CN1076027A - Capillary viscosity is taken into account the assay method of liquid viscosity - Google Patents

Abstract

Capillary viscosimeter of the present invention comprises: kapillary; The sample stopple coupon that is communicated with this kapillary one end; With the sample-sucking device that the kapillary other end is communicated with, lay respectively at the kapillary two ends and be in two liquid pools of sample stopple coupon and sample-sucking device inboard; The differential type drive pressure generating means that links to each other with two liquid pools, this device can be differential air-capacitor chambers, also differential type elastic membrane accumulator; The microcomputer that is installed in the differential pressure pickup on this differential type drive pressure generating means and is attached thereto; Cleaning that is connected with capillary pipeline and drying device; And the valve and the pipe system that make whole viscosity meter and isolated from atmosphere and carry out measurement operation.

Description

Capillary viscosity is taken into account the assay method of liquid viscosity

The invention belongs to a kind ofly, be meant a kind of differential drive-type capillary viscosimeter and assay method thereof especially by the pressure of measuring fluid and proving installation and the assay method thereof that flow predicts its viscosity.

Capillary viscosimeter is widely used in medicine and industrial owing to its principle is simple, reliable.In capillary viscosimeter, stress τ and shear rate γ measure by drive pressure P and flow Q respectively.These physical quantitys are subject to the influence of all factors and are difficult to accurate measurement under low tangent condition, thereby have influenced the lower limit that this method can be surveyed shear rate.Difficulty is mainly from the following aspects:

1. capillary influence, the drive pressure at kapillary two ends is very low under the low tangent condition.With diameter of phi=1mm, the kapillary of long L=200mm is an example, and the mobile required drive pressure that makes the fluid of viscosities il=4 centipoises produce γ=2(1/S) therein only is 0.6mmH ₂O.The additional pressure that this produces much smaller than similarity condition lower surface tension force.To this, solution is to adopt the big direct current liquid pool of symmetry to reduce the additional pressure of capillary outlet place gas-liquid meniscus preferably.And the capillary outlet structure of some other asymmetry (adopting liquid-solid and liquid-gas interface or the like respectively as L type pipe, one-sided horn-type opening, two side outlets) is all not satisfactory.Though large diameter outlet liquid pool has overcome surface tension preferably, introduced the problem of gravity potential head disturbance simultaneously again.Shear flow makes the liquid level relative relief of both sides liquid pool, and consequent gravity potential head is a kind of disturbing factor to the detection of drive pressure.Can suppress this interference though increase radius of liquid pool, the many occasions (as blood) that are increased in of consequent sample size are to be difficult to accept.

2. drive pressure generator, a kind of morning, well known method was to utilize the gravity potential head of measured medium itself to drive.Two kinds of forms of constant voltage and transformation are wherein arranged.The former obviously is not easy to the flow of non-Newtonian fluid, and the latter then is difficult to the parameter of accurately measuring continuously and the occasion that can not be used to have relatively high expectations because kapillary liquid level itself is one again.Though existing a kind of method of determining to drive potential head by the hydrostatic pressing at the bottom of the driving tube pipe, but because used sensor with atmosphere as a reference, make the tension force additional pressure in two exits of kapillary have identical direction, thereby make capillary problem become more complicated.For overcoming above-mentioned shortcoming, propose recently to utilize elastic energy storage to form the new method of drive pressure.This method is determined drive pressure by the strain to energy storage elastic body itself.Compare with the gravity potential head, elastic strain is the physical quantity of easily measuring.And at present, the energy storage elastic body adopts elastic membrane and air-capacitor complex to form more, and all adopts the form of one-sided driving, that is to say that a termination elastic body capillaceous is introduced drive pressure, and the other end then opens at atmosphere.As shown in Figure 4, its basic composition comprises: kapillary 31, stopple coupon 32, sample-sucking device 33, liquid pool 34,35, energy storage elastic body 36, this asymmetrical drives structure have following shortcoming: a. to be subject to the influence that atmospheric pressure rises and falls, and room pressure is easy to reach several mmH in strong wind weather ₂The fluctuating of O, thereby will obviously influence the accuracy that drive pressure is measured.B. the air-capacitor of one-sided sealing very easily is subjected to the influence of temperature fluctuation owing to the good heat expansion of gas makes its interior pressure.

The purpose of this invention is to provide a kind of have symmetrical structure and with the differential drive-type capillary viscosimeter of isolated from atmosphere.

Another purpose of the present invention provides a kind of differential air-capacitor formula capillary viscosimeter with said structure characteristics.

Another object of the present invention provides a kind of differential elasticity membrane type capillary viscosimeter with said structure characteristics.

A further object of the present invention provides a kind of above-mentioned capillary viscosimeter that utilizes, and measures the pressure variation of liquid and flow and predicts the liquid viscosity assay method of its viscosity.

Capillary viscosimeter of the present invention comprises: kapillary; The sample stopple coupon that is communicated with this kapillary one end; With the sample-sucking device that the kapillary other end is communicated with, lay respectively at the kapillary two ends and be in two liquid pools of sample stopple coupon and sample-sucking device inboard; The differential type drive pressure generating means that links to each other with two liquid pools, this device can be differential air-capacitor chambers, also can be differential type elastic membrane accumulators; The microcomputer that is installed in the differential pressure pickup on this differential type drive pressure generating means and is attached thereto; Cleaning that is connected with capillary pipeline and drying device; And the valve and the pipe system that make whole viscosity meter and isolated from atmosphere and carry out measurement operation.

The advantage of capillary viscosimeter of the present invention and outstanding effect are:

Since the generation of pressure reduction and testing process all with the complete isolation of atmosphere under carry out, thereby overcome atmospheric pressure and risen and fallen tonometric influence.

2. symmetrical structure can be cancelled out each other capillary influence fully, has improved accuracy of detection.

3. the differential structure of symmetry makes the remaining air-capacitor of two liquid pools or the heat expansion of the gas in the driving air-capacitor that good self compensation effect be arranged fully, thereby has improved the thermal stability of detection system.

Below, be described with reference to the accompanying drawings embodiments of the invention.

Fig. 1 is the structural representation of first embodiment of the invention.

Fig. 2 is the structural representation of second embodiment of the invention.

Fig. 3 is the structural representation of third embodiment of the invention.

Fig. 4 is existing one-sided drive-type capillary viscosimeter synoptic diagram.

First embodiment of capillary viscosimeter of the present invention, as shown in Figure 1, comprise: kapillary, the sample stopple coupon, sample-sucking device, liquid pool, the drive pressure generator, valve and pipeline, measurement mechanism and microcomputer, and the cleaning of pipe system and drying device, it is characterized in that: described drive pressure generator is a symmetric difference dynamic formula device, one end of kapillary 1 is communicated with stopple coupon 2, the other end is communicated with sample-sucking device 3, inboard at stopple coupon 2 and sample-sucking device 3, kapillary 1 two ends connect two liquid pools 4 and 5 symmetrically, two liquid pools 4 and 5 communicate with two pressure chambers 6 and 7 of described differential type drive pressure generator respectively, described differential type drive pressure generator is differential air-capacitor, has two air-capacitor chambers 61 and 71; On this differential type drive pressure generator pressure transducer 8 is housed, sensor 8 links to each other with microcomputer 9; In pipe system, also be connected to valve, mainly be provided with the valve 10 that is contained in 2 in kapillary 1, stopple coupon, the valve 11 between sample-sucking device 3 and liquid pool 5, the valve 12 between air-capacitor chamber 7 and liquid pool 5, the valve 13 between air-capacitor chamber 6 and liquid pool 4.Wherein, valve 10-valve 13 can have three kinds of mode of communicating, is designated as I-II, II-III and I-III.

In addition, described cleaning device comprises: washing lotion suction pipe 15, and it communicates with kapillary 1 by T-valve 10, and water pump 16 and waste liquid vent pipe 17 join with the other end capillaceous; Described drying device comprises the two-port valve 22 on two-port valve 21, gas bag 20 and liquid pool 5 connecting pipelines on instrument air dryer 18, air pump 19, gas bag 20, gas bag 20 and liquid pool 4 connecting pipelines that link to each other in turn.

System work process is as follows:

1. suction sample: valve is left to as upper/lower positions valve 10(I-II), valve 11(II-III), valve 12(I-II) and, valve 13(II-III), valve 21 is disconnected, and valve 22 is disconnected.Having no progeny starts sample-sucking device 3 with sample suction liquid pool 4,5 and kapillary 1, and liquid level in two liquid pools 4,5 is adjusted to the par height.

2. add negative pressure in advance: valve is left to as upper/lower positions valve 10(II-III), valve 11(I-II), all the other valves are constant.Start sample-sucking device 3 then, 7 to extract volumes out be that a gas of △ V makes air-capacitor chamber 7 form negative pressure from the air-capacitor chamber.

3. adding malleation in advance: valve is left to as upper/lower positions valve 11(II-III) all the other valves are constant.Start sample-sucking device 3 then, the gas of the △ V volume that obtains in 2 is injected air-capacitor chambers 6 through liquid pool 5-kapillary 1-liquid pool 4, make air-capacitor chamber 6 form malleations.

4. test: valve is left to as upper/lower positions valve 11(I-III), all the other valves are constant, and at this moment the sample in the kapillary 1 produces shear flow under the driving of two air-capacitor chambers, 6,7 positive and negative pressures.Detect and write down the change procedure of this pressure reduction with computing machine 9, and, calculate the viscosity number under each shear rate according to the algorithm that (12) formula provides.

5. clean: valve is left to as upper/lower positions valve 11(I-II), valve 13(I-II), all the other valves are constant, start water pump 16 then, and under the cooperation of valve 10 respectively from sample and bottle for handling liquid toilet or cosmetic substance the suction washing lotion the whole pipelines and the liquid pool of sample stream warp washed.

6. dry: as valve to be left to as upper/lower positions valve 10(II-III), valve 21 is logical, and valve 22 leads to.Then the pressurized air after the dried is injected liquid pool and capillary channel, dry up raffinate wherein, for next one experiment is got ready.

The method that is noted that steps such as can realizing sampling of the present invention, pressurization, measurement and cleaning is not to be circumscribed.Said method is one of possible embodiment.For example also can adopt other the connecting line and the configuration of valve position, put upside down pressurization sequence (after adding malleation earlier, adding negative pressure) and at the straightforward pipeline of the low flow resistance of cross-over connection between liquid pool to quicken between liquid pool liquid level equilibrium process and convenient clean or the like.

Below provide the computing formula and the setting method that related parameter is arranged of differential full appearance formula capillary viscosimeter.

Consider the long L that is, radius is the kapillary of R.Note is respectively μ (r) apart from flow velocity, shearing stress and the shear rate at axle r place, τ (r) and

(r), the drive pressure at kapillary two ends is P, and then the constitutive equation of measured medium can be expressed as:

＝f（τ）＝-du/dr ……（1）

Utilize the stocks formula:

τ（r）＝pr/2L ……（2）

Can will manage interior flow Q f(τ) expression, that is:

$\mathrm{Q=}\frac{{\mathrm{<figure-callout\; id="3"\; label="\pi R"\; filenames="921142773\_DRIMG1.png,921142773\_DRIMG2.png"\; state="\{\{state\}\}">\pi R</figure-callout>}}^3}{{\mathrm{<figure-callout\; id="3"\; label="\tau "\; filenames="921142773\_DRIMG1.png,921142773\_DRIMG2.png"\; state="\{\{state\}\}">\tau </figure-callout>}}^3{}_{\omega }}{\&Integral;}_0^{{\tau }_{\omega }}\mathrm{f(\tau )\tau \; d\tau \; \dots \dots (3)}$

τ wherein _ωBe wall shear stress.Have according to (2):

τ _ω＝τ（r）| _r＝R＝PR/2L ……（4）

With (3) to τ _ωDifferentiate can solve f(τ _ω) be: ${\mathrm{f\; (\tau }}_{\omega }\mathrm{)=}\frac{{\tau }_{\omega }}{{\mathrm{\pi R}}^3}\mathrm{(3Q+}\frac{\mathrm{dQ}}{{\mathrm{d\; \tau }}_{\omega }}\mathrm{)\; \dots \dots (5)}$

Note η _aBeing the apparent viscosity of non-Newtonian fluid, is research object if get the fluid at wall place, η _aCan

(5) substitution (6) arrangement can be got:

η wherein _AnWith

_{ω n}Be respectively measured medium be used as apparent viscosity and the wall shear rate that the Newtonian fluid processing is tried to achieve, can be expressed as by definition:

(7) to be measured in (8) is P and Q.Wherein P can directly be recorded by the differential pressure pickup of striding air-capacitor, and Q can utilize the restriction relation of equation of gaseous state to be derived by P.

Note V ₀, P ₀Be respectively the initial volume and the pressure of air-capacitor under the equilibrium condition, △ T and △ V are respectively temperature and the dilatation on the equilibrium state basis.Can get according to equation of gaseous state:

$\mathrm{P=-}\frac{{\mathrm{2P}}_0}{V_0}\mathrm{△V+}\frac{{\mathrm{2P}}_0\mathrm{·\; △V}}{{\mathrm{T\; ·\; V}}_0}\mathrm{△\; T\; \dots \dots (9)}$

Second expression temperature on equation the right is to the influence of drive pressure, and discuss its effect back again, thinks here that this is enough little and ignores.(9) both sides to time t differentiate, can be got:

Note V _pBe the output voltage of pressure-detecting device, it and pressure reduction P differ from a constant at most, remember that it is K, then has: V _p=KgP ... (11)

(10), (11) substitution (7), (8) can be got:

(12) be the fundamental formular of differential air-capacitor energy storage capillary viscosimeter.All constant coefficients are natural constant or geometric constant except that K.

(9) in, (the 2P in second ₀△ V)/(T V ₀) be the temperature coefficient of pressure reduction P.Can be by reducing △ V(or improving the symmetry of air-capacitor) or increase air-capacitor volume V.Reduce △ V/V ₀Ratio, to reach the temperature stability of hope.

Non-Newtonian liquids such as blood have thixotropy.For the change procedure that obtains stable measurement result pressure reduction P should carry out enough slowly, so that the time-varying process of thixotroping can fully be finished.Can get pressure reduction with Newtonian fluid as the mechanical model of sample and satisfy following dynamic process:

TP+P＝0 ……（13）

Wherein

It is the time constant of pressure reduction pressure leak process.Can determine required air-capacitor volume V with reference to this relational expression according to desired time constant T and viscosity measurement scope during enforcement ₀

As if remembering that ρ, A are respectively the weight density and the liquid pool sectional area of sample, then can getting the additional gravity potential head △ P that when drive pressure is P, produces between two liquid pools be because of the liquid level difference according to (9):

$\mathrm{△P=}\frac{{\mathrm{\rho V}}_0}{{\mathrm{2AP}}_0}\mathrm{P\; \dots \dots (14)}$

During detection, available this relational expression of the P value of actual measurement is proofreaied and correct.The pressure reduction P ' that proofreaies and correct through the gravity potential head is:

$\mathrm{P\; \text{'}\; =(1-}\frac{{\mathrm{\rho V}}_0}{{\mathrm{2AP}}_0}\mathrm{)P\; \dots \dots (15)}$

Above algorithm all can realize with microcomputer, and can be designed to the form of recursion, to improve counting yield.All the detection of instrument and control also can realize under computer management, thereby can realize the purpose of detection automatically.

Second embodiment of the invention as shown in Figure 2, its basic structure is identical with first embodiment, difference is: be respectively equipped with elastic membrane 42 and 52 on the liquid pool 4 and 5, post foil gauge on this elastic membrane 42 and 52; Installing one peristaltic pump 25 between two liquid pools 42 and 52; On kapillary 1, installing one valve 26 between two liquid pools 42 and 52; The described differential pressure pickup that is connected between two liquid pools 42 and 52 is a hydraulic pressure transducer 82.

Third embodiment of the invention as shown in Figure 3, its basic structure is identical with second embodiment, difference is: two liquid pools 4 and 5 upper end are connected with air chamber 43 and 53 respectively, elastic membrane 44 and 54 respectively are equipped with in 2 air chambers 43 and 53 top, post foil gauge on the elastic membrane 44 and 54, tipping has differential pressure pickup 8 between the 2 air chambers 43 and 53.

The operating process of second and third two embodiment is identical, and its key step is as follows:

1. utilize aspirator 3 that sample is sucked liquid pool 4 and 5, and adjust the liquid level of two liquid pools consistent.

2. shut-off valve 10 and valve 26 start peristaltic pump 25, and sample is evacuated to another liquid pool from a liquid pool, make between two liquid pools and produce pressure reduction.

3. open valve 26, make sample stream cross kapillary 1, and return to original two pit level consistent balance state, in this process, detect and write down the change procedure of pressure reduction between two liquid pools by differential pressure pickup 8 or 82.

The computing method of second and third two embodiment, basic process is identical with embodiment one, can be according to the elastic modulus of used elastic membrane to derive with previous embodiment one similar derivation, these computing method are delivered on " clinical hemorrheology " to some extent.

Claims (5)

1, a kind of capillary viscosimeter, comprise: kapillary, the sample stopple coupon, sample-sucking device, liquid pool, the drive pressure generator, valve and pipeline, measurement mechanism and microcomputer, and the cleaning of pipe system and drying device, it is characterized in that: described drive pressure generator is a symmetric difference dynamic formula device, one end of kapillary 1 is communicated with stopple coupon 2, the other end is communicated with sample-sucking device 3, inboard at stopple coupon 2 and sample-sucking device 3, kapillary 1 two ends connect two liquid pools 4 and 5 symmetrically, two liquid pools 4 and 5 communicate with two pressure chambers 6 and 7 of described differential type drive pressure generator respectively, described differential type drive pressure generator is differential air-capacitor, has two air-capacitor chambers 61 and 71; On this differential type drive pressure generator pressure transducer 8 is housed, sensor 8 links to each other with microcomputer 9.

2, capillary viscosimeter as claimed in claim 2 is characterized in that: described differential type drive pressure generator is differential air-capacitor, and its two pressure chamber 6 and 7 is two air-capacitor chambers 61 and 71.

3, capillary viscosimeter as claimed in claim 2 is characterized in that: described differential type drive pressure generator is an elasticity membrane type accumulator, is respectively equipped with elastic membrane 42 and 52 on described liquid pool 4 and 5, posts foil gauge on this elastic membrane 42 and 52; Installing one peristaltic pump 25 between two liquid pools 42 and 52; On kapillary 1, install a valve 26 in exit between two liquid pools 42 and 52 near arbitrary liquid pool; The described differential pressure pickup that is connected between two liquid pools 42 and 52 is a hydraulic pressure transducer 82.

4, capillary viscosimeter as claimed in claim 2, it is characterized in that: described differential type drive pressure generator is elastic membrane and air-capacitor combined type accumulator, upper end in described two liquid pools 4 and 5 is connected with air chamber 43 and 53 respectively, elastic membrane 44 and 54 respectively are equipped with in 2 air chambers 43 and 53 top, post foil gauge on the elastic membrane 44 and 54, tipping has differential pressure pickup 8 between the 2 air chambers 43 and 53.

5, a kind of viscosity measurement is characterized in that utilizing as claim 1,2,3,4 described capillary viscosimeters and measures drive pressure P and flow Q, thereby draws newton's apparent viscosity η of fluid to be measured, the steps include:

(1) utilizes aspirator 3 that sample is sucked liquid pool 4 and 5, and adjust the liquid level of two liquid pools consistent;

(2) make in two pressure chambers 6 and 7 of differential type drive pressure generator and form pressure reduction P;

(3) under the driving of described pressure reduction P, sample stream is crossed kapillary 1, and returns to two liquid pools 4 and the initial equilibrium state of 5 liquid levels, detects and write down the variation of pressure reduction P in this process;

Utilize following fundamental formular to calculate:

P＝K·△V ……（1）

＝K·Q ……（2）

${\eta }_{\mathrm{an}}=\frac{{\mathrm{\pi R}}^{4}P}{\mathrm{8LQ}}\mathrm{\dots \dots (3)}$

Wherein: P-differential pressure pickup institute measuring pressure value

Flow in the Q-kapillary

The elasticity coefficient of K-energy-accumulating medium

The volume change of △ V-energy-accumulating medium

η _AnNewton's apparent viscosity of-fluid to be measured

The R-capillary radius

The L-capillary pipe length.

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