CN110579034A - A Two-Stage Multi-Cylinder Free Piston Compressed Air Refrigeration System - Google Patents

Abstract

The invention relates to a two-stage multi-cylinder free piston compressed air refrigeration system, which belongs to the field of energy and power. The free piston linear motor is a new type of energy conversion device formed by the coupling of a free piston compressor and a linear motor. The linear motor compresses the air in the cylinder through reciprocating motion; the whole system uses two-stage compression to provide cooling for the user. The storage tank can store liquid air by taking advantage of the low power consumption at night. The invention has simple structure and is easy to operate. Compared with the single-cylinder compressor, the double-cylinder compressor can improve the utilization rate of energy, and at the same time, it has a compact structure and takes up less space, which has obvious advantages. Compared with conventional one-stage compression, it saves mechanical work and has higher efficiency. At the same time, air is selected as the working medium, which is stable in nature, easy to obtain, low in cost, environmentally friendly and pollution-free, and can be used many times.

Description

A Two-Stage Multi-Cylinder Free Piston Compressed Air Refrigeration System

technical field

The invention relates to a two-stage multi-cylinder free piston compressed air refrigeration system, which belongs to the field of energy and power.

Background technique

Nowadays, refrigeration technology has been widely used in daily life. At the same time, refrigeration technology also plays an important role in cutting-edge scientific fields such as microelectronics technology, optical fiber communication, energy, new raw materials, space development, and bioengineering technology. At present, conventional refrigeration equipment on the market usually uses a single-cylinder compressor for one-stage compression, and the energy utilization efficiency is relatively low. Refrigerants generally use R22, R32 and new CO ₂ refrigerants. R22 has a large cooling capacity, but R22 contains fluorine and chlorine, which destroys the ozone layer and causes the greenhouse effect; although R32 is non-toxic and environmentally friendly, it is costly and flammable; although CO ₂ is non-toxic, non-flammable, and low-viscosity, it The critical pressure is relatively high, about 7.38MPa, which requires a lot of equipment.

Contents of the invention

In order to solve the above technical problems, the present invention proposes a two-stage multi-cylinder free-piston compressed air refrigeration system. The free-piston linear motor is a new type of energy conversion device formed by coupling a free-piston compressor with a linear motor. Movement compresses the air in the cylinder; the whole system adopts two-stage compression, and at the same time, it adopts a liquid air storage tank, which can store liquid air during the low electricity consumption at night.

The specific technical scheme is as follows:

A two-stage multi-cylinder free-piston compressed air refrigeration system. As shown in Figure 1, it mainly includes: free piston compressed air module, liquid air refrigeration module, and control module.

The free piston compressed air module mainly includes: dehumidifier (1), linear motor a (2), cylinder a (3), cylinder b (4), piston a (5), piston b (6), connecting rod a (7), connecting rod b(8), cooler a(9), cooler b(10), linear motor b(11), cylinder c(12), cylinder d(13), piston c(14), Piston d(15), connecting rod c(16), connecting rod d(17), pipe a(46), pipe b(47), pipe c(48), pipe d(49), pipe e(50), Pipeline f(51), pipeline g(52), pipeline h(53); linear motor a(2) and piston a(5) are fixedly connected through connecting rod a(7); linear motor a(2) and piston b( 6) Connected by connecting rod b(8); piston a(5) is in cylinder a(3), piston b(6) is in cylinder b(4); linear motor b(11) and piston c(14) The connecting rod c(16) is fixedly connected; the linear motor b(11) and the piston d(15) are fixedly connected through the connecting rod d(17); the piston c(14) is inside the cylinder c(12), and the piston d(15) In the cylinder d (13); the dehumidifier (1) is connected with the cylinder a (3) through the pipeline a (46), and the dehumidifier (1) is connected with the cylinder b (4) through the pipeline b (47); the cylinder a (3 ) is connected to cooler a(9) through pipe c(48), cooler a(9) is connected to cylinder c(12) through pipe e(50); cylinder b(4) is connected to cooler through pipe d(49) b(10) is connected, the cooler b(10) is connected with the cylinder d(13) through the pipeline f(51); the cylinder c(12) is connected with the liquid air tank (19) through the pipeline g(52), and the cylinder d(13) ) is connected with liquid air tank (19) by pipeline h (53).

The liquid air refrigeration module mainly includes: a liquid air tank (19), a user (20), and a pipeline i (54); wherein the liquid air tank (19) is connected to the user (20) through the pipeline i (54).

Described control module mainly comprises: controller (18), temperature sensor a (21), temperature sensor b (22), temperature sensor c (25), temperature sensor d (26), temperature sensor e (30), pressure sensor a(23), pressure sensor b(24), pressure sensor c(27), pressure sensor d(28), pressure sensor e(29), valve a(31), valve b(32), valve c(33) , valve d(34), valve e(35), valve f(36), valve g(37), valve h(38), valve i(39), valve j(40), valve k(41), valve l (42), valve m (43), valve n (44), valve o (45); wherein the temperature sensor a (21) is fixed on the cylinder a (3) and is connected with the controller (18) by a control line; The temperature sensor b (22) is fixed on the cylinder b (4) and connected to the controller (18) through the control line; the temperature sensor c (25) is fixed on the cylinder c (12) and connected to the controller (18) through the control line connection; the temperature sensor d (26) is fixed on the cylinder d (13) and connected with the controller (18) through the control line; the temperature sensor e (30) is fixed on the user (20) and connected with the controller (18) through the control line ) connection; the pressure sensor a (23) is fixed on the cylinder a (3) and connected with the controller (18) through the control line; the pressure sensor b (24) is fixed on the cylinder b (4) and connected with the controller through the control line (18) is connected; the pressure sensor c (27) is fixed on the cylinder c (12) and is connected with the controller (18) by the control line; the pressure sensor d (28) is fixed on the cylinder d (13) and is connected with the controller (18) by the control line The controller (18) is connected; the pressure sensor e (29) is fixed on the liquid air tank (29) and is connected with the controller (18) by a control line.

The valve a (31) is fixed on the pipeline a (46) and connected with the controller (18) through the control line; the valve b (32) is fixed on the pipeline b (47) and connected with the controller (18) through the control line connection; the valve c(33) is fixed on the side of the pipeline c(48) close to the cylinder a(3) and connected with the controller (18) through the control line; the valve d(34) is fixed on the pipeline d(49) close to One side of the cylinder b (4) is connected with the controller (18) through the control line; the valve e (35) is fixed on the side of the pipeline c (48) close to the side of the cooler a (9) and connected with the controller (18) through the control line ) connection, the valve f(36) is fixed on the side of the pipe d(49) close to the cooler b(10) and connected to the controller (18) through the control line; the valve g(37) is fixed on the pipe e(50) Close to the side of cooler a (9) and connected to the controller (18) through the control line; the valve h (38) is fixed on the side of the pipeline f (51) close to the cooler b (10) and connected to the controller through the control line (18) connection; the valve i (39) is fixed on the side of the pipeline e (50) close to the cylinder c (12) and connected with the controller (18) through the control line; the valve j (40) is fixed on the pipeline f (51) On the side close to the cylinder d (13) and connected to the controller (18) through the control line; the valve k (41) is fixed on the side of the pipeline g (52) close to the cylinder c (12) and connected to the controller ( 18) connection; the valve l (42) is fixed on the side of the pipe h (53) close to the cylinder d (13) and connected to the controller (18) through the control line; the valve m (43) is fixed on the pipe g (52) Close to the side of the liquid air tank (19) and connected to the controller (18) through the control line; the valve n (44) is fixed on the pipe h (53) close to the side of the liquid air tank (19) and connected to the controller through the control line (18) is connected; the valve o (45) is fixed on the pipeline i (54) and is connected with the controller (18) by a control line.

A two-stage multi-cylinder free-piston compressed air refrigeration system, the requirements for each component of the equipment are: dehumidifier (1) is used to remove moisture in the air; cylinder c (12), cylinder d (13), piston c (14 ), the piston d(15) adopts low-temperature-resistant materials; the pipeline c(48), pipeline d(49) adopts high-pressure pipelines; pipeline e(50), pipeline f(51) adopts high-pressure pipelines; pipeline g(52) , pipeline h(53) adopts low temperature and low pressure pipeline; valve c(33), valve d(34), valve e(35), valve f(36) adopt high pressure resistant valve; valve g(37), valve h(38 ), valve i (39), valve j (40), valve k (41), valve l (42), valve m (43), valve n (44), valve o (45) adopt low temperature and high pressure valves.

The working principle of a two-stage multi-cylinder free-piston compressed air refrigeration system is: when the linear motor a(2) drives the connecting rod a(7) and the connecting rod b(8) to move to the right, the valve a(31) opens , air enters cylinder a(3) through valve a(31), valve b(32), valve c(33), valve d(34) are closed, when the pressure sensor b(24) shows that the pressure reaches 1.88MPa, valve d (34), the valve f(36) is opened, the compressed air in the cylinder b(4) passes through the cooler b(10) to reduce the temperature of the compressed air to normal temperature, the valve h(38) and the valve j(40) are opened, and the normal temperature The high-pressure air enters the cylinder d(13) through the pipeline f(51), when all the compressed air enters the cylinder d(13), the linear motor b(11) drives the connecting rod c(16), connecting rod d(17) to Right movement, valve j (40) and valve l (42) are closed, when pressure gauge d (28) shows that the pressure reaches 3.5MPa, valve l (42) and valve n (44) are opened, and liquid air passes through pipe h (53 ) into the liquid air tank (19); at this time, the linear motor a (2) drives the connecting rod a (7), connecting rod b (8) to move to the left, the valve b (32) is opened, and the valve a (31), valve c (33), valve d(34) is closed, when the pressure sensor a(23) shows that the pressure reaches 1.88MPa, valve c(33), valve e(35) are opened, and the compressed air in cylinder a(3) passes through the cooler a(9) lower the temperature of the compressed air to normal temperature, open the valve g(37) and i(39), and when all the compressed air enters the cylinder c(12), the linear motor b(11) drives the connecting rod c( 16), connecting rod d (17) moves to the left, valve i (39), valve k (41) are closed, when the pressure gauge c (27) shows that it reaches 3.5MPa, valve k (41), valve m (43) Open, valve l (42), valve n (44) are closed, and liquid air flows into liquid air tank (19) through pipeline g (52); such reciprocating motion stores liquid air, and when the resident needs refrigeration, temperature sensor e (30 ) transmits the signal to the controller, the controller opens the valve o(45), and the liquid air provides cooling for the user through the pipeline i(54).

Compared with prior art solutions, the present invention has the following advantages:

1. The free piston linear motor is a new type of energy conversion device formed by coupling a free piston compressor and a linear motor. The linear motor compresses the air in the cylinder through reciprocating motion. It has a simple structure and is easy to operate. Compared with the single-cylinder compressor, the double-cylinder compressor can improve the utilization rate of energy, and at the same time, it has a compact structure and takes up less space, which has obvious advantages.

2. The whole system adopts two-stage compression, which saves mechanical work and is more efficient than conventional one-stage compression. At the same time, the use of liquid air storage tanks can take advantage of the low power consumption at night to store liquid air, alleviate the phenomenon of uneven power consumption during the day and night, and make full use of electric energy.

3. The present invention adopts air as refrigerating medium, and air can be compressed to 3.5MPa at normal temperature and just can obtain liquid air, can draw intermediate pressure according to P=(P ₁ P ₂ ) ^0.5 to be 1.88MPa, therefore, by means of free piston compression The air is compressed in two stages. After the first compression, it is cooled to normal temperature by the cooler and then compressed again. This can make the compressor consume less work. At the same time, the compressed air can also be used to make liquid air when the electricity consumption is low at night. Improve the utilization rate of electric energy. Therefore, air is selected as the working medium, which is stable in nature, easy to obtain, low in cost, environmentally friendly and pollution-free, and can be used many times.

Description of drawings

Fig. 1 overall sectional view of a two-stage multi-cylinder free-piston compressed air refrigeration system;

Among them, 1—dehumidifier, 2—linear motor a, 3—cylinder a, 4—cylinder b, 5—piston a, 6—piston b, 7—connecting rod a, 8—connecting rod b, 9—cooler a , 10—cooler b, 11—linear motor b, 12—cylinder c, 13—cylinder d, 14—piston c, 15—piston d, 16—connecting rod c, 17—connecting rod d, 18—controller, 19—liquid air tank, 20—user, 21—temperature sensor a, 22—temperature sensor b, 23—pressure sensor a, 24—pressure sensor b, 25—temperature sensor c, 26—temperature sensor d, 27—pressure sensor c, 28—pressure sensor d, 29—pressure sensor e, 30—temperature sensor e, 31—valve a, 32—valve b, 33—valve c, 34—valve d, 35—valve e, 36—valve f, 37—valve g, 38—valve h, 39—valve i, 40—valve j, 41—valve k, 42—valve l, 43—valve m, 44—valve n, 45—valve o, 46—pipeline a, 47—pipeline b, 48—pipeline c, 49—pipeline d, 50—pipeline e, 51—pipeline f, 52—pipeline g, 53—pipeline h, 54—pipeline i

specific implementation plan

The application is further described in conjunction with the accompanying drawings.

A two-stage multi-cylinder free-piston compressed air refrigeration system. As shown in Figure 1, it mainly includes: free piston compressed air module, liquid air refrigeration module, and control module.

As shown in Figure 1, the free piston compressed air module mainly includes: dehumidifier 1, linear motor a2, cylinder a3, cylinder b4, piston a5, piston b6, connecting rod a7, connecting rod b8, cooler a9, cooler b10, Linear motor b11, cylinder c12, cylinder d13, piston c14, piston d15, connecting rod c16, connecting rod d17, pipe a46, pipe b47, pipe c48, pipe d49, pipe e50, pipe f51, pipe g52, pipe h53; linear motor a2 and piston a5 are fixedly connected through connecting rod a7; linear motor a2 and piston b6 are fixedly connected through connecting rod b8; piston a5 is in cylinder a3, and piston b6 is in cylinder b4; linear motor b11 and piston c14 are fixedly connected through connecting rod c16 ; The linear motor b11 and the piston d15 are fixedly connected through the connecting rod d17; the piston c14 is in the cylinder c12, and the piston d15 is in the cylinder d13; the dehumidifier 1 is connected with the cylinder a3 through the pipeline a46, and the dehumidifier 1 is connected with the cylinder b4 through the pipeline b47; Cylinder a3 is connected to cooler a9 through pipeline c48, cooler a9 is connected to cylinder c12 through pipeline e50; cylinder b4 is connected to cooler b10 through pipeline d49, cooler b10 is connected to cylinder d13 through pipeline f51; cylinder c12 is connected to cylinder c12 through pipeline g52 The liquid air tank 19 is connected, and the cylinder d13 is connected with the liquid air tank 19 through the pipeline h53;

The liquid air refrigeration module mainly includes: a liquid air tank 19, a user 20, and a pipeline i54; wherein the liquid air tank 19 is connected to the user 20 through the pipeline i54;

The control module mainly includes: controller 18, temperature sensor a21, temperature sensor b22, temperature sensor c25, temperature sensor d26, temperature sensor e30, pressure sensor a23, pressure sensor b24, pressure sensor c27, pressure sensor d28, pressure sensor e29 , valve a31, valve b32, valve c33, valve d34, valve e35, valve f36, valve g37, valve h38, valve i39, valve j40, valve k41, valve l42, valve m43, valve n44, valve o45; the temperature sensor a21 Fixed on the cylinder a3 and connected with the controller 18 through the control line; the temperature sensor b22 is fixed on the cylinder b4 and connected with the controller 18 through the control line; the temperature sensor c25 is fixed on the cylinder c12 and connected with the controller 18 through the control line The temperature sensor d26 is fixed on the cylinder d13 and connected with the controller 18 through the control line; the temperature sensor e30 is fixed on the user 20 and connected with the controller 18 through the control line; the pressure sensor a23 is fixed on the cylinder a3 and connected with the control line through the control line The controller 18 is connected; the pressure sensor b24 is fixed on the cylinder b4 and connected to the controller 18 through the control line; the pressure sensor c27 is fixed on the cylinder c12 and connected to the controller 18 through the control line; the pressure sensor d28 is fixed on the cylinder d13 and connected Be connected with controller 18 by control line; Pressure sensor e29 is fixed on the liquid air tank 29 and is connected with controller 18 by control line;

The valve a31 is fixed on the pipeline a46 and connected to the controller 18 through the control line; the valve b32 is fixed on the pipeline b47 and connected to the controller 18 through the control line; the valve c33 is fixed on the side of the pipeline c48 close to the cylinder a3 and passed through The control line is connected to the controller 18; the valve d34 is fixed on the side of the pipeline d49 close to the cylinder b4 and connected to the controller 18 through the control line; the valve e35 is fixed on the side of the pipeline c48 close to the cooler a9 and connected to the control line through the control line The valve f36 is fixed on the side of the pipeline d49 close to the cooler b10 and connected to the controller 18 through the control line; the valve g37 is fixed on the side of the pipeline e50 close to the side of the cooler a9 and connected to the controller 18 through the control line; The valve h38 is fixed on the side of the pipeline f51 close to the cooler b10 and connected to the controller 18 through the control line; the valve i39 is fixed on the side of the pipeline e50 close to the cylinder c12 and connected to the controller 18 through the control line; the valve j40 is fixed on the pipeline The f51 is close to the side of the cylinder d13 and connected to the controller 18 through the control line; the valve k41 is fixed on the side of the pipeline g52 close to the cylinder c12 and connected to the controller 18 through the control line; the valve l42 is fixed on the pipeline h53 close to the cylinder d13- side and connected to the controller 18 through the control line; the valve m43 is fixed on the side of the pipeline g52 close to the liquid air tank 19 and connected to the controller 18 through the control line; the valve n44 is fixed on the side of the pipeline h53 close to the liquid air tank 19 and It is connected with the controller 18 through the control line; the valve o45 is fixed on the pipeline i54 and connected with the controller 18 through the control line.

A two-stage multi-cylinder free-piston compressed air refrigeration system, the requirements for each component of the equipment are: dehumidifier 1 is used to remove moisture in the air; cylinder c12, cylinder d13, piston c14, and piston d15 are made of low-temperature resistant materials; pipeline c48 , pipeline d49, high pressure resistant pipeline; pipeline e50, pipeline f51 adopts high pressure resistant pipeline; pipeline g52, pipeline h53 adopts low temperature and low pressure pipeline; valve c33, valve d34, valve e35, valve f36 adopts high pressure resistant valve; valve g37, valve h38, valve i39, valve j40, valve k41, valve l42, valve m43, valve n44, valve o45 adopt low temperature and high pressure resistant valves;

A two-stage multi-cylinder free-piston compressed air refrigeration system. The working principle is: when the linear motor a2 drives the connecting rod a7 and the connecting rod b8 to move to the right, the valve a31 is opened, and the air enters the cylinder a3 through the valve a31, and the valve b32, Valve c33 and valve d34 are closed, when the pressure sensor b24 shows that the pressure reaches 1.88MPa, valve d34 and valve f36 are opened, the compressed air in the cylinder b4 passes through the cooler b10 to reduce the temperature of the compressed air to normal temperature, and the valve h38 and valve j40 are opened , high-pressure air at normal temperature enters the cylinder d13 through the pipeline f51. When all the compressed air enters the cylinder d13, the linear motor b11 drives the connecting rod c16 and the connecting rod d17 to move to the right, and the valve j40 and the valve l42 are closed. When the pressure gauge d28 shows the pressure When it reaches 3.5MPa, the valve l42 and the valve n44 are opened, and the liquid air flows into the liquid air tank 19 through the pipe h53; at this time, the linear motor a2 drives the connecting rod a7 and the connecting rod b8 to move to the left, the valve b32 is opened, and the valve a31, valve c33, The valve d34 is closed, when the pressure sensor a23 shows that the pressure reaches 1.88MPa, the valve c33 and the valve e35 are opened, the compressed air in the cylinder a3 passes through the cooler a9 to reduce the temperature of the compressed air to normal temperature, the valve g37 and the valve i39 are opened, when the compressed air When all the air enters the cylinder c12, the linear motor b11 drives the connecting rod c16 and the connecting rod d17 to move to the left, the valve i39 and the valve k41 are closed, and when the pressure gauge c27 reaches 3.5 MPa, the valve k41 and the valve m43 are opened, and the valve l42, The valve n44 is closed, and the liquid air flows into the liquid air tank 19 through the pipe g52; such reciprocating motion stores the liquid air, and when the resident needs refrigeration, the temperature sensor e30 sends a signal to the controller, and the controller opens the valve o45, and the liquid air flows through the pipe i54 Provide cooling for users.

Claims (3)

1. The utility model provides a doublestage multi-cylinder free piston compressed air refrigerating system which characterized in that mainly includes: the system comprises a free piston compressed air module, a liquid air refrigeration module and a control module;

The free piston compressed air module mainly comprises: the dehumidifier is characterized by comprising a dehumidifier (1), a linear motor a (2), a cylinder a (3), a cylinder b (4), a piston a (5), a piston b (6), a connecting rod a (7), a connecting rod b (8), a cooler a (9), a cooler b (10), a linear motor b (11), a cylinder c (12), a cylinder d (13), a piston c (14), a piston d (15), a connecting rod c (16), a connecting rod d (17), a pipeline a (46), a pipeline b (47), a pipeline c (48), a pipeline d (49), a pipeline e (50), a pipeline f (51), a pipeline g (52) and a pipeline h (53); the linear motor a (2) is fixedly connected with the piston a (5) through a connecting rod a (7); the linear motor a (2) is fixedly connected with the piston b (6) through a connecting rod b (8); the piston a (5) is arranged in the cylinder a (3), and the piston b (6) is arranged in the cylinder b (4); the linear motor b (11) is fixedly connected with the piston c (14) through a connecting rod c (16); the linear motor b (11) is fixedly connected with the piston d (15) through a connecting rod d (17); the piston c (14) is in the cylinder c (12), and the piston d (15) is in the cylinder d (13); the dehumidifier (1) is connected with the cylinder a (3) through a pipeline a (46), and the dehumidifier (1) is connected with the cylinder b (4) through a pipeline b (47); the cylinder a (3) is connected with a cooler a (9) through a pipeline c (48), and the cooler a (9) is connected with the cylinder c (12) through a pipeline e (50); the cylinder b (4) is connected with a cooler b (10) through a pipeline d (49), and the cooler b (10) is connected with a cylinder d (13) through a pipeline f (51); the cylinder c (12) is connected with the liquid air tank (19) through a pipeline g (52), and the cylinder d (13) is connected with the liquid air tank (19) through a pipeline h (53);

the liquid air refrigeration module mainly comprises: a liquid air tank (19), a user (20), a conduit i (54); wherein the liquid air tank (19) is connected with a user (20) through a pipeline i (54);

the control module mainly comprises: a controller (18), a temperature sensor a (21), a temperature sensor b (22), a temperature sensor c (25), a temperature sensor d (26), a temperature sensor e (30), a pressure sensor a (23), a pressure sensor b (24), a pressure sensor c (27), a pressure sensor d (28), a pressure sensor e (29), a valve a (31), a valve b (32), a valve c (33), a valve d (34), a valve e (35), a valve f (36), a valve g (37), a valve h (38), a valve i (39), a valve j (40), a valve k (41), a valve l (42), a valve m (43), a valve n (44) and a valve o (45); wherein the temperature sensor a (21) is fixed on the cylinder a (3) and is connected with the controller (18) through a control line; the temperature sensor b (22) is fixed on the cylinder b (4) and is connected with the controller (18) through a control line; the temperature sensor c (25) is fixed on the cylinder c (12) and is connected with the controller (18) through a control line; the temperature sensor d (26) is fixed on the cylinder d (13) and is connected with the controller (18) through a control line; the temperature sensor e (30) is fixed on a user (20) and is connected with the controller (18) through a control line; the pressure sensor a (23) is fixed on the cylinder a (3) and is connected with the controller (18) through a control line; the pressure sensor b (24) is fixed on the cylinder b (4) and is connected with the controller (18) through a control line; the pressure sensor c (27) is fixed on the cylinder c (12) and is connected with the controller (18) through a control line; the pressure sensor d (28) is fixed on the cylinder d (13) and is connected with the controller (18) through a control line; the pressure sensor e (29) is fixed on the liquid air tank (29) and is connected with the controller (18) through a control line;

The valve a (31) is fixed on the pipeline a (46) and is connected with the controller (18) through a control line; the valve b (32) is fixed on the pipeline b (47) and is connected with the controller (18) through a control line; the valve c (33) is fixed on one side of the pipeline c (48) close to the cylinder a (3) and is connected with the controller (18) through a control line; the valve d (34) is fixed on one side of the pipeline d (49) close to the cylinder b (4) and is connected with the controller (18) through a control line; the valve e (35) is fixed on the pipeline c (48) close to one side of the cooler a (9) and is connected with the controller (18) through a control line, and the valve f (36) is fixed on the pipeline d (49) close to one side of the cooler b (10) and is connected with the controller (18) through a control line; the valve g (37) is fixed on the pipeline e (50) close to one side of the cooler a (9) and is connected with the controller (18) through a control line; the valve h (38) is fixed on one side of the pipeline f (51) close to the cooler b (10) and is connected with the controller (18) through a control line; the valve i (39) is fixed on one side of the pipeline e (50) close to the cylinder c (12) and is connected with the controller (18) through a control line; the valve j (40) is fixed on one side of the pipeline f (51) close to the cylinder d (13) and is connected with the controller (18) through a control line; the valve k (41) is fixed on one side of the pipeline j (52) close to the cylinder c (12) and is connected with the controller (18) through a control line; the valve l (42) is fixed on one side of the pipeline h (53) close to the cylinder d (13) and is connected with the controller (18) through a control line; the valve m (43) is fixed on the pipeline g (52) close to one side of the liquid air tank (19) and is connected with the controller (18) through a control line; the valve n (44) is fixed on one side of the pipeline h (53) close to the liquid air tank (19) and is connected with the controller (18) through a control line; the valve o (45) is fixed on the pipeline i (54) and is connected with the controller (18) through a control line.

2. The equipment requirement for applying the double-stage multi-cylinder free piston compressed air refrigerating system as claimed in claim 1 is as follows: the dehumidifier (1) is used for removing moisture in the air; the cylinder c (12), the cylinder d (13), the piston c (14) and the piston d (15) are made of low-temperature resistant materials; the pipeline c (48) and the pipeline d (49) adopt high-pressure-resistant pipelines; the pipeline e (50) and the pipeline f (51) adopt high-pressure resistant pipelines; the pipeline g (52) and the pipeline h (53) adopt low-temperature and low-pressure resistant pipelines; the valve c (33), the valve d (34), the valve e (35) and the valve f (36) adopt high-pressure-resistant valves; the valve g (37), the valve h (38), the valve i (39), the valve j (40), the valve k (41), the valve l (42), the valve m (43), the valve n (44) and the valve o (45) adopt low-temperature and high-pressure resistant valves.

3. The working state of the double-stage multi-cylinder free piston compressed air refrigerating system applying the method as claimed in claims 1-2 is as follows: when a linear motor a (2) drives a connecting rod a (7) and a connecting rod b (8) to move rightwards, a valve a (31) is opened, air enters an air cylinder a (3) through the valve a (31), a valve b (32), a valve c (33) and a valve d (34) are closed, when a pressure sensor b (24) displays that the pressure reaches 1.88MPa, the valve d (34) and a valve f (36) are opened, the temperature of the compressed air in the air cylinder b (4) is reduced to normal temperature through a cooler b (10), a valve h (38) and a valve j (40) are opened, the high-pressure air at the normal temperature enters an air cylinder d (13) through a pipeline f (51), when all the compressed air enters the air cylinder d (13), the linear motor b (11) drives the connecting rod c (16) and the connecting rod d (17) to move rightwards, the valve j (40) and the valve l (42) are closed, and when a pressure gauge d (28) displays that the pressure reaches 3.5MPa, the valve l (42) and the valve n (44) are opened, and the liquid air flows into the liquid air tank (19) through the pipeline h (53); at the moment, the linear motor a (2) drives the connecting rod a (7) and the connecting rod b (8) to move leftwards, the valve b (32) is opened, the valve a (31), the valve c (33) and the valve d (34) are closed, when the pressure sensor a (23) displays that the pressure reaches 1.88MPa, the valve c (33) and the valve e (35) are opened, the compressed air in the cylinder a (3) is cooled to the normal temperature through the cooler a (9), the valve g (37) and the valve i (39) are opened, when all the compressed air enters the cylinder c (12), the linear motor b (11) drives the connecting rod c (16) and the connecting rod d (17) to move leftwards, the valve i (39) and the valve k (41) are closed, when the pressure gauge c (27) displays that the pressure reaches 3.5MPa, the valve k (41), the valve m (43) is opened, the valve l (42) and the valve n (44) are closed, liquid air flows into the liquid air tank (19) through a pipe g (52); so as to reciprocate and store liquid air, when the resident needs refrigeration, the temperature sensor e (30) transmits a signal to the controller, the controller opens the valve o (45), and the liquid air provides refrigeration for the user through the pipeline i (54).