CN102997967A - Blowing flow real time measuring device and method for pipeline with rectangular section - Google Patents

Abstract

The invention discloses a blowing flow real time measuring device and a method for a pipeline with rectangular section, and belongs to the field of process parameter detection. The real time measuring device consists of a measuring pipe section, a sensor assembly, a micro differential pressure transmitter, an I/V (Current to Voltage) converter, an A/D (Analogue to Digital) converter, a temperature transmitter, a pressure transmitter, a programmable control sampling switch and a microcomputer signal processing system. The measuring pipe section is hermetically connected with the blowing pipeline through upstream and downstream flanges. According to the invention, with the adoption of m inner cones which are completely the same in structure and size and are arranged on the cross section of the pipeline with rectangular section of the measuring pipe section, a sensor module formed by the cross section of the measuring pipe section is equally divided. A flow rate-area flow measuring scheme by a multi-point inner cone method is designed to overcome the deficiencies that the inner cone method is commonly suitable for pipelines with circular sections, and exert the advantages of the inner core method. The invention provides a solution which is high in efficiency and robustness for the blowing flow of a power generating boiler through feasible practice.

Description

Be used for rectangular-section pipeline air flow rate real-time measurement apparatus and method

Technical field

The invention belongs to technical field of process parameter detection, particularly a kind of for rectangular-section pipeline air flow rate real-time measurement apparatus and method.

Technical background

Will make safe operation of the boiler in the fuel-burning power plant under optimum condition, its air and flue system is regulated, pulverized coal preparation system is regulated, combustion system is regulated all needs reliability height and the high air flow rate signal of validity.Because large-scale electricity generation boiler once, the secondary blast pipeline all is that equivalent diameter is greater than the rectangular duct of 2000mm, and the pressure loss that allows is less, need not to demarcate separately the standard restriction device that has again simultaneously than the high measurement accuracy so in engineering, can't adopt, and have to adopt the even speed tube air velocity transducer based on the dynamic pressure method (to comprise Verabar (Verabar), Verabar (Wellbar), Delta bar (Deltaflow), A Niuba (Annubar), Tuo Ba (Torbar) etc.), measuring air flow rate measures the total head of fluid and the difference of static pressure, namely characterize wind speed with so-called " dynamic pressure ", and then obtain air flow rate by velocity-area method.Because flow area is large, velocity flow profile is inhomogeneous, engineering practice shows, the validity that now widely used aerofoil profile dynamic pressure tube method is measured air flow rate can't be guaranteed, and therefore adopts the rectangular-section pipeline air flow rate measuring method based on the dynamic pressure method of average to comprise that the aerofoil profile dynamic pressure tube still has limitation.

Summary of the invention

The objective of the invention is for prior art being applied to the low and poor present situation of validity of robustness in the measurement of boiler of power plant air flow rate, propose a kind of for rectangular-section pipeline air flow rate real-time measurement apparatus and method, it is characterized in that described rectangular-section pipeline air flow rate real-time measurement apparatus is a kind of boiler air flow rate real-time measurement apparatus based on multiple spot inner cone method; This device forms by measuring pipeline section, temperature transmitter, pressure unit, sensor module, differential pressure transmitter, A/D converter, I/V converter, control sampling switch able to programme and microcomputer signal processing system; Air flow rate is measured pipeline section 1 by upstream side flange 4, downstream flange 5 links to each other with air supply duct 6 sealings, arrange m structure and the identical inner cone 2 of size over against incoming flow on the xsect of air flow rate measurement pipeline section 1 interior measurement pipeline section, m inner cone is fixed on the diverse location formation sensor module of same cross-section of pipeline; Connect with being fixedly connected with fin 3 between the wall of adjacent two inner cones 2 and inner cone and measurement pipeline section 1; The impulse signal pipeline 7 of each inner cone passes tested pipeline 1, access respectively the positive/negative-pressure chamber of the differential pressure transmitter that is complementary with each inner cone, wherein m inner cone joined m differential pressure transmitter, and 4 ~ 20mA current output signal of every differential pressure transmitter is delivered to the microcomputer signal processing system through I/V converter, A/D converter, control sampling switch able to programme again; Also be respectively equipped with pressure tappings and pressure unit joins, temperature sensor and temperature transmitter join in tested pipeline, 4 ~ 20mA DC output signal of pressure unit and temperature transmitter is delivered to the microcomputer signal processing system through I/V converter, A/D converter, control sampling switch able to programme.

Described m is the positive integer more than or equal to 3,

The meeting of every inner cone of a described m inner cone flows into actinal surface all on the cross section of measuring pipeline section, and m inner cone will be measured cross section m five equilibrium.

It is identical that wall 8 interior side-wall surface 9 and the Venturi nozzle on two long limits of described measurement pipeline section 1 xsect prolongs axial longitudinal profile shape.

A kind of adopt rectangular-section pipeline air flow rate real-time measurement apparatus and air flow rate measuring method, it is characterized in that, this air flow rate measuring method adopts speed-area-method, in measuring channel, arrange altogether m(m 〉=3) inner cone, the rectangular duct xsect intangibly is divided into m sub-cross section, measures the flow velocity υ of the individual measuring point of m (m 〉=3) on the cross section _iArithmetic mean as the mean flow rate on this cross section

, then under operating condition (pressure p, temperature t), air supply duct air-supply volumetric flow rate q _vFor:

$q_{\mathrm{vi}}=v_i{s}_i---\left(1\right)$

$q_v=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_{\mathrm{vi}}=\frac{1}{m}({\mathrm{\υ}}_1+{\mathrm{\υ}}_2+......+{\mathrm{\υ}}_m)s=\stackrel{\‾}{\mathrm{\υ}}s---\left(2\right)$

S is the equivalent area that air supply duct is measured the cross section.

I inner cone output differential pressure Δ p _iWith loca wind speed v _iRelations Among

$v_i=\frac{{\mathrm{\β}}_i^2}{\sqrt{1-{\mathrm{\β}}_i^4}}{C}_i\mathrm{\ϵ}\sqrt{\frac{2}{\mathrm{\ρ}}{\mathrm{\Δp}}_i}---\left(3\right)$

(3) β in the formula _iBe i inner cone throttling than coefficient, C _iBe efflux coefficient, ε is inflatable coefficient, and ρ is detected fluid density under the operating condition, β _i, C _i, ε, ρ be constant, the differential pressure transmitter that matches with i inner cone is with Δ p _iBe converted into 4 ~ 20mA DC electric current, be delivered to Single Chip Microcomputer (SCM) system through I/V, A/D, control sampling switch able to programme, calculate operating condition by (2) formula, be i.e. temperature t, volumetric flow rate q during pressure P _v

Rectangular-section pipeline air flow rate measuring system principle of compositionality as shown in Figure 3, temperature transmitter in the measuring channel and pressure unit are measured fluid temperature (F.T.) t and pressure p respectively, the current signal of output becomes 1-5V dc voltage signal through the I/V converter, be converted to again the digital signal of response through A/D converter, deliver to computer system through control sampling switch able to programme, computer system transforms into air-supply volume flow Q under the status of criterion according to equation of gaseous state with air flow rate q _υ:

(4), P _dBe normal atmospheric pressure, generally get P _d=101325P _a

(4) in the formula, q represents that pressure is p(relative pressure, i.e. gauge pressure), working temperature is t(℃) time air flow rate; Q ₀Be P under the expression status of criterion ₀=0.1MPa(absolute pressure), T ₀Boiler air-supply standard volume flow during=293.15K.

The invention has the beneficial effects as follows:

1. the employing inner cone increases substantially measurement sensitivity;

2. every inner cone all is furnished with, one to one differential pressure transmitter supporting with it, and each sub-cross section flow velocity is measured, and makes the validity of flow measurement compare traditional air flow rate measuring method with robustness and is significantly improved.

3. two parallel wall surfaces of measuring pipeline section adopt Venturi nozzle buttock line outline-shaped to shrink cylinder, produce throttling action, under the very little prerequisite of the pressure loss, the Reynolds number of measuring fluid on the cross section is increased, effectively eliminate the inhomogeneous error that causes flow measurement of velocity flow profile that low flow velocity causes, improve and measure sensitivity;

4. make air velocity transducer differential pressure output corresponding under the identical flow velocity be higher than wing dynamic pressure tube method far away, and the validity of measurement result is significantly improved.

Description of drawings

Fig. 1 is that the air flow rate measurement mechanism is measured pipeline section vertical profile (long limit L is parallel with the square-section) face (section is parallel with wind speed) synoptic diagram (B-B section).

Fig. 2 is that the air flow rate measurement mechanism is measured pipeline section cross-sectional (minor face W is parallel with the square-section) face (section is parallel with wind speed) synoptic diagram (A-A section).

Fig. 3 is air flow rate measuring system principle of compositionality figure.

Embodiment

The invention provides a kind of for rectangular-section pipeline air flow rate real-time measurement apparatus and method.Compared with prior art, even this device also has higher sensitivity and larger output differential pressure signal when low flow velocity, and the validity of flow measurement obviously improves, and the invention will be further described below in conjunction with accompanying drawing and best case study on implementation.

If the transversal face length length of side of rectangle air supply duct is L, minor face is long to be W.

In Fig. 1,2, air flow rate is measured pipeline section 1 by upstream side flange 4, and downstream flange 5 is realized being tightly connected with air supply duct 6, on the xsect in measuring pipeline section 1 over against incoming flow υ ₀Arrange m the identical inner cone 2 of physical dimension on the direction, m is the positive integer more than or equal to 3, and the xsect of minute measuring channel such as m inner cone forms sensor module; Be connected with being fixedly connected with fin 3 between adjacent two inner cones 2 and inner cone 2 and the wall of measuring pipeline section 1, two inner cones at described sensor module two ends are close to the minor face wall installation of measuring channel; It is identical that wall 8 interior side-wall surface 9 and the Venturi nozzle of measuring two long limits of pipeline section 1 xsect prolongs axial longitudinal profile shape.The pressure guiding pipe 7 of described inner cone passes tested pipeline, and accessing respectively i is the positive/negative-pressure chamber of each differential pressure transmitter of 1 ~ d, and wherein d is 1,2,3 ... .. positive integer (as shown in Figure 3); Output 4 ~ 20mA DC current signal of differential pressure transmitter is delivered to the microcomputer signal processing system through I/V converter, A/D converter, control sampling switch able to programme; The temperature of detected fluid, pressure convert 4 ~ 20mA DC current signal to by temperature transmitter, pressure unit respectively, are delivered to the microcomputer signal processing system by separately I/V converter, A/D converter, control sampling switch able to programme again.

The air flow rate measuring method of described employing rectangular-section pipeline air flow rate real-time measurement apparatus, this air flow rate measuring method adopts speed-area-method, in measuring channel, arrange altogether m(m 〉=3) inner cone, the rectangular duct xsect intangibly is divided into m sub-cross section, measures the flow velocity υ of the individual measuring point of m (m 〉=3) on the cross section _iArithmetic mean as the mean flow rate on this cross section

, then under operating condition (pressure p, temperature t), air supply duct air-supply volumetric flow rate q _vFor:

$q_{\mathrm{vi}}=v_i{s}_i---\left(1\right)$

$q_v=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{q}_{\mathrm{vi}}=\frac{1}{m}({\mathrm{\υ}}_1+{\mathrm{\υ}}_2+......+{\mathrm{\υ}}_m)s=\stackrel{\‾}{\mathrm{\υ}}s---\left(2\right)$

S is the equivalent area that air supply duct is measured the cross section.

I inner cone output differential pressure Δ p _iWith loca wind speed v _iRelations Among

$v_i=\frac{{\mathrm{\β}}_i^2}{\sqrt{1-{\mathrm{\β}}_i^4}}{C}_i\mathrm{\ϵ}\sqrt{\frac{2}{\mathrm{\ρ}}{\mathrm{\Δp}}_i}---\left(3\right)$

(3) β in the formula _iI inner cone throttling be than coefficient, C _iBe efflux coefficient, ε is inflatable coefficient, and ρ is detected fluid density under the operating condition, β _i, C _i, ε, ρ be constant, the differential pressure transmitter that matches with i inner cone is with Δ p _iBe converted into 4 ~ 20mA DC electric current, be delivered to Single Chip Microcomputer (SCM) system through I/V, A/D, control sampling switch able to programme, calculate operating condition by (2) formula, be i.e. temperature t, volumetric flow rate q during pressure P _v

Rectangular-section pipeline air flow rate measuring system principle of compositionality as shown in Figure 3, temperature transmitter in the measuring channel and pressure unit are measured fluid temperature (F.T.) t and pressure p respectively, the current signal of output becomes 1-5V dc voltage signal through the I/V converter, be converted to again the digital signal of response through A/D converter, deliver to computer system through control sampling switch able to programme, computer system transforms into air-supply volume flow Q under the status of criterion according to equation of gaseous state with air flow rate q _υ:

(4), P _dBe normal atmospheric pressure, generally get P _d=101325P _a

(4) in the formula, q represents that pressure is p(relative pressure, i.e. gauge pressure), working temperature is t(℃) time air flow rate; Q ₀Be P under the expression status of criterion ₀=0.1MPa(absolute pressure), T ₀Boiler air-supply standard volume flow during=293.15K.

The present invention adopts on the xsect of the rectangular-section pipeline of measuring pipeline section, over against incoming flow υ ₀Arrange m the identical inner cone of physical dimension on the direction, the xsect of minute measuring channel such as m inner cone, form sensor module, designed the flow velocity of multiple spot inner cone method-area flow measurement scheme, the wind speed that differential pressure before and after the inner cone characterizes is used as a flow velocity use, overcome the deficiency that the inner cone method is applicable to the round section pipeline usually, given full play to the advantage of inner cone method.

Claims (6)

1. a rectangular-section pipeline air flow rate real-time measurement apparatus is characterized in that, this rectangular-section pipeline air flow rate real-time measurement apparatus is a kind of boiler air flow rate real-time measurement apparatus based on multiple spot inner cone method; This real-time measurement apparatus is by measuring pipeline section, sensor module, differential pressure transmitter, the I/V converter, A/D converter, temperature transmitter, pressure unit, control sampling switch able to programme and microcomputer signal processing system consist of, it is characterized in that: air flow rate is measured pipeline section (1) and is tightly connected with air supply duct (6) by upstream side flange (4) and downstream flange (5), in measuring pipeline section (1), measure on pipeline section (1) xsect and arrange m the identical inner cone of physical dimension (2) on the direction of incoming flow, m inner cone (2) consists of sensor module; Adjacent two inner cones (2) and inner cone (2) are connected with being fixedly connected with fin (3) with measuring between pipeline section (1) wall, are fixed in the measurement pipeline section (1); The pressure guiding pipe of each inner cone (7) passes tested pipeline, access respectively the differential pressure transmitter positive/negative-pressure chamber that matches, every inner cone is equipped with a differential pressure transmitter, m inner cone joined m differential pressure transmitter altogether, and differential pressure transmitter is connected with I/V converter, A/D converter, control sampling switch able to programme and microcomputer signal processing system again.

2. described rectangular-section pipeline air flow rate real-time measurement apparatus according to claim 1 is characterized in that: described m is for more than or equal to 3 positive integer.

3. described rectangular-section pipeline air flow rate real-time measurement apparatus according to claim 1 is characterized in that: the meeting of every inner cone of a described m inner cone flows into actinal surface all on the same xsect of measuring pipeline section, and m inner cone will be measured cross section m five equilibrium.

4. described rectangular-section pipeline air flow rate real-time measurement apparatus according to claim 1, it is characterized in that: two inner cones at described sensor module two ends are close to the minor face wall of measuring channel and are installed.

5. described rectangular-section pipeline air flow rate real-time measurement apparatus according to claim 1 is characterized in that, it is identical that wall (8) interior side-wall surface (9) on two long limits of described measurement pipeline section (1) xsect and Venturi nozzle prolong axial longitudinal profile shape.

6. adopt a rectangular-section pipeline air flow rate real-time measurement apparatus and air flow rate measuring method is characterized in that this air flow rate measuring method adopts speed-area-method, arranges altogether m inner cone in measuring channel, its m 〉=3; The rectangular duct xsect intangibly is divided into m sub-cross section, measures the flow velocity υ of m 〉=3 measuring point on the cross section _iArithmetic mean as the mean flow rate on this cross section

, be p at pressure then, temperature is under the operating condition of t, air supply duct air-supply volumetric flow rate q _vFor:

S is the equivalent area that air supply duct is measured the cross section.

I inner cone output differential pressure Δ p _iWith loca wind speed v _iRelations Among

(3) β in the formula _iBe i inner cone throttling than coefficient, C _iBe efflux coefficient, ε is inflatable coefficient, and ρ is detected fluid density under the operating condition, β _i, C _i, ε, ρ be constant, the differential pressure transmitter that matches with i inner cone is with Δ p _iBe converted into 4 ~ 20mA DC electric current, be delivered to Single Chip Microcomputer (SCM) system through I/V, A/D, control sampling switch able to programme, calculate operating condition by (2) formula, be i.e. temperature t, volumetric flow rate q during pressure P _v

Rectangular-section pipeline air flow rate measuring system principle of compositionality as shown in Figure 3, temperature transmitter in the measuring channel and pressure unit are measured fluid temperature (F.T.) t and pressure p respectively, the current signal of output becomes 1-5V dc voltage signal through the I/V converter, be converted to again the digital signal of response through A/D converter, deliver to computer system through control sampling switch able to programme, computer system transforms into air-supply volume flow Q under the status of criterion according to equation of gaseous state with air flow rate q _υ:

(4), P _dBe normal atmospheric pressure, generally get P _d=101325P _a

(4) in the formula, q represents that pressure is p(relative pressure, i.e. gauge pressure), working temperature is t(℃) time air flow rate; Q ₀Be P under the expression status of criterion ₀=0.1MPa(absolute pressure), T ₀Boiler air-supply standard volume flow during=293.15K.

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