CN109558679A - A kind of hydraulic damper performance simulation method having cavitation simulation capacity - Google Patents

A kind of hydraulic damper performance simulation method having cavitation simulation capacity Download PDF

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CN109558679A
CN109558679A CN201811444721.6A CN201811444721A CN109558679A CN 109558679 A CN109558679 A CN 109558679A CN 201811444721 A CN201811444721 A CN 201811444721A CN 109558679 A CN109558679 A CN 109558679A
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piston
working solution
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hole
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CN109558679B (en
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邹文斌
杨永泰
邹炎火
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Quanzhou Institute of Equipment Manufacturing
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    • G06—COMPUTING; CALCULATING OR COUNTING
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Abstract

The invention discloses a kind of hydraulic damper performance simulation methods for having cavitation simulation capacity of hydraulic damper technical field, interconnected upper cavity and lower chamber and working solution compensated cavity are internally provided with including hydraulic damper, working solution is all filled in the upper cavity and lower chamber, the pressure difference formed in two pistons during being flowed by working solution calculates the damping force of damper, the present invention proposes a kind of computer sim- ulation method based on working solution working condition for the cavitation of hydraulic damper, the time of origin point and air pocket intensity that damper cavitation can quickly be calculated by the emulation mode are even by the quantitative analysis to air pocket intensity, the damping force that can be fed back to damper backhaul quantitatively decays, the it is proposed of the invention compensates for can not control for cavitation in damper development process Situation.

Description

A kind of hydraulic damper performance simulation method having cavitation simulation capacity
Technical field
The present invention relates to hydraulic damper technical fields, have the hydraulic of cavitation simulation capacity more particularly to a kind of Damper performance simulation method.
Background technique
The principle of hydraulic damper are as follows: when vehicle passes through bumpy sections, damper is pressurized, and piston is pushed into connection compartment Another beam barrel；Have standard aperture on piston, working solution by upstream cavity pass through aperture flow to the process of downstream cavity by Resistance, and play the role of damping, conversely, damper tension, working solution flows through the aperture in piston from another direction and generates Reversed damping force.
When pressure of the working solution in hydraulic cylinder is reduced to due to the aperture that high velocity stream is crossed in piston the vaporization of working solution When pressure, working solution begins to local gasification, generates cavitation, and form bubble accumulation in the outflow end of piston hole, at present Hydraulic damper may cause hydraulic damper to be born excessively due to factors such as overload of vehicle, road conditions complexity during the work time Harsh load working condition causes piston movement speed in hydraulic cylinder too fast, piston rod in the process of moving, thus working solution There is cavitation.
Problem brought by cavitation includes: irregular oscillation and noise, cavitation erosion and reduction system damping performance etc. Problem, current detection means are, on the vehicle that hydraulic damper is installed and used, and vehicle simulation real road are run, Then all data is detected, hydraulic damper can only be produced, then be detected by sensor detection means again Whether adapt to, if not all right, produce again, or production one substantially exceeds the damper of use demand, but it is such Damper is not matched with vehicle is used, and using effect is very poor；Above method can not all be judged by required working environment Suitable damper parameters out, it is even more impossible to directly carry out detection early warning to cavitation, in order to solve this problem, we A kind of more efficient method is needed now, the complete working condition for simulating damper, and do not need to be carried out with various vehicles Installation experiment detection, can accurately just judge the parameters demand for meeting the vehicle-mounted damper of vehicle.
Based on this, the present invention devises a kind of hydraulic damper performance simulation method for having cavitation simulation capacity, To solve the above problems.
Summary of the invention
The purpose of the present invention is to provide a kind of hydraulic damper performance simulation method for having cavitation simulation capacity, It does not need to carry out installation experiment detection with various vehicles, can accurately be calculated by function and curve graph, then be judged Meet the parameters demand of the vehicle-mounted damper of vehicle operation out.
The present invention is implemented as follows: a kind of hydraulic damper performance simulation method for having cavitation simulation capacity, Three cavitys that setting is isolated by two pistons in hydraulic damper, three cavitys include upper cavity, lower chamber and working solution Compensated cavity, two pistons include upper piston and lower piston, and the upper cavity and lower chamber are isolated by upper piston, the lower chamber and Working solution compensated cavity is isolated by lower piston, and the upper cavity is connected to lower chamber by the upper piston hole being provided on upper piston, The lower chamber is connected to working solution compensated cavity by the lower piston hole being provided on lower piston, is mounted with to live on the upper piston Stopper rod, the piston rod are arranged in upper cavity, emulation mode the following steps are included:
Step 1, initial input condition is the shift motion formula of piston, and: S=Bsin (2 π ft) passes through the movement of piston Stroke formula, the movement speed V of our available corresponding piston rods, and derivation is carried out to relation above, obtain piston rod Movement speed formula: V=B2 π fcos (2 π ft), wherein B is equal to the amplitude of sinusoidal stroke load, and f is the load frequency of the load Rate, t are the time for applying load；Frequency f value since 1 with 0.1 amplification be incremented by, for each frequency f, time t Value 1/f is incremented to the amplification of 1/20f since 0, complete the load of an oscillation cycle；
When value 0.1 frequency f, cavitation will not occur for the working solution in hydraulic damper；Based on this, if Fixed piston bar is mobile to upper cavity direction, and the movement speed V for setting piston rod passes through upper work as the fixed value in safe range The flow formula of consent working solution calculates QpistonValue, the flow formula of upper piston hole working solution and lower piston hole working solution Flow formula is respectively as follows:
Qpiston=VAA
Qbottom=VArod
Wherein, QpistonThe flow in upper piston hole is flowed through for working solution；AAFor the sectional area of upper cavity；, QbottomFor work Liquid stream crosses the flow in lower piston hole；ArodFor the sectional area of piston rod；
Step 2, the working solution flow velocity in upper piston hole is calculated, working solution passes through the working solution velocity formula in upper piston hole Are as follows:
Wherein, Apiston_holeFor the sectional area in upper piston hole, voilFor flow velocity of the working solution in upper piston hole；
Step 3, it calculates and judges whether working solution occurs cavitation, the method is as follows:
Euler's numbers formula is changed to air pocket exponential formula, and changing name Euler's numbers EU is air pocket index Ca, specifically:
Then it is as follows that air pocket index Ca formula is calculated:
Wherein, pdFor downstream pressure, pvIt is pressure for vaporization, ρ is the density of working solution；
If the standard air pocket index value of the working solution is m, if hydraulic damper to be measured is calculated according to formula (1) Air pocket index Ca be greater than standard air pocket index value m, then illustrate that the working solution in hydraulic damper does not vaporize, no air pocket is existing As occurring, step 4 is carried out；If detecting that the air pocket index Ca of hydraulic damper to be measured is less than or equal to standard air pocket and refers to Numerical value m has cavitation then illustrating that the working solution in hydraulic damper vaporizes, and carries out step 5；
Step 4, when no cavitation occurs, the relation curve of damping force and piston stroke obtains using the following method:
First calculate the flow in upper piston hole and lower piston hole:
Wherein, CqThe discharge coefficient of working solution when for no cavitation, at this time CqValue is constant, QbottomTo flow through lower piston The flow in hole, Abotton_holeFor the sectional area in lower piston hole, Δ ppistonFor the pressure difference at upper piston hole both ends, Δ pbottomUnder being The pressure difference at piston hole both ends；
By the flow rate calculation formula of the flow in upper piston hole and lower piston hole, damping force when no cavitation is obtained Calculation formula:
F=Δ ppistonAA+ΔpbottomArod (2)
Arod=AB-AA, ArodFor the sectional area of piston rod, ABFor the sectional area of lower chamber；
Next the movement speed formula of displacement stroke formula and piston rod is substituted into formula (2), obtains no cavitation When generation, the formula (3) of damping force and piston stroke is as follows:
Step 5, when there is cavitation generation, the relation curve of damping force and piston stroke obtains using the following method:
The discharge coefficient of piston hole when cavitation occurs is stated are as follows:
Wherein Cq caThe discharge coefficient of working solution, at this time C when for cavitation occursq caFor variable, puFor on piston hole Swim pressure, pvIt for the vaporization pressure of working solution, and is constant, pdFor downstream pressure, Cc is that working solution flows through work in air pocket The constriction coefficient of consent, Cc=Ac/ A, wherein AcFor the sectional area in contracted downstream region, A is the piston hole section for being connected to upstream and downstream Product, upstream and downstream refer to working solution flow direction,
When the damping force F for the piston rod that cavitation occurs, need the C in formula (3)qReplace with Cq ca, obtain as Lower formula:
There are 20 calculating test points in the backhaul and return of hydraulic damper inner piston, by each calculating test point It sets out the points of raw cavitation to the detection statistics of cavitation coefficient, Nca(0≤Nca≤20).Gas is calculated in next stroke Cave attenuation correction coefficient:
Wherein, in hydraulic damper, the sum of the test point on piston rod reciprocating stroke is all NcaA, i is next row Corresponding time dot sequency in journey；
It needs to pass through air pocket since influence of the bubble of cavitation generation to next stroke damping force occurs for last stroke Attenuation correction coefficient amendment, by the damping force F after the F decaying in formula (5)finalCalculation formula it is as follows:
Ffinal=CIF × F (6)；
Step 6, piston rod is substituted into formula (3) and formula (6) in the value at different loading frequencies and time point respectively, is obtained To different damping power numerical value, then by each numeric renderings in same curves figure, meter damping force-piston stroke and piston rod are obtained The curve of movement speed, and simulation and prediction is carried out to different hydraulic damper by the two curves.
The beneficial effects of the present invention are: the present invention proposes one kind based on working solution work for the cavitation of hydraulic damper The computer sim- ulation method for making state can quickly calculate the time of origin point and gas of damper cavitation by the emulation mode Even by the quantitative analysis to air pocket intensity, the damping force that can be fed back to damper backhaul quantitatively decays cave intensity, should The it is proposed of invention compensate in damper development process for cavitation can not control situation, can accomplish from product design Initial stage can calculate the finished product speed limit and load limitation of product, Yi Jifa just by the parameters of hydraulic damper The critical point of parameters, can effectively predict the generation of cavitation, by the hydraulic shock-absorption of different size when raw cavitation Device is mounted in suitable operating condition, and damper thus can effectively be avoided to work overloadingly and generate bubble.
Detailed description of the invention
The present invention is further illustrated in conjunction with the embodiments with reference to the accompanying drawings.
Fig. 1 is hydraulic damper schematic diagram of internal structure of the present invention；
Fig. 2 is cavitation test point position view of the present invention；
Fig. 3 is damping force-piston stroke graph of relation；
Fig. 4 is damping force-piston speed graph of relation.
In attached drawing, parts list represented by the reference numerals are as follows:
1- upper cavity, 11- upper piston, 2- lower chamber, 21- working solution compensated cavity, 22- lower piston, 3- upper piston hole, 31- Lower piston hole, 4- piston rod, 5- backhaul test point, 6- return test point.
Specific embodiment
It please refers to shown in Fig. 1 to 4, the present invention provides a concrete application of embodiment are as follows: setting is logical in hydraulic damper Three cavitys of two pistons isolation are crossed, three cavitys include upper cavity 1, lower chamber 2 and working solution compensated cavity 21, two pistons Including upper piston 11 and lower piston 22, the upper cavity 1 and lower chamber 2 are isolated by upper piston 11, the lower chamber 2 and working solution Compensated cavity 21 is isolated by lower piston 22, and the upper cavity 1 and lower chamber logical 2 are crossed the upper piston hole 3 being provided on upper piston 11 and connected Logical, the lower chamber 2 is connected to working solution compensated cavity 21 by the lower piston hole 31 being provided on lower piston 22, the upper piston Piston rod 4 is mounted on 11, the setting of piston rod 4 is additionally provided with logical with lower chamber 1 in upper cavity 1, in hydraulic damper The working solution compensated cavity 21 of the connection of lower piston hole 31 is crossed, 4 script of piston rod is the interposition between upper cavity 1 and lower chamber 2 It sets, when vehicle, which encounters, to jolt, gravity of the hydraulic damper by vehicle, 4 stress of piston rod, and damping force is generated, subtract The speed of slow height of car change in location, makes height of car that change dramatically will not occur, and increases the comfort level for driving vehicle；Piston The stress and hydraulic damper of bar 4 generate damping force and act on piston rod 4, and 4 stress of piston rod is in upper cavity 1 and lower chamber It being slided between 2, working solution passes through upper piston hole 3 between upper cavity 1 and lower chamber 2 and flows, so that damping force is generated, the present invention The emulation mode of 4 travel relationships of damping force and piston rod is exactly calculated by the flow of working solution flowing.
Emulation mode the following steps are included:
Step 1, working solution is first selected, then the characteristic of the working solution is tested, working solution is replaced every time and requires Again the characteristic of working solution being tested, cavitation Shi Douhui, which can occur, for every kind of working solution an accurate numerical value, this The selected working solution of invention, by test, measuring standard air pocket index value is m=0.0745, at this time the vaporization pressure of working solution pvFor 13pa, and the diameter for setting upper piston hole 3 generally only needs to detect upper cavity 1 as 0.61m, because hydraulic again subtract For shake device when being worked, the flow velocity of 1 tensile strength of upper cavity and working solution can all be greater than lower chamber 2, then at this time once on Cavity 1 generates cavitation, indicates that entire hydraulic damper has occurred and that cavitation, but the different fixed output quota at this time of lower chamber 2 Raw cavitation, so only need to examine and calculate the working condition of upper cavity 1, when cavitation is 4 backhaul of piston rod, work Cavitation occurs for liquid, and bubble stays in upper cavity 1 and will not flow away, can be complete by the bubble in upper cavity 1 in 4 return of piston rod Portion crushes, and then working solution and piston can just generate the damping force of interaction, play damping effect, hydraulic in this process Damper can occur the unhelpful state such as to vibrate, fail and fall suddenly, thus seriously affect the normal work of hydraulic damper Make, illustrate hydraulic damper overload operation at this time, is unsuitable to apply to workplace at this time, it is of the invention hydraulic to subtract Shake device refers in particular to vehicle-mounted hydraulic damper, is mounted vertically in bottom of car；
Initial input condition is the shift motion formula of piston: S=Bsin (2 π ft), public by the shift motion of piston Formula, the movement speed V of our available corresponding piston rods, and derivation is carried out to relation above, obtain the movement of piston rod 4 Speed formula: V=B2 π fcos (2 π ft), wherein B is equal to the amplitude of sinusoidal stroke load, and f is the loading frequency of the load, and t is Apply the time of load；Frequency f value since 1 with 0.1 amplification be incremented by, for each frequency f, the value of time t 1/f is incremented to the amplification of 1/20f since 0, completes the load of an oscillation cycle；
When value 0.1 frequency f, cavitation will not occur for the working solution in hydraulic damper；Based on this, if Fixed piston bar 4 is mobile to 1 direction of upper cavity, and the movement speed V for setting piston rod 4 passes through as the fixed value in safe range The flow formula of 3 working solution of upper piston hole calculates QpistonValue, the flow formula of 3 working solution of upper piston hole and lower piston hole 31 The flow formula of working solution is respectively as follows:
Qpiston=VAA
Qbottom=VArod
And calculate QpistonValue and QbottomValue；
Wherein, AAFor the sectional area of upper cavity 1；QpistonThe flow in upper piston hole 3 is flowed through for working solution；ArodFor piston rod 4 sectional area；QbottomThe flow in lower piston hole 31 is flowed through for working solution；
Step 2, the working solution flow velocity in upper piston hole 3 is calculated, working solution passes through the working solution velocity formula in upper piston hole 3 Are as follows:
Wherein, Apiston_holeFor the sectional area in upper piston hole 3, voilFor flow velocity of the working solution in upper piston hole 3；
Step 3, it calculates and judges whether working solution occurs cavitation, the method is as follows:
Euler's numbers formula is changed to air pocket exponential formula, and changing name Euler's numbers EU is air pocket index Ca, specifically:
Then it is as follows that air pocket index Ca formula is calculated:
Wherein, pdFor downstream pressure, pvIt is pressure for vaporization, ρ is the density of working solution；
If the standard air pocket index value of the working solution is m, if hydraulic damper to be measured is calculated according to formula (1) Air pocket index Ca be greater than standard air pocket index value m, then illustrate that the working solution in hydraulic damper does not vaporize, no air pocket is existing As occurring, step 4 is carried out；If detecting that the air pocket index Ca of hydraulic damper to be measured is less than or equal to standard air pocket and refers to Numerical value m has cavitation then illustrating that the working solution in hydraulic damper vaporizes, and carries out step 5；
Step 4, when no cavitation occurs, the flow in upper piston hole 3 and lower piston hole 31 is first calculated, according to J The paper that Huang1991 is delivered on " Journal of Anhui University of Technology ", On Cavitation in fluid power, it can be deduced that following calculation formula:
Wherein, QpistonThe flow in upper piston hole 3, C are flowed through for working solutionqThe flow system of working solution when for no cavitation It counts, at this time CqValue is constant, Apiston_holeFor the sectional area in upper piston hole 3, QbottomFor the flow for flowing through lower piston hole 31, Abotton_holeFor the sectional area in lower piston hole 31, Δ ppistonFor the pressure difference at 3 both ends of upper piston hole, Δ pbottomIt is lower piston hole The pressure difference at 31 both ends；
By the flow rate calculation formula of the flow in upper piston hole 3 and lower piston hole 31, resistance when no cavitation is obtained Buddhist nun's power calculation formula:
F=Δ ppistonAA+ΔpbottomArod (2)
Arod=AB-AA, ArodFor the sectional area of piston rod 4, ABFor the sectional area of lower chamber 2；
Then apply the displacement stroke load of an analog sinus signals, displacement stroke formula are as follows: S=B to piston rod 4 Sin (2 π ft),
By stroke formula, the movement speed V of our available corresponding piston rods 4, and relation above is asked It leads, obtains the movement speed formula of piston rod 4: V=B2 π fcos (2 π ft), wherein B is equal to the amplitude of sinusoidal stroke load, and f is The loading frequency of the load, t are the time for applying load；
Next the movement speed formula of displacement stroke formula and piston rod 4 is substituted into formula (2), obtains no cavitation When generation, the formula (3) of damping force and piston stroke is as follows:
Step 5, when there is cavitation generation, the relation curve of damping force and piston stroke obtains using the following method:
The discharge coefficient of piston hole 3 when cavitation occurs is stated are as follows:
Wherein Cq caThe discharge coefficient of working solution, at this time C when for vaporization phenomenon occursq caFor variable, puFor on piston hole 3 Swim pressure, pvIt for the vaporization pressure of working solution, and is constant, pdFor downstream pressure, CcWork is flowed through in air pocket for working solution The constriction coefficient of consent 3, Cc=Ac/ A, wherein AcThe sectional area of air pocket area occurs for downstream, A is 3 sectional area of piston hole, on Downstream refer to working solution flow direction (such as: when working solution flows to lower chamber 2 by upper cavity 1, pressure in upper cavity 1 is upper Pressure is swum, the pressure in lower chamber 2 is downstream pressure；Treatment fluid flow to it is opposite when, upstream and downstream pressure is opposite),
When the damping force F for the piston rod 4 that cavitation occurs, need the C in formula (3)qReplace with Cq ca, obtain as Lower formula:
We can calculate the damper worked normally in the case of liquid during piston rod is pulled up up to now Damping force in the case of damping force and vaporization working solution, however vaporize the bubble formed and the compression of piston is formed and can be made The case where at backward stroke of the piston idle running, i.e., bubble is crushed by piston in return stroke, causes damping force rapid drawdown, cause that air pocket occurs The backward stroke of the piston damping force calculating of phenomenon is not accurate, to this it is proposed that a kind of quantitative description working solution vaporizes Strength co-mputation side Formula:
By taking damper Tensile stroke as an example, from damper most short status to longest state, we carry out loading cycle Ten equal parts, that is, have 10 calculating test points, vaporization phenomenon occurs once calculating to working solution, i.e. Ca value is less than or equal to 0.0745, we replace the discharge coefficient after normal discharge coefficient occurs to vaporization phenomenon, and She Zhi air pocket counting NcaAdd Cavitation is detected in one, such as the following figure is counted as 5, and accordingly in return i.e. compression travel, we are also selected 10 location points are taken, wherein preceding 5 time points, due to the bubble for having a upper stroke to carry over, we do one to damping force Attenuation coefficient amendment, and practical damping force detected value is fitted to air pocket attenuation correction coefficient:
Wherein, in hydraulic damper, the sum of the test point on 4 reciprocating stroke of piston rod is all NcaA, i is corresponding position Set dot sequency；
When the damping force F for the piston rod 4 that cavitation occurs is needed through the amendment of air pocket attenuation correction coefficient, formula (5) In damping force F decaying after return correct damping force FfinalCalculation formula it is as follows:
Ffinal=CIF × F (6)；
Step 6, by displacement stroke formula frequency f carry out value, value from 0.1/0.2/0.3/0.4. always To complete closed curve elliptical ring is made, corresponding is exactly the circle one by one in damping force-stroke curve Fig. 3, Wo Menke With the damping force of hydraulic damper under step by step calculation difference movement speed, by taking for the different loading frequencies of piston rod 4 and time point Value substitutes into formula 3 and formula 6 respectively, obtains different damping power numerical value, then each numeric renderings are obtained in same curves figure Count damping force-piston stroke and 4 movement speed of piston rod curve, and by the two curves to different hydraulic damper into Row simulation and prediction.
By the data point of multiple speed and stroke, data point is more, more accurate, and data point of the invention is greater than 100, Then the corresponding damping force numerical value of data point up stroke is calculated, carries out each point to be fitted to complete curve figure, it can from figure To find out, damping force has the lifting of apparent abrupt slope formula in the curve that cavitation occurs, such as the Y mark point on Fig. 3, at present Damping force calculation method can detect cavitation compressing and stretching in two strokes, and can be to produced Cavitation carry out quantization counting, and then feed back to the damping force variation in next stroke, can pass through damping force Whether function and damping force-piston stroke curve, the hydraulic damper for calculating different parameters can occur under various working conditions Cavitation, and the limiting figure of meeting cavitation, form a closed loop with 0 axis curve symmetrical above and below, Each closed loop is exactly backhaul-return curve, and wherein obvious cataclysm occurs for damping force in these curves, is said Bright to have had cavitation, which is pioneering in current hydraulic drive field, and is being actually used Industrial value is realized in the process, this method is made by MATLAB software, and user interface is formed, and it is easy to operate, Also it is suitble to the researcher of non-hydraulic damper to use, that is, vehicle manufacture personnel, software can be used, easy giving is required The suitable hydraulic damper of vehicle dispensing of production, without being found by repetition test.
Contracted downstream region: referring to fluid flow through orifice hole, can generate vortex in hole downstream, and fluid flows into after hole, A fluid stream can be shunk, and lead to the sectional area for being just less than hole across the fluid cross-section product of hole.
In addition, numerical value unit use all in the present invention is as follows:
Pressure unit uses: pa；
Density unit uses: kg/m3；
Pressure unit uses: N；
Speed unit uses: m/s；
Flow rate uses: m3/s；
Chronomere is equal: s.
Although specific embodiments of the present invention have been described above, those familiar with the art should be managed Solution, we are merely exemplary described specific embodiment, rather than for the restriction to the scope of the present invention, it is familiar with this The technical staff in field should be covered of the invention according to modification and variation equivalent made by spirit of the invention In scope of the claimed protection.

Claims (1)

1. a kind of hydraulic damper performance simulation method for having cavitation simulation capacity, it is characterised in that: hydraulic damper Three cavitys that interior setting is isolated by two pistons, three cavitys include upper cavity, lower chamber and working solution compensated cavity, and two Piston includes upper piston and lower piston, and the upper cavity and lower chamber are isolated by upper piston, the lower chamber and working solution compensation Chamber is isolated by lower piston, and the upper cavity is connected to lower chamber by the upper piston hole being provided on upper piston, the lower chamber It is connected to working solution compensated cavity by the lower piston hole being provided on lower piston, piston rod is mounted on the upper piston, it is described Piston rod be arranged in upper cavity, emulation mode the following steps are included:
Step 1, initial input condition is the shift motion formula of piston, and: S=B sin (2 π ft) passes through the mobile row of piston Journey formula, the movement speed V of our available corresponding piston rods, and derivation is carried out to relation above, obtain piston rod Movement speed formula: V=B2 π f cos (2 π ft), wherein B is equal to the amplitude of sinusoidal stroke load, and f is the load frequency of the load Rate, t are the time for applying load；Frequency f value since 1 with 0.1 amplification be incremented by, for each frequency f, time t Value 1/f is incremented to the amplification of 1/20f since 0, complete the load of an oscillation cycle；
When value 0.1 frequency f, cavitation will not occur for the working solution in hydraulic damper；Based on this, setting is lived Stopper rod is mobile to upper cavity direction, and the movement speed V for setting piston rod passes through upper piston hole as the fixed value in safe range The flow formula of working solution calculates QpistonValue, the flow formula of upper piston hole working solution and the flow of lower piston hole working solution Formula is respectively as follows:
Qpiston=VAA
Qbottom=VArod
Wherein, QbottomThe flow in lower piston hole is flowed through for working solution；ArodFor the sectional area of piston rod；QpistonFor treatment fluid flow Cross the flow in upper piston hole；AAFor the sectional area of upper cavity；
Step 2, the working solution flow velocity in upper piston hole is calculated, working solution passes through the working solution velocity formula in upper piston hole are as follows:
Wherein, Apiston_holeFor the sectional area in upper piston hole, voilFor flow velocity of the working solution in upper piston hole；
Step 3, it calculates and judges whether working solution occurs cavitation, the method is as follows:
Euler's numbers formula is changed to air pocket exponential formula, and changing name Euler's numbers EU is air pocket index Ca, specifically:
Then it is as follows that air pocket index Ca formula is calculated:
Wherein, pdFor downstream pressure, pvIt is pressure for vaporization, ρ is the density of working solution；
If the standard air pocket index value of the working solution is m, if the gas of hydraulic damper to be measured is calculated according to formula (1) Cave index Ca is greater than standard air pocket index value m, then illustrate that the working solution in hydraulic damper does not vaporize, no cavitation hair It is raw, carry out step 4；If detecting that the air pocket index Ca of hydraulic damper to be measured is less than or equal to standard air pocket index value M has cavitation then illustrating that the working solution in hydraulic damper vaporizes, and carries out step 5；
Step 4, when no cavitation occurs, the relation curve of damping force and piston stroke obtains using the following method:
First calculate the flow in upper piston hole and lower piston hole:
Wherein, CqThe discharge coefficient of working solution when for no cavitation, at this time CqValue is constant, QbottomTo flow through lower piston hole Flow, Abotton_holeFor the sectional area in lower piston hole, Δ ppistonFor the pressure difference at upper piston hole both ends, Δ pbottomIt is lower piston The pressure difference at hole both ends；
By the flow rate calculation formula of the flow in upper piston hole and lower piston hole, show that damping force when no cavitation calculates Formula:
F=Δ ppistonAA+ΔpbottomArod (2)
Arod=AB-AA, ArodFor the sectional area of piston rod, ABFor the sectional area of lower chamber；
Next the movement speed formula of displacement stroke formula and piston rod is substituted into formula (2), obtains no cavitation and occurs When, the formula (3) of damping force and piston stroke is as follows:
Step 5, when there is cavitation generation, the relation curve of damping force and piston stroke obtains using the following method:
The discharge coefficient of piston hole when cavitation occurs is stated are as follows:
Wherein Cq caThe discharge coefficient of working solution, at this time C when for cavitation occursq caFor variable, puFor piston hole upstream pressure By force, pvIt for the vaporization pressure of working solution, and is constant, pdFor downstream pressure, Cc is that working solution flows through piston hole in air pocket Constriction coefficient, Cc=Ac/ A, wherein AcFor the sectional area in contracted downstream region, A is the piston hole sectional area for being connected to upstream and downstream, Upstream and downstream refers to working solution flow direction,
When the damping force F for the piston rod that cavitation occurs, need the C in formula (3)qReplace with Cq ca, obtain following public affairs Formula:
Have 20 calculating test points in the backhaul and return of hydraulic damper inner piston, by each calculating test point to gas The detection statistics of cave coefficient are set out the points of raw cavitation, Nca(0≤Nca≤20).Air pocket is calculated in next stroke to decline Subtract correction factor:
Wherein, in hydraulic damper, the sum of the test point on piston rod reciprocating stroke is all NcaA, i is in next stroke Corresponding time dot sequency；
It needs to decay by air pocket since influence of the bubble of cavitation generation to next stroke damping force occurs for last stroke Correction factor amendment, by the damping force F after the F decaying in formula (5)finalCalculation formula it is as follows:
Ffinal=CIF × F (6)；
Step 6, piston rod is substituted into formula (3) and formula (6) in the value at different loading frequencies and time point respectively, is obtained not With damping force numerical value, then by each numeric renderings in same curves figure, obtains meter damping force-piston stroke and piston rod is mobile The curve of speed, and simulation and prediction is carried out to different hydraulic damper by the two curves.
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