CN118462669B - Hydraulic control two-stage piston type supercharging device - Google Patents

Abstract

A hydraulic control double-stage piston type supercharging device relates to the field of oil extraction engineering equipment of oil fields, and comprises a supercharging assembly, wherein an air chamber and an oil chamber are arranged in the supercharging assembly, an air pressure pipeline is connected to the air chamber, and a hydraulic pipeline is connected to the oil chamber, so that the air chamber and the oil chamber participate in forming a hydraulic system and an air pressure system; the supercharging assembly comprises a high-pressure cylinder sleeve, a high-pressure piston, a low-pressure cylinder sleeve and a low-pressure piston, wherein the high-pressure piston is slidably arranged in the high-pressure cylinder sleeve, and the low-pressure piston is slidably arranged in the low-pressure cylinder sleeve; the high-pressure cylinder sleeves are coaxial and fixedly connected, the low-pressure cylinder sleeves are two, the two low-pressure cylinder sleeves are respectively and fixedly connected to two ends of a connecting body formed by the two high-pressure cylinder sleeves, and a low-pressure piston is arranged in each low-pressure cylinder sleeve. The invention improves the existing supercharger, simplifies the structure of the air pressure system, reduces the complexity, reduces the failure rate and lowers the maintenance difficulty.

Description

A hydraulically controlled two-stage piston booster device

Technical Field

The invention belongs to the field of oilfield production engineering equipment, and in particular relates to a hydraulically controlled two-stage piston type boosting device.

Background Art

The gas lift technology currently used in oilfield development mainly uses piston reciprocating compressors to pressurize gas in its ground compressor station. The piston reciprocating compressor uses a crank-connecting rod mechanism to convert the rotary motion of the driver into the reciprocating motion of the piston. The piston and the cylinder together form the compressor working chamber. Relying on the reciprocating motion of the piston in the cylinder and the automatic opening and closing of the inlet and exhaust valves, the gas periodically enters the cylinder working chamber for compression and discharge. There are problems such as large inertial force, the speed cannot be too high, the machine is relatively heavy, the structure is complex, there are many vulnerable parts, the maintenance workload is large, and the maintenance cost is relatively high.

The invention patent document with application number CN201810366010.5 discloses a multi-stage multi-purpose hydraulic supercharger with variable boost ratio. This supercharger realizes boosting through the reciprocating motion of multi-stage pistons in the cylinder, which effectively solves the above-mentioned problems existing in centrifugal compressors. However, this supercharger has shortcomings: 1. Up to 13 electromagnetic reversing valves are used in this supercharger, and the flow channel of the electromagnetic reversing valve is usually small. The large-scale use of electromagnetic reversing valves will not only affect the working efficiency of the hydraulic and pneumatic systems, but also greatly increase the complexity and failure rate of the equipment. 2. In this supercharger, the diameter of the hydraulically driven transfer piston is the largest, and the diameter of the other stages of boosting pistons is smaller. Limited by the hydraulic flow rate, the boosting efficiency of this supercharger is low. 3. In this supercharger, all boosting cylinders are single-acting cylinders, that is, they only work in the compression stroke, and the expansion stroke inhales the medium to be compressed, which limits the improvement of boosting efficiency from another aspect.

Summary of the invention

The purpose of the present invention is to study a hydraulically controlled two-stage piston booster device, which is suitable for a variety of media such as high-temperature gas, liquid, gas-liquid mixture, etc., and has a simpler structure and higher boosting efficiency.

The technical problem solved by the present invention is achieved by the following technical solution: The present invention provides a hydraulically controlled two-stage piston booster device, including a booster assembly, wherein an air chamber and an oil chamber are arranged in the booster assembly, an air pressure pipeline is connected to the air chamber, and a hydraulic pipeline is connected to the oil chamber, so that the air chamber and the oil chamber participate in forming a hydraulic system and a pneumatic system;

The supercharging assembly includes a high-pressure cylinder sleeve, a high-pressure piston, a low-pressure cylinder sleeve and a low-pressure piston. The high-pressure piston is slidably installed in the high-pressure cylinder sleeve, and the low-pressure piston is slidably installed in the low-pressure cylinder sleeve.

There are two high-pressure cylinder sleeves, which are coaxial and fixedly connected. A high-pressure piston is arranged in each of the two high-pressure cylinder sleeves. A piston rod is connected between the two high-pressure pistons, which is called the high-pressure piston rod. The high-pressure piston rod passes through the center of the partition at the connection between the two high-pressure cylinder sleeves and cooperates with the partition in a sliding and sealing manner. The internal space of each high-pressure cylinder sleeve is divided into an air chamber and an oil chamber by the high-pressure piston. The air chamber is called a high-pressure air chamber, wherein the two high-pressure air chambers are respectively located between the two high-pressure pistons and the low-pressure cylinder sleeves on their corresponding sides, and the two oil chambers are located between the two high-pressure pistons.

There are two low-pressure cylinder sleeves, which are fixedly connected to the two ends of the connecting body composed of two high-pressure cylinder sleeves, respectively. A low-pressure piston is arranged in each low-pressure cylinder sleeve, and a piston rod is connected between each low-pressure piston and the adjacent high-pressure piston, which is called a low-pressure piston rod. The low-pressure piston rod passes through the center of the partition at the connection between the high-pressure cylinder sleeve and the low-pressure cylinder sleeve, and is slidably sealed with the partition; the internal space of each low-pressure cylinder sleeve is divided into two left and right air chambers by the low-pressure piston, and the two air chambers are called low-pressure air chambers;

The diameter of the high-pressure cylinder sleeve where the oil chamber is located is smaller than the diameter of the low-pressure cylinder sleeve;

The hydraulic system comprises a first oil circuit and a second oil circuit, wherein the first oil circuit is formed by connecting an oil tank, an oil pump, a three-position four-way solenoid reversing valve and an oil chamber in sequence through a hydraulic oil pipe, and the second oil circuit is formed by connecting an oil tank, a three-position four-way solenoid reversing valve and another oil chamber in sequence through a hydraulic oil pipe, and the oil tank is filled with hydraulic oil; by controlling the three-position four-way solenoid reversing valve, the flow direction of the hydraulic oil in the hydraulic oil pipe between the three-position four-way solenoid reversing valve and the high-pressure cylinder sleeve can be switched, thereby realizing the controllable inflow and outflow of the hydraulic oil in the two oil chambers, and finally enabling each piston in the booster assembly to reciprocate under hydraulic drive;

The air pressure system includes an air intake pipeline, a filter and an air outlet pipeline; the gas entering from the air intake pipeline is filtered by the filter and then transported through pipelines to four low-pressure air chambers respectively located in two low-pressure cylinder sleeves; the gas is compressed and discharged by the low-pressure piston in the low-pressure air chamber, and the discharged gas is transported to the high-pressure air chamber through the pipeline for secondary compression, and the gas after secondary compression enters the air outlet pipeline from the high-pressure air chamber.

A check valve is provided at the connection between the air pressure pipeline and each air chamber to prevent backflow.

As a preferred solution, a heat exchange tube is provided in the oil tank, both ends of the heat exchange tube are connected in series in the main air circuit of the air pressure system, and are located between the outlet of the low-pressure air chamber and the inlet of the high-pressure air chamber, and the heat exchange tube is immersed in the hydraulic oil.

As a preferred solution, the check valve is built into the partition at the end of each air chamber and in the low-pressure cylinder sleeve at a position corresponding to the end of the low-pressure air chamber;

The structure of the one-flow valve includes a valve ball and a valve seat. The valve ball is placed above the valve seat. The inlet and outlet of the one-flow valve are processed on the partition or on the end of the low-pressure air chamber to achieve communication between the inside and outside of each air chamber. When the one-flow valve is in a closed state, the valve ball rests on the inner side of the upper end of the valve seat under the action of its own gravity to achieve sealing between the valve ball and the valve seat. When the one-flow valve is in a conducting state, the valve ball is pushed away from the valve seat by the fluid to achieve conduction between the inlet and outlet of the one-flow valve.

As a preferred solution, a bypass valve is respectively provided at both ends of the boost assembly, and the two bypass valves are connected in parallel with each low-pressure air chamber.

As a preferred solution, the diameters of the high-pressure piston rod and the low-pressure piston rod are the same.

As a preferred solution, an electric contact pressure gauge for detecting the pressure in the oil chamber is respectively installed on the outside of the two oil chambers. The two electric contact pressure gauges and the three-position four-way solenoid reversing valve are connected to an automatic controller through wires. The automatic controller continuously monitors the pressure in the oil chamber through the electric contact pressure gauge. In the process of the oil pump continuously pumping the hydraulic oil into the oil chamber, the pressure in the oil chamber continuously increases. When the pressure value in an oil chamber monitored by the automatic controller is equal to a predetermined value, the automatic controller sends an instruction to the three-position four-way solenoid reversing valve to make it perform a reversing action. After the reversing, the hydraulic oil in the oil chamber with higher pressure flows out in the opposite direction to reduce the pressure. At the same time, the hydraulic oil is pumped into another oil chamber to increase the pressure in that oil chamber.

The beneficial effects of the present invention are:

1. The present invention improves the existing supercharger by redesigning the arrangement of the air chambers, oil chambers and pistons in the supercharging assembly, thereby reducing the number of electromagnetic reversing valves to one. On the one hand, the structure of the air pressure system is simplified, the complexity is reduced, the failure rate is reduced, and the maintenance difficulty is reduced. On the other hand, by controlling the switching state of the two bypass valves, the function of variable boost ratio that can be achieved in the prior art can still be achieved.

2. The present invention can effectively improve the boosting efficiency. The two oil chambers are isolated from each other by a partition in the middle of the high-pressure cylinder sleeve. Two high-pressure pistons and two low-pressure pistons are arranged in the boosting assembly. The pistons are rigidly connected in series. Taking the left high-pressure piston as an example, the left side of the high-pressure piston is the gas to be compressed, and the right side is the hydraulic oil for driving the reversing. The low-pressure piston is a double-acting piston, which can compress and inhale the gas to be compressed on both sides of the piston at the same time, thereby improving the boosting efficiency. In addition, while the high-pressure piston plays the hydraulic drive function, it can also compress the gas to be compressed in one direction, thereby further improving the boosting efficiency.

3. The present invention sets a heat exchange tube in the oil tank. Before the compressed gas flows out from the low-pressure gas chamber and enters the high-pressure gas chamber, it is cooled or heated through the heat exchange tube in the oil tank to meet the medium temperature requirements of the working environment.

4. The one-way valve in the present invention adopts a springless gravity ball form, which has better adaptability to media in different states, is not easily affected by impurities, and has higher reliability. In addition, the present invention creatively combines the one-flow valve in the low-pressure cylinder sleeve at the end of the partition or the low-pressure air chamber, which can greatly reduce the workload of the supercharging equipment installation and is also conducive to reducing the volume of the supercharging equipment.

5. In the present invention, the automatic controller monitors the pressure in the two oil chambers through two electric contact pressure gauges, and compares the monitored pressure value with the set pressure value. If the pressure in the oil chamber rises to the set pressure value, the three-position four-way electromagnetic reversing valve is controlled to operate, thereby realizing automatic reversing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the overall structure of the present invention.

FIG. 2 is a schematic diagram of the structure of the supercharging assembly.

FIG. 3 is a schematic diagram showing the arrangement of the check valve at the end of the partition or the low-pressure cylinder sleeve.

In the figure, 1, check valve, 2, low-pressure air chamber, 3, low-pressure piston, 4, low-pressure piston rod, 5, high-pressure air chamber, 6, high-pressure piston, 7, oil chamber, 8, electric contact pressure gauge, 9, high-pressure piston rod, 10, bypass valve, 11, three-position four-way solenoid reversing valve, 12, oil pump, 13, oil tank, 14, heat exchange tube, 15, partition, 16, low-pressure cylinder liner, 17, high-pressure cylinder liner, 18, valve ball, 19, valve seat.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the accompanying drawings:

As shown in FIG. 1 , the present embodiment includes a supercharging assembly, in which an air chamber and an oil chamber 7 are provided, the air chamber is connected to an air pressure pipeline, and the oil chamber 7 is connected to a hydraulic pipeline, so that the air chamber and the oil chamber 7 participate in forming a hydraulic system and a pneumatic system. The function of the hydraulic system is to drive the movable parts in the supercharging assembly, thereby providing power for the supercharging process of the supercharging assembly, and the function of the pneumatic system is to sequentially transport the gas to be pressurized to each supercharging chamber (air chamber) in the supercharging assembly, so that the gas pressure is increased and then used.

As shown in FIG. 2 , the boost assembly includes two high-pressure cylinder sleeves 17 , two high-pressure pistons 6 , two low-pressure cylinder sleeves 16 and two low-pressure pistons 3 . The high-pressure pistons 6 are slidably installed in the high-pressure cylinder sleeves 17 , and the low-pressure pistons 3 are slidably installed in the low-pressure cylinder sleeves 16 .

As shown in FIG2 , two high-pressure cylinder sleeves 17 are coaxial and fixedly connected, each of the two high-pressure cylinder sleeves 17 is provided with a high-pressure piston 6, and a piston rod is connected between the two high-pressure pistons 6, which is called a high-pressure piston rod 9; the high-pressure piston rod 9 passes through the center of the partition 15 at the connection between the two high-pressure cylinder sleeves 17 and cooperates with the partition 15 in a sliding and sealing manner; the internal space of each high-pressure cylinder sleeve 17 is divided into an air chamber and an oil chamber 7 by the high-pressure piston 6, and the air chamber is called a high-pressure air chamber 5, wherein the two high-pressure air chambers 5 are respectively located between the two high-pressure pistons 6 and the low-pressure cylinder sleeves 16 on their respective corresponding sides, and the two oil chambers 7 are located between the two high-pressure pistons 6. During operation, the high-pressure piston 6 is driven by alternately pumping and discharging hydraulic oil into the two oil chambers 7, thereby realizing the linear reciprocating motion of the high-pressure piston 6.

As shown in FIG2 , two low-pressure cylinder sleeves 16 are fixedly connected to the two ends of the connecting body composed of two high-pressure cylinder sleeves 17. A low-pressure piston 3 is arranged in each low-pressure cylinder sleeve 16. A piston rod, called a low-pressure piston rod 4, is connected between each low-pressure piston 3 and the adjacent high-pressure piston 6. The low-pressure piston rod 4 passes through the center of the partition 15 at the connection between the high-pressure cylinder sleeve 17 and the low-pressure cylinder sleeve 16, and slides and seals with the partition 15. The internal space of each low-pressure cylinder sleeve 16 is divided into two left and right air chambers by the low-pressure piston 3. Both air chambers are called low-pressure air chambers 2. When working, the two low-pressure pistons 3 move synchronously with the two high-pressure pistons 6 under the drive of the high-pressure piston 6.

In this embodiment, the diameter of the high-pressure cylinder sleeve 17 where the oil chamber is located is smaller than the diameter of the low-pressure cylinder sleeve 16, which is beneficial for providing a larger gas compression space when the flow rate of the hydraulic system is constant, thereby effectively improving the boosting efficiency.

As shown in FIG1 , the hydraulic system includes a first oil circuit and a second oil circuit, which are connected end to end to form a complete hydraulic circuit. The first oil circuit is formed by connecting the oil tank 13, the oil pump 12, the three-position four-way electromagnetic reversing valve 11 and an oil chamber 7 in sequence through a hydraulic oil pipe, and the second oil circuit is formed by connecting the oil tank 13, the three-position four-way electromagnetic reversing valve 11 and another oil chamber 7 in sequence through a hydraulic oil pipe, and the oil tank 13 is filled with hydraulic oil. When working, in the first oil circuit, the oil pump 12 pumps the hydraulic oil in the oil tank 13 into an oil chamber 7, and then pushes the high-pressure piston 6 at the end of the oil chamber 7 to move, and the space of the oil chamber 7 increases. At the same time, in the second oil circuit, the movement of the high-pressure piston 6 in the other oil chamber 7 reduces the space in the oil chamber 7, and then squeezes the hydraulic oil in the oil chamber 7 to be squeezed out, and the squeezed hydraulic oil flows back to the oil tank 13 along the second oil circuit. By controlling the three-position four-way electromagnetic reversing valve 11, the switching of the flow direction of the hydraulic oil in the hydraulic oil pipe between the three-position four-way electromagnetic reversing valve 11 and the high-pressure cylinder sleeve 17 can be realized, thereby realizing the controllable inflow and outflow of the hydraulic oil in the two oil chambers 7, and finally making each piston in the boosting assembly reciprocate under hydraulic drive. The two oil chambers 7 are isolated from each other by the partition 15 in the middle of the high-pressure cylinder sleeve 17. Two high-pressure pistons 6 and two low-pressure pistons 3 are arranged in the boosting assembly, and each piston is rigidly connected in series. Taking the left high-pressure piston 6 as an example, the left side of the high-pressure piston 6 is the gas to be compressed, and the right side is the hydraulic oil for driving the reversing. The low-pressure piston 3 is a double-acting piston, which can compress and inhale the gas to be compressed on both sides of the piston at the same time, thereby improving the boosting efficiency. In addition, while playing the hydraulic driving function, the high-pressure piston 6 can also compress the gas to be compressed in one direction, thereby further improving the boosting efficiency.

As shown in Fig. 1, the air pressure system includes an air intake pipeline, a filter and an air outlet pipeline; the gas entering from the air intake pipeline is filtered by the filter and then transported to four low-pressure air chambers 2 respectively located in two low-pressure cylinder sleeves 16 through pipelines; the gas is compressed and discharged by the low-pressure piston 3 in the low-pressure air chamber 2, and the discharged gas is transported to the high-pressure air chamber 5 through pipelines for secondary compression, and the gas after secondary compression enters the air outlet pipeline from the high-pressure air chamber 5. A one-way valve 1 for preventing backflow is provided at the connection between the air pressure pipeline and each air chamber. The one-way valve in the present invention adopts a springless gravity ball form, which has better adaptability to media in different states, is not easily affected by impurities, and has higher reliability.

As shown in FIG1 , a heat exchange tube 14 is provided in the oil tank 13. Both ends of the heat exchange tube 14 are connected in series in the main air path of the air pressure system and are located between the outlet of the low-pressure air chamber 2 and the inlet of the high-pressure air chamber 5. The heat exchange tube 14 is immersed in the hydraulic oil. Before the compressed gas flows out of the low-pressure air chamber 2 and enters the high-pressure air chamber 5, it is cooled or heated through the heat exchange tube in the oil tank 13 to meet the medium temperature requirements of the working environment.

As shown in FIGS. 2 and 3 , the check valve 1 is built into the partition 15 at the end of each air chamber and in the low-pressure cylinder 16 at a position corresponding to the end of the low-pressure air chamber 2 .

The structure of the one-flow valve 1 includes a valve ball 18 and a valve seat 19. The valve ball 18 is placed above the valve seat 19. The inlet and outlet of the one-flow valve 1 are processed on the partition 15 or the end of the low-pressure air chamber 2 to achieve the connection between the inside and outside of each air chamber. When the one-flow valve 1 is in a closed state, the valve ball 18 is pressed against the inner side of the upper end of the valve seat 19 under the action of its own gravity to achieve the sealing between the valve ball 18 and the valve seat 19. When the one-flow valve 1 is in a conducting state, the valve ball 18 is pushed away from the valve seat 19 by the fluid to achieve the conduction of the inlet and outlet of the one-flow valve 1. In specific implementation, the structures of the two one-flow valves 1 at the air inlet and outlet ends of each air chamber will be slightly different, and this difference is mainly reflected in the setting of the inlet and outlet positions of each one-flow valve 1. FIG3 shows the structure of two one-way valves 1 at the air inlet and air outlet of each air chamber. The inlet of the one-way valve 1 at the air inlet leads to the outside of the supercharging assembly, and the outlet leads to the inside of the air chamber. The inlet of the one-way valve 1 at the air outlet is connected to the internal space of the air chamber, and the outlet is connected to the outside of the supercharging assembly.

As shown in FIG. 1 , a bypass valve 10 is respectively provided at both ends of the boost assembly, and two bypass valves 10 are connected in parallel with each low-pressure air chamber 2 .

In this embodiment, the diameters of the high-pressure piston rod 9 and the low-pressure piston rod 4 are the same.

As shown in FIG1 , an electric contact pressure gauge 8 for detecting the pressure in the oil chamber 7 is installed on the outer side of each of the two oil chambers 7. The two electric contact pressure gauges 8 and the three-position four-way electromagnetic reversing valve 11 are connected to an automatic controller through wires. The automatic controller continuously monitors the pressure in the oil chamber 7 through the electric contact pressure gauge 8. During the process of the oil pump 12 continuously pumping the hydraulic oil into the oil chamber 7, the pressure in the oil chamber 7 continuously increases. When the pressure value in one of the oil chambers 7 monitored by the automatic controller is equal to the predetermined value, the automatic controller sends an instruction to the three-position four-way electromagnetic reversing valve 11 to make it perform the reversing action. After the reversing, the hydraulic oil in the oil chamber 7 with higher pressure flows out in the reverse direction to reduce the pressure. At the same time, the hydraulic oil is pumped into the other oil chamber 7 to increase the pressure in the oil chamber 7. In the present invention, the automatic controller monitors the pressure in the two oil chambers 7 through the two electric contact pressure gauges 8, and compares the monitored pressure value with the set pressure value. If the pressure in the oil chamber 7 increases to the set pressure value, the three-position four-way electromagnetic reversing valve is controlled to act, thereby realizing automatic reversing.

Working principle:

1. Two-stage compression mode (bypass valve 10 between low-pressure cylinders is closed)

The gas to be compressed enters from the gas inlet line and is directed to the gas filter (25 micron filter, designed for a maximum working pressure of 1500psi). A 1250psi safety valve can be set on the gas filter, and the safety valve should be connected to a suitable skid-side vent or flare through a pipeline. The gas to be compressed flows from the gas filter to the inlet of the low-pressure gas chamber 2, using a check valve 1 (a gravity ball check valve 1 closed by gravity). When the gas pressure in the low-pressure gas chamber 2 drops below the inlet gas pressure, the gas pressure lifts the valve ball 18 from the valve seat 19, allowing the gas to fill the low-pressure gas chamber 2.

When the pressure in the low-pressure chamber 2 approaches the intake pressure, the valve ball 18 in the gravity ball check valve 1 will fall back onto the valve seat 19 under the action of its own gravity. Once the gas is compressed to a pressure higher than the interstage pipeline pressure, the valve ball 18 in the outlet check valve 1 will rise from the valve seat 19, allowing the gas to leave the low-pressure chamber 2. Once the low-pressure piston 3 completes its stroke, gravity will return the valve ball 18 to the valve seat 19.

The gas flowing out of the low-pressure air chamber 2 enters the heat exchange tube 14 in the hydraulic oil tank 13 through the pipeline. The temperature in the hydraulic oil tank 13 should not exceed 165 degrees Fahrenheit. The outlet gas temperature of the low-pressure air chamber 2 needs to be cooled before entering the high-pressure air chamber 5. The gas flows from the heat exchange tube 14 to the high-pressure air chamber 5 and is transported to the outlet pipeline after being compressed by the high-pressure air chamber 5. The low-pressure air chamber 2 is compressed in both directions of the piston stroke as two double-acting air chambers, while the high-pressure air chamber 5 is squeezed only in one direction of the piston travel as two single-acting air chambers. The working pressure of the two-stage mode is limited to a discharge pressure of 1500psig. The maximum discharge temperature is limited to 400F.

2. Single-stage compression mode (bypass valve 10 between low-pressure air chamber 2 is open)

The gas to be compressed enters from the gas inlet and is directed to the gas filter (25 micron filter, designed for a maximum working pressure of 1500psi). The gas flows from the filter to the check valve 1 at the inlet of the low-pressure chamber 2. Since the bypass valve 10 is open, the inlet and outlet pressures of the low-pressure chamber 2 are the same, so the gas only needs to flow through the two low-pressure chambers 2 (when the low-pressure piston 3 moves) and the bypass valve 10. The low-pressure chamber 2 does not work or rarely works. The gas enters the heat exchange pipe 14 in the hydraulic oil tank 13 from the low-pressure chamber 2 through the interstage pipeline, and then enters the gas outlet pipeline after passing through the high-pressure chamber 5.

Claims (3)

1. A hydraulically controlled two-stage piston booster device, characterized in that it comprises a booster assembly, wherein an air chamber and an oil chamber (7) are arranged in the booster assembly, the air chamber is connected to an air pressure pipeline, and the oil chamber (7) is connected to a hydraulic pipeline, so that the air chamber and the oil chamber (7) participate in forming a hydraulic system and an air pressure system; A booster assembly comprises a high-pressure cylinder sleeve (17), a high-pressure piston (6), a low-pressure cylinder sleeve (16) and a low-pressure piston (3), wherein the high-pressure piston (6) is slidably mounted in the high-pressure cylinder sleeve (17), and the low-pressure piston (3) is slidably mounted in the low-pressure cylinder sleeve (16); There are two high-pressure cylinder sleeves (17) in total. The two high-pressure cylinder sleeves (17) are coaxial and fixedly connected. A high-pressure piston (6) is disposed in each of the two high-pressure cylinder sleeves (17). A high-pressure piston rod is connected between the two high-pressure pistons (6). The high-pressure piston rod (9) passes through the center of a partition (15) at the connection between the two high-pressure cylinder sleeves (17) and cooperates with the partition (15) in a sliding and sealing manner. The internal space of each high-pressure cylinder sleeve (17) is divided into a high-pressure gas chamber and an oil chamber (7) by the high-pressure piston (6), wherein the two high-pressure gas chambers (5) are respectively located between the two high-pressure pistons (6) and the low-pressure cylinder sleeves (16) on their corresponding sides, and the two oil chambers (7) are located between the two high-pressure pistons (6). There are two low-pressure cylinder sleeves (16) in total. The two low-pressure cylinder sleeves (16) are respectively fixedly connected to the two ends of a connecting body composed of two high-pressure cylinder sleeves (17). A low-pressure piston (3) is arranged in each low-pressure cylinder sleeve (16). A low-pressure piston rod is connected between each low-pressure piston (3) and the adjacent high-pressure piston (6). The low-pressure piston rod (4) passes through the center of the partition (15) at the connection between the high-pressure cylinder sleeve (17) and the low-pressure cylinder sleeve (16), and is in sliding sealing cooperation with the partition at the connection between the high-pressure cylinder sleeve (17) and the low-pressure cylinder sleeve (16); the internal space of each low-pressure cylinder sleeve (16) is divided into two left and right low-pressure air chambers by the low-pressure piston (3); The diameter of the high-pressure cylinder liner (17) where the oil chamber is located is smaller than the diameter of the low-pressure cylinder liner (16); The hydraulic system comprises a first oil circuit and a second oil circuit, wherein the first oil circuit is formed by connecting an oil tank (13), an oil pump (12), a three-position four-way electromagnetic reversing valve (11) and an oil chamber (7) in sequence through a hydraulic oil pipe, and the second oil circuit is formed by connecting an oil tank (13), the three-position four-way electromagnetic reversing valve (11) and another oil chamber (7) in sequence through a hydraulic oil pipe, and the oil tank (13) contains hydraulic oil; by controlling the three-position four-way electromagnetic reversing valve (11), the flow direction of the hydraulic oil in the hydraulic oil pipe between the three-position four-way electromagnetic reversing valve (11) and the high-pressure cylinder sleeve (17) can be switched, thereby realizing the controllable inflow and outflow of the hydraulic oil in the two oil chambers (7), and finally enabling each piston in the booster assembly to reciprocate under hydraulic drive; A one-way valve (1) is provided at the inlet connection and outlet connection of the air pressure pipeline and each air chamber to prevent backflow; A heat exchange tube (14) is arranged in the oil tank (13), and both ends of the heat exchange tube (14) are connected in series in the main air path of the air pressure system, and the low-pressure air chamber of the left rodless chamber and the low-pressure air chamber of the right rodless chamber are both connected to one end of the heat exchange tube through a one-way valve at the outlet, and the other end of the heat exchange tube is connected to the two high-pressure air chambers through the one-way valves at the inlets of the two high-pressure air chambers. The heat exchange tube (14) is immersed in the hydraulic oil; The air pressure system comprises an air inlet pipeline, a filter and an air outlet pipeline; the gas entering from the air inlet pipeline is filtered by the filter and then transported through the pipeline to two low-pressure air chambers among four low-pressure air chambers (2) respectively located in two low-pressure cylinder sleeves (16); the gas is compressed and discharged by the low-pressure piston (3) in the other two low-pressure air chambers (2); the discharged gas is transported to a high-pressure air chamber (5) through the pipeline and the heat exchanger for secondary compression; when the three-position four-way electromagnetic reversing valve is reversed, the gas after secondary compression enters the air outlet pipeline from the one high-pressure air chamber (5) through the one-way valve at the outlet. 2. A hydraulically controlled two-stage piston booster device according to claim 1, characterized in that the diameters of the high-pressure piston rod (9) and the low-pressure piston rod (4) are the same. 3. A hydraulically controlled two-stage piston booster device according to claim 1, characterized in that: an electric contact pressure gauge (8) for detecting the pressure in the oil chamber (7) is respectively installed on the outer side of the two oil chambers (7), and the two electric contact pressure gauges (8) and the three-position four-way electromagnetic reversing valve (11) are connected to an automatic controller through wires. The automatic controller continuously monitors the pressure in the oil chamber (7) through the electric contact pressure gauge (8). During the process of the oil pump (12) continuously pumping the hydraulic oil into the oil chamber (7), the pressure in the oil chamber (7) continuously increases. When the pressure value in one of the oil chambers (7) monitored by the automatic controller is equal to a predetermined value, the automatic controller sends a command to the three-position four-way electromagnetic reversing valve (11) to make it perform a reversing action. After the reversing, the hydraulic oil in the oil chamber (7) with higher pressure flows out in the reverse direction to reduce the pressure. At the same time, the hydraulic oil is pumped into the other oil chamber (7) to increase the pressure in the other oil chamber (7).