CN116104822A - High-energy-density double-piston hydraulic accumulator and working method - Google Patents

High-energy-density double-piston hydraulic accumulator and working method Download PDF

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CN116104822A
CN116104822A CN202211740111.7A CN202211740111A CN116104822A CN 116104822 A CN116104822 A CN 116104822A CN 202211740111 A CN202211740111 A CN 202211740111A CN 116104822 A CN116104822 A CN 116104822A
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cavity
piston
pressure
energy
liquid
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周连佺
杨成
王金凤
杨存智
叶果
徐添
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Jiangsu Normal University
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Jiangsu Normal University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
    • F15B1/02—Installations or systems with accumulators
    • F15B1/04—Accumulators
    • F15B1/08—Accumulators using a gas cushion; Gas charging devices; Indicators or floats therefor
    • F15B1/24—Accumulators using a gas cushion; Gas charging devices; Indicators or floats therefor with rigid separating means, e.g. pistons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
    • F15B1/02—Installations or systems with accumulators
    • F15B1/04—Accumulators
    • F15B1/08—Accumulators using a gas cushion; Gas charging devices; Indicators or floats therefor
    • F15B1/22—Liquid port constructions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2201/00—Accumulators
    • F15B2201/20—Accumulator cushioning means
    • F15B2201/205—Accumulator cushioning means using gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2201/00—Accumulators
    • F15B2201/30—Accumulator separating means
    • F15B2201/31—Accumulator separating means having rigid separating means, e.g. pistons
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/16—Mechanical energy storage, e.g. flywheels or pressurised fluids

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Supply Devices, Intensifiers, Converters, And Telemotors (AREA)

Abstract

The invention discloses a high-energy-density double-piston hydraulic accumulator and a working method thereof, and belongs to the technical field of hydraulic energy storage. The variable-diameter double-piston comprises a variable-diameter double-piston cavity formed by combining two piston cavities with a small upper part and a large lower part, wherein the two double-piston cavities are respectively provided with a linkage piston which is connected with each other through a connecting mechanism, the linkage piston divides the variable-diameter double-piston cavity into three cavities with a small upper part, a middle part and a small lower part, the top bottom of the variable-diameter double-piston cavity is respectively provided with an oil port, the side surface of the large piston cavity of the double-piston, which is close to the small piston cavity, is connected with a gas cylinder through a pipeline, so that the upper piston cavity and the lower piston cavity are oil cavities, the middle piston cavity is an air cavity, the diameter of the upper cavity is small, the diameter of the lower cavity is large, a rod piece rises, the volume of the middle piston cavity is reduced, and air in the compression middle piston cavity is stored. The energy accumulator has the advantages of simple structure, small volume, low cost and energy density twice that of the traditional energy accumulator.

Description

High-energy-density double-piston hydraulic accumulator and working method
Technical Field
The invention relates to the technical field of hydraulic energy storage, in particular to a high-energy-density double-piston hydraulic energy accumulator and a working method thereof.
Background
Hydraulic transmission is one of the important forms of modern industrial transmission. With the rapid development of engineering machinery, automobiles, aerospace and other industries, the requirements of a transmission system on related products are continuously improved, and a hydraulic transmission system gradually becomes one of the most important energy transmission modes in modern industrial equipment by virtue of the advantages of high power ratio, high reliability, stepless speed regulation and the like.
However, with the rapid development of global economy, the use of fossil fuels by humans is increasing, and the problems of exhaustion of fossil energy, environmental pollution and the like are also receiving more and more attention. In order to solve the above problems, how to improve the utilization rate of energy is one of the important concerns. Therefore, energy efficiency in the hydraulic system needs to be improved to realize green low-carbon and sustainable production, and the problem of energy shortage is relieved. The recovery, storage and reuse of energy in a hydraulic system are important methods for improving the energy efficiency of the hydraulic system.
By adopting a proper and efficient energy storage method, the energy in the hydraulic system is effectively stored, and the purposes of energy conservation and emission reduction can be achieved. The piston type energy accumulator is a commonly used hydraulic energy storage device in the hydraulic system of the excavator, and is used for converting hydraulic energy in the hydraulic system into gas compression energy to be stored at proper time, and converting the gas compression energy into hydraulic energy to be released when the system is needed for supplementing the hydraulic system. At present, the gas loading type hydraulic energy storage technology is widely applied to the aspects of engineering machinery energy recovery, vehicle braking kinetic energy recovery and the like. In practical application, it is found that although the power density of the hydraulic accumulator is higher than that of other energy storage elements, the energy density of the hydraulic accumulator is far lower than that of the energy storage elements such as common fuel cells, and the hydraulic accumulator has the defects of large volume, high cost and the like. In addition, due to the energy loss of the system, the output pressure of the traditional energy accumulator when releasing energy is slightly lower than the pressure of hydraulic oil when storing energy, so that the normal operation of the hydraulic system can be ensured by the extra liquid supply of the hydraulic pump, the whole hydraulic system is complicated, and the efficiency is reduced.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art, the high-energy-density double-piston hydraulic accumulator and the working method are provided, the pressure in the air cavity is increased by utilizing two piston cavities with different sizes and matched pistons, and the output hydraulic pressure is larger than the pressure during storage by utilizing an electromagnetic reversing valve, so that the problem of the excessively low output pressure of the accumulator is solved.
In order to achieve the technical aim, the high-energy-density double-piston hydraulic accumulator comprises a variable-diameter double-piston cavity formed by combining two piston cavities with a small upper part and a large lower part, wherein the two piston cavities are respectively provided with two linkage pistons with a small upper part and a large lower part which are mutually connected through a connecting mechanism, the upper piston of the linkage piston moves in the small-diameter piston cavity above the variable-diameter double-piston cavity, the lower piston moves in the large-diameter piston cavity below the variable-diameter double-piston cavity, the two pistons with the small upper part and the large lower part are connected through a piston rod, the linkage piston divides the variable-diameter double-piston cavity into three cavities, and the variable-diameter double-piston cavity comprises an upper piston cavity positioned between the small piston and the top of the piston cavity, a middle piston cavity between the two pistons and a lower piston cavity between the large piston and the bottom of the large piston cavity; the bottom of the variable-diameter double-piston cavity top is respectively provided with an oil port, the side surface of the large piston cavity of the double-piston, which is close to the small piston cavity, is connected with an air bottle through a pipeline, so that the upper piston cavity and the lower piston cavity are oil cavities, the middle piston cavity is an air cavity, the diameter of the upper cavity is small, the diameter of the lower cavity is large, a rod piece is lifted, the volume of the middle piston cavity is reduced, and air in the middle piston cavity is compressed for energy storage.
The device specifically comprises a lower cavity cylinder barrel and an upper cavity cylinder barrel, wherein a lower cavity end cover is arranged at the bottom of the lower cavity cylinder barrel, a lower cavity oil inlet is formed in the center of the lower cavity end cover, an upper cavity end cover is arranged at the top of the upper cavity cylinder barrel, and an upper cavity oil inlet is formed in the center of the upper cavity end cover; the lower cavity cylinder barrel and the upper cavity cylinder barrel are mutually connected and sealed at the opening parts to form a diameter-variable double-piston cylinder body with a small upper part and a large lower part, wherein a lower cavity piston is arranged in the lower cavity cylinder barrel, an upper cavity piston is arranged in the upper cavity cylinder barrel, piston rods connected with each other are arranged between the lower cavity piston and the upper cavity piston, the circle centers of the piston rods and the lower cavity piston are connected through lower cavity spherical hinges, and the circle centers of the piston rods and the upper cavity piston are connected through upper cavity spherical hinges, so that linkage is realized between the lower cavity piston and the upper cavity piston; an upper cavity liquid cavity is formed between the upper cavity piston and the upper cavity end cover in the double-piston cylinder body, an air cavity is formed between the upper cavity piston and the lower cavity piston in the double-piston cylinder body, and a lower cavity liquid cavity is formed between the lower cavity piston and the lower cavity end cover in the double-piston cylinder body; the side surface of the lower cavity cylinder barrel, which is close to the upper cavity cylinder barrel, is connected with a gas cylinder communicated with the gas cavity through a pipeline, when energy is stored, the upper cavity liquid cavity is communicated with the oil tank, and the initial pressure in the gas cylinder is greater than the oil inlet pressure of the lower cavity liquid cavity, so that the stored gas internal energy is improved.
The working method of the high-energy-density double-piston hydraulic accumulator comprises the following steps that a lower cavity oil inlet and an upper cavity oil inlet are connected with an electromagnetic valve for controlling high-pressure oil to enter and exit through a pipeline:
when energy is stored, the electromagnetic valve is powered off, the electromagnetic valve works in the right position, the upper cavity oil inlet is communicated with the oil tank, high-pressure oil enters the lower cavity liquid cavity of the energy accumulator through the lower cavity oil inlet, the lower cavity liquid cavity with increased pressure pushes the piston rod to move upwards by pushing the lower cavity piston, gas in the air cavity is compressed, the pressure in the gas cylinder is increased, and the hydraulic energy in the lower cavity liquid cavity is converted into the pneumatic energy of the air cavity and the gas cylinder; in the process, the upper cavity liquid cavity is communicated with the oil tank, the upper cavity piston is not subjected to hydraulic pressure, the piston rod is subjected to three forces, namely the hydraulic pressure of the lower cavity liquid cavity, the air cavities respectively act on the air pressures of the lower cavity piston and the upper cavity piston, and when energy is stored, the piston rod moves at a constant speed to obtain a current force balance equation; when the energy is stored, the pressure of the air cavity is increased, the hydraulic pressure in the liquid cavity of the lower cavity is slowly increased until the pressure of the liquid cavity of the lower cavity reaches the maximum pressure, the energy cannot be stored, the piston rod is not moved, and the energy storage is completed at the moment;
when the energy is released, the electromagnetic valve is electrified, the electromagnetic valve works in the left position, the oil way of the upper cavity liquid cavity and the oil way of the lower cavity liquid cavity of the energy accumulator are communicated, the high-pressure oil enables the upper cavity liquid cavity and the lower cavity liquid cavity to be communicated through the pipeline, the upper cavity liquid cavity pressure and the lower cavity liquid cavity pressure are equal at the moment, the internal energy in the gas cylinder is released, the piston rod receives 4 forces at the moment, the piston rod moves downwards, the internal energy of the gas cavity and the gas cylinder is converted into hydraulic energy to be output through the pipeline, the gas cavity pressure and the lower cavity liquid cavity pressure are equal when the energy is released, and the gas cavity pressure is larger than the lower cavity liquid cavity pressure when the energy is stored, so that the oil liquid pressure when the energy is released is larger than the oil liquid pressure when the energy is stored, and the supercharging effect is realized.
Further, because the upper cavity liquid cavity is connected with the oil tank when storing energy, the hydraulic pressure is 0, only the total volume of the lower cavity liquid cavity is considered when storing energy, and the initial position of the piston rod is positioned at the lowest end, so that the volume of the initial state of the lower cavity liquid cavity is 0, the final state of the lower cavity liquid cavity is the allowable maximum pressure in the night, and the piston rod is raised to the state of the limit position;
when the energy is stored, the pressure of the initial state of the liquid cavity of the lower cavity is set as P y1 The pressure of the lower cavity liquid at the end state is P y2 The initial volume of the air cavity is V q1 ；
The upper cavity liquid cavity is stressed to the piston rod in the initial state:
P y1 A 2 +P q1 (A 1 -A 0 )＝P q1 (A 2 -A 0 ) (6)
the pressure of the lower cavity liquid cavity reaches the maximum liquid inlet pressure in the last state, and the piston rod is stressed:
P y2 A 2 +P q2 (A 1 -A 0 )＝P q2 (A 2 -A 0 ) (7)
the relation between the pressure of the air cavity and the pressure of the liquid cavity of the lower cavity can be obtained by combining the formula (6) and the formula (7):
Figure BDA0004033434010000031
the relation between the volume of the air cavity and the volume change of the lower cavity liquid cavity (13) can be known:
Figure BDA0004033434010000032
the pressure of the air cavity is known by using a gas state equation from P q1 Rising to P q2 The following relationship is satisfied:
P q1 V q1 n ＝P q2 V q2 n (10)
wherein: p (P) y1 The pressure of the low-pressure oil in the lower cavity is the initial state; p (P) y2 The pressure of the low-pressure oil in the lower cavity is the final state; p (P) q1 The pressure of the air cavity is the initial state; p (P) q2 The air cavity pressure when the state is the final state; a is that 1 Is the area of the upper cavity piston; a is that 2 For the area of the lower cavity piston, A 2 ＞A 1 ；A 0 Is the cross-sectional area of the piston rod; v (V) q1 An initial volume for the air cavity; v (V) q2 Is the end state volume of the air cavity, deltaV y The volume change of the liquid cavity of the energy accumulator is the volume change; deltaV q The volume change of the air cavity is obtained;
by bringing formula (8) into formula (10)
Figure BDA0004033434010000033
Substituting formula (11) into formula (9) to obtain the lower cavity liquid cavity pressure from P y1 Rising to P y2 After that, the volume change of the liquid cavity of the lower cavity is delta V y ：
Figure BDA0004033434010000041
Further, the stored energy is calculated from the gas function formula:
Figure BDA0004033434010000042
the energy density mu can be obtained by bringing the formula (11) into simplification 2 The expression:
Figure BDA0004033434010000043
pressure P of lower chamber liquid chamber in initial state y1 Last statePressure P y2 Initial volume of air cavity V q1 All the same, formula (3) and formula (12) are compared, since
Figure BDA0004033434010000044
Therefore, the volume change of the liquid cavity of the energy accumulator is larger than that of the traditional energy accumulator, and the volume of stored oil is larger;
comparing the energy density of ordinary accumulator to the expression mu 1 And the energy density expression μ of the present invention 2 It can be seen that the energy density of the accumulator of the present invention is that of a conventional accumulator
Figure BDA0004033434010000045
Doubling; due to->
Figure BDA0004033434010000046
Thus the energy density mu of the invention 2 Energy density mu greater than ordinary accumulator 1 ；
Increase in energy density and cross-sectional area A of two pistons 1 And A 2 Related, A 1 The larger, i.e. A 1 The closer to A 2 The greater the energy density; if the maximum pressure of the air cavity is P qmax The maximum pressure of the liquid cavity is P ymax From formula (8):
Figure BDA0004033434010000047
from the formula (15), A 1 The larger the energy density of the accumulator, the larger the maximum pressure P of the liquid cavity ymax Is determined by the actual working condition, if A is to be increased 1 It is necessary to increase the maximum pressure P of the air cavity qmax But the accumulator maximum air pressure is limited, so A is limited 1 At the maximum pressure P of the oil to be stored ymax Maximum pressure P of air cavity qmax When approaching, at this time A 1 The density of the material is small and cannot be increased, so that A needs to be reasonably selected according to actual working conditions 1 And A 2 Is a ratio of (2).
Further, releaseThe pressure of the air cavity during energy is the pressure P during the last state of energy storage q2 And (3) analyzing the stress of the piston rod:
P y ′A 2 +P q2 (A 1 -A 0 )＝P q2 (A 2 -A 0 )+P y ′A 1 (16)
the method can obtain:
Figure BDA0004033434010000051
wherein: a is that 1 Is the effective cross-sectional area of the upper cavity piston rod cavity; a is that 2 For the effective cross-sectional area of the lower cavity piston, A 2 ＞A 1 ；A 0 Is the cross-sectional area of the piston rod; p (P) y ' is the high pressure oil pressure of the liquid cavity when releasing energy;
it can be seen that the high-pressure oil pressure output when releasing energy is the high-pressure oil pressure when storing energy
Figure BDA0004033434010000052
The accumulator of the invention can thus act as a booster.
The beneficial effects are that:
1) The accumulator of the present invention increases the pressure of the air chamber over conventional piston accumulators, thereby increasing the stored energy. The energy accumulator can release larger force under the same volume, and in the excavator, only the energy accumulator can reduce the weight and the volume of the energy accumulator and reduce the cost when the energy accumulator can store the descending energy of the movable arm;
2) Under the action of throttling pressure difference of a hydraulic system, the traditional energy accumulator is insufficient to push a piston rod to rise when releasing energy, so that a booster pump is required to increase pressure to push a movable arm to rise. The energy accumulator can boost pressure through the electromagnetic directional valve when releasing energy, so as to push the movable arm to rise, simplify the hydraulic system and improve the dynamic performance of the system.
3) By calculating the energy densities of both, the energy accumulator of the invention is twice as dense as a conventional accumulator under this condition.
Drawings
FIG. 1 is a schematic illustration of the structure of a high energy density dual piston hydraulic accumulator of the present invention;
fig. 2 is a schematic diagram of the operation of the high energy density dual piston hydraulic accumulator of the present invention, wherein (a) is a schematic diagram of the energy storage and (b) is a schematic diagram of the energy release.
In the figure: 1. a lower cavity oil inlet; 2. a lower cavity end cap; 3. a lower chamber liquid chamber; 4. a lower chamber piston; 5. a lower cavity spherical hinge; 6. a piston rod; 7. a lower chamber cylinder; 8. an upper chamber cylinder; 9. an upper cavity spherical hinge; 10. an upper chamber piston; 11. an upper cavity end cap; 12. an upper cavity oil inlet; 13. an upper chamber liquid chamber; 14. an air cavity; 15. an air cavity air port; 16. and (3) a gas cylinder.
Detailed Description
Embodiments of the invention are further described below with reference to the accompanying drawings:
as shown in fig. 1, the high-energy-density double-piston hydraulic accumulator comprises a lower cavity cylinder 7 and an upper cavity cylinder 8, wherein a lower cavity end cover 2 is arranged at the bottom of the lower cavity cylinder 7, a lower cavity oil inlet 1 is formed in the center of the lower cavity end cover 2, an upper cavity end cover 11 is arranged at the top of the upper cavity cylinder 8, and an upper cavity oil inlet 12 is formed in the center of the upper cavity end cover 11; the openings of the lower cavity cylinder 7 and the upper cavity cylinder 8 are mutually connected and sealed to form a diameter-variable double-piston cylinder body with a small upper part and a large lower part, wherein a lower cavity piston 4 is arranged in the lower cavity cylinder 7, an upper cavity piston 10 is arranged in the upper cavity cylinder 8, a piston rod 6 connected with each other is arranged between the lower cavity piston 4 and the upper cavity piston 10, the circle centers of the piston rod 6 and the lower cavity piston 4 are connected through a lower cavity spherical hinge, and the circle centers of the piston rod 6 and the upper cavity piston 10 are connected through an upper cavity spherical hinge 9, so that linkage is realized between the lower cavity piston 4 and the upper cavity piston 10; an upper cavity liquid cavity 13 is formed between the upper cavity piston 10 and the upper cavity end cover 11 in the double-piston cylinder body, an air cavity 14 is formed between the upper cavity piston 10 and the lower cavity piston 4 in the double-piston cylinder body, and a lower cavity liquid cavity 3 is formed between the lower cavity piston 4 and the lower cavity end cover 2 in the double-piston cylinder body; the side surface of the lower cavity cylinder barrel 7, which is close to the upper cavity cylinder barrel 8, is connected with a gas cylinder 16 communicated with a gas cavity 14 through a pipeline, when energy is stored, the upper cavity liquid cavity 13 is communicated with a fuel tank, and the initial pressure in the gas cylinder 16 is greater than the fuel inlet pressure of the lower cavity liquid cavity 3, so that the stored gas internal energy is improved.
As shown in fig. 2, in a working method of a high-energy-density double-piston hydraulic accumulator, a lower cavity oil inlet 1 and an upper cavity oil inlet 12 are connected with an electromagnetic valve for controlling high-pressure oil to enter and exit through a pipeline, and the working method comprises the following steps:
when the energy is stored, the electromagnetic valve is powered off, the electromagnetic valve works in the right position, the upper cavity oil inlet 12 is communicated with the oil tank, high-pressure oil enters the lower cavity liquid cavity 3 of the energy accumulator through the lower cavity oil inlet 1, the lower cavity liquid cavity 3 with the pressure increased pushes the piston rod 6 to move upwards by pushing the lower cavity piston 4, the gas in the gas cavity 14 is compressed, the pressure in the gas cylinder 15 is increased, and the hydraulic energy in the lower cavity liquid cavity 3 is converted into the pneumatic energy of the gas cavity 14 and the gas cylinder 16; in the process, the upper cavity liquid cavity 13 is communicated with an oil tank, the upper cavity piston 10 is not subjected to hydraulic pressure, the piston rod 6 is subjected to three forces, namely the hydraulic pressure of the lower cavity liquid cavity, the air cavity 14 acts on the air pressure of the lower cavity piston 4 and the air pressure of the upper cavity piston 10 respectively, and when energy is stored, the piston rod 6 moves at a constant speed to obtain the current force balance equation; when the energy is stored, as the pressure of the air cavity 14 is increased, the hydraulic pressure in the lower cavity liquid cavity 3 is slowly increased until the pressure of the lower cavity liquid cavity 3 reaches the maximum pressure, the energy cannot be stored, the piston rod 6 is not moved, and the energy storage is finished at the moment;
when the energy is released, the electromagnetic valve is electrified, the electromagnetic valve works in the left position, the oil way of the upper cavity liquid cavity 3 and the lower cavity liquid cavity 13 of the energy accumulator is communicated, the high-pressure oil enables the upper cavity liquid cavity 3 and the lower cavity liquid cavity 13 to be communicated through the pipeline, the pressure of the upper cavity liquid cavity 3 and the pressure of the lower cavity liquid cavity 13 are equal at the moment, the internal energy in the gas cylinder 16 is released, the piston rod 6 receives 4 forces at the moment, the piston rod 6 moves downwards, the internal energy of the gas cavity 14 and the gas cylinder 16 is converted into hydraulic energy to be output through the pipeline, the pressure of the gas cavity 14 and the pressure of the lower cavity liquid cavity 13 are equal when the energy is released, and the pressure of the gas cavity 14 is larger than the pressure of the lower cavity liquid cavity 13 when the energy is stored, so that the pressure of the oil liquid when the energy is released is larger than the pressure of the oil when the energy is stored, and the supercharging effect is realized.
Energy storage principle of high-energy-density double-piston hydraulic energy accumulator
And the accumulator with the same initial gas volume and initial pressure has the same liquid cavity pressure variation, and if the volume of the stored oil liquid is large, the energy storage density of the accumulator is high. The high energy storage density of the present invention will now be described.
The traditional accumulator realizes the functions of filling and discharging liquid by means of the change of the volume and the pressure of an inflatable cavity. As can be seen from the gas state equation, if the liquid cavity pressure is defined by P y1 Rising to P y2 The air cavity pressure is also defined by P q1 Rising to P q2 The following relationship is satisfied:
P q1 V q1 n ＝P q2 V q2 n (1)
wherein: p (P) q1 The pressure of the air cavity is the initial state; p (P) q2 The air cavity pressure when the state is the final state; n is a polytropic exponent, adiabatic process n=1.4, v q1 An initial volume for the air cavity; v (V) q2 Is the end state volume of the air cavity; deltaV q Is the volume change of the air cavity.
Can be obtained
Figure BDA0004033434010000071
Simplifying to obtain the variable quantity DeltaV of the liquid cavity volume of the traditional energy accumulator q ：
Figure BDA0004033434010000072
The stored energy is essentially the energy that the liquid applies work to the piston to be converted into gas internal energy, and the stored energy is calculated by the following formula:
Figure BDA0004033434010000073
bringing formula (2) into, and simplifying to obtain energy density μ 1 Expression type
Figure BDA0004033434010000074
The principle of the high energy density dual piston hydraulic accumulator of the present invention when storing energy is shown in fig. 2 (a). When the energy is stored, the electromagnetic valve is powered off, the right position works, the upper cavity oil inlet 12 of the energy accumulator is communicated with the oil tank, high-pressure oil enters the lower cavity liquid cavity 3 of the energy accumulator through the lower cavity oil inlet 1, the piston rod 6 is pushed to move upwards, the gas in the gas cavity 14 is compressed, the pressure in the gas cylinder 16 is increased, and the hydraulic energy is converted into the internal energy of the gas cavity and the gas cylinder.
For comparison with conventional accumulators, the pressure P of the accumulator fluid chamber according to the invention in the initial state y1 Last state pressure P y2 Initial volume of air cavity V q1 Equal to a conventional accumulator.
And (3) analyzing the stress of the piston rod in the initial state:
P y1 A 2 +P q1 (A 1 -A 0 )＝P q1 (A 2 -A 0 ) (6)
and in the final state, analyzing the stress of the piston rod:
P y2 A 2 +P q2 (A 1 -A 0 )＝P q2 (A 2 -A 0 ) (7)
the relation between the air cavity pressure and the liquid cavity pressure can be obtained by combining the formulas (6-7):
Figure BDA0004033434010000081
according to the structure of the energy accumulator, the relation between the volume of the air cavity and the volume variation of the liquid cavity can be known:
Figure BDA0004033434010000082
from the gas state equation, if the gas cavity pressure is defined by P q1 Rising to P q2 The following relationship is satisfied:
P q1 V q1 n ＝P q2 V q2 n (10)
wherein: p (P) y1 The pressure of the low-pressure oil in the lower cavity is the initial state; p (P) y2 The pressure of the low-pressure oil in the lower cavity is the final state; p (P) q1 The pressure of the air cavity is the initial state; p (P) q2 The air cavity pressure when the state is the final state; a is that 1 Is the area of the upper cavity piston; a is that 2 For the area of the lower cavity piston, A 2 ＞A 1 ；A 0 Is the cross-sectional area of the piston rod; v (V) q1 An initial volume for the air cavity; v (V) q2 Is the end state volume of the air cavity, deltaV y The volume change of the liquid cavity of the energy accumulator is the volume change; deltaV q Is the volume change of the air cavity.
By bringing formula (8) into formula (10)
Figure BDA0004033434010000083
Substituting formula (11) into formula (9) can obtain the pressure of the liquid cavity from P y1 Rising to P y2 After that, the volume change of the liquid cavity is delta V y ：
Figure BDA0004033434010000084
The stored energy is calculated by the gas functional formula:
Figure BDA0004033434010000085
the energy density mu can be obtained by bringing the formula (11) into simplification 2 Expression type
Figure BDA0004033434010000086
Pressure P of liquid chamber in initial state y1 Last state pressure P y2 Initial volume of air cavity V q1 All the same, formula (3) and formula (12) are compared, since
Figure BDA0004033434010000091
It can be seen that the volume change of the liquid cavity of the accumulator is larger than that of the traditional accumulator, and the volume of the stored oil is larger. By definition, the inventive energy storage device has a higher energy storage density than conventional energy storage devices.
Comparing the energy density of ordinary accumulator to the expression mu 1 And the energy density expression μ of the present invention 2 It can be seen that the energy density of the accumulator of the present invention is that of a conventional accumulator
Figure BDA0004033434010000092
Multiple times. Due to->
Figure BDA0004033434010000093
Thus the energy density mu of the invention 2 Energy density mu greater than ordinary accumulator 1 。
Increase in energy density and cross-sectional area A of two pistons 1 And A 2 Related to the following. A is that 1 The larger, i.e. A 1 The closer to A 2 The greater the energy density. If the maximum pressure of the air cavity is P qmax The maximum pressure of the liquid cavity is P ymax From formula (8):
Figure BDA0004033434010000094
from the formula (15), A 1 The larger the energy density of the accumulator, the larger the maximum pressure P of the liquid cavity ymax Is determined by the actual working condition, if A is to be increased 1 It is necessary to increase the maximum pressure P of the air cavity qmax But the accumulator maximum air pressure is limited, so A is limited 1 Is a maximum value of (a). When the maximum pressure P of the oil liquid to be stored is required ymax Maximum pressure P of air cavity qmax When approaching, at this time A 1 And is small, so that the volume density cannot be increased. Therefore, rationally select A 1 And A 2 Is considered according to the actual working condition.
Principle of releasing energy of high-energy-density double-piston hydraulic accumulator
The principle of the high energy density dual piston hydraulic accumulator of the present invention when storing energy is shown in fig. 2 (b). When the energy is released, the electromagnetic valve is electrified, the left position works, the upper cavity liquid cavity 3 of the energy accumulator is communicated with the lower cavity liquid cavity 13, the upper cavity and the lower cavity are communicated through the high-pressure oil, the internal energy in the gas cylinder 16 is released, the piston rod 6 moves downwards, and the internal energy of the air cavity and the gas cylinder is converted into hydraulic energy.
The pressure of the air cavity is the pressure P when the energy is released and the pressure is in the last state of the stored energy q2 And (3) analyzing the stress of the piston rod:
P y ′A 2 +P q2 (A 1 -A 0 )＝P q2 (A 2 -A 0 )+P y ′A 1 (16)
the method can obtain:
Figure BDA0004033434010000095
wherein: a is that 1 Is the effective cross-sectional area of the upper cavity piston rod cavity; a is that 2 For the effective cross-sectional area of the lower cavity piston, A 2 ＞A 1 ；A 0 Is the cross-sectional area of the piston rod; p (P) y ' is the high pressure oil pressure of the liquid cavity when releasing energy;
it can be seen that the high-pressure oil pressure output when releasing energy is the high-pressure oil pressure when storing energy
Figure BDA0004033434010000101
Multiple times. The accumulator of the invention is thus able to act as a booster.
Embodiment 1,
The energy storage densities of the conventional energy storage device and the energy storage device are compared by comparing the two energy storage densities when the energy storage device is applied to the potential energy recovery system of the movable arm of the excavator.
The movable arm of a medium-sized excavator is driven by two hydraulic cylinders, the diameters of a piston and a piston rod of the movable arm are 120mm and 85mm respectively, the stroke is 1.7m, the total volume of one cylinder can be calculated to be 19.2L, and about 38.4L of hydraulic oil enters an energy accumulator when the movable arm descends once, and the pressure of a lower cavity of the hydraulic cylinder is about 12MPa when the movable arm descends. In a hydraulic system, there is a pressure differential to flow and there is a pressure differential to flow. The hydraulic system of an excavator is complex, and usually comprises a plurality of throttle oil paths, and in order to control the speed of a movable oil cylinder, the minimum pressure difference between the movable arm oil cylinder and an accumulator is 1MPa.
Recovering excavator boom energy using conventional piston accumulator
When the movable arm descends, the lower cavity pressure is about 12MPa, the system throttling pressure difference is 1MPa, the working pressure of the traditional energy accumulator is estimated to be 11MPa when the traditional energy accumulator exists, when the traditional energy accumulator is released, the pressure of hydraulic oil entering the lower cavity of the movable arm is about 10MPa due to the throttling pressure difference of 1MPa, and the hydraulic oil is insufficient to push a piston rod to ascend, so that the hydraulic pump is required to supplement pressure to push the movable arm to ascend under the working condition that the energy accumulator releases energy.
If the pressure of the liquid cavity of the energy accumulator rises from 7MPa to 11MPa and the volume change amount of the liquid cavity is 38.4L when the energy is stored, the initial volume of the traditional energy accumulator can be calculated according to the formula (3):
Figure BDA0004033434010000102
the stored energy can be calculated from equation (4):
Figure BDA0004033434010000103
from formula (5), the energy density μ can be calculated 1 ：
Figure BDA0004033434010000104
(2) Recovery of energy with an accumulator according to the invention
The maximum pressure at the time of energy recovery is:
P amax ≈12MPa-△P＝11MPa (21)
in order to meet the requirement that the pressurized pressure can push the movable arm to rise, the pressure of the lower cavity of the movable arm is at least 13MPa, and the minimum working pressure during release is as follows:
P bmin ≈13MPa+△P＝14MPa (22)
wherein: ΔP is the system throttling pressure differential.
If the pressure of the liquid cavity of the energy accumulator rises from 7MPa to 11MPa during energy storage, the pressure of the liquid cavity can be calculated from the formula (8)
Figure BDA0004033434010000111
Rising to +.>
Figure BDA0004033434010000112
From the minimum operating pressure, it can be calculated:
Figure BDA0004033434010000113
obtainable A 2 ＝2A 1 The initial volume of the accumulator is calculated from the boom down once again with approximately 38.4L hydraulic oil entering the accumulator and equation (12):
Figure BDA0004033434010000114
the stored energy can be calculated from equation (13) as:
Figure BDA0004033434010000115
from equation (14), the energy density is calculated as:
Figure BDA0004033434010000116
in summary, under the working condition of energy recovery of the excavator, the high-pressure oil in the lower cavity enters the energy accumulator through the system, the pressure of the liquid cavity of the energy accumulator rises from 7MPa to 11MPa, the pressure of the liquid cavity of the energy accumulator rises from 14MPa to 22MPa, and when the energy accumulator is released, the pressure of the liquid cavity falls from 22MPa to 14MPa through pressurization, and after the pressure is throttled by 1MPa through the system, the pressure of the liquid cavity is higher than the pressure of the lower cavity of the movable arm and is 13MPa at the lowest, so that the movable arm can be lifted.

Claims (6)

1. A high energy density dual piston hydraulic accumulator, characterized by: the variable-diameter double-piston comprises a variable-diameter double-piston cavity formed by combining an upper piston cavity and a lower piston cavity, wherein the upper piston cavity and the lower piston cavity are respectively provided with a linkage piston with the upper piston cavity, the lower piston cavity and the lower piston cavity, the linkage piston is connected with the lower piston cavity, the upper piston cavity is connected with the lower piston cavity, the linkage piston is connected with the lower piston cavity, the lower piston cavity is connected with the upper piston cavity, the linkage piston is connected with the lower piston cavity, and the linkage piston is connected with the lower piston cavity; the bottom of the variable-diameter double-piston cavity top is respectively provided with an oil port, the side surface of a large piston cavity of the double-piston, which is close to a small piston cavity, is connected with an air bottle (16) through a pipeline, so that an upper piston cavity and a lower piston cavity are oil cavities, a middle piston cavity is an air cavity (14), and the rod piece is lifted due to the fact that the diameter of the upper cavity is small, the volume of the middle piston cavity is reduced, and air in the middle piston cavity is compressed for energy storage.
2. The high-energy-density double-piston hydraulic accumulator according to claim 1 is characterized by comprising a lower cavity cylinder barrel (7) and an upper cavity cylinder barrel (8), wherein a lower cavity end cover (2) is arranged at the bottom of the lower cavity cylinder barrel (7), a lower cavity oil inlet (1) is formed in the center of the lower cavity end cover (2), an upper cavity end cover (11) is arranged at the top of the upper cavity cylinder barrel (8), and an upper cavity oil inlet (12) is formed in the center of the upper cavity end cover (11); the lower cavity cylinder barrel (7) and the upper cavity cylinder barrel (8) are connected and sealed at the opening, so that a reducing double-piston cylinder body with a small upper part and a large lower part is formed, wherein a lower cavity piston (4) is arranged in the lower cavity cylinder barrel (7), an upper cavity piston (10) is arranged in the upper cavity cylinder barrel (8), a piston rod (6) connected with each other is arranged between the lower cavity piston (4) and the upper cavity piston (10), the piston rod (6) is connected with the center of the lower cavity piston (4) through a lower cavity spherical hinge (5), and the piston rod (6) is connected with the center of the upper cavity piston (10) through an upper cavity spherical hinge (9), so that linkage is realized between the lower cavity piston (4) and the upper cavity piston (10); an upper cavity liquid cavity (13) is formed between the upper cavity piston (10) and the upper cavity end cover (11) in the double-piston cylinder body, an air cavity (14) is formed between the upper cavity piston (10) and the lower cavity piston (4) in the double-piston cylinder body, and a lower cavity liquid cavity (3) is formed between the lower cavity piston (4) and the lower cavity end cover (2) in the double-piston cylinder body; the side surface of the lower cavity cylinder barrel (7) close to the upper cavity cylinder barrel (8) is connected with a gas cylinder (16) communicated with the gas cavity (14) through a pipeline, when energy is stored, the upper cavity liquid cavity (13) is communicated with the oil tank, and the initial pressure in the gas cylinder (16) is larger than the oil inlet pressure of the lower cavity liquid cavity (3), so that the stored gas internal energy is improved.
3. The working method of the high-energy-density double-piston hydraulic accumulator is characterized in that an electromagnetic valve for controlling high-pressure oil to enter and exit is connected with a lower cavity oil inlet (1) and an upper cavity oil inlet (12) through pipelines, and comprises the following steps:
when energy is stored, when the electromagnetic valve is powered off, the electromagnetic valve works in the right position, an upper cavity oil inlet (12) is communicated with an oil tank, high-pressure oil enters a lower cavity liquid cavity (3) of the energy accumulator through a lower cavity oil inlet (1), the lower cavity liquid cavity (3) with increased pressure pushes a piston rod (6) to move upwards by pushing a lower cavity piston (4), gas in a gas cavity (14) is compressed, the pressure in a gas cylinder (15) is increased, and hydraulic energy in the lower cavity liquid cavity (3) is converted into pneumatic energy of the gas cavity (14) and the gas cylinder (16); in the process, the upper cavity liquid cavity (13) is communicated with the oil tank, the upper cavity piston (10) is not subjected to hydraulic pressure, the piston rod (6) is subjected to three forces, namely the hydraulic pressure of the lower cavity liquid cavity, the air cavity (14) acts on the air pressures of the lower cavity piston (4) and the upper cavity piston (10) respectively, and when energy is stored, the piston rod (6) moves at a constant speed to obtain a current force balance equation; when the energy is stored, as the pressure of the air cavity (14) is increased, the hydraulic pressure in the lower cavity liquid cavity (3) is slowly increased until the pressure of the lower cavity liquid cavity (3) reaches the maximum pressure, the energy cannot be stored, the piston rod (6) is not moved, and the energy storage is completed at the moment;
when the energy is released, the electromagnetic valve is electrified, the electromagnetic valve works in the left position, the oil way of the upper cavity liquid cavity (3) and the lower cavity liquid cavity (13) of the energy accumulator is communicated, the high-pressure oil enables the upper cavity liquid cavity (3) to be communicated with the lower cavity liquid cavity (13) through the pipeline, the pressure of the upper cavity liquid cavity (3) is equal to the pressure of the lower cavity liquid cavity (13), internal energy in the gas cylinder (16) is released, the piston rod (6) is subjected to 4 forces, the piston rod (6) moves downwards, the internal energy of the air cavity (14) and the gas cylinder (16) is converted into hydraulic energy to be output through the pipeline, the pressure of the air cavity (14) is equal to the pressure of the lower cavity liquid cavity (13) when the energy is released, and the pressure of the air cavity (14) is larger than the pressure of the lower cavity liquid cavity (13) when the energy is stored, so that the oil pressure is larger than the oil pressure when the energy is stored when the energy is released, and the supercharging effect is realized.
4. A method according to claim 3, characterized in that, since the upper chamber (3) is connected to the tank and the hydraulic pressure is 0 when storing energy, only the total volume of the lower chamber (13) is considered when storing energy, the initial position of the piston rod (6) is at the lowest end, the volume of the initial state of the lower chamber (13) is 0, the final state of the lower chamber (13) is the maximum allowable present pressure, and the piston rod (6) is raised to the state of the extreme position;
when storing energy, the pressure of the lower cavity liquid cavity (13) in the initial state is set as P y1 The pressure of the lower cavity liquid cavity (13) in the final state is P y2 The initial volume of the air cavity is V q1 ；
When in an initial state, the upper cavity liquid cavity (3) is stressed on the piston rod (6) as follows:
P y1 A 2 +P q1 (A 1 -A 0 )＝P q1 (A 2 -A 0 ) (6)
in the final state, the liquid cavity pressure of the lower cavity liquid cavity (13) reaches the maximum liquid inlet pressure, and the piston rod (6) is stressed:
P y2 A 2 +P q2 (A 1 -A 0 )＝P q2 (A 2 -A 0 ) (7)
the relation between the pressure of the air cavity (14) and the pressure of the lower cavity liquid cavity (13) can be obtained by combining the formula (6) and the formula (7):
Figure FDA0004033433000000021
from this, the relation between the volume of the air chamber (14) and the volume change of the lower chamber liquid chamber (13) is known:
Figure FDA0004033433000000022
the pressure of the air cavity (14) is known from P by using a gas state equation q1 Rising to P q2 The following relationship is satisfied:
P q1 V q1 n ＝P q2 V q2 n (10)
wherein: p (P) y1 The pressure of the low-pressure oil in the lower cavity is the initial state; p (P) y2 The pressure of the low-pressure oil in the lower cavity is the final state; p (P) q1 The pressure of the air cavity is the initial state; p (P) q2 The air cavity pressure when the state is the final state; a is that 1 Is the area of the upper cavity piston; a is that 2 For the area of the lower cavity piston, A 2 ＞A 1 ；A 0 Is the cross-sectional area of the piston rod; v (V) q1 An initial volume for the air cavity; v (V) q2 Is the end state volume of the air cavity, delta V y The volume change of the liquid cavity of the energy accumulator is the volume change; deltaV q The volume change of the air cavity is obtained;
by bringing formula (8) into formula (10)
Figure FDA0004033433000000031
Substituting formula (11) into formula (9) to obtain the pressure of the lower cavity liquid cavity (13) from P y1 Rising to P y2 After that, the volume change DeltaV of the lower cavity liquid cavity (13) y ：
Figure FDA0004033433000000032
5. A method of operating a high energy density dual piston hydraulic accumulator according to claim 3 wherein the stored energy is calculated from the gas functional formula:
Figure FDA0004033433000000033
the energy density mu can be obtained by bringing the formula (11) into simplification 2 The expression:
Figure FDA0004033433000000034
/>
pressure P of the lower chamber (13) in the initial state y1 Last state pressure P y2 Initial volume V of air cavity (14) q1 All the same, formula (3) and formula (12) are compared, since
Figure FDA0004033433000000035
Therefore, the volume change of the liquid cavity of the energy accumulator is larger than that of the traditional energy accumulator, and the volume of stored oil is larger;
comparing the energy density of ordinary accumulator to the expression mu 1 And the energy density expression μ of the present invention 2 It can be seen that the energy density of the accumulator of the present invention is that of a conventional accumulator
Figure FDA0004033433000000036
Doubling; due to->
Figure FDA0004033433000000037
Thus the energy density mu of the invention 2 Energy density mu greater than ordinary accumulator 1 ；
Increase in energy density and cross-sectional area A of two pistons 1 And A 2 Related, A 1 The larger, i.e. A 1 The closer to A 2 The greater the energy density; if the maximum pressure of the air cavity is P qmax The maximum pressure of the liquid cavity is P ymax From formula (8):
Figure FDA0004033433000000041
from the formula (15), A 1 The larger the energy density of the accumulator, the larger the maximum pressure P of the liquid cavity ymax Is determined by the actual working condition, if A is to be increased 1 It is necessary to increase the maximum pressure P of the air cavity qmax But the accumulator maximum air pressure is limited, so A is limited 1 At the maximum pressure P of the oil to be stored ymax Maximum pressure P of air cavity qmax When approaching, at this time A 1 The density of the material is small and cannot be increased, so that A needs to be reasonably selected according to actual working conditions 1 And A 2 Is a ratio of (2).
6. A method of operating a high energy density dual piston hydraulic accumulator according to claim 3 wherein,
the pressure of the air cavity is the pressure P when the energy is released and the pressure is in the last state of the stored energy q2 And (3) carrying out stress analysis on the piston rod (6):
P y ′A 2 +P q2 (A 1 -A 0 )＝P q2 (A 2 -A 0 )+P y ′A 1 (16)
the method can obtain:
Figure FDA0004033433000000042
wherein: a is that 1 Is the effective cross-sectional area of the upper cavity piston rod cavity; a is that 2 For the effective cross-sectional area of the lower cavity piston, A 2 ＞A 1 ；A 0 Is the cross-sectional area of the piston rod; p (P) y ' is the high pressure oil pressure of the liquid cavity when releasing energy;
it can be seen that the high-pressure oil pressure output when releasing energy is the high-pressure oil pressure when storing energy
Figure FDA0004033433000000043
The accumulator of the invention can thus act as a booster. />
CN202211740111.7A 2022-12-31 2022-12-31 High-energy-density double-piston hydraulic accumulator and working method Pending CN116104822A (en)

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