CN1125314C - Vortex street type biphase gas and liquid flow double parameter measuring method - Google Patents

Abstract

The present invention relates to a method for measuring the flow rate and the component of gas and liquid two-phase flow. The present invention comprises the following basic steps: a quasi-triangular cylinder is used as a vortex street generator, and is put in gas and liquid two-phase flow for generating vortex streets and detecting impact force on the quasi-triangular cylinder in an upstream direction and the frequency of the vortex streets; a flow rate and components are calculated according to a calculation module which is relevant to the two-phase flow. The present invention can simultaneously detect the two parameters of the gas and liquid two-phase flow by one measurement element. The measurement components used by the method are simple and reliable, and have low price. The method can also directly output electric signals. The present invention has the advantages of rapid and convenient processing and high measurement precision. The method has loosened requirements for environmental conditions, and is suitable for industrial on-line detection on site.

Description

Vortex street type biphase gas and liquid flow double parameter measuring method

The present invention relates to the measuring method of a kind of biphase gas and liquid flow flow and component.

So-called biphase gas and liquid flow is meant flowing of the material that has gas, two kinds of phases of liquid simultaneously.Because exist interfacial effect and relative velocity between the two-phase in the biphase gas and liquid flow, phase interface all is variable at random on time and space, causes its flow characteristics more than the single-phase flow complexity, characteristic parameter is also many than single-phase flow.The flow of biphase gas and liquid flow and component are the important parameters in the biphase gas and liquid flow, their measurement also are the two-parameter measurement of biphase gas and liquid flow.

Because biphase gas and liquid flow extensively exists in nature and industrial process, the detection technique of its parameter has been caused scientific and technological circle and engineering technical personnel's extensive concern.And one of the focus of research in the current technical field of measurement and test and difficult point have been become.People do a lot of work, and the technology path of employing can be classified as three major types substantially: adopt traditional single-phase flow instrument and polyphasic flow test model combined method 1.; 2. application Modern New Technology; 3. on the hardware foundation of maturation, be support platform, use flexible measurement method based on soft-measuring technique with the computer technology.Use the Modern New Technology method and measure, have untouchablely, precision height, but install more complicated costs an arm and a leg, and service condition requires high, measure field is required harsh, runs into many difficulties in the online application of industry spot meeting.Also be in the starting stage at present for the soft technique Measurement Study, it must have ripe hardware supported, and its equipment price also relatively needs expensive, and precision is not high, and the scope of application is less.Ripe single-phase flow instrument is applied in the measurement of biphase gas and liquid flow parameter and goes, be one of people's direction of making great efforts to study always.At present, adopt the two-parameter of single-phase flow instrument measurement biphase gas and liquid flow, all need two measuring sensors.For example, the combination of gamma ray density meter and target type meter (1.Anderson J.L.and Fincke J.R.Mass flow Measurement in air/water mixtures using devices and gamma densitome-ter.ISA Trana, 1980,19 (1), 19 (1): 37-48.2.Han K-FF-L; Banerjrr S.Mea-surement of mass flux in two-phase flow using Combination of pitot tubes and gam-ma densitometer.AICHE J.1981; 27:177-184.); the combination of orifice plate and even speed tube is (3. pair rich; utilize orifice plate and even speed tube to carry out the research of gas (vapour) liquid two-phase flow two-parameter measurement; [PhD dissertation]; Shanghai Machinery College; 1990); (Lin Zonghu writes, and gas-liquid-solid multiphase flow is measured, Beijing in the spectacle plate combination; China Measuring Press, 1988).Still more complicated is calculated in this measurement.

The objective of the invention is to propose a kind of needs to use a measuring sensor to get final product the method for while high-acruracy survey biphase gas and liquid flow flow and component.

The ultimate principle of the method that biphase gas and liquid flow double parameter is measured that the present invention proposes is as follows: the vortex shedder of a blunt form is placed biphase gas and liquid flow, in order to produce vortex street, and detect impulsive force and the vortex street frequency that is subjected on the vortex shedder fluoran stream surface, according to the relevant calculation model of two-phase flow, calculate and obtain the two-parameter of biphase gas and liquid flow again.Its concrete steps are as follows:

Select for use accurate triangle cylindricality as vortex shedder, place biphase gas and liquid flow, in order to produce vortex street.Its size and caliber size coupling.

On the fluoran stream surface of vortex shedder, settle a semiconductor diffusion silicon pressure sensor, in order to detect the impulsive force F that is subjected on the fluoran stream surface _Dm, a vortex detector is set, in order to detect the vortex street frequency f in the back of vortex shedder _tF _DmAnd f _tSend into computing machine (or single-chip microcomputer) through the corresponding signal process device, calculate for Computer Analysis.

In analytical calculation, diphasic flow is adopted the homogeneous flow model.

Wherein, the pressure F that is subjected to of vortex shedder fluoran stream surface _DmCan be represented by the formula: $F_{\mathrm{Dm}}=C_{\mathrm{Dm}}\frac{1}{2}{\mathrm{\ρ}}_m{u}_m^{2}A-----\left(1\right)$

ρ _m=ρ _G+ ρ _L(2) in the formula: C _Dm-average resistance coefficient;

ρ _m-gas-fluid two-phase mixture density (kg/m ³)

u _m-gas-fluid two-phase mixture flow velocity (m/s);

A-vortex shedder fluoran stream surface area (m ²)

ρ _G-density of gas phase (kg/m ³);

ρ _L-density of liquid phase (kg/m ³).

In the present invention, adopt following formula to represent gas-liquid two-phase vortex street frequency: $f_t=\mathrm{St}\frac{u_m}{W}-----\left(3\right)$ In the formula: f _t-two-phase vortex street frequency (Hz);

St-gas-liquid two-phase Si Tuolahe number;

W-vortex shedder fluoran stream surface width (m).

Can get by formula (3): $\mathrm{St}=\frac{f_t\mathrm{WA}}{Q_m}-----\left(4\right)$ In the formula: Q _m-mixture flow rate, it equals liquid phase flow and gas phase flow sum (m ³/ s).

Q _m＝Q _G+Q _L (5)

Q _m=u _mIn the A formula: Q _G-gas phase flow (m ³/ s);

Q _L-liquid phase flow (m ³/ s).Formula (1), (4) are that vortex street type biphase gas and liquid flow flow and component are measured the fundamental formular of calculating.

Under the condition of given vortex shedder shape and specification, if known St and C _DmAs long as measure F _DmAnd f _t, can obtain two-phase mixture flow Q by formula (1) and (4) _mWith component ρ _m

St and C _DmAvailable statistical computation obtains.

Among the present invention, select for use accurate triangle cylinder as the vortex street generator, its concrete structure can be following form: the xsect of establishing this cylinder is an isosceles triangle, three angles fritter of all being pruned, the last base b that forms is parallel with the bottom, the limit c of the both sides that forms is parallel with axis of symmetry, and the formation height is h, and the bottom is W.Its cross section is actually the axisymmetric hexagon (as shown in Figure 1) of a likeness in form isosceles triangle.Because it is very little that three little angles of pruning account for the ratio of area of isosceles triangle, so be called accurate triangle.Usually, the ratio of b and W is 0.1～0.3, and the ratio of h and W is 0.8～1.5, and the ratio of c and W is 0.05～0.2.Cylinder length is L, the area A=L * W that goes to the bottom of cylinder.Because bottom surface is facing to the inflow direction of gas-liquid flow, so be referred to as fluoran stream surface.According to the caliber size of gas-liquid flow pipeline, determine the size of corresponding vortex shedder.

Corresponding to above-mentioned measuring method, its measurement mechanism can be connected to form through circuit by accurate triangle cylinder formula vortex shedder, pressure transducer, piezoelectricity vortex detector, pressure signal processor, vortex signal processor, single-chip microcomputer (or computing machine).Vortex shedder is in order to produce vortex street, and pressure transducer is arranged on the fluoran stream surface of vortex shedder, in order to detect the impulsive force that is subjected on the fluoran stream surface.The piezoelectricity vortex detector is placed in the back of vortex shedder, is used to detect the frequency of vortex street.The pressure signal processor is connected with pressure transducer, and in order to reception, processing pressure signal, the vortex signal processor is connected with vortex detector, in order to receive, to handle the vortex street frequency signal.Pressure signal processor, vortex signal processor are connected with single-chip microcomputer respectively, respectively treated pressure signal, vortex street frequency signal are sent into single-chip microcomputer.Analytical calculation in the single-chip microcomputer is carried out according to formula (1), (4) etc.

The present invention has realized only can measuring biphase gas and liquid flow flow and two parameters of component simultaneously with a measuring sensor first in biphase gas and liquid flow, and its measurement component is simple and reliable, low price, and can directly export electric signal, handle quick and convenient, the measuring accuracy height.This method requires loose to environmental baseline, be suitable for the online detection of industry spot.

Fig. 1 is the vortex shedder cross-sectional illustration among the present invention.

Fig. 2 is a detection diagram of the present invention.

Number in the figure: 1 piezoelectricity vortex detector, 2 vortex shedders, 3 semiconductor diffusion silicon pressure sensors, 4 tube walls, 5 vortex signal processors, 6 single-chip microcomputers, 7 pressure signal processors.

Embodiment: corresponding to caliber is the biphase gas and liquid flow of 25mm, and vortex shedder 2 adopts accurate triangle cylinder, its W=7mm that goes to the bottom, long L=24mm, high h=9.2mm, upper base b=1.5mm, the high c=0.8mm in limit.Pressure transducer 3, piezoelectricity vortex detector 1, pressure signal processor 7, vortex signal processor 5 adopt common components and parts and circuit.Vortex shedder 2 is placed biphase gas and liquid flow, by pressure transducer detect the impulsive force F on the fluoran stream surface _Dm=1.775N, by the piezoelectricity vortex detector detect the vortex street frequency f _t=96HZ.

Corresponding computation model calculates St and C by statistics _DmValue as follows:

C _Dm＝3.35 (6)

S _t/ St ₀=1.00+1.122 β-9.327 β ²(7) wherein, St ₀=0.2482, β is a gas volume fraction, β and ρ _mFollowing relation is arranged:

ρ _m=β ρ _G+ (r β) ρ _L(8), can calculate the flow Q of biphase gas and liquid flow according to formula (1), (4) and relational expression (7), (8) _m=12.45 * 10 ^-4m ³/ second, ρ _m=939.13kg/m ³

Claims (2)

1. the measuring method of biphase gas and liquid flow flow and component is characterized in that

---as vortex shedder, place biphase gas and liquid flow with accurate triangle cylinder, in order to produce vortex street;

---a pressure transducer is set, in order to detect the impulsive force F that is subjected on the fluoran stream surface on the fluoran stream surface of vortex shedder _Dm, settle a vortex detector in the back of vortex shedder, in order to detect the frequency f of vortex _t, F _DmAnd f _tSend into computing machine through the corresponding signal process device, calculate for Computer Analysis;

---calculate acquisition gas-liquid two-phase Si Tuolahe with statistical method and count S _tWith average resistance coefficient C _Dm

---calculate acquisition gas-liquid two-phase mixed flow flow Q by following formula _mWith component ρ _m: $F_{\mathrm{Dm}}=\frac{1}{2}{C}_{\mathrm{Dm}}{\mathrm{\ρ}}_m{u}_m^{2}A$ $\mathrm{St}=\frac{f_t\mathrm{WA}}{Q_m}$ In the formula: u _mBe gas-fluid two-phase mixture flow velocity (m/s);

W is the width (m) of vortex shedder;

A is the fluoran stream surface area (m of vortex shedder ²).

2. the measuring method of biphase gas and liquid flow flow according to claim 1 and component, the xsect that it is characterized in that vortex shedder is the rotational symmetry hexagon of a likeness in form isosceles triangle, its upper base is 0.1～0.3 with the ratio of the W that goes to the bottom, the ratio of height overall h and W is 0.8～1.5, and the ratio of high c in limit and W is 0.05-0.2.

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