CN1664513A - Momentum flowmeter and measuring method thereof - Google Patents

Abstract

The invention discloses a momentum-type flowmeter and a measuring method of it, which comprises a water retaining barrier, a pressure sensing device and a secondary instrument, a group of water retaining grid is on the water retaining barrier which can be set on the channel, the pressure sensing devices are set on the upper and lower of the water retaining barrier individually and both are connected with the secondary instrument which can receive, process, store and output the date. When measuring, fix the momentum-type flowmeter on the channel vertically and connect the pressure sensing device with the secondary instrument fast, then get the information from the secondary instrument.

Description

Momentum flowmeter and measuring method thereof

One, technical field

The present invention relates to water measure equipment and the method used in a kind of field irrigation, specifically a kind of momentum flowmeter and measuring method thereof.

Two, background technology

Water gaging is accompanied by the history in existing more than 100 year of hydraulics development, and classical water measure equipment such as Venturi tube, Bashel flume are still breadboard main water gaging means so far.Along with the needs of irrigation water, not only these laboratory water-measuring devices are used to canal water gauging, and have developed the new method of a lot of water gagings.In short, the irrigated area water-measuring device can be divided three classes: hydraulic structure water gaging, ad hoc water measure equipment water gaging and contactless water gaging.

Utilizing the hydraulic structure water gaging, is exactly the overcurrent rule according to hydraulic structure, by observing flow and the water side that buildings upstream and downstream water level and gatage are calculated buildings.Along with level sensing technology and development of electronic technology, begin the beginning of the eighties to adopt computing machine to carry out the automatic detection and the accumulated water volume of sluice upstream and downstream and gatage.On principle, this flow measurement method requirement buildings goes out stream and has stronger regularity, and general big-and-middle-sized buildings can meet this requirement.But this flow measurement plant investment is bigger, not too is fit to middle-size and small-size channel and uses.

Adopting ad hoc water measure equipment water gaging is a kind of classic methods, and this type of water measure equipment has triangle weir, Cipolletti weir, orifice plate, water gaging nozzle, Venturi tube, Bashel flume, no larynx section flume.Be characterized in water gaging precision height.The same with hydraulic structure, need observation and record water levels of upstream and downstream could calculate flow.This method water gaging need be provided with ad hoc water measure equipment, and manufacturing cost is higher, and the big more expense of channel is high more, has limited its use on large channel.

Contactless water gaging also has various ways according to the difference of its principle, comparative maturity and electromagnetic type flow meter and the ultrasonic flow meter of mainly containing commonly used.Electromagnetic type flow meter mainly is fit to the measuring channel water yield, has developed into and the incorporate product of microcomputer, and measuring accuracy is higher.The electromagnetic flowmeter market price of one rice diameter is held economically for the channel of various lots of farmland and is dared not accept about 100,000 yuan.Ultrasonic flow meter is born in the seventies, along with making rapid progress of computer technology, has driven the research success of developing rapidly of ultrasonic flow meter, particularly Doppler Ultrasonic Flowmeter, has expanded the measurement range of ultrasonic flow meter greatly.Ultrasonic flow meter is fit to the flow measurement of large channel.Owing to be subjected to the influence of temperature drift, the precision instability of ultrasonic flow meter need be carried out temperature drift and be corrected.The present ultrasonic flow meter that uses, based on import, price is higher.Homemade ultrasonic flow meter core component also is based on import, but reliability is relatively poor.

In sum, the shortcoming of standing crop wetting system is: equipment is the top-grade instrument instrument, and price is higher, and general middle-size and small-size agricultural feed ditch road is to hold to dare not accept.

Three, summary of the invention

The purpose of this invention is to provide a kind of momentum flowmeter and measuring method thereof, this momentum flowmeter is simple in structure, and is cheap, and wide adaptability uses this momentum flowmeter measurement convenience and measuring accuracy high.

The objective of the invention is to be achieved through the following technical solutions:

A kind of momentum flowmeter is characterized in that: it comprise as ad hoc water measure equipment (flow measuring device) block boom, pressure transducer and secondary instrument, block the boom bar can placing blocking in the channel to be provided with one group on the boom; Pressure transducer is separately positioned on the upper and lower of blocking boom, and described pressure transducer all is connected with the secondary instrument that can carry out data acceptance, processing, storage and export.The boom profile of blocking among the present invention can be a rectangle or trapezoidal.Evenly arrange grizzly bar n root on barrier, every grizzly bar is wide to be B ₁, under flow action, blocking boom and can produce pressure pressure transducer, the quantity of grizzly bar and the width of every grizzly bar can be determined according to the concrete condition of current.The present invention utilizes the flowing water flow bump to block the boom bar and produces impulsive force to blocking boom, by the determination of pressure sensor impulsive force, calculates the depth of water, flow velocity and flow in the channel according to momentum principle and force balance principle.

Among the present invention, the barrier material can be metal, concrete, timber, plastics or fiberglass etc.

Among the present invention, described pressure transducer can be separately positioned on the top and the bottom of blocking boom; Pressure transducer has the teletransmission interface, it can be accepted and transmit and block the pressure that the boom bar produces under flow action, its riding position also can be in the upper and lower of blocking the boom bar, and according to the difference of its installation position, the derivation formula of principle part should be adjusted accordingly.

A kind of measuring method of momentum flowmeter of the present invention is characterized in that it may further comprise the steps:

A) momentum flowmeter is vertically put into channel and fixing, current flow through from blocking between the boom bar;

B) determine that the pressure transducer in the momentum flowmeter all is connected firmly with secondary instrument;

C) from secondary instrument, read the channel depth of water, flow and the water yield.

Secondary instrument is data acceptance, processing, storage and output unit, it accepts the information of pressure transducer, calculate the water velocity and the degree of depth in the channel according to this information, and according to flow in the flow formula calculating canal, according to flow and the water consumption of each period of Time Calculation, calculate water rate according to the water yield and water price, and above-mentioned information and computing result are stored, as required output or above-mentioned information of teletransmission and result.Secondary instrument can be connected with print out equipment, and desired data is printed, and simultaneously it also can be by wireless or wiredly be connected with other communication facilities.

Principle of work of the present invention is as follows:

According to principle of conservation of momentum and force balance principle, by the counter flow and the depth of water of releasing water in the channel of two end supports power about the mensuration hurdle boom, thereby realization is to the metering of canal capacity.

$F_d=\mathrm{\ρQ}\frac{A_0}{A}({\mathrm{\α}}_1{V}_1-{\mathrm{\α}}_2{V}_2)$

In the formula, F _dBe flowing pressure, ρ is the density of water, and Q is a canal capacity, V ₁Be water velocity in the channel, V ₂For striking the water velocity behind the hurdle boom, A ₁Be channel discharge section area, A ₀For flooding the barrier batten area in the water, A is the barrier total area that floods in the water.

Wherein, $V_1=\frac{Q}{A_1}=\frac{Q}{B\·h};$

$V_2=0;$

$A_0=n{B}_{1}h.$

$A=B\·h$

Therefore have $F_d=\mathrm{\ρ}\frac{{\mathrm{\α}}_{1}n{B}_1\·Q^2}{B^{2}h}$

Measure boom bar upper end, hurdle supported on both sides power and be F ₁, lower end two end supports power is F ₂,, can get hydrostatic pressure according to depth of water h

$F_j=\frac{1}{2}n{B}_1\·\mathrm{\γ}\·h^2$

According to the equilibrium of forces principle, have

$\left\{\begin{array}{cc}2F_1\·H-\frac{h}{2}\·F_d-\frac{h}{3}\·F_j=0& \left(1\right)\\ 2F_1+2F_2-F_d-F_j=0& \left(2\right)\end{array}\right.$

In the formula, H is for blocking the boom height.

With F _d, F _jSystem of equations obtains above the substitution

$\left\{\begin{array}{cc}2F_1\·H-\frac{{\mathrm{\α}}_1\·\mathrm{\ρ}\·n\·B_1\·Q^2}{2B^2}-\frac{n\·\mathrm{\γ}\·B_1\·h^3}{6}=0& \left(3\right)\\ 2F_1+2F_2-\mathrm{\ρ}{\mathrm{\α}}_1\frac{n{B}_1\·Q^2}{B^{2}h}-\frac{1}{2}n{B}_1\·\mathrm{\γ}\·h^2=0& \left(4\right)\end{array}\right.$

In above-mentioned two formulas, H, ρ, γ, n, B ₁, B, α ₁Be known quantity, F ₁, F ₂Can record by pressure transducer, unknown quantity is Q and h, and the system of equations of finding the solution above-mentioned simultaneous promptly can obtain flow and water depth value in the gool.

Present middle-size and small-size irrigation canal is a main body, large in number and widely distributed, the water measure equipment that the present invention proposes blocks grid as the flow measurement device with dash, fixed support power by determination of pressure sensor dash barrier, according to the law of conservation of momentum in the hydraulics and outer force balance principle, instead release the discharge and the depth of water in the channel.Compared with prior art, advantage of the present invention is: device structure is simple, cheap, wide adaptability; Use this momentum flowmeter, measurement is convenient and measuring accuracy is high, can satisfy the needs of middle-size and small-size canal water gauging fully.

Three, description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the structural representation of intermediate hurdles boom of the present invention.

Five, embodiment

A kind of momentum flowmeter of the present invention comprises and blocks boom 1, pressure sensing 2 and secondary instrument 3.The profile of blocking boom 1 is a rectangle, highly is H, and width is B, block be provided with on the boom 1 one group totally 4 block boom bar 4, every grizzly bar is wide to be B ₁The material of hurdle boom 1 is a metal, blocks boom 1 and is fixed in the channel.Two pressure transducers 2 are separately positioned on the top and the bottom of blocking boom bar 4, and pressure transducer 2 also can be four, are separately positioned on four angles of blocking boom 1; Pressure transducer 2 is the UP sensor, and band teletransmission interface all is connected with secondary instrument 3.Secondary instrument 3 is a kind of acceptance, processing, storage and output unit, it accepts the information of pressure transducer 2, calculate the water velocity and the degree of depth in the channel according to this information, and according to flow in the flow formula calculating canal, according to flow and the water consumption of each period of Time Calculation, calculate water rate according to the water yield and water price, and above-mentioned information and computing result are stored, as required output or above-mentioned information of teletransmission and result.

A kind of measuring method of momentum flowmeter of the present invention may further comprise the steps:

A) at first momentum flowmeter is vertically put into channel and fixing, current flow through from blocking between the boom bar;

B) determine that the pressure transducer in the momentum flowmeter all is connected firmly with secondary instrument;

C) secondary instrument is accepted the information of pressure transducer, calculate the water velocity and the degree of depth in the channel according to this information, and,, from secondary instrument, read the channel depth of water, flow velocity and the water yield according to flow and the water consumption of each period of Time Calculation according to flow in the flow formula calculating canal.

Among the present invention, boom upper end, the hurdle supported on both sides power that records by pressure transducer is F ₁, lower end two end supports power is F ₂, F ₁And F ₂Be respectively 90 newton and 240 newton, known, block the wide B=0.8m of boom, have 4 and block the boom bar, the wide B of each grizzly bar ₁=0.05m blocks the high H=1m of boom, and the density p of water is 1 * 10 ³Kg/m ³, α ₁=1, calculate the channel depth of water and the water yield by computing formula.

With known conditions substitution following formula:

$\left\{\begin{array}{cc}2F_1\·H-\frac{{\mathrm{\α}}_1\·\mathrm{\ρ}\·n\·B_1\·Q^2}{2B^2}-\frac{n\·\mathrm{\γ}\·B_1\·h^3}{6}=0& \left(3\right)\\ 2F_1+2F_2-\mathrm{\ρ}{\mathrm{\α}}_1\frac{n{B}_1\·Q^2}{B^{2}h}-\frac{1}{2}n{B}_1\·\mathrm{\γ}\·h^2=0& \left(4\right)\end{array}\right.$

Obtaining depth of water h is that 0.8m, flow Q are 0.32m ²/ s.

According to above flow that obtains and time, can calculate the water consumption of each period, calculate water rate according to the water yield and water price, and above-mentioned information and computing result are stored, as required output or above-mentioned information of teletransmission and result.Secondary instrument can be connected with print out equipment, and desired data is printed.

Claims (7)

1, a kind of momentum flowmeter is characterized in that: it comprise as ad hoc water measure equipment block boom (1), pressure transducer (2) and secondary instrument (3), block boom bar (4) can placing blocking in the channel to be provided with one group on the boom (1); Pressure transducer (2) is separately positioned on the upper and lower of blocking boom (1), and described pressure transducer (2) all is connected with the secondary instrument (3) that can carry out data acceptance, processing, storage and export.

2, momentum flowmeter according to claim 1 is characterized in that: the described boom (1) that blocks is provided with one group and makes when flowing water flow is clashed into and block boom (1) and produce impulsive force and can block boom bar (4) to what pressure transducer (2) produced pressure.

3, momentum flowmeter according to claim 1 is characterized in that: described pressure transducer (2) is separately positioned on the top and the bottom of blocking boom (1).

4, momentum flowmeter according to claim 1 is characterized in that: described profile of blocking boom (1) is a rectangle or trapezoidal.

5, momentum flowmeter according to claim 1 is characterized in that: the described boom (1) that blocks can be made by metal, concrete, timber, plastics or fiberglass.

6, the measuring method of the described momentum flowmeter of a kind of claim 1 is characterized in that it may further comprise the steps:

A) momentum flowmeter is vertically put into channel and fixing, current flow through from blocking between boom bar (4);

B) determine that the pressure transducer (2) in the momentum flowmeter all is connected firmly with secondary instrument (3);

C) from secondary instrument (3), read the channel depth of water, flow and the water yield.

7, the measuring method of momentum flowmeter according to claim 6 is characterized in that: described secondary instrument (3) is connected with print out equipment.