High-energy-density hydraulic energy accumulator based on adsorption and desorption principle

Abstract

The high-energy-density hydraulic energy accumulator based on the adsorption and desorption principle comprises a cylinder body and a piston installed in the cylinder body in a sliding fit mode, the piston divides an inner cavity of the cylinder body into an air cavity and an oil cavity which are vertically isolated, an inflation opening is formed in the top end of the air cavity, and the air cavity is inflated through the inflation opening and contains a gas medium; a hydraulic oil port is formed in the bottom end of the oil cavity; the oil cavity is communicated with an external hydraulic system loop through the hydraulic oil port; an adsorption material assembly is arranged in the air cavity and comprises an adsorption material with a large specific surface area and a microporous film packaged outside the adsorption material, and the microporous film allows free circulation of air. Compared with a traditional hydraulic energy accumulator which utilizes a gas medium to conduct conversion energy storage, the hydraulic energy accumulator can achieve high energy density and high conversion accumulation stability on the premise that the size is small, and is particularly suitable for mobile hydraulic equipment application scenes which have requirements for the energy storage capacity and are limited in installation space.

Description

Technical Field

[0001] The invention relates to a hydraulic accumulator, in particular to a hydraulic accumulator with high energy density, belonging to the technical field of hydraulic accumulators. Background Art

[0002] Hydraulic accumulator is an energy storage device in hydraulic system. It converts the energy in the system into compression energy or potential energy and stores it at the right time. When the system needs it, it converts the compression energy or potential energy into hydraulic or air pressure energy and releases it to replenish the system. Therefore, hydraulic accumulator is an important device for hydraulic system to realize functions such as energy storage, pressure pulsation absorption and auxiliary power source.

[0003] Hydraulic oil is an incompressible liquid, so it is impossible to store pressure energy using hydraulic oil. It is necessary to rely on other media to convert the stored pressure energy. The method of using compressible gas media to convert and store energy is currently a common method of hydraulic accumulators. However, traditional hydraulic accumulators that use gas media to convert and store energy have always had the problem of low energy density. Taking the common piston hydraulic accumulator as an example, it relies on the piston to isolate oil and gas and stores energy through gas compression. However, within a certain pressure variation range, the gas compression volume is limited, resulting in a small effective filling volume. This problem is particularly prominent in application scenarios such as engineering machinery and mobile hydraulic equipment that require energy storage capacity. Usually, the only way to solve the problem of small effective filling volume is to increase the volume of the hydraulic accumulator. For example, if the energy storage oil volume is required to be 30L and the pressure variation range is 15-20MPa, it can be calculated that the required hydraulic accumulator volume is 190L and the external volume is 250L. A larger hydraulic accumulator will not only occupy a lot of valuable space, increase equipment weight and cost, but also limit the flexibility and performance improvement of the equipment. In addition, the gas pressure fluctuates greatly when the traditional hydraulic accumulator stores energy, which is not conducive to the stable operation of the system. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a high-energy density hydraulic accumulator based on the principle of adsorption and desorption. Compared with traditional hydraulic accumulators that use gas media for conversion and storage, it can achieve higher energy density and higher conversion and accumulation stability under the premise of smaller volume. It is particularly suitable for mobile hydraulic equipment application scenarios that have requirements for energy storage capacity and limited installation space.

[0005] To achieve the above purpose, the high energy density hydraulic accumulator based on the adsorption and desorption principle is a piston structure, including a cylinder body and a piston slidably mounted inside the cylinder body, the piston divides the inner cavity of the cylinder body into an air cavity and an oil cavity separated from each other, the top of the air cavity is provided with an air charging port, the air cavity is filled with and contains a gas medium through the air charging port, the bottom of the oil cavity is provided with a hydraulic oil port, the oil cavity is connected to an external hydraulic system circuit through the hydraulic oil port;

[0006] An adsorption material component is arranged in the air cavity. The adsorption material component comprises an adsorption material with a large specific surface area and a microporous film encapsulated outside the adsorption material. The microporous film allows the gas to flow freely.

[0007] As a further improvement of the present invention, a temperature control device is further provided on the outside of the cylinder.

[0008] As a further improvement of the present invention, a countersunk hole structure is provided on the top surface of the piston, and the adsorption material is arranged in the countersunk hole structure of the piston through microporous film packaging.

[0009] As a further improvement of the present invention, the inflation port is connected to the gas medium pressure cylinder through a pipeline and a control valve group.

[0010] As an embodiment of the present invention, the gas medium is nitrogen, carbon dioxide, or an inert gas.

[0011] As an embodiment of the present invention, the adsorption material is bamboo activated carbon, or zeolite molecular sieve, or metal organic framework material.

[0012] As an embodiment of the present invention, the microporous film is made of polytetrafluoroethylene, polyethylene, or polyurethane.

[0013] Compared with the prior art, when the high energy density hydraulic accumulator based on the adsorption and desorption principle is installed on an external hydraulic system circuit for use, the gas medium is filled into the air cavity through the charging port to the initial pressure. When the pressure of the external hydraulic system circuit increases (energy storage state of the hydraulic accumulator), the external hydraulic oil enters the oil cavity through the hydraulic oil port and pushes the piston to compress the gas medium in the air cavity. The pressure of the gas medium increases and accumulates pressure energy. Part of the gas medium is adsorbed by the adsorption material through the microporous film, which reduces the number of gas moles. Therefore, the internal energy increase and the pressure increase amplitude of the gas medium are reduced, thereby achieving more hydraulic oil storage under the same pressure change; when the pressure of the external hydraulic system circuit decreases (energy release state of the hydraulic accumulator), the gas medium in the air cavity releases pressure energy and pushes the piston to squeeze the hydraulic oil in the oil cavity and discharge it through the hydraulic oil port. During the process of releasing the pressure energy of the gas medium, the pressure decreases, and the gas medium adsorbed by the adsorption material is desorbed and released to maintain the gas pressure in the air cavity, thereby achieving stable output of the hydraulic oil in the oil cavity and improving the conversion and accumulation stability.

[0014] This high-energy-density hydraulic accumulator based on the principle of adsorption and desorption can greatly improve the energy density, reduce the volume of the accumulator, save space and reduce costs with the help of gas adsorption and desorption mechanism. At the same time, the stable adsorption and desorption process can improve the operating stability of the hydraulic system and optimize the overall performance of the hydraulic system. It is particularly suitable for mobile hydraulic equipment application scenarios that have requirements for energy storage capacity and limited installation space. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention.

[0016] In the figure: 1. inflation port; 2. cylinder body; 3. air cavity; 4. microporous film; 5. piston; 6. oil cavity; 7. hydraulic oil port; 8. adsorption material; 9. temperature control device. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings (hereinafter referred to as Figure 1 The up and down directions are described as the up and down directions).

[0018] like Figure 1 As shown, the high energy density hydraulic accumulator based on the adsorption and desorption principle is a piston structure, including a cylinder body 2 and a piston 5 slidably mounted inside the cylinder body 2. The piston 5 divides the inner cavity of the cylinder body 2 into an air cavity 3 and an oil cavity 6 isolated from each other. A charging port 1 is provided at the top of the air cavity 3. The air cavity 3 is filled with and contains a gas medium through the charging port 1. The charging port 1 can be directly connected to a gas medium pressure cylinder. The gas medium can be a relatively highly compressed gas such as nitrogen, carbon dioxide, or an inert gas. A hydraulic oil port 7 is provided at the bottom of the oil cavity 6. The oil cavity 6 is connected to an external hydraulic system circuit through the hydraulic oil port 7.

[0019] An adsorption material component is provided in the air cavity 3, and the adsorption material component includes an adsorption material 8 with a large specific surface area and a microporous film 4 encapsulated outside the adsorption material 8. The adsorption material 8 has a stable gas adsorption capacity under normal temperature and a certain pressure range. It can be made of bamboo activated carbon, zeolite molecular sieve, metal organic framework material and other materials. The microporous film 4 can be made of high molecular polymer materials such as polytetrafluoroethylene (PTFE), polyethylene (PE), polyurethane (PU), etc. The microporous film 4 allows gas to flow freely while blocking water, dust and other pollutants.

[0020] When the high energy density hydraulic accumulator based on the adsorption and desorption principle is installed on an external hydraulic system circuit for use, the gas medium is charged into the air chamber 3 through the charging port 1 to the initial pressure. When the pressure of the external hydraulic system circuit increases (hydraulic accumulator energy storage state), the external hydraulic oil enters the oil chamber 6 through the hydraulic oil port 7 and pushes the piston 5 to compress the gas medium in the air chamber 3. The pressure of the gas medium increases and accumulates pressure energy. Part of the gas medium passes through the microporous film 4 and is adsorbed by the adsorption material 8 to reduce the number of gas moles. Therefore, the internal energy increase and the pressure increase amplitude of the gas medium are reduced, thereby achieving more hydraulic oil storage under the same pressure change; when the pressure of the external hydraulic system circuit decreases (hydraulic accumulator energy release state), the gas medium in the air chamber 3 releases pressure energy and pushes the piston 5 to squeeze the hydraulic oil in the oil chamber 6 and discharge it through the hydraulic oil port 7. During the process of releasing the pressure energy of the gas medium, the pressure decreases, and the gas medium adsorbed by the adsorption material 8 is desorbed and released to maintain the gas pressure in the air chamber 3, thereby achieving stable output of the hydraulic oil in the oil chamber 6 and improving the conversion and accumulation stability.

[0021] Since carbon dioxide has stable physical and chemical properties, can be well matched with the adsorption-desorption characteristics of the adsorption material 8, and has low cost, carbon dioxide is selected as the gas medium as a preferred embodiment of the present invention.

[0022] Since the temperature rise of the gas medium during compression will affect the pressure and volume of the gas medium, as a further improvement of the present invention, a temperature control device 9 is further provided on the outside of the cylinder body 2. The temperature of the gas medium in the gas cavity 3 is adjusted by the temperature control device 9, so that the adsorption material 8 is in the optimal adsorption temperature range, thereby achieving the best gas adsorption effect. The temperature control device 9 is a prior art and will not be described in detail here.

[0023] In order to further reduce the volume of the accumulator and improve the utilization rate of the energy storage space, as a further improvement scheme of the present invention, a countersunk structure is provided on the top surface of the piston 5, and the adsorption material 8 is encapsulated by the microporous film 4 and arranged in the countersunk structure of the piston 5. Take the case where the gas medium is carbon dioxide, the total volume of the accumulator is 13L (i.e., the volume of the gas medium in the initial stage is 13L), the pre-charge pressure is 5MPa, and the initial temperature is 300K as an example: Based on Boyle's law, it can be known that the molar number of carbon dioxide is about 26mol. When a traditional accumulator is used, if the maximum working pressure is 8.5MPa and the final temperature is 320K, the volume of carbon dioxide gas becomes 8L, i.e., 5L of oil can be stored in the oil chamber 6; assuming that 500g of bamboo activated carbon is placed in the countersunk structure of the piston 5 as the adsorption material 8, the adsorption rate of carbon dioxide at 5MPa pressure and 300K temperature is 20mmol / g. When ignoring the pressure and temperature changes, it can absorb about 10mol of carbon dioxide. Therefore, the molar number of carbon dioxide in the final stage is 16mol. If the maximum working pressure is 8.5MPa and the final temperature is 320K, the volume of carbon dioxide gas becomes about 5L, i.e., 8L of oil can be stored in the oil chamber 6, and the oil storage capacity is increased by 60%. By comparison, it can be seen that under the same gas pressure change, the high energy density hydraulic accumulator based on the adsorption and desorption principle can store more hydraulic oil, thereby achieving a higher energy density.

Claims

1. A high energy density hydraulic accumulator based on the adsorption and desorption principle is a piston type structure, comprising a cylinder body (2) and a piston (5) slidably mounted inside the cylinder body (2), the piston (5) dividing the inner cavity of the cylinder body (2) into an air cavity (3) and an oil cavity (6) separated from each other, the top of the air cavity (3) is provided with an air filling port (1), the air cavity (3) is filled with and contains a gas medium through the air filling port (1), the bottom of the oil cavity (6) is provided with a hydraulic oil port (7), the oil cavity (6) is connected to an external hydraulic system circuit through the hydraulic oil port (7); characterized in that, An adsorption material component is arranged in the air cavity (3), and the adsorption material component comprises an adsorption material (8) having a large specific surface area and a microporous film (4) encapsulated outside the adsorption material (8), and the microporous film (4) allows gas to flow freely.

2. The high energy density hydraulic accumulator based on the adsorption and desorption principle according to claim 1 is characterized in that: A temperature control device (9) is also provided outside the cylinder body (2).

3. The high energy density hydraulic accumulator based on the adsorption and desorption principle according to claim 1 is characterized in that: A countersunk hole structure is provided on the top surface of the piston (5), and the adsorption material (8) is encapsulated and arranged in the countersunk hole structure of the piston (5) through a microporous film (4).

4. The high energy density hydraulic accumulator based on the adsorption and desorption principle according to claim 1, 2 or 3, characterized in that: The charging port (1) is connected to a gas medium pressure cylinder through a pipeline and a control valve group.

5. The high energy density hydraulic accumulator based on the adsorption and desorption principle according to claim 1, 2 or 3, characterized in that: The gas medium is nitrogen, carbon dioxide, or an inert gas.

6. The high energy density hydraulic accumulator based on the adsorption and desorption principle according to claim 1, 2 or 3, characterized in that: The adsorption material (8) is bamboo activated carbon, or zeolite molecular sieve, or metal organic framework material.

7. The high energy density hydraulic accumulator based on the adsorption and desorption principle according to claim 1, 2 or 3, characterized in that: The microporous film (4) is made of polytetrafluoroethylene, polyethylene, or polyurethane.

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