CN113756458B - Piezoelectric viscous damper - Google Patents
Piezoelectric viscous damper Download PDFInfo
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- CN113756458B CN113756458B CN202010504118.3A CN202010504118A CN113756458B CN 113756458 B CN113756458 B CN 113756458B CN 202010504118 A CN202010504118 A CN 202010504118A CN 113756458 B CN113756458 B CN 113756458B
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- 238000013016 damping Methods 0.000 claims abstract description 102
- 238000006073 displacement reaction Methods 0.000 claims abstract description 88
- 239000012530 fluid Substances 0.000 claims abstract description 65
- 230000033001 locomotion Effects 0.000 claims abstract description 16
- 229910001220 stainless steel Inorganic materials 0.000 claims description 2
- 239000010935 stainless steel Substances 0.000 claims description 2
- 239000003921 oil Substances 0.000 description 46
- 239000010720 hydraulic oil Substances 0.000 description 27
- 230000000694 effects Effects 0.000 description 19
- 238000005265 energy consumption Methods 0.000 description 14
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- 238000003199 nucleic acid amplification method Methods 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
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- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
- E04B1/62—Insulation or other protection; Elements or use of specified material therefor
- E04B1/92—Protection against other undesired influences or dangers
- E04B1/98—Protection against other undesired influences or dangers against vibrations or shocks; against mechanical destruction, e.g. by air-raids
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
- E04H9/00—Buildings, groups of buildings or shelters adapted to withstand or provide protection against abnormal external influences, e.g. war-like action, earthquake or extreme climate
- E04H9/02—Buildings, groups of buildings or shelters adapted to withstand or provide protection against abnormal external influences, e.g. war-like action, earthquake or extreme climate withstanding earthquake or sinking of ground
- E04H9/021—Bearing, supporting or connecting constructions specially adapted for such buildings
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Abstract
The invention discloses a piezoelectric viscous damper, which changes a bypass pipe from a general circular pipe into a flat pipe, and enables the flat pipe to play a role of a damping hole in the circular pipe damper. The control system can control the piezoelectric driver to generate mechanical strain to output displacement, and the required output displacement can be achieved without installing an amplifier device. The height of the flat tube can be adjusted by adjusting the movement of the control plate according to the real-time acting force, so that the purpose of controlling the flow speed of viscous fluid by adjusting the size of the damping hole is achieved, and impact energy of force on a building structure is absorbed and consumed to the maximum extent; the damper can achieve the purpose of adjusting the damping hole without adopting a displacement amplifying device, avoids the problems of time lag and precision caused by the displacement amplifying device, and reduces the cost and the volume of the damper.
Description
Technical Field
The invention belongs to the technical field of civil engineering vibration control, and particularly relates to a piezoelectric viscous damper, which is a semi-active control system with the highest theoretical response speed in the world at present.
Background
As vibration control in structural engineering has been attracting more and more attention, many civil engineering structures (such as industrial production rooms of buildings, bridges, and nuclear power stations) have more and more stringent requirements on vibration environments, and vibration isolation or vibration reduction treatment must be performed on these civil engineering structures.
The vibration control of the civil engineering structure is to install a control device structure or a mechanism at a specific part of the civil engineering structure to scientifically and reasonably control the engineering structure, reduce the influence of acceleration and displacement in earthquake or strong wind and ensure the safety of the engineering structure, instruments and equipment and personnel. The control devices or mechanisms can share the vibration action of the engineering in the earthquake, weaken the energy born by the engineering, and can increase the damping force of the structure, apply the control force and the like by adjusting the self-vibration frequency of the structure so as to reduce various reactions under the vibration action of the structure.
Many passive control devices tend to be ineffective due to the strong randomness and unpredictability of the earthquake. And partial semi-active and active control devices fail and cannot control because the response speed of the semi-active and active control devices cannot keep pace with the control signals. The time required for the control signals to be completed by the control equipment is called time lag, the time lag is related to the system, and the system is unstable due to the fact that the time lag is smaller for the same control equipment, and the control effect of the system is better. For the above reasons, the problems of time lag and time lag compensation of the system become the core problem of vibration reduction of engineering structures.
A viscous fluid energy dissipation damper (Viscous Fluid Damper, i.e., VFD, for short, a viscous damper) is one of the structures or mechanisms of the vibration damping control device, which means that damping force is generated by flowing viscous fluid in the piston hole and/or the gap, and vibration energy is dissipated, so as to achieve the purpose of vibration damping or vibration isolation. The piezoelectric ceramic is widely applied to the fields of civil engineering structures, aerospace, automobiles, machinery and the like by the advantages of high output, quick response, no electromagnetic interference, low energy consumption, easiness in control and the like. The piezoelectric viscous damper is used as one kind of adjustable viscous damper, the structure of which is shown in figure 1, and comprises a cylinder barrel formed by a main cylinder barrel and an auxiliary cylinder barrel 1, a piston 4, a piston rod 5, an external oil pipe 8 (bypass pipeline), a piezoelectric driver 6, a control system and a displacement amplifying device 7, wherein the main cylinder barrel is filled with viscous fluid, the piston rod 5 is inserted into the main cylinder barrel and extends into the auxiliary cylinder barrel 1, the piston 4 in the main cylinder barrel divides the main cylinder barrel into a first damping chamber 2 and a second damping chamber 3, the external oil pipe 8 is arranged outside the main cylinder barrel, two ports of the external oil pipe 8 are respectively communicated with the first damping chamber 2 and the second damping chamber 3, the piezoelectric driver 6 electrically connected with the control system is arranged in the displacement amplifying device 7, the displacement output end of the piezoelectric driver 6 is connected with the displacement amplifying device 7, the control needle 9 of the displacement amplifying device 7 is connected with the piston 10 in the external oil pipe, the control system controls the piezoelectric driver 6 to generate mechanical strain to output displacement, the displacement is amplified by the displacement amplifying device 7 to control the movement of the piston 10 in the external oil pipe later, and therefore the size of a damping hole (a hole between the piston 10 of the external oil pipe and the inner wall of the external oil pipe) is adjusted, the purpose of controlling the flow rate of viscous fluid is achieved, the positioning precision is high, the corresponding speed is high, the time lag influence can be reduced, and the output force is improved.
The bypass pipeline (external oil pipe) of the piezoelectric viscous damper is generally a circular pipeline, and the piezoelectric driver arranged on the circular pipeline utilizes the inverse piezoelectric effect principle to apply an alternating electric field on the piezoelectric block, so that the piezoelectric block can generate alternating mechanical strain in a certain direction, and displacement output is realized. Because the piezoelectric block has limited displacement (i.e. small output displacement) based on piezoelectric effect, the piezoelectric block is generally only tens of micrometers, and cannot be directly used in occasions with large vibration amplitude (such as a piezoelectric driver with the model of PST150/14/80, the nominal displacement is 80um, and the maximum displacement is 105 um). Based on this, the existing circular tube piezoelectric viscous damper generally needs to increase the deformation amount of the piezoelectric block by adding a displacement amplifying device, so as to achieve the effect of increasing the output displacement (95% of piezoelectric viscous dampers need to add a displacement amplifying device). For example, patent publication CN103603912B, entitled piezoelectric driven damping continuously adjustable shock absorber, wherein the disclosed adjustable shock absorber comprises a displacement mechanism and a piezoelectric element which generates mechanical deformation in the axial direction of a valve element when energized to form an axial pushing force in the direction, the displacement amount generated by the piezoelectric element is transmitted to the valve element through a displacement amplifying mechanism to cause the valve element to axially move, thereby adjusting the flow rate of viscous fluid between an upper chamber and a lower chamber. The invention discloses an active and passive integrated vibration reduction and isolation device applicable to large amplitude and wide frequency bands, which is disclosed by the invention patent with the publication number CN106286693B, wherein the vibration reduction and isolation device comprises a composite elastic displacement amplification mechanism and a piezoelectric ceramic driver arranged in the composite elastic displacement amplification mechanism, the composite elastic displacement amplification mechanism is in active vibration isolation fit with the piezoelectric ceramic driver to realize wide frequency band vibration control, and in addition, the composite elastic displacement amplification mechanism amplifies the output displacement of the piezoelectric ceramic driver, so that the vibration output with larger amplitude is ensured.
However, the addition of the displacement amplifying device causes time lag of the piezoelectric viscous damper, which is specifically caused by the following steps: 1. the displacement amplifying device is used as a secondary amplifying mechanism, and once loss is increased every time the displacement amplifying device is added, so that theoretical amplifying displacement cannot be achieved; 2. because of the limitation of the rigidity of materials, the lever in the displacement amplifying device can slightly deform, so that the amplified displacement can be lost; 3. the rotating chain of the displacement amplifying device adopts a flexible hinge, the hinge can generate strain (lateral bending deformation and axial deformation) due to stress, and the more the hinge is connected, the more the loss of amplifying displacement is caused; 4. the internal reaction force of the displacement amplifying device also causes the loss of amplified displacement; 5. the displacement amplifying device is of a sealing structure, and the amplifying displacement is deviated due to the fatigue effect of materials under long-time use.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a piezoelectric viscous damper to solve the problems of time lag and precision caused by the fact that a displacement amplifying device is additionally arranged to amplify output displacement of the traditional piezoelectric viscous damper. For the above reasons, a damper with very high response speed (with very small time lag) is needed, and the present invention proposes a novel piezoelectric viscous damper. Based on the characteristics and the design method of the piezoelectric material, the response speed of the magneto-rheological damper can reach one thousand times that of the magneto-rheological damper, which is ten thousand times that of the magnetostrictive material. Because the response speed is high, time lag compensation is not needed, and the accuracy and stability of civil structure engineering are greatly improved.
The invention solves the technical problems by the following technical scheme: a piezoelectric viscous damper comprises a cylinder barrel, a piston rod, a bypass pipeline, a piezoelectric driver and a control system, wherein the cylinder barrel consists of a main cylinder barrel and an auxiliary cylinder barrel; the main cylinder barrel is filled with viscous fluid, the piston rod is inserted into the main cylinder barrel and extends into the auxiliary cylinder barrel, and the piston in the main cylinder barrel divides the main cylinder barrel into a first closed damping chamber and a second closed damping chamber; the bypass pipeline is arranged outside the main cylinder barrel, and two ports of the bypass pipeline are respectively communicated with the first damping chamber and the second damping chamber; the piezoelectric driver electrically connected with the control system is arranged on the bypass pipeline, and is characterized in that:
the control board is connected with the displacement output end of the piezoelectric driver; the bypass pipeline comprises a flat pipe which is arranged in parallel with the main cylinder, and a first variable cross-section pipeline and a second variable cross-section pipeline which are arranged at two ends of the flat pipe; the inner wall of the flat pipe is provided with a groove matched with the size of the control plate, and the control plate is arranged in the groove.
The piezoelectric viscous damper changes a bypass pipe from a universal circular pipe into a flat pipe, so that the flat pipe plays a role of a damping hole in the circular pipe damper, the piezoelectric driver is controlled by a control system to generate mechanical strain to output displacement, when the groove is positioned on the inner top wall, the output displacement of the piezoelectric driver is 0, a control plate is positioned in the groove of the inner top wall, the damping hole is reduced by increasing the output displacement of the piezoelectric driver, when the groove is positioned on the inner bottom wall, the output displacement of the piezoelectric driver is maximum, the control plate is positioned in the groove of the inner bottom wall, the damping hole is reduced by reducing the output displacement of the piezoelectric driver, and the height of the flat pipe is regulated by regulating the up-down movement of the control plate, so that the purpose of regulating the damping hole to control the flow velocity of viscous fluid is achieved; the damper can achieve the purpose of adjusting the damping hole without adopting a displacement amplifying device, avoids the problems of time lag and precision caused by the displacement amplifying device, and reduces the cost and the volume of the damper.
Further, the groove is formed in the inner top wall or the inner bottom wall of the flat tube.
Further, the ratio of the width to the height of the flat tube is greater than or equal to 10:1.
Further, the width of the flat tube is greater than the diameter of the master cylinder. When the width of the flat tube is larger than the diameter of the main cylinder under the condition of the same output displacement, the damping force generated in the flat tube is larger.
Further, the first variable cross-section pipeline and the second variable cross-section pipeline are respectively communicated with the first damping chamber and the second damping chamber, the diameters of the lower ends of the first variable cross-section pipeline and the second variable cross-section pipeline are the same as the diameter of the main cylinder barrel, the diameters of the upper ends of the first variable cross-section pipeline and the second variable cross-section pipeline are the same as the width of the flat pipe, and liquid can flow into the flat pipe from the main cylinder barrel conveniently and then flow into the main cylinder barrel from the flat pipe.
Further, the cross section of the flat tube is rectangular.
Further, the flat tube is made of stainless steel.
Further, the damping force F generated by the piezoelectric viscous damper is:
wherein: mu is a hydrodynamic viscosity coefficient, and l is the length of the flat tube; v is the relative movement speed of the piston rod, D is the inner diameter of the main cylinder barrel, D 1 C is a function of the aspect ratio of the rectangular cross section of the flat tube, C being a constant for a given tube; d, d h Is the hydraulic diameter; a, b are respectively 1/2 of the length and the width of the flat tube; z is the displacement output by the piezoelectric driver; ρ is the density of the fluid in the flat tube.
Advantageous effects
Compared with the prior art, the piezoelectric viscous damper provided by the invention has the advantages that the bypass pipe is changed into the flat pipe from the universal circular pipe, so that the flat pipe plays a role of a damping hole in the circular pipe damper, the control system generates mechanical strain to output displacement by controlling the piezoelectric driver, when the groove is positioned on the inner top wall, the output displacement of the piezoelectric driver is 0, the control plate is positioned in the groove of the inner top wall, the damping hole (the cross section of the flat pipe) is reduced by increasing the output displacement of the piezoelectric driver, when the groove is positioned on the inner bottom wall, the output displacement of the piezoelectric driver is the largest, the control plate is positioned in the groove of the inner bottom wall, the damping hole is reduced by reducing the output displacement of the piezoelectric driver, and the height of the flat pipe is regulated by regulating the movement of the control plate, so that the purpose of regulating the damping hole to control the viscous fluid flow rate is achieved; the damper can achieve the purpose of adjusting the damping hole without adopting a displacement amplifying device, avoids the time lag problem caused by the displacement amplifying device, and reduces the cost and the volume of the damper.
Drawings
In order to more clearly illustrate the technical solutions of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawing in the description below is only one embodiment of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a circular tube piezoelectric viscous damper in the background of the invention;
FIG. 2 is a schematic view of a piezoelectric viscous damper (flat tube) according to an embodiment of the invention;
FIG. 3 is a schematic side view of a portion of a piezoelectric viscous damper in accordance with an embodiment of the invention;
FIG. 4 is a schematic cross-sectional view of a flat tube and a master cylinder barrel in an embodiment of the invention;
FIG. 5 is a schematic view of a flat tube in a rectangular coordinate system according to an embodiment of the present invention;
FIG. 6 is a schematic flow diagram of hydraulic oil at the junction of the flat tube and the master cylinder in an embodiment of the present invention, with the left arrow indicating hydraulic oil flowing from the master cylinder into the bypass line and the right arrow indicating hydraulic oil flowing from the bypass line into the master cylinder;
FIG. 7 is a schematic view of the angle of the bend of the flat pipe in an embodiment of the present invention, with arrows indicating the flow direction of hydraulic oil in the pipe;
FIG. 8 is a schematic diagram of the pore-creating fluid distribution of a round tube in an embodiment of the invention;
the hydraulic cylinder comprises a 1-auxiliary cylinder barrel, a 2-first damping chamber, a 3-second damping chamber, a 4-piston, a 5-piston rod, a 6-piezoelectric driver, a 7-displacement amplifying device (black part), an 8-external oil pipe, a 9-control needle, a 10-external oil pipe piston, an 11-oil inlet, a 12-oil outlet, a 13-connecting piece of the piezoelectric driver and the external oil pipe, a 14-main cylinder barrel wall, a 15-flat pipe, a 16-control board, a 17-main cylinder barrel, an 18-second variable cross-section pipeline and a 19-first variable cross-section pipeline.
Detailed Description
The following description of the embodiments of the present invention will be made more apparent and fully by reference to the accompanying drawings, in which it is shown, however, only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 2 and 3, the piezoelectric viscous damper provided by the invention comprises a cylinder barrel formed by a main cylinder barrel 17 and an auxiliary cylinder barrel 1, a piston 4, a piston rod 5, a bypass pipeline, a piezoelectric driver 6, a control system and a control board 16 connected with a displacement output end of the piezoelectric driver 6; the main cylinder 17 is filled with viscous fluid, the piston rod 5 is inserted into the main cylinder 17 and extends into the auxiliary cylinder 1, and the piston 4 in the main cylinder 17 divides the main cylinder 17 into a sealed first damping chamber 2 and a sealed second damping chamber 3; the bypass pipeline is arranged outside the main cylinder barrel 17, and two ports of the bypass pipeline are respectively communicated with the first damping chamber 2 and the second damping chamber 3; the piezoelectric driver 6 electrically connected with the control system is arranged on a bypass pipeline, the bypass pipeline comprises a flat pipe 15 which is arranged in parallel with a main cylinder barrel 17, a first variable cross-section pipeline 19 and a second variable cross-section pipeline 18 which are arranged at two ends of the flat pipe 15, a groove which is matched with the size of a control board 16 is formed in the inner top wall of the flat pipe 15, and the control board 16 is arranged in the groove. When the width of the control plate 16 is equal to the width of the flat tube 15 and the height of the control plate 16 is greater than or equal to the height of the flat tube 15, the control plate 16 can completely block the flat tube 15 when the piezoelectric driver 6 outputs the maximum displacement. The initial position of the control plate 16 is in the groove of the flat tube 15.
As shown in fig. 2,3 and 4, the flat tube 15 communicates with the master cylinder tube 17 through a first variable cross-section tube 19 and a second variable cross-section tube 18 at the left and right ends. Since the width of the flat tube 15 is larger than the diameter of the master cylinder tube 17, the flat tube is connected with the master cylinder tube by a variable cross-section tube, which gradually expands from the connection to the flat tube until the diameter of the variable cross-section tube is consistent with the width of the flat tube.
Because the piezoelectric actuator has limited displacement based on the piezoelectric effect, as shown in the following table 1, the maximum displacement of the piezoelectric actuator of the type is 105um, the diameter of a circular tube is 2mm (the circular tube is provided with double damping holes), the target damping force is achieved by controlling the aperture size, the piezoelectric damper of the circular tube needs a displacement amplifying device to increase the deformation of the piezoelectric actuator to achieve the expected effect, and the displacement amplifying device can cause time lag. If the round tube is changed into the flat tube, the height of the flat tube is 0.3mm, the width of the flat tube is 21mm, the cross section area of the flat tube is approximately equal to that of the round tube, and the target damping force can be achieved under the condition that a displacement amplifying device is not needed, so that the expected control effect is achieved.
Table 1 technical index of piezoelectric actuator
The traditional circular tube piezoelectric viscous damper needs a displacement amplifying device, the displacement output by the piezoelectric driver can be output to the bypass pipeline for adjusting the damping hole after being amplified by the displacement amplifying device, and the displacement is amplified for a long time, so that the displacement output to the bypass pipeline is delayed or time-delayed, the adjustment of the damping hole and the generation of damping force are delayed, and for natural disasters such as earthquakes or strong winds, even a few seconds of time delay or delay can cause huge loss; meanwhile, the displacement output by the piezoelectric driver is amplified by the displacement amplifying device according to theory, in fact, according to the description of the background technology, the loss of the displacement amplifying device causes deviation in amplification, namely the displacement output by the displacement amplifying device at last cannot reach a theoretical displacement value, so that the damping force generated by the bypass pipeline is reduced, and the damping effect is reduced.
The piezoelectric viscous damper changes the bypass pipe from a universal circular pipe into a flat pipe, so that the flat pipe plays a role of a damping hole in the circular pipe damper, the piezoelectric driver is controlled by the control system to generate mechanical strain to output displacement, and the displacement adjusts the height of the flat pipe by adjusting the movement of the control plate, thereby achieving the purpose of adjusting the damping hole to control the flow rate of viscous fluid; the damper can achieve the purpose of adjusting the damping hole and the damping force without adopting a displacement amplifying device, avoids the problems of time lag and precision caused by the displacement amplifying device, and reduces the cost and the volume of the damper.
1. Flat tube damper in this application
The flat tube plays a role equivalent to a damping hole in the circular tube damper, and because damping medium (viscous fluid) is influenced by factors such as friction, a part of energy of the kinetic energy of the viscous fluid is converted into heat energy, so that the energy input by vibration is dissipated, pressure loss can be generated at two sides of a piston in a main cylinder in the process, and pressure difference exists at two sides, so that damping force is generated. The damping force is equal to the product of the effective pressure area of the piston and the pressure differential across the piston:
F＝A s ×ΔP (1)
wherein A is s Is the effective pressure area of the piston; ΔP is the pressure differential across the piston.
Wherein, the pressure difference of the two sides of the piston is composed of the following parts:
ΔP＝ΔP 1 +ΔP 2 +ΔP 3 (2)
wherein DeltaP 1 Pressure loss due to fluid friction at the flat tube; ΔP 2 Is the pressure loss at the piezoelectric actuator; ΔP 3 Local pressure loss in the damper.
When viscous fluid flows through the wall of the flat tube, the interface of the wall is not completely smooth, so that certain friction exists between the fluid and the wall, and a part of energy is consumed, which is called friction energy consumption. The friction energy consumption is uniformly distributed along the length direction of the damping hole (flat tube), and the size of the consumed energy is only related to the length of the flat tube. For ease of calculation, the following assumptions are made for the viscous fluid in the flat tube: a. the viscous fluid flows in laminar flow and moves only along the axial direction; b. the viscous fluid is incompressible; c. the mass of the viscous fluid is negligible.
1. Pressure loss due to fluid friction at damping hole (flat tube)
The speed distribution rule of the viscous fluid in the flat tube is deduced as follows: as shown in fig. 5, the origin of the rectangular coordinate system is set in the geometric center of the rectangular section of the flat tube, the X axis is consistent with the flow direction, and the long side and the short side of the rectangular section are 2a and 2b respectively. Velocity distribution of laminar flow motion of rectangular pipe and friction calculation (haerbin Proc. Architecture Proc. Acad.) 1991,3 (24) by reference Mao Jiansu the velocity distribution of each point in the flat pipe satisfies the following poisson equation (only the magnitude of the calculated force does not distinguish between directions):
wherein u is the point flow rate; p is the point pressure; μ is the hydrodynamic viscosity coefficient.
The speed at the point of the boundary is 0, i.e. the boundary condition is:
solving equation (3) by a separation variable method to obtain the flow velocity distribution as
Velocity distribution and friction calculation of laminar flow movement of rectangular pipe (haerbin institute of construction and engineering) 1991,3 (24) by reference to Mao Jiansu, relationship between flow Q and pressure p:
according to Donald S.Miller:. Internal Flow A guide to losses in pipe and duct systems, friction lambda during laminar flow:
where Re is the Reynolds number.
The speed distribution and friction calculation of laminar flow movement of rectangular pipeline (haerbin Proc. Of construction engineering) 1991,3 (24) proposed by reference Mao Jiansu is derived from the following formula
Wherein d h Is a hydraulic diameter, which is the ratio of four times the area of the flow cross section to the perimeter, and which does not represent the meaning of a diameter, but is simply equivalent to a diameter in the hydraulic sense, which is:
wherein A is the cross-sectional area of the flat tube: s is the wet cycle length (the length of the boundary line between the fluid and the solid wall surface on the flow cross section).
It can be seen that C is a function of the aspect ratio of the rectangular cross section of the flat tube, and for a given tube, C is a constant, ranging from 79.34 to 95.59.
The integration of equation (6) in the x-direction can be obtained:
in the formula (10), C 2 As a constant of unknown value, the value of the constant,since Δp when x=0 1 =0, so C 2 =0. As can be deduced from equation (10), when x=l: />
In the formula (11), l is the length of a flat tube; q=a s V，
Wherein V is the relative movement speed of the piston rod; d is the inner diameter of the main cylinder barrel; d (D) 1 The diameter of the piston rod; so there is
Order theDamping force F due to fluid friction 1 The method comprises the following steps: f (F) 1 ＝C 1 V。 (13)
2. Damping force generated by a semi-active damper piezoelectric driver
The magnitude of the damping force generated by the piezoelectric control valve (or piezoelectric actuator) in the semi-active piezoelectric viscous damper is related to the relative movement speed of the piston and the cylinder barrel and the opening size of the piezoelectric control valve. Let the pressure at two ends of the piezoelectric control valve be p 1 ,p 2 ，V b For the flow rate of hydraulic oil into the control zone, V c In order to obtain the flow rate of the hydraulic oil after passing through the piezoelectric control valve, ρ is the density of the hydraulic oil, and g is the gravity acceleration.
According to the bernoulli equation:
according to the principle of fluid continuous fluidity, the mass of hydraulic oil passing through each section of a conduit (flat pipe) in unit time is equal under the condition that the hydraulic oil is not increased or reduced, and the hydraulic oil is expressed as:
ρV b A 1 ＝ρV c A 2 (15)
wherein ρ, A 1 ,A 2 The density of the hydraulic oil and the sectional area of the pipeline before and after entering the piezoelectric control valve are respectively.
The combined type (15) and (16) can be known that:
wherein A is 1 ＝2a*2b,A 2 = (2 b-z) ×2a, z is the output displacement of the piezo valve.
From the fluid continuity principle it is known that: v (V) b A 1 ＝A s V (18)
Damping force F generated by a piezoelectric actuator 2 The method comprises the following steps:
3. damping force generated by local pressure loss
Hydraulic oil flows to the flat tube from the main cylinder of the damper under the action of the piston, the hydraulic oil passes through the joint of the main cylinder and the flat tube, pressure loss can be generated due to abrupt change of the section of the joint of the main cylinder and the flat tube, and then the hydraulic oil also can generate pressure loss when passing through the 90-degree elbow of the flat tube, and the two parts are local pressure loss in the damper. Local pressure loss Δp 3 The expression of (2) is:
△p 3 ＝△p j +△p ω (20)
wherein Deltap is j For the pressure loss of the hydraulic oil flowing through the joint of the main cylinder barrel and the flat pipe, deltap ω The pressure loss of the hydraulic oil flowing through the 90-degree elbow of the flat pipe is shown.
The calculation of the local pressure loss is:
wherein ζ is local resistance coefficient, V 1 Is the flow velocity of hydraulic oil in the flat pipe. It can be deduced from the principle of fluid continuity:
wherein A is 1 Is the cross-sectional area of the flat tube. The local pressure loss calculation formula of the damper can be obtained by combining (21) and (22) as follows:
the viscous fluid (hydraulic oil) generates local pressure loss when passing through the joint of the main cylinder tube and the flat tube pipeline, and the local resistance coefficient of the hydraulic oil at the branch of the pipeline is shown in the following table 2.
TABLE 2 local drag coefficient of fluid at the pipe branches
In the damper, hydraulic oil flows from a first damping chamber of a main cylinder barrel to a flat pipe under the drive of the movement of a piston, flows out from the other side of a flat pipe pipeline through a piezoelectric driver and flows to a second damping chamber at the other side of the piston, and the condition of the hydraulic oil flowing is shown in fig. 6.
From Table 2, it can be seen that the local resistance coefficient ζ of the damper at which the hydraulic oil flows through the flat tube conduit 1 The pressure loss of the hydraulic oil flowing through the joint of the main cylinder and the flat pipe pipeline can be obtained by substituting the formula (23) =1.3+3=4.3:
the hydraulic oil also generates pressure loss when passing through the flat pipe elbow, because the flat pipe elbow is a sharp bend, the resistance coefficient zeta at the elbow 2 As shown in table 3 below.
As shown in FIG. 7, the angle α of the bend of the flat tube was 90℃and the resistance coefficient ζ was found from Table 3 2 1.1 due to liquidWhen the pressure oil flows through the flat pipe, the pressure oil passes through two elbows, so the resistance coefficient corresponding to the pressure loss at the two elbows is 2 zeta 2 。
TABLE 3 resistance coefficients for different elbow angles
| Elbow angle | 30° | 40° | 50° | 60° | 70° | 80° | 90° |
| ζ 2 | 0.20 | 0.30 | 0.40 | 0.55 | 0.70 | 0.90 | 1.10 |
As can be seen from equation (23), the pressure loss at the bend of the flat tube is:
substitution of formulas (24) and (25) into formula (20) can be obtained
Thus, a damping force F due to local pressure loss is obtained 3 The method comprises the following steps:
the damping force of the semi-active piezoelectric viscous damper consists of three parts, namely friction energy consumption generated by friction of viscous fluid (such as hydraulic oil) at a damping hole (flat pipe), energy generated by the viscous fluid flowing through a piezoelectric driver and energy generated by local pressure loss.
Unsuitable for supporting connection, the calculation is assumed to be right-angle connection, and the mechanical model of the semi-active piezoelectric viscous damper is as follows:
wherein: mu is a hydrodynamic viscosity coefficient, and l is the length of the flat tube; v is the relative movement speed of the piston rod, D is the inner diameter of the main cylinder barrel, D 1 C is a function of the aspect ratio of the rectangular cross section of the flat tube, C being a constant for a given tube; d, d h Is the hydraulic diameter; a, b are respectively 1/2 of the length and the width of the flat tube; z is the displacement output by the piezoelectric driver; ρ is the density of the fluid.
2. Traditional circular tube damper
1. Pressure loss due to fluid friction at the damping orifice:
reference Zhang Zhijiang et al, titled "design for viscous damping of building structures", chinese building industry Press (P22-31), newtonian fluid friction energy dissipation Stokes equation (N-S):
because in stable laminar flow the fluid particles do not flow laterally, v x ＝v z ＝0,v y =v ignores the pressure line gravity, so:
f x ＝0,f y ＝0,f z ＝0 (30)
thereby obtaining the following steps:
for incompressible fluids, the continuous differential equation is:
substituting the above conditions into the N-S equation to obtain:
the pressure is independent of the x, z coordinates, so there are:
in order to calculate the integral of the equation more conveniently, the column coordinate is selected to represent
x 2 +z 2 ＝r 2 ,x＝rcosθ,z＝rsinθ (35)
The arrangement is substituted into the (N-S) equation:
if the pressure drop over the tube length l is given by Δp
From the tube axis r=0, the flow velocity v is a finite value, C can be obtained 1 =0. Also known as the pipe wall r=r0, v=0, to obtainFinally, obtaining:
for calculating the flow, a microcell annular area with the width dr is taken at the radius r on the flow cross section. The flow through the entire flow cross section is thus obtained as:
thus the average flow rateThe method comprises the following steps:
further, the pressure drop Δp after the fluid flows a distance l in the circular tube is:
also known isAnd then can obtain:
let N be the number of damping holes on the piston, then the fluid continuity equation that flows through the piston damping holes is:
the method is obtained by the two types of arrangement:
2. energy consumption due to pore shrinkage effect
Because the aperture of the damping hole is far smaller than that of the oil cylinder, when viscous fluid flows into the damping hole from the oil cylinder or flows to the oil cylinder from the damping hole under the pushing of the piston, certain energy loss is generated due to sudden change of the section, and the energy loss is called a hole shrinkage effect. The orifice shrinkage effect of the viscous fluid includes two parts, i.e., an inlet stream contraction energy consumption and an outlet stream expansion energy consumption. The resistance created by the sudden abrupt change in the cross-section of the fluid through the pipe is independent of the viscosity of the fluid, so there are two assumptions:
(1) The fluid is ideal fluid, the viscosity of the fluid is zero, and viscous friction energy consumption can be ignored;
(2) The velocity of the fluid is non-negative.
FIG. 8 is a schematic diagram of the fluid distribution during orifice contraction, c-c being the flow constriction at the orifice inlet, d-d being the flow expansion, e-e being the stage of flow stabilization in the orifice, e-e being followed by the flow expansion energy dissipation stage; the pressure at the two ends of the pore is p 1 、p 2 V is the flow velocity of oil before the external oil pipeline enters the damping hole, v e V is the flow velocity of the fluid in the damping hole in the steady flow stage c Is the systolic phase flow rate.
The bernoulli equation can be said according to the law of conservation of energy:
wherein alpha is 0 The dynamic correction coefficient of the external pipeline section is obtained; alpha c The dynamic correction coefficient is the dynamic correction coefficient of the contracted section; e (E) w Is a loss of the shrinkage effect.
Taking two sections of power correction coefficient alpha 0 ＝α 1 Considering that the damper is a closed space, according to the principle of fluid continuous fluidity, the mass of hydraulic oil passing through each section of the conduit in unit time is equal under the condition that no increase or decrease or leakage occurs, expressed as:
ρ 1 v 1 A 1 ＝ρ 2 v 2 A 2 (46)
wherein ρ, v, A are the density, flow rate and pipeline cross-sectional area of the hydraulic oil, respectively;
because an oil liquid is adopted, the density is kept unchanged, and the cross-sectional area of the damping hole is far smaller than that of an external oil pipeline, namely A1<<An external oil duct is arranged, so that the flow velocity of the oil liquid in the damping hole is far greater than the flow velocity of the oil liquid in the external oil duct, namely v<<v c So v is relative to v c To be negligible, equation (46) may be rewritten as:
E w the energy consumption for generating the shrinkage effect for the damping hole can be recorded as:
wherein ζ is the coefficient of resistance loss.
Substituting formula (48) into formula (47) is also because v c ＝v e Then
Thus the flow equation is
And can be obtained according to the continuity of the fluid
A 1 v e ＝A S V＝Q (51)
Simultaneous (48) - (51) of
/>
Due to F 2 ＝△p 2 A S ，And->The bonding (51) can then be obtained:
when the number of the damping holes is N, the damping force generated by the hole shrinkage effect is as follows:
in Σζ=ζ c +ζ e Σζ is the total drag loss coefficient; zeta type c An inlet shrinkage loss coefficient; zeta type e A stream expansion loss coefficient; the Σζ values are shown in table 4:
table 4 damping energy consumption coefficient of damper
Because the damping hole of the semi-active piezoelectric viscous damper adopts a capillary damping hole, the damping force generated by the hole shrinkage effect is as follows:
wherein F is 2 ＝C 2 V 2 ，
3. Damping force due to local pressure loss
The control force generated by the piezoelectric control valve of the semi-active viscous damper in the piezoelectric semi-active viscous damper is related to the relative movement speed of the piston and the cylinder of the piezoelectric semi-active viscous damper and the opening size of the piezoelectric valve, and the flow rate of oil flowing through the control valve can be known according to the fluid mechanics principle by reference to Zhao Xinze, namely the hydraulic transmission foundation (P31):
wherein Q is 3 For the flow through the control valve, m 3 /s；C d For flow coefficient, for Newtonian fluid, C d ＝1；A k To control the valve flow area, m 2 。
From the principle of fluid continuity, the flow rate Q of the liquid through the control valve is known 3 Half the flow Q generated by the piston movement, i.e
Q 3 ＝Q＝0.5A S V (57)
Substituting (56) the above can push out the pressure differential created where oil flows through the control valve:
when 0< x is less than or equal to 2R,
damping force generated by the control valve F 3 ＝C 3 V 2 Wherein, the method comprises the steps of, wherein,obtaining the product
Then the first time period of the first time period,
calculation of local losses with reference to the New Hydraulic engineering Manual (P19-29) edited by Lei Tianjiao
Wherein ζ is a local damping coefficient; v w Is the flow rate of oil in an external oil pipeline.
From the principle of fluid continuity, one can deduce from equation (46):
wherein A is w The cross-sectional area of the external oil pipeline; d is the inner diameter of the damper cylinder; d (D) 1 The diameter of the piston rod of the damper is; d (D) w Is the inner diameter of an external oil pipeline.
The local pressure loss calculation formula of the damper obtained by combining (62) and (63) is as follows:
the viscous fluid generates pressure loss through the connection part of the oil cylinder and the external oil pipeline, and the table 2 can know the local resistance coefficient of the damper at the position where the fluid flows through the external oil pipeline: zeta type 1 ＝1.3+3＝4.3。
The pressure loss of the oil flowing through the junction of the oil cylinder and the external oil pipeline can be obtained by combining the formulas (64) and (63):
the oil also causes pressure loss when passing through the external oil line elbow. Because the elbow of the external oil pipeline is a sharp bend, the resistance coefficient at the elbow is shown in table 3.
As shown in fig. 6, the case of the elbow of the external oil pipeline is a 90 ° elbow, so ζ=1.1 is obtained by looking up table 3, and since the oil passes through two elbows when flowing through the external oil pipeline, there is pressure loss at the two elbows, ζ 2 ＝2ζ＝2.2。
Pressure loss at the elbow of the external oil line:
substitution of (65) and (66) into (64) can result in
Thereby, a damping force generated by the local loss can be obtained:
ratio of energy consumption caused by local energy loss and pore shrinkage effect of viscous fluid in oil pipe flowing in damper
Substituting the formulas (55), (68) into the above formula yields:
due to d 4 Far smaller thanApproaching 0, the viscous fluid is considered to have negligible local energy loss in the tubing flow in the damper.
The damping force of the piezoelectric semi-active viscous damper consists of three parts, namely friction energy consumption generated by viscous fluid friction at a damping hole, energy consumption caused by a shrinkage effect and energy loss generated by viscous fluid flowing through a piezoelectric control valve of the damper.
The mechanical model of the (traditional circular tube) piezoelectric semi-active viscous damper is as follows:
wherein N is the number of damping holes.
3. Comparison of Flat tube damper and traditional round tube damper
According to formulas (28) and (69), the damping force generated by the flat tube piezoelectric viscous damper and the circular tube piezoelectric viscous damper can be equal to F=F 1 +F 2 ＝C 1 V+C 2 V 2 This form is shown, and therefore, the magnitude of the damping force generated by the flat tube piezoelectric viscous damper and the circular tube piezoelectric viscous damper can be determined by C 1 And C 2 Is determined by the size of (a).
C of flat tube 1 And C 2 The method comprises the following steps:
round tubeC 1 And C 2 The method comprises the following steps:
under the condition that the cross-sectional areas of the round pipe and the flat pipe are approximately equal, the diameter of the round pipe is 2mm (the round pipe is a double damping hole), the height of the flat pipe is 0.3mm, the width of the flat pipe is 21mm (the flat pipe is a single damping hole), and the cross-sectional areas are calculated by matlab:
flat tube: c (C) 1 ＝2.1674×10 8 n(m/s) -1 ,C 2max ＝3.5644×10 7 C 2min ＝2.5296×10 7 n(m/s) -2 ；
Round tube: c (C) 1 ＝3.2519×10 6 n(m/s) -1 ,C 2 ＝C 2max ＝1.5458×10 7 C 2min ＝1.3779×10 7 n(m/s) -2 ；
The comparison shows that the output of the flat tube is larger than that of the round tube under the condition of control or no control. The energy consumption of the flat tube damper is higher than that of the circular tube damper, namely, the flat tube damper can achieve the target damping force and the expected control effect under the condition that a displacement amplifying device is not needed.
The foregoing disclosure is merely illustrative of specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art will readily recognize that changes and modifications are possible within the scope of the present invention.
Claims (6)
1. A piezoelectric viscous damper comprises a cylinder barrel formed by a main cylinder barrel (17) and an auxiliary cylinder barrel (1), a piston (4), a piston rod (5), a bypass pipeline, a piezoelectric driver (6) and a control system; the main cylinder (17) is filled with viscous fluid, the piston rod (5) is inserted into the main cylinder and extends into the auxiliary cylinder (1), and the piston (4) in the main cylinder (17) divides the main cylinder (17) into a first closed damping chamber (2) and a second closed damping chamber (3); the bypass pipeline is arranged outside the main cylinder (17), and two ports of the bypass pipeline are respectively communicated with the first damping chamber (2) and the second damping chamber (3); and a piezoelectric driver (6) electrically connected with the control system is arranged on the bypass pipeline, and is characterized in that:
the piezoelectric actuator also comprises a control board (16) connected with the displacement output end of the piezoelectric actuator (6); the bypass pipeline comprises a flat pipe (15) which is arranged in parallel with the main cylinder (17), and a first variable cross-section pipeline (19) and a second variable cross-section pipeline (18) which are arranged at two ends of the flat pipe (15); a groove matched with the control board (16) in size is formed in the inner wall of the flat pipe (15), and the control board (16) is arranged in the groove;
the grooves are formed in the inner top wall or the inner bottom wall of the flat tube (15), and the ratio of the width to the height of the flat tube (15) is greater than or equal to 10:1.
2. A piezoelectric viscous damper as defined in claim 1, wherein: the width of the flat tube (15) is larger than the diameter of the main cylinder (17).
3. A piezoelectric viscous damper as defined in claim 1, wherein: the first variable cross-section pipeline (19) and the second variable cross-section pipeline (18) are respectively communicated with the first damping chamber (2) and the second damping chamber (3), the diameters of the lower ends of the first variable cross-section pipeline (19) and the second variable cross-section pipeline (18) are the same as the diameter of the main cylinder (17), and the diameters of the upper ends of the first variable cross-section pipeline (19) and the second variable cross-section pipeline (18) are the same as the width of the flat pipe (15).
4. A piezoelectric viscous damper as defined in claim 1, wherein: the cross section of the flat tube (15) is rectangular.
5. A piezoelectric viscous damper as defined in claim 1, wherein: the flat tube (15) is made of stainless steel.
6. A piezoelectric viscous damper as defined in claim 1, wherein: the damping force F generated by the damper is:
wherein: mu is a hydrodynamic viscosity coefficient, and l is the length of the flat tube; v is the relative movement speed of the piston rod, D is the inner diameter of the main cylinder barrel, D 1 C is a function of the aspect ratio of the rectangular cross section of the flat tube, C being a constant for a given tube; d, d h Is the hydraulic diameter; a, b are respectively 1/2 of the length and the width of the flat tube; z is the displacement output by the piezoelectric driver; ρ is the density of the fluid in the flat tube.
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