CN110259656A - Pump concrete nonstationary flow pumping pressure dynamic analysing method - Google Patents
Pump concrete nonstationary flow pumping pressure dynamic analysing method Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B15/00—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts
- F04B15/02—Pumps adapted to handle specific fluids, e.g. by selection of specific materials for pumps or pump parts the fluids being viscous or non-homogeneous
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B51/00—Testing machines, pumps, or pumping installations
Abstract
The present invention relates to a kind of pump concrete nonstationary flow pumping pressure dynamic analysing methods, belong to field of fluid mechanics.This method are as follows: the flowing of concrete is regarded as the plug flow for making unsteady laminar motion in the duct, speed and pressure do not change on same cross section with the variation of radius；According to concrete pumping system pumping theory, learn that concrete intensity is the waveform of a cycle variation, start push in piston and acceleration and deceleration motion is presented into commutation phase, steady push stage approximation uniform motion, the mathematical model for establishing speed has found out the mathematical model of pressure loss dynamic change.Finally by the correctness of example calculation verifying dynamic model.The principle that the present invention flows in the duct from concrete establishes mathematical model, can more intuitively represent the pumping load i.e. dynamic change of concrete cylinder outlet pressure, and the research for the vibration of subsequent pump truck provides the dynamic loading of input.
Description
Technical field
The invention belongs to field of fluid mechanics, are related to pump concrete nonstationary flow pumping pressure dynamic analysing method.
Background technique
Concrete mixer has in the engineering that various construction etc. need pump concrete widely to be applied, according to construction
Object, place, pumping height difference, cantilever crane posture of the concrete mixer under each operating condition is also different, and corresponding is every
Pumping pressure needed for one posture is also different, by calculating the available pumped concrete of the pressure loss of concrete in the duct
Pressure required for soil provides important parameter for the design and construction of concrete mixer.Meanwhile concrete mixer was being constructed
Cheng Zhonghui generates biggish vibration, and it is the basic reason for causing cantilever crane and chassis to vibrate that pumping pressure, which changes with time, because
The dynamic characteristic of this research concrete pump truck pumping pressure has the design and Analysis of Vibration Characteristic of concrete mixer important
Theory significance and practical value.
OR í o has measured the concrete pressure of different ratio and the corresponding data of flow, with mathematical method fitting pressure with
The curve of changes in flow rate obtains pressure linear relationship approximate with flow.ChoiM by experiment measured pressure and flow,
The rheological parameters corresponding data such as duct length, concrete specifications passes through the line of the CFD pressure loss size and flow being calculated
Linearity curve and experiment curve obtained fitting are preferable；The coefficient of friction that clock talent uses Bernoulli equation combination S.Morinaga to propose
Calculating formula is deduced the pressure loss of the concrete in straight tube, bend pipe, Taper Pipe；Zhao Zhi red silk analyzes concrete in the duct
Flow regime, it is believed that meet Bingham body pipe laminar characteristic when concrete flows in the duct, flowing in the duct is column
Plug flow, and it has been derived from the empirical equation of Calculation of pressure loss；Yang Zhiqiang has carried out waste rock & tailings mixed slurry in endless tube
Pressure loss experiment when conveying, analyzes the barren rock sand of different ratio and the changing rule of the slurry pressure loss in the duct；
Zhang Lei obtains the one-to-one data point of pressure loss size and velocity magnitude by experiment, has obtained pressure with straight line fitting
The calculating formula of loss.
Existing pressure loss research mainly calculates the numerical value of pumping pressure, it is considered that the flowing of concrete in the duct
For Steady Flow, in fact, with pumping oil cylinder piston cycle alternating movement pump concrete it is found that concrete in pipeline
Interior flow velocity is in cyclically-varying, and by commutation phase concrete is not in the pumping incipient stage and i.e. uniform motion, is to be badly in need of
The problem overcome.
Summary of the invention
In view of this, the purpose of the present invention is to provide a kind of pump concrete nonstationary flow pumping pressure dynamic analysis sides
Method, Calculation of pressure loss formula when showing that concrete makees UNSTEADY FLOW in the duct by theory deduction, and pass through piston position
It moves and strain signal figure obtains the change curve of concrete flow velocity, the mathematical model of concrete flow velocity is established with Fourier space,
It substitutes into Calculation of pressure loss formula, obtains the dynamic change calculating formula of concrete duct pressure at any time.
In order to achieve the above objectives, the invention provides the following technical scheme:
Pump concrete nonstationary flow pumping pressure dynamic analysing method, method includes the following steps:
S1: the rheological properties of pump concrete are analyzed；
S2: the pressure loss dynamic change formula of concrete in the duct is derived.
Further, the step S1 specifically:
Normal concrete is the Bingham body in non-newtonian fluid, and constitutive equation isτ0It cuts and answers for the limit
Power, ηpFor plastic viscosity, when shearing stress is less than Limiting shear stress, internal fluid is without relative motion, when shearing stress is greater than the limit
Shearing stress τ0When, fluid ability setting in motion, shearing stress is changed linearly with shear strain rate, slope ηp；
According to drilling fluid mechanics, when judging that Bingham body is flowed in the duct for laminar flow or turbulent flow, referring to newton
Fluid judgment method, works as Reynolds numberIn range, fluid flowing is laminar flow；Reynolds number Re≤2320 obtain
The flow regime of pump concrete in the duct is laminar flow；
When Bingham body makees permanent laminar motion in the duct, is known according to Bingham body constitutive equation, cut and answer when maximum
Power τw< τ0When, concrete does not generate flowing, is stationary state；As maximum shear stress τw> τ0When, in τ≤τ0, i.e. R≤R0Range
Interior, internal fluid particle is without relative motion, and the movement velocity of fluid is identical, in τ >=τ0, i.e. R >=R0In range, shearing stressThe flowing velocity curve of fluid parabolically form, speed is when Steady FlowR=R0Shi Sudu is maximum, and speed is 0 at tube wall；
The flowing of concrete in the duct is regarded as plug flow, i.e., speed is all identical at any radius on a section,
The same flow forward of concrete statuary column plug in pipeline, the surface only contacted with inner wall of the pipe is there are frictional force, in concrete
Portion's zerofriction force.
Further, the step S2 specifically:
S21: pressure loss empirical equation is derived；
Calculation of pressure loss formula are as follows:
ΔpH--- pressure loss when concrete flows in unit length horizontal pipe, unit Pa/m；
K1--- adhesion coefficient, unit Pa, K1Calculating formula be K1=300-S, S are the slump of concrete；
K2--- velocity coeffficient, unit Pas/m, K2Calculating formula be K2=400-S；
The radius of R--- concrete flow duct, unit m；
--- distribution valve of concrete pump switching time and piston push the ratio between concrete time；
The mean flow rate of V--- concrete, unit m/s, calculating formula areQ is the discharge capacity of concrete, and unit is
m3/h；
α2--- the ratio between radial pressure and axial compressive force, normal concrete generally take 0.9；
S22: pressure loss dynamic change computation model is derived
(1) the straight pipeline pressure loss is analyzed
The flowing of concrete in the duct is approximately plug flow, and on a cross section of pipeline, speed and pressure are not
With radius change, the straight pipeline pressure loss is analyzed, the concrete that taking length is dx, radius is pipe radius r is control volume, by
Along the pressure of pipe lengths, the frictional force along tube wall and gravity, fluid motion equation is obtained are as follows:
F is coefficient of friction in formula, is expressed as f=K1+K2V, K1And K2Calculating and pressure loss empirical equation in calculate it is public
Formula is consistent；After f is substituted into, the equation of motion is solved
If can obtain concrete flowing velocity to change with time relationship, the time history that can find out pumping pressure is bent
Line；
(2) foundation of rate pattern
According to the principle of concrete pump truck pumping system, when being pumped by, cylinder rod chamber connection, from rodless cavity fuel feeding,
When oil cylinder piston reaches range, connects the S pipe valve of concrete cylinder and master cylinder while commutating, main oil pump is given another
A oil cylinder fuel feeding, the corresponding cylinder full of concrete continue pump concrete, the rule periodically pumped are presented；
Stablizing delivery phase, approximation is changed linearly at any time for oil cylinder piston displacement, and speed is constant, is started in pumping
And commutation phase, piston displacement change with time be not it is linear, the trend for accelerating and slowing down can be presented in speed,
The variation for obtaining concrete intensity accelerates from 0 to a steady state value in pumping incipient stage concrete intensity, defeated stablizing
The stage is sent, concrete intensity is a steady state value, and slowing down in commutation phase concrete intensity is 0, the mathematical modulo shown in formula (4)
Type indicates that speed changes with time:
WhereinQ is concrete discharge capacity, unit m3/ h, r are the radius of pipeline；(-t2,-t4) add for piston
Speed pushes concrete to the time steadily pushed, (t1,t2) it is buffer piston deceleration time, (t2,t3) it is distributing valve commutating period
Half；
The expression formula of V (t) Fourier expansion formula
Wherein a0、an、bnIt calculates as follows
Speed V expression formula is
(3) pressure loss dynamic change model solves
V after V and derivation is substituted into above-mentioned fluid motion equation (3), obtains pressure p calculation formula
The pressure of concrete cylinder pumping outlet the losing along stroke pressure in straight pipeline flowing that include it, bend pipe, Taper Pipe,
The local resistance loss and gravity losses of the attachmentes such as junction, the pressure loss at bend pipe and Taper Pipe are equivalent to unit length straight tube
Along stroke pressure loss multiple, then concrete cylinder outlet pressure be
Wherein x is length of straight pipe, and y is the equivalent length of straight pipe of bend pipe, and z is the equivalent length of straight pipe of Taper Pipe, and w is that other are attached
The equivalent length of straight pipe of part, l, m, n are respectively the number of bend pipe, Taper Pipe and other attachmentes.
The beneficial effects of the present invention are:
The model for having calculating pumping pressure at present only calculates the size of the pressure loss, or passes through hydraulic system of pump
Simulation model show that the pressure change of main oil pump outlet, the principle that the present invention flows in the duct from concrete establish one
Mathematical model is covered, the pumping load i.e. dynamic change of concrete cylinder outlet pressure can be more intuitively represented, be subsequent pump truck
The research of vibration provides the dynamic loading of input.
Other advantages, target and feature of the invention will be illustrated in the following description to a certain extent, and
And to a certain extent, based on will be apparent to those skilled in the art to investigating hereafter, Huo Zheke
To be instructed from the practice of the present invention.Target of the invention and other advantages can be realized by following specification and
It obtains.
Detailed description of the invention
To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention is made below in conjunction with attached drawing excellent
The detailed description of choosing, in which:
Fig. 1 is Bingham body rheological curve；
Fig. 2 is the permanent laminar velocity curve of Bingham body pipeline；
Fig. 3 is force diagram when concrete flows in the duct；
Fig. 4 is concrete pumping schematic diagram；
Fig. 5 is pumping oil cylinder piston stroke figure；
Fig. 6 is that pumping oil cylinder piston strains pressure signal variation；
Fig. 7 is concrete intensity change curve；
Fig. 8 is 150l/min experiment condition；
Fig. 9 is unit length-tension dynamic change；
Figure 10 is experiment main oil pump pressure history；
Figure 11 is that model calculates gained main oil pump pressure history.
Specific embodiment
Illustrate embodiments of the present invention below by way of specific specific example, those skilled in the art can be by this specification
Other advantages and efficacy of the present invention can be easily understood for disclosed content.The present invention can also pass through in addition different specific realities
The mode of applying is embodied or practiced, the various details in this specification can also based on different viewpoints and application, without departing from
Various modifications or alterations are carried out under spirit of the invention.It should be noted that diagram provided in following embodiment is only to show
Meaning mode illustrates basic conception of the invention, and in the absence of conflict, the feature in following embodiment and embodiment can phase
Mutually combination.
Wherein, the drawings are for illustrative purposes only and are merely schematic diagrams, rather than pictorial diagram, should not be understood as to this
The limitation of invention；Embodiment in order to better illustrate the present invention, the certain components of attached drawing have omission, zoom in or out, not
Represent the size of actual product；It will be understood by those skilled in the art that certain known features and its explanation may be omitted and be in attached drawing
It is understood that.
The same or similar label correspond to the same or similar components in the attached drawing of the embodiment of the present invention；It is retouched in of the invention
In stating, it is to be understood that if there is the orientation or positional relationship of the instructions such as term " on ", "lower", "left", "right", "front", "rear"
To be based on the orientation or positional relationship shown in the drawings, be merely for convenience of description of the present invention and simplification of the description, rather than indicate or
It implies that signified device or element must have a particular orientation, be constructed and operated in a specific orientation, therefore is described in attached drawing
The term of positional relationship only for illustration, is not considered as limiting the invention, for the ordinary skill of this field
For personnel, the concrete meaning of above-mentioned term can be understood as the case may be.
In the present invention, concrete pumping oil cylinder replaces pump concrete, and it is unsteady for flowing concrete in delivery pipe
Stream, concrete duct stream is close with the flow behavior of bingham body in the duct, the flowing of concrete can be regarded as in the duct
Make the plug flow of unsteady laminar motion, speed and pressure not change with the variation of radius on same cross section.Then, root
According to concrete pumping system pumping theory, learns that concrete intensity is the waveform of a cycle variation, start to push in piston
With acceleration and deceleration motion is presented into commutation phase, it is steady to push stage approximation uniform motion, establish the mathematical model of speed, find out
The mathematical model of pressure loss dynamic change.Finally, the correctness of example calculation verifying dynamic model.
1. the rheological properties of pump concrete
Concrete is a kind of cement mortar mixture, shear stress and shear strain when being flowed in the duct according to concrete
It is unsatisfactory for newton law of viscosity known to the variation relation of rate, is non-newtonian fluid, and normal concrete is generally non-newtonian fluid
In Bingham body, constitutive equation isτ0For Limiting shear stress, ηpFor plastic viscosity, rheological curve is as schemed
Shown in 1, when shearing stress is less than Limiting shear stress, internal fluid is without relative motion, when shearing stress is greater than Limiting shear stress τ0When,
Fluid ability setting in motion, shearing stress are changed linearly with shear strain rate, slope ηp。
As two oil cylinder piston alternating pump concretes of concrete pumping system enter in pipeline, it is known that concrete is in pipe
Flowing in road is the UNSTEADY FLOW changed at some cycles.According to drilling fluid mechanics, judging Bingham body in pipeline
When middle flowing is laminar flow or turbulent flow, Newtonian fluid judgment method can refer to, it can according to J.Nikuradse experiment curve and Moody chart
Know, works as Reynolds numberIn range, fluid flowing is laminar flow.Zhao Zhi red silk is according to the plasticity for commonly using pump concrete
Range of viscosities, pipe flow speed range and pump truck pipe radius range computation reynolds number Re≤2320, it can be deduced that pumped concrete
The flow regime of soil in the duct is laminar flow.
When Bingham body makees permanent laminar motion in the duct, according to Bingham body constitutive equation it is found that when maximum is cut
Stress τw< τ0When, concrete does not generate flowing, is stationary state；As maximum shear stress τw> τ0When, flowing velocity such as Fig. 2
It is shown, in τ≤τ0, i.e. R≤R0In range, internal fluid particle is without relative motion, and the movement velocity of fluid is identical, in τ >=τ0,
That is R >=R0In range, shearing stressThe flowing velocity curve of fluid parabolically form, speed when Steady Flow
ForR=R0Shi Sudu is maximum, and speed is 0 at tube wall.
According to the above analysis, the flowing of concrete in the duct can be regarded as plug flow by we, i.e., on a section
Speed is all identical at any radius, the same flow forward of concrete statuary column plug in pipeline, the table only contacted with inner wall of the pipe
There are frictional force, inside concrete zerofriction forces in face.
2. the pressure loss dynamic change derivation of equation of concrete in the duct
2.1 pressure loss empirical equations
The Calculation of pressure loss formula being widely used both at home and abroad at present is to be obtained by S.Morinaga according to theoretical and experimental summary
Empirical equation out, and " Concrete Pumping Construction technical regulation "] formula that is recommended to use, what this formula calculated is concrete
The numerical value of the pressure loss when steady motion of a fluid moves.
ΔpH--- the pressure loss (Pa/m) when concrete flows in unit length horizontal pipe
K1--- adhesion coefficient, unit Pa, K1Calculating formula be K1=300-S, S are the slump of concrete
K2--- velocity coeffficient, unit Pas/m, K2Calculating formula be K2=400-S
The radius of R--- concrete flow duct, unit m
--- distribution valve of concrete pump switching time and piston push the ratio between concrete time
The mean flow rate of V--- concrete, unit m/s, calculating formula areQ is the discharge capacity of concrete, and unit is
m3/h
α2--- the ratio between radial pressure and axial compressive force, normal concrete generally take 0.9
2.2 pressure loss dynamic change computation models
2.2.1 the straight pipeline pressure loss is analyzed
The flowing of concrete in the duct is approximately plug flow, and on a cross section of pipeline, speed and pressure are not
With radius change, the straight pipeline pressure loss is analyzed, the concrete that taking length is dx, radius is pipe radius r is control volume, by
Along the pressure of pipe lengths, the frictional force along tube wall and gravity, stress condition is as shown in figure 3, can show that fluid is transported
Dynamic equation is formula 2.
F is coefficient of friction in formula, and S.Morinaga sums up concrete in pipeline by lot of experiment validation binding isotherm
Coefficient of friction when middle flowing is represented by f=K1+K2V, K1And K2Calculating and above-mentioned pressure loss empirical equation in calculate it is public
Formula is consistent.After f is substituted into, the equation of motion is solved
It changes with time relationship in above formula as can obtaining concrete flowing velocity, the time that can find out pumping pressure is gone through
Journey curve.
2.2.2 the foundation of rate pattern
According to the principle of concrete pump truck pumping system, concrete pumping schematic diagram such as Fig. 4, when being pumped by, oil cylinder has
Rod cavity connection connects the S pipe valve and main oil of concrete cylinder when an oil cylinder piston reaches range from rodless cavity fuel feeding
Cylinder commutates simultaneously, and main oil pump gives another oil cylinder fuel feeding, and the corresponding cylinder full of concrete continues pump concrete, week is presented
The rule of phase property pumping.
Change in displacement rule such as Fig. 5 of oil cylinder piston, the trip map of piston is measured for Zhejiang University Huang Qianchun, and Lv Pengmin is real
Testing room, to have measured piston rod strain signal as shown in Figure 6, it can be seen that stablizing delivery phase, approximation is at any time for piston displacement
Linear change, speed are constant, and in pumping beginning and commutation phase, it is not linear, speed that piston displacement, which changes with time,
The trend for accelerating and slowing down can be presented, thus, it is possible to obtain the variation diagram shape of concrete intensity as shown in fig. 7,
Pumping incipient stage concrete intensity accelerates from 0 to a steady state value, is stablizing delivery phase, concrete intensity is one
Steady state value, commutation phase concrete intensity slow down be 0, it is possible to the mathematical model shown in formula (4) come indicate speed with
The variation of time, speed time history plot are as shown in Figure 7.
WhereinQ is concrete discharge capacity, unit m3/ h, r are the radius of pipeline.(-t2,-t4) add for piston
Speed pushes concrete to the time steadily pushed, (t1,t2) it is buffer piston deceleration time, (t2,t3) it is distributing valve commutating period
Half.
V (t) is write as an expression formula with Fourier expansion formula
Wherein a0、an、bnIt calculates as follows
Then speed V expression formula is
2.2.3 pressure loss dynamic change model solves
V after V and derivation is substituted into above-mentioned fluid motion equation (3), pressure p calculation formula can be obtained
The pressure of concrete cylinder pumping outlet the losing along stroke pressure in straight pipeline flowing that include it, bend pipe, Taper Pipe,
The local resistance loss and gravity losses of the attachmentes such as junction are ground according to the experiment of black rock show Jie of Japanese scholars et al. and theory
Study carefully, the pressure loss at bend pipe and Taper Pipe can be equivalent to the multiple that unit length straight tube loses along stroke pressure, then concrete cylinder
Outlet pressure is
Wherein x is length of straight pipe, and y is the equivalent length of straight pipe of bend pipe, and z is the equivalent length of straight pipe of Taper Pipe, and w is that other are attached
The equivalent length of straight pipe of part, l, m, n are respectively the number of bend pipe, Taper Pipe and other attachmentes.
3. pumping pressure calculated examples
With reference in the laboratory Chang An University Lv Pengmin, Yang Xiaogan and Central South University's Zhang great Qing research paper pipe parameter,
The conditions such as pumping system parameter, experiment condition, experiment condition as shown in figure 8, the flow 150l/min frequency 0.296Hz period be
3.38s t1=0.8, t2=1.69, t3=0.7, discharge capacity 80m3/ h, r=0.0625m, slump S=180mm.With above-mentioned
Concrete duct nonstationary flow Calculation of pressure loss model only considers the calculating of straight pipeline pressure loss dynamic change, calculates
Dynamic change result such as Fig. 9 of the unit length pressure loss, pressure is in cyclic fluctuation, from size, unit length pressure
The mean value of loss be 0.0166MPa, empirical equation calculate unit length pressure loss size be 0.0172MPa can such as formula (12)
Know mathematical model mean value that derived pressure loss dynamic change calculates and empirical equation size calculated very close to；From pressure
It is seen in power variation, starts to accelerate push concrete stage, i.e. speed ascent stage in piston, pressure has an impact, in piston
Steady push concrete stage, i.e. constant velocity stage, pressure also slow down in piston close to a steady state value and reach stroke by smooth change
At maximum and commutation, pressure is then reduced rapidly as close to 0 value.
Main oil pump oil inlet rodless cavity pressure and concrete cylinder pump can be found out from concrete pumping schematic diagram shown in Fig. 4
Send the relationship between outlet pressure, PIntoIndicate rodless cavity inlet pressure, PEvenIndicate that bar is connected to cavity pressure, PIt returnsIndicate rodless cavity
Return pressure, PIt is negativeIndicate the negative pressure that sucking concrete needs, PConcreteIndicate concrete cylinder outlet pressure, f1,a1And f2,a2Respectively
Suffered frictional force and acceleration of motion when for the movement of upper and lower two-piston, can the column two-piston equation of motion it is as follows:
PInto·SRodless cavity-PEvenSRod chamber=PConcreteSConcrete+f1+Ma1 (13)
PEvenSRod chamber-PIt returns·SRodless cavity=PIt is negativeSConcrete+f2+Ma2 (14)
It is added to obtain PInto·SRodless cavity-PIt returnsSRodless cavity=PConcrete-PIt is negativeSConcrete+f1+f2+M(a1+a2) (15)
P when uniform motionInto·SRodless cavity-PIt returnsSRodless cavity=PConcrete-PIt is negativeSConcrete+f1+f2 (16)
P when pumping idle runningIt is empty·SRodless cavity-PIt returnsSRodless cavity=f1+f2 (17)
Equation when by idle running substitutes into uniform motion equation, and concrete cylinder outlet pressure and oil inlet oil cylinder can be obtained
The relationship of pressure
It can be seen that oil inlet oil cylinder working-pressure and concrete cylinder outlet pressure are in a linear relationship, can be indicated with formula (18)
PInto=aPConcrete+b (19)
Wherein
Concrete cylinder pumps outlet pressure such as formula (11), can be rewritten as formula (20), PIt is singleFor unit length straight pipeline pressure damage
It loses
PConcrete=a2PIt is single+b2, a2=x+ly+mz+nw, b2=ρ gh (20)
Then main oil pump oil inlet oil cylinder working-pressure PInto=aPIt is single+ b, a=a1a2, b=a1b2+b1 (21)
By formula (21) it is found that main oil pump oil inlet oil cylinder working-pressure linear pass approximate with the unit length straight tube pressure loss
System, in the paper of the laboratory Lv Pengmin outflow main oil pump inlet pressure variation empirical curve such as Figure 10 institute when being 150l/min
Show, before calculate to obtain the unit length pressure loss such as Fig. 9, it can be seen that empirical curve is approximate with unit length pressure curve linear
Relationship works as a=830, b=1 × 106When, it calculates main oil pump pressure curve such as Figure 11 and empirical curve trend is coincide preferably.
4. conclusion
1) concrete pumping oil cylinder replaces pump concrete, flows concrete in delivery pipe for nonstationary flow, coagulation
Native pipeline stream is close with the flow behavior of bingham body in the duct, the flowing of concrete can be regarded as make in the duct it is non-fixed
The plug flow of normal laminar motion, speed and pressure do not change on same cross section with the variation of radius.
2) according to concrete pumping system pumping theory, learn that concrete intensity is the waveform of a cycle variation,
Piston starts to push and acceleration and deceleration motion is presented in commutation phase, steady to push stage approximation uniform motion, establishes speed
Mathematical model has found out the mathematical model of pressure loss dynamic change.
3) by a calculated examples obtain concrete pressure lose dynamic change results, it can be seen that the pressure loss
In cyclically-varying, mean value and empirical equation calculate gained size and approach, and can generate periodically in pump truck commutation phase pressure
Fluctuation, shows the concrete compression shock that UNSTEADY FLOW state generates pump truck in pipeline.
4) concrete cylinder outlet pressure and main oil pump oil inlet rodless cavity pressure are in a linear relationship, and concrete cylinder outlet pressure
Power and the approximately linear relationship of the unit length straight tube pressure loss, it can be deduced that the change curve of main oil pump outlet pressure, with reality
It tests curve to compare, coincide preferably with the curvilinear trend of experiment institute's measuring pressure variation, it is dynamic to demonstrate the established pressure loss
The correctness of state variation computation model.
Finally, it is stated that the above examples are only used to illustrate the technical scheme of the present invention and are not limiting, although referring to compared with
Good embodiment describes the invention in detail, those skilled in the art should understand that, it can be to skill of the invention
Art scheme is modified or replaced equivalently, and without departing from the objective and range of the technical program, should all be covered in the present invention
Scope of the claims in.
Claims (3)
1. pump concrete nonstationary flow pumping pressure dynamic analysing method, it is characterised in that: method includes the following steps:
S1: the rheological properties of pump concrete are analyzed；
S2: the pressure loss dynamic change formula of concrete in the duct is derived.
2. pump concrete nonstationary flow pumping pressure dynamic analysing method according to claim 1, it is characterised in that: institute
State step S1 specifically:
Normal concrete is the Bingham body in non-newtonian fluid, and constitutive equation isτ0For Limiting shear stress, ηp
For plastic viscosity, when shearing stress is less than Limiting shear stress, internal fluid is without relative motion, when shearing stress is greater than Limiting shear stress
τ0When, fluid ability setting in motion, shearing stress is changed linearly with shear strain rate, slope ηp；
According to drilling fluid mechanics, when judging that Bingham body is flowed in the duct for laminar flow or turbulent flow, referring to Newtonian fluid
Judgment method works as Reynolds numberIn range, fluid flowing is laminar flow；Reynolds number Re≤2320 show that pumping is mixed
The flow regime of solidifying soil in the duct is laminar flow；
When Bingham body makees permanent laminar motion in the duct, known according to Bingham body constitutive equation, as maximum shear stress τw<
τ0When, concrete does not generate flowing, is stationary state；As maximum shear stress τw> τ0When, in τ≤τ0, i.e. R≤R0In range, stream
Internal portion's particle is without relative motion, and the movement velocity of fluid is identical, in τ >=τ0, i.e. R >=R0In range, shearing stressThe flowing velocity curve of fluid parabolically form, speed is when Steady FlowR=R0Shi Sudu is maximum, and speed is 0 at tube wall；
The flowing of concrete in the duct is regarded as plug flow, i.e., speed is all identical at any radius on a section, pipeline
The interior the same flow forward of concrete statuary column plug, the surface only contacted with inner wall of the pipe there are frictional force, inside concrete without
Frictional force.
3. pump concrete nonstationary flow pumping pressure dynamic analysing method according to claim 2, it is characterised in that: institute
State step S2 specifically:
S21: pressure loss empirical equation is derived；
Calculation of pressure loss formula are as follows:
ΔpH--- pressure loss when concrete flows in unit length horizontal pipe, unit Pa/m；
K1--- adhesion coefficient, unit Pa, K1Calculating formula be K1=300-S, S are the slump of concrete；
K2--- velocity coeffficient, unit Pas/m, K2Calculating formula be K2=400-S；
The radius of R--- concrete flow duct, unit m；
--- distribution valve of concrete pump switching time and piston push the ratio between concrete time；
The mean flow rate of V--- concrete, unit m/s, calculating formula areQ is the discharge capacity of concrete, unit m3/h；
α2--- the ratio between radial pressure and axial compressive force, normal concrete generally take 0.9；
S22: pressure loss dynamic change computation model is derived
(1) the straight pipeline pressure loss is analyzed
The flowing of concrete in the duct is approximately plug flow, and on a cross section of pipeline, speed and pressure is not with half
Diameter variation, analyzes the straight pipeline pressure loss, and the concrete that taking length is dx, radius is pipe radius r is control volume, by along pipe
The pressure of road length direction, the frictional force along tube wall and gravity, obtain fluid motion equation are as follows:
F is coefficient of friction in formula, is expressed as f=K1+K2V, K1And K2Calculating and pressure loss empirical equation in calculation formula one
It causes；After f is substituted into, the equation of motion is solved
If concrete flowing velocity can be obtained to change with time relationship, the time history curve of pumping pressure can be found out；
(2) foundation of rate pattern
According to the principle of concrete pump truck pumping system, when being pumped by, cylinder rod chamber connection, from rodless cavity fuel feeding, when one
When a oil cylinder piston reaches range, connects the S pipe valve of concrete cylinder and master cylinder while commutating, main oil pump is oily to another
Oil supply cylinder, the corresponding cylinder full of concrete continue pump concrete, the rule periodically pumped are presented；
Stablizing delivery phase, approximation is changed linearly at any time for oil cylinder piston displacement, and speed is constant, is started and is changed in pumping
To the stage, piston displacement change with time be not it is linear, the trend for accelerating and slowing down can be presented in speed, obtain
The variation of concrete intensity accelerates to a steady state value from 0 in pumping incipient stage concrete intensity, conveys rank stablizing
Section, concrete intensity be a steady state value, commutation phase concrete intensity slow down be 0, the mathematical model shown in formula (4) come
Indicate that speed changes with time:
WhereinQ is concrete discharge capacity, unit m3/ h, r are the radius of pipeline；(-t2,-t4) it is that piston acceleration pushes away
Send concrete to the time steadily pushed, (t1,t2) it is buffer piston deceleration time, (t2,t3) it is the one of distributing valve commutating period
Half；
The expression formula of V (t) Fourier expansion formula
Wherein a0、an、bnIt calculates as follows
Speed V expression formula is
(3) pressure loss dynamic change model solves
V after V and derivation is substituted into above-mentioned fluid motion equation (3), obtains pressure p calculation formula
The pressure of concrete cylinder pumping outlet includes its losing along stroke pressure in straight pipeline flowing, in bend pipe, Taper Pipe, connection
The local resistance loss and gravity losses of the attachmentes such as place, the pressure loss at bend pipe and Taper Pipe are equivalent to unit length straight tube along journey
The multiple of the pressure loss, then concrete cylinder outlet pressure be
Wherein x is length of straight pipe, and y is the equivalent length of straight pipe of bend pipe, and z is the equivalent length of straight pipe of Taper Pipe, and w is other attachmentes etc.
The length of straight pipe of effect, l, m, n are respectively the number of bend pipe, Taper Pipe and other attachmentes.
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