CN100529711C - Method for testing performance of micro-dimension labyrinth type unit flow passage waterpower - Google Patents

Abstract

A kind of test method of the micro-scale maze unit runner hydraulic performance which makes the measuring experiment part cut-in to the pipe of the experiment equipment and then measures the export-import pressure difference Delta P after the water through the maze runner adopting the pressure difference transducer with the high degree of accuracy gradation and then determines the local lossDelta P of the export-import by utilizing the two different test piece length measurement method and then gets the actual pressure loss Delta P runner of the maze runner; At the same time measures the flow mass M through the maze runner in unit time by the precise electronic balance then inverts it into the volume flow Q through the formula. The real-time data measured by two devices is input to the computer and displayed and storage by the high precise A/D transfer card in order to ensure the synchronism and accuracy of the data acquisition.

Description

A kind of method for testing performance of micro-dimension labyrinth type unit flow passage waterpower

Technical field

The present invention relates to a kind of unit flow passage hydraulic performance method of testing, particularly a kind of method for testing performance of micro-dimension labyrinth type unit flow passage waterpower.

Background technology

Microscale fluid mechanics is the research field between classical macrofluid mechanics and Micromechanics, mainly studies characteristic dimension at the fluid flowing law of mm to the mu m range.Labyrinth runner under the microscale is because its border complications can make fluid get muddled, thereby reduced this characteristic of susceptibility of pressure versus flow amount and be used widely, the measurement of its unit flow passage hydraulic performance parameter has great role to research microfluid characteristic and flow passage structure characteristic thereof.The labyrinth type douche is exactly an exemplary, its channel size is mostly in the mm level, the douche runner is generally formed by the unit combination of some same shapes (as triangle, trapezoidal), selects the cellular construction and the unit number of different parameters according to the designing requirement of douche flow.Thereby the design of cellular construction and the selection of quantity will influence the performance of douche to a great extent.In the computing formula of its flow and working head, coefficient of flow k is all relevant with the structure of runner with fluidised form index x.At present, the labyrinth type douche is carried out analysis of experiments mostly draw two relations between the performance parameter, be the flow Q of douche and the working head H in the pipeline, because water can think atmospheric pressure at the pressure at emitter outlet place, so the time working head H generally be approximately current on the engineering through the pressure drop Δ P behind the labyrinth flow-path _Runner, but if come accurately to study the hydraulic performance parameter of labyrinth flow-path theoretically, then the two can not be replaced.Because working head H has comprised the pressure drop Δ P of current through runner _RunnerThe local loss of import and export Δ P with runner _Decrease,, import and export local loss Δ P for the flow field problem of this small runner _DecreaseCan not ignore.

To the research of this content, there is the part scholar once to propose a kind of hydraulic performance parameter test method based on the douche runner, promptly channel size is amplified several times on year-on-year basis, thereby measure current pressure drop or Flow Field Distribution rule in the runner according to the principle of similitude.The main cause that they adopt this method is because the channel size of douche is small, can't be with pressure tap cloth in the middle of the runner of reality, so with its processing and amplifying.But (irrigation technique of Q=0.5～3L/h), the flow passage structure size of douche mostly is in below the 1mm, belongs to the fluid channel category nowadays more and more to advocate low discharge.Thereby the way of front just ignored some basic problems in the microfluidic theory, will influence fluid to a greater degree as the surfaceness of runner and flow etc.

Summary of the invention

One object of the present invention is to overcome the shortcoming of above-mentioned prior art, and a kind of method for testing performance of micro-dimension labyrinth type unit flow passage waterpower is provided.

The hydraulic performance method of testing of microscale dimension labyrinth type unit flow passage of the present invention is: at first design two cross section of fluid channel shapes, the first straight channel test block 1 all the same with size and the flow channel length of the second straight channel test block, 2, the first straight channel test blocks 1 and the second straight channel test block 2 and be respectively L ₁And L ₂, L ₂＞L ₁Adopt same joint, respectively the first straight channel test block 1 and the second straight channel test block 2 are inserted in the device for testing micro-dimension labyrinth type unit flow passage waterpower performance, this device for testing micro-dimension labyrinth type unit flow passage waterpower performance comprises gas cylinder and the airtight water tank that is connected with gas cylinder, between gas cylinder and airtight water tank, also be provided with reduction valve, the outlet of airtight water tank is in series with the spherical valve that is interconnected successively by pipeline, filtrator, needle valve, glass rotameter and labyrinth flow-path test block, exit at the labyrinth flow-path test block is provided with conical beaker, conical beaker is placed on by on A/D transition card and the Precision Electronics Balance that computing machine is connected, also is parallel with the differential pressure transmitter that links to each other with computing machine by threeway and A/D transition card on the labyrinth flow-path test block; Measure pressure drop Δ P under some same flow values by being connected on differential pressure transmitter on the labyrinth flow-path test block ₁With Δ P ₂, the local loss of the import and export sum that connects test runner interface so is:

So, the pressure drop that produces by runner:

Δ P _Runner=Δ P-Δ P _Decrease

Δ P _RunnerBe the water channel total pressure drop;

By the flow theory Reynolds number of fluid as can be known:

$\mathrm{Re}=\frac{\mathrm{\ρ}\·\stackrel{\‾}{u}\·D_h}{\mathrm{\μ}}=\frac{\mathrm{\ρ}\·Q\·D_h}{\mathrm{\μ}\·A_c}$

In the formula, ρ is the density of fluid; U is the average velocity of fluid; D _hEquivalent diameter for runner; μ is the kinetic viscosity of fluid; Q is a volumetric flow rate, measures a certain section time labyrinth flow-path test block by Precision Electronics Balance and flows into the mass M of the water in the conical beaker [10], thereby be converted into volume flow Q; A _cArea of section for runner;

Then according to the drop formula of classical theory:

$\mathrm{\ΔP}=f\frac{l}{D}\frac{\mathrm{\ρ}{\stackrel{\‾}{u}}^2}{2}$

Δ P is the runner pressure drop

Because runner is a labyrinth type, so adopt equivalent darcy coefficient of frictional resistance to replace along the journey coefficient of frictional resistance:

In the formula, l _cBe the border Center Length of unit flow passage, n is the number of unit flow passage;

As represent the form parameter of labyrinth runner, then equivalent coefficient of friction resistance f with X _cBe exactly the function of X,

f _c＝f(X)

Thereby flow Q and pressure drop Δ P _RunnerBetween relation:

Can obtain the flow of douche according to given flow passage structure and pressure drop numerical value.

Because the present invention is by the mass rate of a certain period of Precision Electronics Balance, this mass rate is converted into volumetric flow rate, the high-low pressure of the differential pressure transmitter by being connected on physical part inlet again, obtain pressure drop Δ P, this method of testing based on unit flow passage, measured parameter is more accurate than method in the past, can work out the influence degree of each physical dimension of runner in view of the above to the hydraulic performance parameter, and return out corresponding relational expression, for the flow passage structure design of labyrinth type douche provides theoretical foundation.

Description of drawings

Fig. 1 is the hydraulic performance parameter test device synoptic diagram of labyrinth type douche unit flow passage of the present invention;

Fig. 2 is the structural representation of labyrinth flow-path test block 9, and wherein Fig. 2 a is its CAD outside drawing, and Fig. 2 b is the CAD sectional view of triangle runner, and Fig. 2 c is the CAD sectional view of trapezoidal runner, and Fig. 2 d is the CAD sectional view of circular arc runner;

Fig. 3 a is the manufacturing process flow diagram of labyrinth flow-path test block, and Fig. 3 b is based on the produced prototype test spare of SL technology;

Fig. 4 is a maze microflow path data acquisition system (DAS) surface chart;

Fig. 5 is the unit fluid channel topology example that the present invention proposes.

Embodiment

The present invention is described in further detail below in conjunction with accompanying drawing.

Referring to Fig. 1, the airtight water tank 3 that the present invention includes gas cylinder 1 and be connected with gas cylinder 1, between gas cylinder 1 and airtight water tank 3, also be provided with reduction valve 2, the outlet of airtight water tank 3 is in series with the spherical valve 4 that is interconnected successively by pipeline, filtrator 5, needle valve 6, glass rotameter 7 and labyrinth flow-path test block 9, in the exit of labyrinth flow-path test block 9 conical beaker 10 is set, conical beaker 10 is placed on by on A/D transition card and the Precision Electronics Balance 11 that computing machine 13 is connected, also is parallel with the differential pressure transmitter 12 that links to each other with computing machine 13 by threeway 8 and A/D transition card on labyrinth flow-path test block 9.

Because the flow in the pipeline of the present invention is less and require pressure stability, so adopt gas cylinder 1 voltage supply, roughly reach the required pressure of test by regulating reduction valve 2, the hydraulic pressure that air pressure will seal in the stainless steel water tank 3 is gone in the pipeline, the aperture of control spherical valve 4 reaches the effect of coarse adjustment flow, requirement with reference to the irrigation water standard, one 200 purpose filtrators 5 are being set to remove anhydrate middle impurity thereafter, insert needle valve 6 afterwards and come the Control Flow accurate adjustment, real-time traffic in the pipeline can roughly be read by glass rotameter 7, then current enter in the labyrinth flow-path test block 9, at last current are collected with a conical beaker 10, measure the flow mass M of a certain period by Precision Electronics Balance 11, thereby be converted into volume flow Q.Respectively the high-low pressure that the current of runner import and export are introduced differential pressure transmitter 12 by connecting pipe is entered the mouth with threeway 8, so just can measure its pressure drop Δ P.The real-time traffic data M of differential pressure value Δ P and electronic scales is all exported in computing machine 13 and is stored by high-precision A/D transition card, with simultaneity and the accuracy of guaranteeing its data acquisition.

Referring to Fig. 2, a is the outside drawing of labyrinth flow-path test piece C AD, and two of test specimen is that pressure is convenient with its amplification; B, c, d are the sectional view of test block, can see in the middle of the test block being labyrinth flow-path by figure, can adopt the runner of various ways, for example triangle, trapezoidal, circular arc or the like.When design labyrinth flow-path test block, all test block joint geometries, size are all the same, equate to guarantee the local losses under its identical operating mode.

Referring to Fig. 3, a is for adopting the technological process of laser curing shaping (SL) manufacturing test part in the Rapid Prototyping technique.The SL method is a kind ofly can automatically, directly, quickly and accurately design philosophy be turned materially the prototype parts with certain function, in all fast shaping technologies, its precision height, surface quality is good, utilization rate of raw materials is nearly 100%, and suitable making has the micro parts of labyrinth.Making on the labyrinth flow-path test block, runner can be designed to triangle, trapezoidal, circular arc type or the like version, do not needing corresponding mould just can create, this be the traditional handicraft method inaccessiable.At first design the cad model of test block with 3D sculpting software, according to common action and angle cad model being carried out gridding handles, promptly generate three-dimensional polyhedral model (STL form), then this form model is imported general RPdata software and carry out entity layering, promptly use series of parallel in the XY plane, cut polyhedral model on Z direction plane at regular intervals, generate hierarchical information, the border of each layer is made up of many little line segments, again hierarchical information is carried out the NC aftertreatment at last, generate the numerical control code of control forming machine motion, aspect data input SL forming machine can be processed the test block prototype, at last test block is cleaned and solidify processing, intact back just can be inserted testing table and test.The test block outside drawing of Fig. 3 b for adopting this processes to come out.

Referring to Fig. 4, the data on flows of the labyrinth flow-path test block of synchronization and differential pressure data can show in this acquisition system in real time.Acquisition method can adopt automatic collection and manually gather two kinds, and collection can set up acquisition time on their own at interval according to system's characteristics automatically.Obtaining of differential pressure value can convert current value to by the magnitude of voltage that capture card is obtained, and with the range linear transformation of transmitter, can finish afterwards.

The pressure drop Δ P that is measured by differential pressure transmitter 12 among Fig. 1 has comprised the pressure drop Δ P of labyrinth flow-path _RunnerLocal losses Δ P with the runner import and export _Decrease, in order to obtain Δ P _Runner, the present invention adopts twice different test specimen linear measure longimetry method to obtain local losses Δ P _Decrease, concrete scheme is as follows:

Local losses Δ P _DecreaseOnly relevant with local losses coefficient δ and flow rate of water flow.All two ends of testing the labyrinth flow-path test block of usefulness are designed to same structure size, have guaranteed that then the import and export of all test blocks has same local losses coefficient δ.As flow velocity, then just can guarantee the local losses Δ P under two operating modes _DecreaseEquate.According to this principle, design two straight channel test blocks 1 and 2, its cross section of fluid channel shape is all the same with size, and flow channel length is respectively L ₁And L ₂(L ₂＞L ₁), adopt same joint.Respectively with in the two test block access devices, measure pressure drop Δ P under some same flow values by differential pressure transmitter ₁With Δ P ₂, the local loss of the import and export sum that connects test runner interface so can be represented with following formula:

So, the pressure drop that produces by runner:

Δ P _Runner=Δ P-Δ P _Decrease

By the flow theory Reynolds number of fluid as can be known:

$\mathrm{Re}=\frac{\mathrm{\ρ}\·\stackrel{\‾}{u}\·D_h}{\mathrm{\μ}}=\frac{\mathrm{\ρ}\·Q\·D_h}{\mathrm{\μ}\·A_c}$

In the formula, ρ is the density of fluid; U is the average velocity of fluid; D _hEquivalent diameter for runner; μ is the kinetic viscosity of fluid; Q is a volumetric flow rate, measures the mass M that a certain section time test specimen 9 flows into the water in the conical beaker 10 by Precision Electronics Balance 11; A _cArea of section for runner.

Drop formula according to classical theory:

$\mathrm{\ΔP}=f\frac{l}{D}\frac{\mathrm{\ρ}{\stackrel{\‾}{u}}^2}{2}$

Because runner is a labyrinth type, so adopt equivalent darcy coefficient of frictional resistance to replace along the journey coefficient of frictional resistance:

In the formula, l _cBe the border Center Length of unit flow passage, n is the number of unit flow passage, and other is the same.As represent the form parameter of labyrinth runner, then equivalent coefficient of friction resistance f with X _cBe exactly the function of X,

f _c＝f(X)

Referring to Fig. 5, (Fig. 5 a), X comprises three parameters: width of flow path W, unit flow passage span L, runner angle theta for triangular element; For trapezoidal element (Fig. 5 b), X comprises four parameters: width of flow path W, unit flow passage span L, cell height H, runner inclination angle [theta]; For circular arc unit (Fig. 5 c), X comprises three parameters: width of flow path W, runner center line radius R, runner central angle θ.

Thereby flow Q and pressure drop Δ P _RunnerBetween relation:

With reference to this relational expression, can calculate the flow of douche according to given flow passage structure and pressure drop numerical value, provide theoretical foundation for designing novel douche fast.

Claims (1)

1, a kind of method for testing performance of micro-dimension labyrinth type unit flow passage waterpower is characterized in that:

At first design two cross section of fluid channel shapes, the first straight channel test block 1 all the same and the flow channel length of the second straight channel test block, 2, the first straight channel test blocks 1 and the second straight channel test block 2 and be respectively L with size ₁And L ₂, L ₂＞L ₁Adopt same joint, respectively the first straight channel test block 1 and the second straight channel test block 2 are inserted in the device for testing micro-dimension labyrinth type unit flow passage waterpower performance, this device for testing micro-dimension labyrinth type unit flow passage waterpower performance comprises gas cylinder [1] and the airtight water tank [3] that is connected with gas cylinder [1], between gas cylinder [1] and airtight water tank [3], also be provided with reduction valve [2], the outlet of airtight water tank [3] is in series with the spherical valve [4] that is interconnected successively by pipeline, filtrator [5], needle valve [6], glass rotameter [7] and labyrinth flow-path test block [9], in the exit of labyrinth flow-path test block [9] conical beaker [10] is set, conical beaker [10] is placed on by on A/D transition card and the Precision Electronics Balance [11] that computing machine [13] is connected, also is parallel with the differential pressure transmitter [12] that links to each other with computing machine [13] by threeway [8] and A/D transition card on labyrinth flow-path test block [9]; Measure pressure drop Δ P under some same flow values by being connected on differential pressure transmitter [12] on the labyrinth flow-path test block [9] ₁With Δ P ₂, the local loss of the import and export sum that connects test runner interface so is:

So, the pressure drop that produces by runner:

Δ P _Runner=Δ P-Δ P _Decrease

Δ P _RunnerBe the water channel total pressure drop;

By the flow theory Reynolds number of fluid as can be known:

$\mathrm{Re}=\frac{\mathrm{\ρ}\·\stackrel{\‾}{u}\·D_h}{\mathrm{\μ}}=\frac{\mathrm{\ρ}\·Q\·D_h}{\mathrm{\μ}\·A_c}$

In the formula, ρ is the density of fluid; U is the average velocity of fluid; D _hEquivalent diameter for runner; μ is the kinetic viscosity of fluid; Q is a volumetric flow rate, measures the mass M that a certain section time labyrinth flow-path test block [9] flows into the water in the conical beaker [10] by Precision Electronics Balance [11], thereby is converted into volume flow Q; A _cArea of section for runner;

Then according to the drop formula of classical theory:

$\mathrm{\ΔP}=f\frac{l}{D}\frac{\mathrm{\ρ}{\stackrel{\‾}{u}}^2}{2}$

Δ P is the runner pressure drop

Because runner is a labyrinth type, so adopt equivalent darcy coefficient of frictional resistance to replace along the journey coefficient of frictional resistance:

In the formula, l _cBe the border Center Length of unit flow passage, n is the number of unit flow passage;

As represent the form parameter of labyrinth runner, then equivalent coefficient of friction resistance f with X _cBe exactly the function of X,

f _c＝f(X)

Thereby flow Q and pressure drop Δ P _RunnerBetween relation:

Can obtain the flow of douche according to given flow passage structure and pressure drop numerical value.

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