stainless steel. The regenerator is filled with regenerating materials, such as stainless steel wire mesh, copper mesh, lead balls, HoCu ₂ balls and other regenerating materials.

The three-stage step push piston system 4a is made up of a three-stage step push piston 461, a three-stage step cylinder 462, a push piston rod 463, a rear cover 464, a leaf spring 465, and a push piston gas storehouse 466, and the leaf spring 465 supports the push piston rod 463, The push piston rod 463 is connected with the three-stage step push piston 461, so that the three-stage step push piston 461 remains non-contact in the three-stage step cylinder 462 to form a gap seal. Gap seal means that there is a small gap between the cylinder and the piston so that the gas only leaks slightly. Simultaneously, leaf spring 465 forms a vibrating system axially with three-stage step pushing piston 461 and pushing piston rod 463, and this vibrating system has a natural frequency, which becomes the natural frequency of moving piston. The three-stage stepped push piston 461 and the three-stage stepped cylinder 462 form the first working chamber 41 of the pushed piston, the second working chamber 42 of the pushed piston, the third working chamber 43 of the pushed piston and the back working chamber 44 of the pushed piston, and the air storage space 45 of the pushed piston Keep the pressure basically constant. The connecting pipe 47 of the back working chamber of the push piston is connected with the connecting pipe 54 of the compressor.

Compressor 5 is made up of compression piston 521 , compression cylinder 522 , linear motor 53 and compressor connecting pipe 54 , compression piston 521 and compression cylinder 522 form compression chamber 51 . The general linear motor 53 is composed of an inner stator, an outer stator, a coil, a magnet and a leaf spring, and the leaf spring supports the piston in the cylinder to keep the gap sealed. Gap seal means that there is a small gap between the cylinder and the piston so that the gas only leaks slightly.

The first-stage connecting pipe 101, the second-stage connecting pipe 201, and the third-stage connecting pipe 301 are connected to the compressor connecting pipe 54, and the connecting pipe 47 of the working chamber behind the pushing piston is also connected to the connecting pipe 54 of the compressor, so that the moving piston back works The chamber 44 compresses gas together with the compression chamber 51 to supply the third-stage cold head 1a. And the work of moving the back working chamber 44 of the piston comes from the first working chamber 41 of the moving piston, the second working chamber 42 of the moving piston and the third working chamber 43 of the moving piston.

The first stage working chamber 41 of the push piston is connected with the first stage vessel connecting pipe 114, the second stage working chamber 42 of the push piston is connected with the second stage vessel connection pipe 214, and the third stage working chamber 43 of the push piston is connected with the third stage vessel connecting pipe 114. The vessel connecting pipes 314 are connected, so that the expansion work of each vessel is recovered by the first working cavity 41 of the pushing piston, the second working cavity 42 of the pushing piston and the third working cavity 43 of the pushing piston.

Pushing the piston rod 463 plays the role of driving the pushing piston. The pressure in the gas storage space 45 of the push piston is basically constant, which is the average pressure. The pressures of the first working chamber 41 of the moving piston, the second working chamber 42 of the moving piston, the third working chamber 43 of the moving piston and the back working chamber 44 of the moving piston are basically in the form of Sinusoidal variation centered on mean pressure. In this way, there is an alternating net force acting on the push piston, which overcomes the flow resistance and moves it.

What drives the linear motor is alternating current, and its frequency is called the operating frequency of the refrigerator. After the linear motor is supplied with alternating current, the linear motor 53 drives the compression piston 521 to perform reciprocating motion, so that the volume of the compression chamber 51 changes periodically, so that the gas pressure changes approximately in a sine wave. The gas can reciprocate between the compression chamber, the working chambers of the push piston, the first-stage cold head, the second-stage cold head, and the third-stage cold head, and the flow velocity is basically a sine wave.

The phase difference between the gas flow and the pressure change at the cold end of the pulse tube has an optimal value, so that the efficiency of the regenerator is maximized, and thus the efficiency of the refrigerator is maximized. The phase difference between the flow of the gas at the cold end of each stage of the pulse tube and the optimum value of the pressure change is different, which can be realized by adjusting the volume of the adjustment cavity of each stage.

The ratio of the scavenging volume of each working chamber of the step-moving piston determines the ratio of the work flow of the compressor to each stage, and the cooling capacity of each stage is determined by the application, and the cooling capacity is determined by the input work. Therefore, for a refrigeration As far as the machine is concerned, the scavenging volume ratio of each working chamber of the stepped piston is basically determined by the cooling capacity of each stage.

In the design, although the ratio of the scavenging volume of the working chambers of each pushing piston is determined, the scavenging volume of each working chamber of the moving pistons can be designed to be larger, and the gas in each working chamber is first supplied to the adjustment chamber, and the remaining supply pulses Tube, by adjusting the volume of the adjustment cavity, the gas supplied to the vessels at all levels is optimal, so that each vessel works in the best state.

For the push piston system with a given scavenging volume of each push piston working chamber, corresponding to a total scavenging volume, that is, the sum of the volumes of each push piston working chamber, there is a group of optimal adjustment chamber volumes, in which there is a set of The volume of the adjustment cavity may be zero. At this time, the total scavenging volume of the moving piston is the smallest, and the adjustment chamber can be reduced by one. That is, in Fig. 1, only two adjustment chambers are sufficient.

However, if there is no adjustment chamber, it is difficult to adjust all three pulse tubes in an optimal state. Therefore, at least one adjustment chamber is required in the three-stage piston precooling pulse tube refrigerator shown in FIG. 1 .

Generally, the third-stage refrigeration temperature can reach 4K, and the second-stage refrigeration temperature can reach 20K. In this way, the temperature difference between the two ends of the second-stage pulse tube and the third-stage pulse tube is very large. The first-level cold head can be connected with about the middle of the second-level vessel and the third-level vessel near the hot end with a thermal bridge, and the second-level cold head can be connected with the third-level About one-third of the pulse tube near the cold end is connected by a thermal bridge, so that the leakage heat generated by the heat conduction of the pulse tube is balanced by a higher level of cooling capacity, thereby further improving the efficiency.

Here, the adjustment chamber can degenerate into a connecting pipe with a considerable volume, and can also degenerate into a dead volume of a step-push piston working chamber with a considerable volume, where the dead volume refers to the minimum volume between the step-push piston cylinder top and the step-push piston top.

Here, too, the compressors can be used in pairs, and the push-piston system can also be used in pairs to reduce vibrations.

Example 2

The structure of the two-stage piston pre-cooling pulse tube refrigerator is shown in Figure 2, including a two-stage step moving piston system 4b, a compressor 5 and a two-stage pre-cooling cold head 1b.

The two-stage pre-cooling cold head 1 b includes a first-stage cold head 11 and a second-stage cold head 12 .

Compared with Fig. 1, the second-stage pre-cooling cold head 1b lacks the third-stage cold head, and the step-push piston and step cylinder of the two-stage step-push piston system 4b have become two-stage step-push piston 461b and two-stage step cylinder 462b. The two-stage stepped push piston 461b and the two-stage stepped cylinder 462b form the first working chamber 41 of the pushing piston and the second working chamber 42 of the pushing piston.

As shown in FIG. 2 , the two-stage step-moving piston pre-cooling pulse tube refrigerator of this embodiment may have two adjustment chambers or only one adjustment chamber.

It can be seen that, in an n-stage pulse tube refrigerator, the number of adjustment chambers may be n-1, but at least one. That is, in a multi-stage pulse tube refrigerator, at least one pulse tube should be connected with an adjustment chamber between the stepped moving piston working chamber connected to it.

If there is an adjustment cavity between only one vessel and the working cavity of the stepped piston connected to it, the vessel can be in the best working state, and at this time, other vessels may not be in the best state.

Example 3

The three-stage stepped moving piston coupled pulse tube refrigerator, as shown in FIG. 3 , includes a three-stage stepped moving piston system 4a, a compressor 5 and a three-stage coupled cold head 1c.

The three-stage coupled cold head 1c includes a first-stage cold head 11, a second-stage coupled cold head 12b, and a third-stage coupled cold head 13b.

The second-stage coupling cold head 12b is composed of a second-stage cold connection pipe 221, a second-stage second regenerator gas homogenizer 222, a second-stage second regenerator 206, a second-stage cooling heat exchanger 211, and a second-stage second regenerator 206. The second-stage vessel 212 , the hot-end gas homogenizer 213 of the second-stage vessel and the second-stage vessel connection pipe 214 are sequentially connected, and the second-stage vessel connection pipe 214 is connected with a second-stage adjustment chamber 215 . Gas can flow back and forth between the various components.

The third-stage coupling cold head 13b is composed of a third-stage cold connection pipe 321, a third-stage third regenerator gas homogenizer 322, a third-stage third regenerator 309, a third-stage cooling heat exchanger 311, a third-stage The third-stage vessel 312 , the third-stage vessel hot-end gas homogenizer 313 and the third-stage vessel connecting pipe 314 are sequentially connected, and the third-stage vessel connecting pipe 314 is connected with a third-stage adjustment chamber 315 . Gas can flow back and forth between the various components.

The second-stage coupling cold head 12b is connected to the first-stage cooling heat exchanger 111 by the second-stage cold connecting pipe 221, and the third-stage coupling cold head 13b is connected to the second-stage cooling heat exchanger by the third-stage cold connecting pipe 321. Heater 211. The gas can flow back and forth between the components of the three-stage coupling cold head.

The third regenerator 309 of the third stage may be directly connected with the second regenerator 206 of the second stage, and the connection of the second regenerator 206 of the second stage may be directly connected with the first regenerator 103 .

The structures of the three-stage moving piston system 4a and the compressor 5 in the three-stage piston coupled pulse tube refrigerator are the same as those of the three-stage piston precooling pulse tube refrigerator in Embodiment 1, and its working principle is also the same as that of the three-stage piston precooling pulse tube refrigerator The working principle of the three-stage stepped piston system 4a and the compressor 5 in Embodiment 1 are the same.

In this embodiment, the first-stage cold head 11 , the second-stage coupling cold head 12b or the third-stage coupling cold head 13b are all provided with adjustment chambers.

As other implementations, only one of the first-stage cold head 11, the second-stage coupling cold head 12b, or the third-stage coupling cold head 13b may be provided in the three-stage stepped piston-coupled pulse tube refrigerator or There are two adjustment chambers.

Example 4

The two-stage stepped piston-coupled pulse tube refrigerator, as shown in FIG. 4 , includes a two-stage stepped piston system 4b, a compressor 5 and a two-stage coupled cold head 1d.

The secondary coupling cold head 1d includes a first coupling cold head 11 and a second coupling cold head 12b.

Compared with Fig. 3, the second-stage coupling cold head 1d lacks the third-stage coupling cold head 13b, and the step-push piston and step cylinder of the two-stage step-push piston system 4b become the two-stage step push piston 461b and the two-step step cylinder. Cylinder 462b. The two-stage stepped push piston 461b and the two-stage stepped cylinder 462b form the first working chamber 41 of the pushing piston and the second working chamber 42 of the pushing piston.

As shown in FIG. 2 , the two-stage stepped piston-coupled pulse tube refrigerator in this embodiment may have two adjustment chambers or only one adjustment chamber.

Example 5

A multi-stage stepped piston type pulse tube refrigerator includes a compressor, an n-stage cold head and an n-stage stepped moving piston system, wherein n is an integer greater than 1, and the cold head is composed of a cooler, a regenerator, and a cooling capacity exchange Heater, pulse tube, pulse tube hot end gas homogenizer and pulse tube connecting pipe are connected. The cold heat exchanger in the nth stage cold head is used as the nth stage cold output end. The compression of the compressor The cavity is connected to the cooler in the cold head through a connecting pipe, and the moving piston working chamber of the n-level stepped moving piston system is respectively connected to the vessel through the connecting pipe of the vessel, and the moving piston of the n-level stepped moving piston system The back working chamber communicates with the compression chamber of the compressor, and an adjustment chamber is connected between the vessel in at least one stage of the cold head and the working chamber of the push piston connected thereto.

The volume of the compression chamber changes periodically, so that the gas pressure basically changes in a sine wave. The gas reciprocates between the compression chamber, the cold heads of all levels and the working chamber of the push piston, and the flow velocity basically shows a sine wave. By adjusting the volume of the chamber , so that the phase difference between the gas flow at the cold end of the pulse tube and the pressure change reaches an optimal value.

The n-level cold heads are pre-cooled or coupled.

When the n-level cold heads are connected in a pre-cooling type, the n-th level cold head contains n regenerators, n-1 pre-cooling heat exchangers, a cooling heat exchanger, a pulse tube, and a pulse tube hot end A gas homogenizer, a pulse tube connecting pipe, the regenerator and the pre-cooling heat exchanger are alternately connected between the cooler and the cooling heat exchanger, the cooling heat exchanger, the pulse tube, and the hot end of the pulse tube The gas homogenizer and the pulse tube connecting pipe are connected in sequence, and the pre-cooling heat exchanger of the adjacent cold head is connected with the cooling heat exchanger of the same level through a thermal bridge; the compression chamber of the compressor is respectively connected with each stage The coolers in the cold head are connected by connecting pipes.

When the n-stage cold heads are coupled, the compression chamber of the compressor is connected to the cooler in the first-stage cold head through a connecting pipe, and the regenerator in the first-stage cold head is connected to the second-stage cold head. The regenerator in the head is connected, the regenerator in the second-stage cold head is connected with the regenerator in the third-stage cold head, until the regenerator in the n-1th cold head is connected to the n-th cold head The regenerator in the head is connected.

Further, there is an adjustment chamber connected between the vessel in the n-1 stage cold head and the working chamber of the step-moving piston connected to it.

Furthermore, there is an adjustment chamber connected between the vessel in each stage of the cold head and the working chamber of the step-moving piston connected to it.

Claims (10)

1. a multistage stepped-piston type vascular refrigerator, comprise compressor, n level cold head and n level ladder pass piston system, wherein, n be greater than 1 integer, cold head comprises cooler, regenerator, cold heat exchanger and vascular, cold heat exchanger in n-th grade of cold head is as n-th grade of cold output, the compression chamber of described compressor is connected with the cooler in cold head, the pushing piston working chamber that described n level ladder passes piston system is connected with vascular respectively, the pushing piston back of the body working chamber that described n level ladder passes piston system is communicated with the compression chamber of compressor, it is characterized in that, vascular at least in one-level cold head and coupled ladder are passed between pistons work chamber and are connected with adjustment chamber.

2. the multistage stepped-piston type vascular refrigerator of one according to claim 1, it is characterized in that, compression chamber volume is cyclically-varying, thus make gas pressure be sinusoidal wave change substantially, gas back and forth flows between compression chamber, cold head at different levels and pushing piston working chamber, flowing velocity is sinusoidal wave substantially, by regulating the volume in adjustment chamber, makes the phase difference that the gas of vascular cold junction flows and pressure changes reach optimum value.

3. the multistage stepped-piston type vascular refrigerator of one according to claim 1, is characterized in that, for pre-cooling type connects or manifold type connects between n level cold head.

4. the multistage stepped-piston type vascular refrigerator of one according to claim 3, it is characterized in that, between n level cold head for pre-cooling type connect time, n-th grade of cold head contains n regenerator, n-1 precool heat exchanger device, a cold heat exchanger, a vascular, a vascular hot junction gas uniform device and a vascular tube connector, described regenerator and precool heat exchanger device are alternately connected between cooler and cold heat exchanger successively, cold heat exchanger, vascular, vascular hot junction gas uniform device and vascular tube connector are connected successively, be connected by heat bridge between described precool heat exchanger device and the cold heat exchanger of peer, the compression chamber of described compressor is connected by tube connector with the cooler in every one-level cold head respectively.

5. the multistage stepped-piston type vascular refrigerator of one according to claim 3, it is characterized in that, between n level cold head for manifold type connect time, the compression chamber of described compressor is connected by tube connector with the cooler in first order cold head, regenerator in first order cold head is connected with the regenerator in the cold head of the second level, regenerator in the cold head of the second level is connected with the regenerator in third level cold head, until the regenerator in (n-1)th grade of cold head is connected with the regenerator in n-th grade of cold head.

6. the multistage stepped-piston type vascular refrigerator of one according to claim 1, is characterized in that, has the vascular in n-1 level cold head and coupled ladder to pass between pistons work chamber and is connected with adjustment chamber.

7. the multistage stepped-piston type vascular refrigerator of one according to claim 1, is characterized in that, the vascular in every one-level cold head and coupled ladder are passed between pistons work chamber and be all connected with adjustment chamber.

8. the multistage stepped-piston type vascular refrigerator of one according to claim 1, is characterized in that, described adjustment chamber is the dead volume being equivalent to the pushing piston working chamber adjusting chamber volume.

9. the multistage stepped-piston type vascular refrigerator of one according to claim 1, is characterized in that, described adjustment chamber is the connecting pipe being equivalent to adjust chamber volume.

10., according to the arbitrary described multistage stepped-piston type vascular refrigerator of one of claim 1 ~ 9, its feature is being done, n=2 or 3.