CN1082708A - Momentum complex differencial pressure type mass flowmetre - Google Patents

Abstract

This flow in respect of a step "

" the stream pipe, constitute by two square elbows.The pressure three that the power of surging of fluid and working pressure of pipeline and fluid density cause superposes and forms the pipe internal pressure.Be loaded on two differential pressure devices of two elbows respectively, because low-pressure chamber introduction pipeline pressure all, in the measurement result, working pressure is cancelled out each other.One of them only comprises surge force signal and fluid density signal, and another only comprises the force signal that surges.If the electric signal of the two output is subtracted each other, can obtain the signal that is directly proportional with density, carry out multiplication and extracting operation then, can obtain the output signal that is directly proportional with mass rate.

Description

Momentum complex differencial pressure type mass flowmetre

The present invention produces the mass rate that interactional principle is measured fluid with tube wall when utilizing fluid by bend pipe.

When fluid passed through bend pipe, because its incompressibility, the flow velocity numerical values recited of entrance point equated with endpiece.Yet the velocity reversal of endpiece is with the direction difference of entrance point, and the speed of considering is vector, therefore say that variation has taken place speed,, must have an external force to act on the fluid according to Newton second law, fluid velocity is changed, and this power is that elbow internal wall provides.

According to Newton third law, elbow internal wall A position (circle 1.a) has been subjected to the equal and opposite in direction from fluid, the direction opposite reaction, and the back is called the power of surging.

Fluid when the bend pipe, being analyzed as follows of acting force (circle 1.a):

Fluid in the speed of entrance point along the Y direction, therefore, u _x=0, u _y=u _oThrough behind the elbow, speed is along the x direction, therefore, and u _x=u _o, u _y=0.Because speed component u in the x direction _xBe added to u from zero altar _o, therefore, fluid is subjected to one along the x direction, comes from the directed force F of tube wall _x(see figure 1)

In interaction process, the relation between power, quality, the speed three meets theorem of momentum:

M（u _1x-u _ox）＝F _x（t ₂-t ₁）………（1）

The quality of M-liquid particle wherein

(u _1x-u _Ox)-particle is through (t ₂-t ₁) after the time, the variation of speed;

(t ₂-t ₁)-particle is with the interactional time of tube wall;

F _x-particle is subjected to the interaction force of tube wall.

As everyone knows, the mass rate of the fluid by bend pipe is as follows with the relation that elbow internal wall is subjected between the power of surging:

N wherein _x-tube wall is subjected to the acting force of fluid

The average density of p-fluid (can comprise impurity)

The xsect of A-stream pipe latus rectum

The mass rate of G-fluid

The another kind of form of formula (2):

P wherein _x-change the power of defeating of surging that causes, P Yin momentum _x=N _x/ A

Flowmeter involved in the present invention, have a step "

" stream pipe (Fig. 1 b) since the stream pipe of step can regard two right-angle bends as and be formed by connecting, so above-mentioned to the analysis of fluid in the right-angle bend and the power of surging with formula (2) and (3) of discharge relation, also be suitable at this.The stream pipe firmly connects together (Fig. 2) with body, and the corner of stream pipe does not have the transition of angle, garden.Corner is by import straight length 1 and middle straight pipeline section 5, the formation that intersects vertically of outlet straight length 3 and middle straight pipeline section.Import straight length 1 is parallel to each other equal in length with outlet straight length 3.

For altar adds the rigidity that flows pipe, prevent stream pipe stress deformation in measuring process, in the interior angle side of bend pipe corner, weldering is with reinforcement 7.

At two right-angled corner positions of step stream pipe, import straight length 1 and outlet straight length 3 extend one section 2 and 4 respectively again after having crossed middle straight pipeline section 5, and the space of this extension straight tube is for by putting into mouthful and the bellows and the diaphragm of outlet differential pressure transporting device.Extension 2 and 4 length are definite like this, so that the hyperbaric chamber diaphragm 9 of differential pressure transporting device and 10(Fig. 3) do not protrude from stream tube passage or consistent with channel edge, do not hinder fluid and in the stream pipe, pass through.

Be installed in import straight length differential pressure transporting device 13, claim import differential pressure transporting device (as follows), the pressure containing disk 10 in its hyperbaric chamber faces toward entrance point, the normal direction follow-up mouthful straight length axis parallel of diaphragm, and stream pipe inside near the pressure of this diaphragm is:

P _A＝Po+P _x………（4）

P in the formula _AThe pressure at-import high pressure diaphragm place

P _OWorking pressure in the-pipeline

P _xPower P is defeated in surging of-liquid _x=F _x/ A

Device weighs up a mouthful differential pressure transporting device (as follows) at the differential pressure transporting device 14 of outlet straight length, and the pressure containing disk in its hyperbaric chamber is facing to endpiece, and the normal direction of diaphragm parallels with outlet straight length axial line, and the pressure near this diaphragm in the stream pipe is:

P _B＝P _O+P _x+ pgH …………（5）

P in the formula _BThe pressure at-outlet high pressure diaphragm place

P _OWorking pressure in the-pipeline

P _xThe power of defeating of surging of-liquid

The average density of p-liquid

The length of H-stream pipe interlude

The low-pressure chamber of import and outlet differential pressure transporting device respectively by connecting pipe 12 and 15 with corresponding straight length all press the chamber and 11 and 16 and insulated chamber 17 and 18 in corrugated tube communicate, the working pressure in the straight tube is incorporated into low-pressure chamber.Therefore, the differential pressure that receives of import and outlet differential pressure transporting device 13 and 14 is respectively:

△P _A＝P _A-P _O

＝（P _O+P _x）-P _O

＝P _x…………（6）

With △ P _B=P _B-P _O

＝P _O+P _x+ pgH-P _O

＝P _x+ pgH…………（7）

△ P in the formula _APressure differential on the-import differential pressure transporting device 13

△ P _BPressure differential on the-outlet differential pressure transporting device 14

At the low-pressure chamber 19 of import differential pressure transporting device, all be full of working fluid (silicone oil) in the corrugated tube of connecting pipe 12 and insulated chamber 17.The appropriate section of outlet differential pressure transporting device also is full of silicone oil (DCZOO).Said structure can avoid liquid to follow the low-pressure chamber diaphragm directly to contact, and prevents that diaphragm from being corroded.The material of corrugated tube is stainless steel 1Cr18Ni9Ti.

, have respectively and all press chamber 11 and 16 apart from the distance that corner equates at import straight length and outlet straight length.All the chamber of pressure is one section chuck shape pipeline (Fig. 4), and internal layer is the stainless steel straight length, is uniform-distribution with sieve aperture on its surface, and the back claims screen casing 31; Skin is a Sealed casing pipe 36; The below of Sealed casing pipe, the inner chamber that the garden is cup-shaped of ining succession again, promptly insulated chamber 13, and the two communicates.Corrugated tube 35 is arranged in the insulated chamber 13.Import, the working pressure in the outlet conduit by screen casing 31, can be delivered to and all press chamber and insulated chamber, affacts corrugated tube 35 then.Be out of shape behind the corrugated tube pressurized, by the silicone oil of the inside and pass through connecting pipe 12 respectively and 15(Fig. 3), be delivered to the low-pressure chamber of import differential pressure transporting device 13 and outlet differential pressure transporting device 14 respectively.All pressing the effect of chamber screen casing 31, is to prevent from that solid particle in the fluid from depositing to all to press chamber 33(Fig. 4), secondly be when transmitting pressure, do not influence the flow state of fluid at straight length.

In the flowmeter involved in the present invention, a bar printing wiring board is arranged, integrated operational amplifier circuit and electronic devices and components are arranged on it, can realize two tunnel analog quantity electric signal V _AAnd V _BFollowing computing:

$\mathrm{V\; =}\sqrt{V_A{}^X{\mathrm{(\; V}}_B\mathrm{-\; V}{}_A)}\mathrm{\dots \dots \dots \dots (\; 8\; )}$

V wherein _AThe output electric signal of-import differential pressure transporting device

V _BThe output electric signal of-outlet differential pressure transporting device

The electric signal manservant of an official of the output of import and outlet differential pressure device presses the sexual intercourse of signal retention wire:

V _A＝K·△P _A…………（9）

V _B＝K·△P _B…………（10）

K-proportionality constant wherein

With (6) .(7) formula substitution (9) .(10 respectively) formula has:

V _A＝K·P _x…………（11）

V _B＝K·（P _x+ pgH） …………（12）

With (11) .(12) formula substitution (8) formula:

Contrast (3) formula and (13) formula draw:

G∝V…………（14）

Illustrate that mass rate is directly proportional with output electric signal V.Also can adopt microcomputer to realize above-mentioned multiplication, extracting operation.Existing coriolis mass flowmeters also has shortcoming:

(a) working mechanism owing to it is based upon on the basis of vibrating flow tube, so it is very sensitive to the vibration and the fluid pulsation of pipe network.

(b) in running order vibrating flow tube can produce harmful stress at the deflection position, cause the fatigue of material, influences the life-span.

(c) be based upon flowmeter on the Coriolis principle basis, complicated with respect to this flowmeter technology, cost is higher.

(d) the actual proof of using, when the gas dutycycle in the detected fluid greater than 10% the time, each partly produces complicated collision phenomenon between fluid, causes the decline of measuring accuracy.

More than the basic reason that occurs of these shortcomings be that Coriolis flowmeter work is to carry out with stream tube vibration form, therefore be shortcoming in essence.

Flowmeter of the present invention is static because of the stream pipe, can avoid the problems referred to above.

Related flowmeter of the present invention is followed the difference of elbow type flow in the past in respect of essence:

(a) bend pipe of elbow type flowmeter has a radius-of-curvature, comprises an intrinsic curvature radius r and outer curvature radius R, parameter (r/R), as everyone knows, be a vital parameter for the elbow type flowmeter in past, and in flow equation, reflect.The sweep of this flowmeter is that the straight length by two quadratures forms, and does not have garden arc and radius-of-curvature.

(b) two of the elbow type flowmeter pressure points are just in elbow, on the camber line of outer two sides.Inboard promptly near a side of the center of curvature, radius-of-curvature is r; The outside is promptly away from a side of the center of curvature, and radius-of-curvature is R.The pressure position of flowmeter involved in the present invention is on the extension of outlet/inlet straight length.

(c) normal direction of pressure direction of elbow type flowmeter (being the direction of axis line of connecting pipe) or differential pressure gauge diaphragm is to point to the center of curvature.This is because measuring method is based upon fluid particle and does on the principle basis of circular motion.The normal direction of the detection diaphragm of the flowmeter that the present invention relates to is to point to import respectively, exports pipe end, and follows the axis parallel of straight length.

(d) diameter of the aperture of the pressure tap of elbow type flowmeter or pressure measurement diaphragm comes compared with radius-of-curvature r or R, should be much smaller, and also little of it being regarded as one " point ", handle as a pressure tap.The diameter of the pressure measurement diaphragm of this flowmeter, then comparable with the latus rectum of stream pipe.

The above embodiments are not limited to by it just in order to illustrate.If needed, also can be in the two end extensions (crossing bend pipe) that the differential pressure pick-up unit are installed in the middle straight pipeline section; Two adjacent straight lengths can not intersect vertically yet.

Under the situation that does not break away from the spirit and scope of the present invention, can carry out a lot of other modification or increases and decreases to the embodiment that exemplifies.

Claims (15)

1, a kind of mass flowmeter of static stream pipe is characterized in that:

The body that support and shell are connected as a single entity

A continuous step "

" the stream pipe, its import and endpiece firmly are contained on the casing, and stream pipe the center of gravity position, be fixed on the support.

A pair of differential pressure transporting device is contained in two bend parts of stream pipe.

The computing circuit that energy is handled two road electric signal.

2, according to claim 1, step flows the shape of two elbows of pipe, and being intersected vertically by two straight garden pipes forms, and does not have the garden segmental arc.

3, according to claim 1, the step conduit comprises three straight lengths, and the axial line of every section straight length has certain flatness; The axial line of adjacent two straight lengths is vertical mutually; Three sections axial lines are in the same plane.

4, according to claim 3, the import of step stream pipe, outlet straight length are extended one section again crossing the corner so that when the differential pressure transporting device being installed in the extension, the diaphragm position of assurance device not in the convection tube fluid produce barrier effect.

5, according to claim 3, the equal in length of import pipeline section and outlet pipe section.The import pipeline section parallels with the axial line of outlet pipe section.

6, according to claim 3, step stream pipe has certain rigid, in stream pipe bend inboard leg-of-mutton reinforcement welding is arranged especially, to strengthen its rigidity.

7, according to claim 1, two differential pressure transporting devices are installed in respectively on the position, two extensions of stream pipe, and the hyperbaric chamber communicates with stream pipe inside.The diaphragm of import differential pressure transporting device is facing to stream pipe entrance point; The diaphragm of outlet differential pressure transporting device is facing to the endpiece of stream pipe.

8, according to claim 1, the diaphragm size that bears high pressure of two differential pressure transporting devices equates with the through hole cross section of flowing pipe or is not less than 70%.

9, according to claim 7, the axial line of the diaphragm follow-up of bearing high pressure of two differential pressure transporting devices mouthful, outlet straight length is perpendicular.

10, according to claim 7, the low-pressure side of import differential pressure transporting device communicates by a conduit follow-up mouthful straight length; The low-pressure side of outlet differential pressure transporting device communicates with the outlet straight length by conduit.

11, according to claim 1, two differential pressures become device all can produce the electric signal of following the pressure reduction that held to be directly proportional.

12, according to claim 1, electronic circuit device has two road analog electrical signal V ₁And V ₂Carry out the function of following computing:

$\mathrm{V\; =}\sqrt{V_1\mathrm{\times \; (\; V}{}_2\mathrm{-\; V}{}_1)}$

V wherein ₁-be the electric signal of import differential pressure transporting device output

V ₂-for exporting the electric signal of differential pressure transporting device output

Electronic circuit is generally integrated circuit and printed wire combination, also can realize with special IC or microcomputer.

13, according to claim 10, the trend of described two conduits, parallel with import, the outlet straight length of correspondence respectively.

14, according to claim 10, conduit communicates with the corrugated tube of all pressing the chamber of corresponding straight length respectively.Fill silicone oil in low-pressure chamber, conduit and the corrugated tube and drain bubble.

15, according to claim 14, all the chamber of pressure is one section chuck shape straight tube.Internal layer is the stainless steel straight length, and its sidewall evenly is covered with sieve aperture; Skin is a sealing shroud, communicates with an insulated chamber.One corrugated tube is arranged in the insulated chamber, and interior dress silicone oil communicates with connecting pipe, and the outside of corrugated tube communicates with corresponding straight length by screen casing.

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