A high energy density hydraulic energy storage device and energy storage method

Abstract

A high energy density hydraulic energy storage device and energy storage method, the device includes an air storage tank, a first, a second and a third energy storage cylinder with the same volume and an effective area of ​​the air cavity from large to small, the upper air cavities of the three energy storage cylinders are connected in series with the air storage tank through pipelines in order from near to far from the air storage tank, the pistons in the cylinders have the same area, and the liquid cavities are connected to the charging / discharging ports through pipelines and electromagnetic valves arranged on the pipelines; the method: when storing energy, the energy is stored in sequence, so that the oil pressure when the second energy storage cylinder starts to store energy is smaller than the pressure when the first energy storage cylinder ends energy storage, and the oil pressure when the third energy storage cylinder starts to store energy is smaller than the pressure when the second energy storage cylinder ends energy storage; when releasing energy, the liquid is discharged according to the process opposite to the energy storage, thereby improving the discharge efficiency. In the present invention, when the initial volume and initial pressure of the air cavity remain unchanged, the same amount of gas compression, the stored oil volume is large, the amount of oil is large, and the energy storage capacity and energy utilization rate of the accumulator are greatly improved.

Description

Technical Field

[0001] The invention relates to a high energy density hydraulic energy storage device and an energy storage method, belonging to the technical field of hydraulic transmission and control. Background Art

[0002] As one of the important forms of modern industrial transmission, hydraulic transmission has the advantages of high power ratio, high reliability, and stepless speed regulation, but it has throttling loss and overflow loss during operation, which makes the transmission efficiency relatively low. In order to improve the transmission efficiency, one method is to minimize the throttling loss and overflow loss in the design or use, but the efficiency improvement of this method is limited; another method is to recover, store and reuse the energy of throttling loss and overflow loss in the hydraulic system, which is an important means to improve the energy efficiency of the hydraulic system.

[0003] Only by adopting appropriate and efficient energy storage methods to effectively store energy in the hydraulic system can the operating efficiency of the hydraulic system be improved and the purpose of energy conservation and emission reduction be achieved. The piston accumulator is a commonly used hydraulic energy storage device in the hydraulic system of the excavator. It converts the hydraulic energy in the hydraulic system into gas compression energy and stores it at the appropriate time. When the system needs it, it converts the gas compression energy into hydraulic energy and releases it to replenish the hydraulic system. However, in actual applications, it is found that although the power density of the hydraulic accumulator is higher than that of other energy storage elements, its energy density is far lower than that of commonly used energy storage elements such as fuel cells, and it has the disadvantages of large size and high cost. In addition, due to the energy loss of the system, the output pressure of the traditional accumulator when releasing energy is slightly lower than the hydraulic oil pressure when storing energy. Therefore, additional fluid supply from the hydraulic pump is often required to ensure the normal operation of the hydraulic system, which not only complicates the entire hydraulic system, but also reduces efficiency.

[0004] Energy storage density, power density and efficiency are three important indicators of hydraulic energy storage. At present, the high power density of hydraulic accumulators can ensure the rapidity of their energy storage and release. In order to achieve better energy storage effects and make the accumulators small in size and low in cost, further improvements are needed to the accumulators at this stage so that they have sufficient energy storage and higher energy utilization during operation. Summary of the invention

[0005] The purpose of the present invention is to provide a high energy density hydraulic energy storage device and energy storage method, which can achieve higher energy storage density under the premise of small accumulator volume and low cost.

[0006] In order to achieve the above object, the present invention provides a high energy density hydraulic energy storage device, comprising a gas storage tank, and also comprising a first energy storage cylinder, a second energy storage cylinder and a third energy storage cylinder of the same volume, wherein the upper air cavities of the first energy storage cylinder, the second energy storage cylinder and the third energy storage cylinder are connected in series with the gas storage tank through pipelines in order from near to far from the gas storage tank;

[0007] The first energy storage cylinder, the second energy storage cylinder and the third energy storage cylinder are all provided with pistons of the same area slidingly along their inner walls, the upper end surface of each piston is connected to a piston rod with one end extending out of the top of the cylinder body, and the extending section of each piston rod is provided with an extending stroke switch and a retracting stroke switch; below each piston is a lower liquid chamber of the cylinder body, and each liquid chamber is connected to the charging / discharging port through a pipeline and a solenoid valve provided on the pipeline;

[0008] The area of ​​the first energy storage cylinder's air cavity gas acting on its internal piston is larger than the area of ​​the second energy storage cylinder's air cavity gas acting on its internal piston, and the area of ​​the second energy storage cylinder's air cavity gas acting on its internal piston is larger than the area of ​​the third energy storage cylinder's air cavity gas acting on its internal piston.

[0009] Further, the lower liquid chamber of the first energy storage cylinder is connected to the charging / discharging port through a pipeline and a first solenoid valve arranged on the pipeline, a piston is slidably arranged in the upper air chamber along the inner wall thereof, the upper end surface of the piston is connected to the lower end of the piston rod, the upper end of the piston rod extends out of the top cover of the first energy storage cylinder, and an extension stroke switch and a retraction stroke switch are arranged on the extension section, wherein the extension stroke switch is located on the rod body close to the upper end of the piston rod, and the maximum stroke of the retraction stroke switch matches the maximum distance between the lower end surface of the piston and the bottom of the lower liquid chamber of the first energy storage cylinder;

[0010] The lower liquid chamber of the second energy storage cylinder is connected to the charging / discharging port through a pipeline and a second solenoid valve arranged on the pipeline, and a second piston is slidably arranged in the upper air chamber along the inner wall thereof, and the upper end surface of the second piston is connected to the lower end of the second piston rod, and the upper end of the second piston rod extends out of the top cover of the second energy storage cylinder, and an extension stroke switch 2 and a retraction stroke switch 2 are arranged on the extension section, wherein the extension stroke switch 2 is located on the rod body close to the upper end of the second piston rod, and the maximum stroke of the retraction stroke switch 2 is adapted to the maximum distance between the lower end surface of the second piston and the bottom of the lower liquid chamber of the second energy storage cylinder;

[0011] The lower liquid chamber of the third energy storage cylinder is connected to the charging / discharging port through a pipeline and a third solenoid valve arranged on the pipeline, a piston three is slidably arranged in the upper air chamber along the inner wall thereof, the upper end surface of the piston three is connected to the lower end of the piston rod three, the upper end of the piston rod three extends out of the top cover of the third energy storage cylinder, and an extension stroke switch three and a retraction stroke switch three are arranged on the extension section, wherein the extension stroke switch three is located on the rod body near the upper end of the piston rod three, and the maximum stroke of the retraction stroke switch three is adapted to the maximum distance between the lower end surface of the piston three and the bottom of the lower liquid chamber of the third energy storage cylinder;

[0012] The rod body diameter of piston rod one is smaller than the rod body diameter of piston rod two, and the rod body diameter of piston rod two is smaller than the rod body diameter of piston rod three.

[0013] A high energy density hydraulic energy storage method comprises the following steps:

[0014] Step 1: Before storing energy, the first solenoid valve, the second solenoid valve and the third solenoid valve are all powered, and the oil in the liquid chambers of the first energy storage cylinder, the second energy storage cylinder and the third energy storage cylinder is discharged through the filling / discharging port; the air chambers of the first energy storage cylinder, the second energy storage cylinder and the third energy storage cylinder are inflated respectively through the gas storage tank, so that the lower end surfaces of the pistons 1, 2 and 3 are respectively in contact with the bottom of the liquid chambers of the first energy storage cylinder, the second energy storage cylinder and the third energy storage cylinder, and the position is detected by the retraction stroke switch 1, the retraction stroke switch 2 and the retraction stroke switch 3 respectively; the oil inside the first energy storage cylinder, the second energy storage cylinder and the third energy storage cylinder is emptied through the filling / discharging port under the compression of the piston; at this time, the air pressure in the air chambers of the first energy storage cylinder, the second energy storage cylinder and the third energy storage cylinder and the gas storage tank reaches the initial pressure P q1 , the total initial gas volume is:

[0015] V q1 =V0++V1++V2++V3;

[0016] Wherein, V0 is the volume of the air chamber of the air storage tank, V1 is the maximum volume of the air chamber of the first energy storage cylinder; V2 is the maximum volume of the air chamber of the second energy storage cylinder; V3 is the maximum volume of the air chamber of the third energy storage cylinder;

[0017] Step 2: During energy storage, the first solenoid valve is powered, the second solenoid valve and the third solenoid valve are powered off, and the first energy storage cylinder liquid cavity is filled with liquid and energy is stored through the first solenoid valve. At this time, the piston 1 moves upward under the action of the oil, and the gas in the air cavity of the first energy storage cylinder is compressed and discharged until the piston 1 moves upward to contact the top of the inner wall of the first energy storage cylinder. At the same time, the extended stroke switch 1 sends a signal, the first solenoid valve is powered off, and the energy storage of the first energy storage cylinder is stopped. In this process, the compression amount of the air cavity of the first energy storage cylinder is V1, and the oil volume in the liquid cavity of the first energy storage cylinder is V y1 , then V y1 The relationship with V1 is:

[0018]

[0019] Wherein, A is the area of ​​the piston, and the areas of piston 1, piston 2 and piston 3 are equal, all A; A1 is the effective area of ​​the air cavity of the first energy storage cylinder, that is, the effective area of ​​the gas in the air cavity of the first energy storage cylinder acting on piston 1;

[0020] The pressure P when the first energy storage cylinder starts to store energy y11 for:

[0021]

[0022] From the gas state equation, the liquid pressure P of the liquid chamber of the first energy storage cylinder when the first energy storage cylinder finishes storing energy is obtained. y12 for:

[0023]

[0024] Step 3: When the first energy storage cylinder ends, the first solenoid valve is powered off and the second solenoid valve is powered on. The pressurized oil is filled into the liquid cavity of the second energy storage cylinder through the second solenoid valve to store energy. At this time, the second piston moves up under the action of the oil, and the gas in the air cavity of the second energy storage cylinder is compressed and discharged until the second piston moves up to contact the top of the inner wall of the second energy storage cylinder. At the same time, the second extended stroke switch sends a signal, the second solenoid valve is powered off, and the energy storage of the second energy storage cylinder is stopped. In this process, the compression amount of the air cavity of the second energy storage cylinder is V2, and the oil volume in the liquid cavity of the first energy storage cylinder is V y2 , then V y2 The relationship with V2 is:

[0025]

[0026] Wherein, A2 is the effective area of ​​the air cavity of the second energy storage cylinder, and the effective area of ​​the gas in the air cavity of the second energy storage cylinder acting on the second piston;

[0027] The pressure P when the second energy storage cylinder starts to store energy y21 for:

[0028]

[0029] From the gas state equation, the liquid pressure P of the liquid chamber of the second energy storage cylinder when the second energy storage cylinder finishes storing energy is obtained. y22 for:

[0030]

[0031] Step 4: When the second energy storage cylinder ends and the second solenoid valve is powered off, the third solenoid valve is powered on, and the pressurized oil is filled into the liquid cavity of the third energy storage cylinder through the third solenoid valve to store energy. At this time, the piston three moves up under the action of the oil, and the gas in the air cavity of the third energy storage cylinder is compressed and discharged until the piston three moves up to contact the top of the inner wall of the third energy storage cylinder. At the same time, the extended stroke switch three sends a signal, the third solenoid valve is powered off, and the energy storage of the third energy storage cylinder is stopped. In this process, the compression amount of the air cavity of the third energy storage cylinder is V3, and the oil volume in the liquid cavity of the first energy storage cylinder is V y3 , then V y3 The relationship with V3 is:

[0032]

[0033] Wherein, A3 is the effective area of ​​the air cavity of the third energy storage cylinder, that is, the effective area of ​​the gas in the air cavity of the third energy storage cylinder acting on the piston three;

[0034] The pressure P when the third energy storage cylinder starts to store energy y31 for:

[0035]

[0036] From the gas state equation, the liquid pressure P of the liquid chamber of the third energy storage cylinder when the third energy storage cylinder finishes storing energy is obtained. y32 for:

[0037]

[0038] Step 5: When the third energy storage cylinder finishes storing energy, the entire energy storage device finishes storing energy, and the total compression of the air cavity is:

[0039] ΔV q =V1++V2++V3;

[0040] The total volume of hydraulic oil stored in the three energy storage cylinders ΔV y for:

[0041]

[0042] Since the piston area A is larger than the effective area of ​​the gas in the air chamber acting on each piston, the total volume of the stored hydraulic oil ΔV is obtained. y Greater than the total compression of the air cavity ΔV q ;

[0043] Step 6: When releasing energy, first energize the third solenoid valve, and the third energy storage cylinder releases oil through the charging / discharging port under the action of the air cavity, and the piston three moves downward. When the piston three moves downward to contact the bottom end of the inner wall of the third energy storage cylinder, the retracted stroke switch three sends a signal, and the third energy storage cylinder ends energy release; energize the second solenoid valve, and the second energy storage cylinder releases oil through the charging / discharging port under the action of the air cavity, and the piston two moves downward. When the piston two moves downward to contact the bottom end of the inner wall of the second energy storage cylinder, the retracted stroke switch two sends a signal, and the second energy storage cylinder ends energy release; energize the first solenoid valve, and the first energy storage cylinder releases oil through the charging / discharging port under the action of the air cavity, and the piston moves downward. When the piston moves downward to contact the bottom end of the inner wall of the first energy storage cylinder, the retracted stroke switch one sends a signal, and the first energy storage cylinder ends energy release.

[0044] The present invention provides a first energy storage cylinder, a second energy storage cylinder and a third energy storage cylinder of the same volume, and connects the air cavities of the three energy storage cylinders in series with the air storage tank through pipelines in sequence, and the effective area of ​​the air cavity of the first energy storage cylinder is larger than the effective area of ​​the air cavity of the second energy storage cylinder, and the effective area of ​​the air cavity of the second energy storage cylinder is larger than the effective area of ​​the air cavity of the third energy storage cylinder. When storing energy, energy is stored in sequence respectively, so that the oil pressure when the second energy storage cylinder starts to store energy is smaller than the pressure when the first energy storage cylinder ends energy storage, and the oil pressure when the third energy storage cylinder starts to store energy is smaller than the pressure when the second energy storage cylinder ends energy storage, thereby realizing rapid energy storage and improving the energy density of energy storage; when releasing energy, liquid is discharged according to the process opposite to that of energy storage, the third energy storage cylinder first releases oil, the second energy storage cylinder releases oil, and the first energy storage cylinder releases oil last; the pressure when the second energy storage cylinder starts to release oil is higher than the final pressure when the third energy storage cylinder releases oil, and the pressure when the first energy storage cylinder starts to release oil is higher than the final pressure when the second energy storage cylinder releases oil, thereby improving the discharge efficiency. Compared with the prior art, the present invention has a large volume of stored oil and a large amount of stored oil for the same amount of gas compression while keeping the initial volume and initial pressure of the air cavity unchanged, thereby greatly improving the energy storage capacity and energy utilization rate of the accumulator during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the device structure of the present invention;

[0046] Figure 2 It is a curve diagram of the pressure changes of the air cavity and the filling / discharging port during the energy storage process of the present invention.

[0047] In the figure: 1, gas storage tank, 2, first energy storage cylinder, 3, second energy storage cylinder, 4, third energy storage cylinder, 5, charging / discharging port, 6, first solenoid valve, 7, piston one, 8, piston rod one, 9, extension stroke switch one, 10, retraction stroke switch one, 11, second solenoid valve, 12, piston two, 13, piston rod two, 14, extension stroke switch two, 15, retraction stroke switch two, 16, third solenoid valve, 17, piston three, 18, piston rod three, 19, extension stroke switch three, 20, retraction stroke switch three. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings.

[0049] like Figure 1 As shown, a high energy density hydraulic energy storage device includes a gas storage tank 1, and also includes a first energy storage cylinder 2, a second energy storage cylinder 3 and a third energy storage cylinder 4 of the same volume, wherein the upper air cavities of the first energy storage cylinder 2, the second energy storage cylinder 3 and the third energy storage cylinder 4 are connected in series with the gas storage tank 1 through pipelines in the order from near to far from the gas storage tank 1;

[0050] The first energy storage cylinder 2, the second energy storage cylinder 3 and the third energy storage cylinder 4 are all provided with pistons of the same area slidingly along their inner walls, and the upper end surface of each piston is connected to a piston rod with one end extending out of the top of the cylinder body, and the extending section of each piston rod is provided with an extending stroke switch and a retracting stroke switch; below each piston is a liquid chamber at the lower part of the cylinder body, and each liquid chamber is connected to the filling / discharging port 5 through a pipeline and a solenoid valve provided on the pipeline;

[0051] The area of ​​the gas in the air cavity of the first energy storage cylinder 2 acting on the internal piston thereof is larger than the area of ​​the gas in the air cavity of the second energy storage cylinder 3 acting on the internal piston thereof, and the area of ​​the gas in the air cavity of the second energy storage cylinder 3 acting on the internal piston thereof is larger than the area of ​​the gas in the air cavity of the third energy storage cylinder 4 acting on the internal piston thereof.

[0052] As a preferred embodiment, the lower liquid chamber of the first energy storage cylinder 2 is connected to the charging / discharging port 5 through a pipeline and a first solenoid valve 6 arranged on the pipeline, and a piston 7 is slidably arranged along the inner wall of the upper air chamber thereof, and the upper end surface of the piston 7 is connected to the lower end of the piston rod 8, and the upper end of the piston rod 8 extends out of the top cover of the first energy storage cylinder 2, and an extension stroke switch 9 and a retraction stroke switch 10 are arranged on the extension section, wherein the extension stroke switch 9 is located on the rod body close to the upper end of the piston rod 8, and the maximum stroke of the retraction stroke switch 10 is adapted to the maximum distance between the lower end surface of the piston 7 and the bottom of the lower liquid chamber of the first energy storage cylinder 2;

[0053] The lower liquid chamber of the second energy storage cylinder 3 is connected to the charging / discharging port 5 through a pipeline and a second solenoid valve 11 arranged on the pipeline, and a piston 12 is slidably arranged in the upper air chamber along the inner wall thereof, and the upper end surface of the piston 12 is connected to the lower end of the piston rod 13, and the upper end of the piston rod 13 extends out of the top cover of the second energy storage cylinder 3, and an extension stroke switch 14 and a retraction stroke switch 15 are arranged on the extension section, wherein the extension stroke switch 14 is located on the rod body close to the upper end of the piston rod 13, and the maximum stroke of the retraction stroke switch 15 is adapted to the maximum distance between the lower end surface of the piston 12 and the bottom of the lower liquid chamber of the second energy storage cylinder 3;

[0054] The lower liquid chamber of the third energy storage cylinder 4 is connected to the charging / discharging port 5 through a pipeline and a third solenoid valve 16 arranged on the pipeline, and a piston 3 17 is slidably arranged in the upper air chamber along the inner wall thereof, and the upper end surface of the piston 3 17 is connected to the lower end of the piston rod 3 18, and the upper end of the piston rod 3 18 extends out of the top cover of the third energy storage cylinder 4, and an extension stroke switch 3 19 and a retraction stroke switch 3 20 are arranged on the extension section, wherein the extension stroke switch 3 19 is located on the rod body near the upper end of the piston rod 3 18, and the maximum stroke of the retraction stroke switch 3 20 is adapted to the maximum distance between the lower end surface of the piston 3 and the bottom of the lower liquid chamber of the third energy storage cylinder 4;

[0055] The rod body diameter of piston rod one 8 is smaller than the rod body diameter of piston rod two 13 , and the rod body diameter of piston rod two 13 is smaller than the rod body diameter of piston rod three 18 .

[0056] Traditional accumulators rely on the changes in the volume and pressure of their gas chambers to achieve the functions of filling and discharging. When the inlet pressure increases, the volume of the gas chamber is compressed, the volume decreases, the volume of the oil chamber increases, and energy is stored; when the inlet pressure decreases, the volume of the gas chamber increases, the fluid is discharged, and energy is released. If the initial volume of the gas chamber is V q1 , the initial pressure is P q1 , the final volume of the air cavity is V q2 , the final state air cavity pressure is P q2 , the volume change of the air cavity is ΔV q , from the gas state equation:

[0057]

[0058] The final volume of the air cavity V can be obtained q2 for:

[0059]

[0060] Simplified, the change in the volume of the liquid chamber of the traditional accumulator ΔV can be obtained y :

[0061]

[0062] That is, the volume of liquid stored in the traditional accumulator is equal to the compression of the gas volume. During the energy storage process, the pressure in the liquid chamber changes from P y1 Rise to P y2 .

[0063] The present invention provides a high energy density hydraulic energy storage method, comprising the following steps:

[0064] Step 1: Before storing energy, the first solenoid valve 6, the second solenoid valve 11 and the third solenoid valve 16 are all energized, and the oil in the liquid chambers of the first energy storage cylinder 2, the second energy storage cylinder 3 and the third energy storage cylinder 4 is discharged through the filling / discharging port 5; the air chambers of the first energy storage cylinder 2, the second energy storage cylinder 3 and the third energy storage cylinder 4 are inflated respectively through the gas storage tank 1, so that the lower end surfaces of the piston 1 7, the piston 2 12 and the piston 3 17 are respectively in contact with the bottom of the liquid chambers of the first energy storage cylinder 2, the second energy storage cylinder 3 and the third energy storage cylinder 4, and the position detection is performed by the retracting stroke switch 1 10, the retracting stroke switch 2 15 and the retracting stroke switch 3 20 respectively; the oil inside the first energy storage cylinder 2, the second energy storage cylinder 3 and the third energy storage cylinder 4 is emptied through the filling / discharging port 5 under the compression of the piston; at this time, the air pressure in the air chambers of the first energy storage cylinder 2, the second energy storage cylinder 3 and the third energy storage cylinder 4 and the gas storage tank 1 reaches the initial pressure P q1 , the total initial gas volume is:

[0065] V q1 =V0++V1+V2+V3;

[0066] Wherein, V0 is the volume of the air cavity of the air storage tank 1, V1 is the maximum volume of the air cavity of the first energy storage cylinder 2; V2 is the maximum volume of the air cavity of the second energy storage cylinder 3; V3 is the maximum volume of the air cavity of the third energy storage cylinder;

[0067] Step 2: During energy storage, the first solenoid valve 6 is energized, the second solenoid valve 11 and the third solenoid valve 16 are de-energized, and the liquid is filled into the liquid cavity of the first energy storage cylinder 2 through the first solenoid valve 6 to store energy. At this time, the piston 7 moves upward under the action of the oil, and the gas in the air cavity of the first energy storage cylinder 2 is compressed and discharged until the piston 7 moves upward to contact the top of the inner wall of the first energy storage cylinder 2. At the same time, the extended travel switch 9 sends a signal, the first solenoid valve 6 is de-energized, and the energy storage of the first energy storage cylinder 2 is stopped; in this process, the compression amount of the air cavity of the first energy storage cylinder 2 is V1, and the oil volume in the liquid cavity of the first energy storage cylinder 2 is V y1 , then V y1 The relationship with V1 is:

[0068]

[0069] Wherein, A is the area of ​​the piston, the areas of piston 1 7, piston 2 12 and piston 3 17 are equal, all of which are A; A1 is the effective area of ​​the air cavity of the first energy storage cylinder 2, that is, the effective area of ​​the gas in the air cavity of the first energy storage cylinder 2 acting on the piston 1 7;

[0070] The pressure P when the first energy storage cylinder 2 starts to store energy y11 for:

[0071]

[0072] From the gas state equation, the liquid pressure P of the liquid chamber of the first energy storage cylinder 2 when the first energy storage cylinder 2 finishes storing energy is obtained. y12 for:

[0073]

[0074] Step 3, when the first solenoid valve 6 of the first energy storage cylinder 2 is powered off, the second solenoid valve 11 is powered on, and the pressurized oil is filled into the liquid cavity of the second energy storage cylinder 3 through the second solenoid valve 11 to store energy. At this time, the second piston 12 moves up under the action of the oil, and the gas in the air cavity of the second energy storage cylinder 3 is compressed and discharged until the second piston 12 moves up to contact the top of the inner wall of the second energy storage cylinder 3. At the same time, the second travel switch 14 sends a signal, the second solenoid valve 11 is powered off, and the energy storage of the second energy storage cylinder 3 is stopped. In this process, the compression amount of the air cavity of the second energy storage cylinder 3 is V2, and the oil volume in the liquid cavity of the first energy storage cylinder 2 is V y2 , then V y2 The relationship with V2 is:

[0075]

[0076] Wherein, A2 is the effective area of ​​the air cavity of the second energy storage cylinder 3, that is, the effective area of ​​the gas in the air cavity of the second energy storage cylinder 3 acting on the piston 2 12;

[0077] The pressure P when the second energy storage cylinder 3 starts to store energy y21 for:

[0078]

[0079] From the gas state equation, the liquid pressure P of the liquid chamber of the second energy storage cylinder 3 when the second energy storage cylinder 3 finishes storing energy is obtained. y22 for:

[0080]

[0081] Step 4: When the second solenoid valve 11 of the second energy storage cylinder 3 is powered off, the third solenoid valve 16 is powered on, and the pressurized oil is filled into the liquid cavity of the third energy storage cylinder 4 through the third solenoid valve 16 to store energy. At this time, the piston 3 17 moves up under the action of the oil, and the gas in the air cavity of the third energy storage cylinder 4 is compressed and discharged until the piston 3 17 moves up to contact the top of the inner wall of the third energy storage cylinder 4. At the same time, the extended travel switch 3 19 sends a signal, the third solenoid valve 16 is powered off, and the energy storage of the third energy storage cylinder 4 is stopped. In this process, the compression amount of the air cavity of the third energy storage cylinder 4 is V3, and the oil volume in the liquid cavity of the first energy storage cylinder 2 is V y3 , then V y3 The relationship with V3 is:

[0082]

[0083] Wherein, A3 is the effective area of ​​the air cavity of the third energy storage cylinder 4, that is, the effective area of ​​the gas in the air cavity of the third energy storage cylinder 4 acting on the piston 3 17;

[0084] The pressure P when the third energy storage cylinder 4 starts to store energy y31 for:

[0085]

[0086] The gas state equation gives the liquid pressure P of the liquid chamber of the third energy storage cylinder 4 when the third energy storage cylinder 4 finishes storing energy. y32 for:

[0087]

[0088] Step 5: When the third energy storage cylinder 4 finishes storing energy, the entire energy storage device finishes storing energy, and the total compression amount of the air cavity is:

[0089] ΔV q =V1+V2+V3;

[0090] The total volume of hydraulic oil stored in the three energy storage cylinders ΔV y for:

[0091]

[0092] Since the piston area A is larger than the effective area of ​​the gas in the air chamber acting on each piston, the total volume of the stored hydraulic oil ΔV is obtained. y Greater than the total compression of the air cavity ΔV q ;like Figure 2As shown, it is the pressure change curve of the air cavity and the filling / discharging port 5 during the energy storage process. Curve a is the pressure and volume change curve of the air cavity during the energy storage process. As the volume of the air cavity decreases, its pressure continues to increase, which is a continuous change process; Curve b is the air cavity volume and the pressure change curve of the filling port during the energy storage process of the first energy storage cylinder 2; Curve c is the air cavity volume and the pressure change curve of the filling port during the energy storage process of the second energy storage cylinder 3; Curve d is the air cavity volume and the pressure change curve of the filling port during the energy storage process of the third energy storage cylinder 4; It can be seen from the above curves that the change of the air cavity pressure during the energy storage process is much greater than the change of the filling port pressure, which shows that the high energy density energy storage device can store more hydraulic energy than the traditional accumulator with the same initial gas volume and the same gas compression under the condition that the initial gas pressure of the accumulator remains unchanged, so the present invention has a higher energy storage density.

[0093] Step 6: When releasing energy, first energize the third solenoid valve 16, and the third energy storage cylinder 4 releases oil through the charging / discharging port 5 under the action of the air cavity, and the piston three 17 moves downward. When the piston three 17 moves downward to contact the bottom end of the inner wall of the third energy storage cylinder 4, the retracted stroke switch three 20 sends a signal, and the third energy storage cylinder 4 ends the energy release; energize the second solenoid valve 11, and the second energy storage cylinder 3 releases oil through the charging / discharging port 5 under the action of the air cavity, and the piston two 12 moves downward. When the piston two 12 moves downward to contact the bottom end of the inner wall of the second energy storage cylinder 3, the retracted stroke switch two 15 sends a signal, and the second energy storage cylinder 3 ends the energy release; energize the first solenoid valve 6, and the first energy storage cylinder 2 releases oil through the charging / discharging port 5 under the action of the air cavity, and the piston one 7 moves downward. When the piston one 7 moves downward to contact the bottom end of the inner wall of the first energy storage cylinder 2, the retracted stroke switch one 10 sends a signal, and the first energy storage cylinder 2 ends the energy release.

Claims

1. A high energy density hydraulic energy storage device, comprising a gas storage tank (1), characterized in that: It also comprises a first energy storage cylinder (2), a second energy storage cylinder (3) and a third energy storage cylinder (4) of the same volume, wherein the upper air chambers of the first energy storage cylinder (2), the second energy storage cylinder (3) and the third energy storage cylinder (4) are connected in series with the gas storage tank (1) via pipelines in the order of distance from the gas storage tank (1) from near to far; The first energy storage cylinder (2), the second energy storage cylinder (3) and the third energy storage cylinder (4) are all provided with pistons of the same area slidingly arranged along their inner walls, the upper end surface of each piston is connected to a piston rod with one end extending out of the top of the cylinder body, and the extending section of each piston rod is provided with an extending stroke switch and a retracting stroke switch; below each piston is a liquid chamber at the lower part of the cylinder body, and each liquid chamber is connected to a filling / discharging port (5) through a pipeline and a solenoid valve arranged on the pipeline; The area of ​​the gas in the air cavity of the first energy storage cylinder (2) acting on the internal piston thereof is larger than the area of ​​the gas in the air cavity of the second energy storage cylinder (3) acting on the internal piston thereof, and the area of ​​the gas in the air cavity of the second energy storage cylinder (3) acting on the internal piston thereof is larger than the area of ​​the gas in the air cavity of the third energy storage cylinder (4) acting on the internal piston thereof.

2. The high energy density hydraulic energy storage device according to claim 1, characterized in that: The lower liquid chamber of the first energy storage cylinder (2) is connected to the liquid charging / discharging port (5) through a pipeline and a first electromagnetic valve (6) arranged on the pipeline, and a piston (7) is slidably arranged along the inner wall of the upper air chamber, the upper end surface of the piston (7) is connected to the lower end of a piston rod (8), the upper end of the piston rod (8) extends out of the top cover of the first energy storage cylinder (2), and an extension stroke switch (9) and a retraction stroke switch (10) are arranged on the extension section, wherein the extension stroke switch (9) is located on the rod body close to the upper end of the piston rod (8), and the maximum stroke of the retraction stroke switch (10) is adapted to the maximum distance between the lower end surface of the piston (7) and the bottom of the lower liquid chamber of the first energy storage cylinder (2); The lower liquid chamber of the second energy storage cylinder (3) is connected to the liquid charging / discharging port (5) through a pipeline and a second solenoid valve (11) arranged on the pipeline, and a second piston (12) is slidably arranged in the upper air chamber along the inner wall thereof, the upper end surface of the second piston (12) is connected to the lower end of the second piston rod (13), the upper end of the second piston rod (13) extends out of the top cover of the second energy storage cylinder (3), and an extension stroke switch (14) and a retraction stroke switch (15) are arranged on the extension section, wherein the extension stroke switch (14) is located on the rod body close to the upper end of the second piston rod (13), and the maximum stroke of the retraction stroke switch (15) is adapted to the maximum distance between the lower end surface of the second piston (12) and the bottom of the lower liquid chamber of the second energy storage cylinder (3); The lower liquid chamber of the third energy storage cylinder (4) is connected to the liquid charging / discharging port (5) through a pipeline and a third solenoid valve (16) arranged on the pipeline, and a piston three (17) is slidably arranged along the inner wall of the upper air chamber thereof, the upper end surface of the piston three (17) is connected to the lower end of the piston rod three (18), the upper end of the piston rod three (18) extends out of the top cover of the third energy storage cylinder (4), and an extension stroke switch three (19) and a retraction stroke switch three (20) are arranged on the extension section, wherein the extension stroke switch three (19) is located on the rod body close to the upper end of the piston rod three (18), and the maximum stroke of the retraction stroke switch three (20) is adapted to the maximum distance between the lower end surface of the piston three (17) and the bottom of the lower liquid chamber of the third energy storage cylinder (4); The rod body diameter of piston rod one (8) is smaller than the rod body diameter of piston rod two (13), and the rod body diameter of piston rod two (13) is smaller than the rod body diameter of piston rod three (18).

3. An energy storage method using the high energy density hydraulic energy storage device according to claim 2, characterized in that: The steps include: Step 1: Before storing energy, the first solenoid valve (6), the second solenoid valve (11) and the third solenoid valve (16) are all energized, and the oil in the liquid chambers of the first energy storage cylinder (2), the second energy storage cylinder (3) and the third energy storage cylinder (4) is discharged through the filling / discharging port (5); the air chambers of the first energy storage cylinder (2), the second energy storage cylinder (3) and the third energy storage cylinder (4) are inflated through the air storage tank (1), so that the lower end surfaces of the piston 1 (7), the piston 2 (12) and the piston 3 (17) are respectively in contact with the first energy storage cylinder (2), the second energy storage cylinder (3) and the third energy storage cylinder (4). The bottoms of the liquid chambers of the second energy storage cylinder (3) and the third energy storage cylinder (4) are in contact, and the position detection is performed by the retracting stroke switch 1 (10), the retracting stroke switch 2 (15) and the retracting stroke switch 3 (20) respectively; the oil inside the first energy storage cylinder (2), the second energy storage cylinder (3) and the third energy storage cylinder (4) is emptied through the charging / discharging port (5) under the compression of the piston; at this time, the air pressure in the air chambers of the first energy storage cylinder (2), the second energy storage cylinder (3) and the third energy storage cylinder (4) and the air storage tank (1) reaches the initial pressure P q1 , the total initial gas volume is: V q1 =V0+V1+V2+V3; In the formula, V0 is the volume of the air cavity of the air storage tank (1), V1 is the maximum volume of the air cavity of the first energy storage cylinder (2); V2 is the maximum volume of the air cavity of the second energy storage cylinder (3); V3 is the maximum volume of the air cavity of the third energy storage cylinder; Step 2: During energy storage, the first solenoid valve (6) is energized, the second solenoid valve (11) and the third solenoid valve (16) are de-energized, and the liquid cavity of the first energy storage cylinder (2) is filled with liquid through the first solenoid valve (6) to store energy. At this time, the piston (7) moves upward under the action of the oil, and the gas in the air cavity of the first energy storage cylinder (2) is compressed and discharged until the piston (7) moves upward to contact the top of the inner wall of the first energy storage cylinder (2). At the same time, the extended travel switch (9) sends a signal, the first solenoid valve (6) is de-energized, and the energy storage of the first energy storage cylinder (2) is stopped. In this process, the compression amount of the air cavity of the first energy storage cylinder (2) is V1, and the oil volume in the liquid cavity of the first energy storage cylinder (2) is V y1 , then V y1 The relationship with V1 is: Wherein, A is the area of ​​the piston, and the areas of piston 1 (7), piston 2 (12) and piston 3 (17) are equal, namely, A; A1 is the effective area of ​​the air cavity of the first energy storage cylinder (2), that is, the effective area of ​​the gas in the air cavity of the first energy storage cylinder (2) acting on piston 1 (7); The pressure P when the first energy storage cylinder (2) starts to store energy y11 for: From the gas state equation, the liquid pressure P of the liquid cavity of the first energy storage cylinder (2) is obtained when the first energy storage cylinder (2) finishes storing energy. y12 for: Step 3: When the energy storage of the first energy storage cylinder (2) is completed and the first electromagnetic valve (6) is powered off, the second electromagnetic valve (11) is powered on, and the pressurized oil is passed through the second electromagnetic valve (11) to fill the liquid cavity of the second energy storage cylinder (3) and store energy. At this time, the second piston (12) moves upward under the action of the oil, and the gas in the air cavity of the second energy storage cylinder (3) is compressed and discharged until the second piston (12) moves upward to contact the top of the inner wall of the second energy storage cylinder (3). At the same time, the second travel switch (14) sends a signal, and the second electromagnetic valve (11) is powered off, stopping the energy storage of the second energy storage cylinder (3). In this process, the compression amount of the air cavity of the second energy storage cylinder (3) is V2, and the oil volume in the liquid cavity of the second energy storage cylinder (3) is V y2 , then V y2 The relationship with V2 is: Wherein, A2 is the effective area of ​​the air cavity of the second energy storage cylinder (3), that is, the effective area of ​​the gas in the air cavity of the second energy storage cylinder (3) acting on the piston 2 (12); The pressure P when the second energy storage cylinder (3) starts to store energy y21 for: From the gas state equation, the liquid pressure P of the liquid cavity of the second energy storage cylinder (3) is obtained when the second energy storage cylinder (3) finishes storing energy. y22 for: Step 4: When the energy storage of the second energy storage cylinder (3) is completed and the second electromagnetic valve (11) is powered off, the third electromagnetic valve (16) is powered on, and the pressurized oil is passed through the third electromagnetic valve (16) to fill the liquid cavity of the third energy storage cylinder (4) and store energy. At this time, the piston (17) moves upward under the action of the oil, and the gas in the air cavity of the third energy storage cylinder (4) is compressed and discharged until the piston (17) moves upward to contact the top of the inner wall of the third energy storage cylinder (4). At the same time, the extended travel switch (19) sends a signal, and the third electromagnetic valve (16) is powered off, stopping the energy storage of the third energy storage cylinder (4). In this process, the compression amount of the air cavity of the third energy storage cylinder (4) is V3, and the oil volume in the liquid cavity of the third energy storage cylinder (4) is V y3 , then V y3 The relationship with V3 is: Wherein, A3 is the effective area of ​​the air cavity of the third energy storage cylinder (4), that is, the effective area of ​​the gas in the air cavity of the third energy storage cylinder (4) acting on the piston three (17); The pressure P when the third energy storage cylinder (4) starts to store energy y31 for: The gas state equation is used to obtain the liquid pressure P of the liquid cavity of the third energy storage cylinder (4) when the third energy storage cylinder (4) finishes storing energy. y32 for: Step 5: When the third energy storage cylinder (4) finishes storing energy, the entire energy storage device finishes storing energy, and the total compression amount of the air cavity is: ΔV q =V1+V2+V3; The total volume of hydraulic oil stored in the three energy storage cylinders ΔV y for: Since the piston area A is larger than the effective area of ​​the gas in the air chamber acting on each piston, the total volume of the stored hydraulic oil ΔV is obtained. y Greater than the total compression of the air cavity ΔV q ; Step 6: When releasing energy, firstly, the third solenoid valve (16) is energized, and the third energy storage cylinder (4) releases oil through the filling / discharging port (5) under the action of the air cavity, and the piston (17) moves downward. When the piston (17) moves downward to contact the bottom end of the inner wall of the third energy storage cylinder (4), the retracted travel switch (20) sends a signal, and the third energy storage cylinder (4) ends the energy release; the second solenoid valve (11) is energized, and the second energy storage cylinder (3) releases oil through the filling / discharging port (5) under the action of the air cavity, and the piston (12) moves downward. The piston (12) moves downward, and when the piston (12) moves downward to contact the bottom end of the inner wall of the second energy storage cylinder (3), the retracting stroke switch (15) sends a signal, and the second energy storage cylinder (3) ends energy release; the first solenoid valve (6) is energized, and the first energy storage cylinder (2) releases oil through the charging / discharging port (5) under the action of the air cavity, and the piston (7) moves downward. When the piston (7) moves downward to contact the bottom end of the inner wall of the first energy storage cylinder (2), the retracting stroke switch (10) sends a signal, and the first energy storage cylinder (2) ends energy release.

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