CN105403730A - Fluid instantaneous flow velocity measure apparatus and method based on Helmholtz instability - Google Patents

Fluid instantaneous flow velocity measure apparatus and method based on Helmholtz instability Download PDF

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Publication number
CN105403730A
CN105403730A CN201510776803.0A CN201510776803A CN105403730A CN 105403730 A CN105403730 A CN 105403730A CN 201510776803 A CN201510776803 A CN 201510776803A CN 105403730 A CN105403730 A CN 105403730A
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fluid
helmholtz
velocity
oscillator
flow velocity
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CN105403730B (en
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康勇
李登
丁小龙
方珍龙
王晓川
黄满
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Wuhan University WHU
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Wuhan University WHU
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/24—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting acoustical wave

Abstract

The invention discloses a fluid instantaneous flow velocity measure apparatus and method based on Helmholtz instability. The apparatus includes a speed change member, a Helmholtz oscillator, a microphone (7) and a noise frequency spectrum analyzer (8). The speed change member is in threaded connection with the Helmholtz oscillator. The microphone (7) is arranged in a through hole (15) on the Helmholtz oscillator and communicates with an oscillation cavity (14). The microphone (7) is also connected with the noise frequency spectrum analyzer (8). The speed change member is composed by a flange (1) and a speed change pipe (2). The Helmholtz oscillator is composed of a cavity (3), a volume adjusting disc (4), an end cap (5) and a screw (6). The flow velocity of the fluid can be obtained in real time through the relation of a dominant frequency of the noise in the Helmholtz oscillation cavity and the flow velocity. The apparatus is simple, the cost is low and the measure accuracy is high. The liquid flow velocity and the gas flow velocity can be measured. The flow velocity of the fluids in the pipes and air can be measured. Thus the application range is wide. A new method is provided for measuring the fluid instantaneous flow velocity.

Description

Based on fluid instantaneous velocity measurement mechanism and the method for helmholtz instability
Technical field
The present invention relates to rate of flow of fluid field of measuring technique, specifically a kind of fluid instantaneous velocity measurement mechanism based on helmholtz instability and method.
Background technology
Usually need to obtain the flow velocity of fluid in some specific region in many engineer applied and scientific research, to study the impact of its flow state on the course of work and performance.Therefore, the Measurement accuracy of fluid flow rate is significant.At present, the classic method measuring rate of flow of fluid mainly contains mechanical means, rate of heat dissipation method, power manometry and laser velocimetry.Wherein, mechanical velocimetry is that the principle be directly proportional to rate of flow of fluid by the anglec of rotation of impeller in fluid is measured, and is generally applicable to the situation of rate of flow of fluid lower than 30m/s.Rate of heat dissipation method is the proportional feature of rate of heat dissipation and the rate of flow of fluid of the tachogenerator of heating, and obtain rate of flow of fluid by the rate of heat dissipation of determination sensor, but this measuring method needs are placed in flow field probe, thus stream field has certain interference.Power manometry is the speed by measurement pressure reduction recycling Bernoulli equation, pressure being converted into fluid, thus obtains flow velocity, but when recording pressure and being less, the flow rate error of acquisition is larger.Laser velocimetry utilizes Doppler effect that the frequency departure amount between scattered light and incident light is converted into the flow velocity of fluid, and this method stream field is noiseless, and the scope that tests the speed is wide, and measuring accuracy is high, but the cost of laser velocimeter is very high.
For this situation, new rate of flow of fluid measuring method is constantly suggested.The patent application being CN103792384A as publication number discloses a kind of rate of flow of fluid measuring method adjustable based on the range ratio of ultrasound wave cross-correlation technique, but adopt and need ultrasonic transmitter, ultrasonic receiver, noise signal processor etc. in this way, required measuring sensor is many, and cost is higher.Notification number is that the patent of invention of CN102645553B discloses a kind of rate of flow of fluid flow measurement device and method, it is the method realizing rate of flow of fluid measurement based on non-contact electric conductivity measuring technique, but this method needs the elements such as conductivity sensor, signal processing module, data acquisition module, inductor module, measuring method is comparatively complicated.At present, a kind of simple to operate, measuring accuracy is high, cost is low, applied widely fluid instantaneous velocity measuring method and device is not also had.
Summary of the invention
The object of the invention is to be difficult to the simply defect of Measurement accuracy to solve fluid instantaneous velocity, a kind of fluid instantaneous velocity measurement mechanism based on helmholtz instability and method are provided.
Principle of the present invention, be utilize fluid flow through Helmholtz vibrate chamber time chamber air can be caused to produce this feature of resonance of certain frequency, and be proportional to the dominant frequency of noise and the relation of amplitude based on the flow velocity of fluid, by the analysis to noise frequency in vibration chamber, thus accurately obtain a kind of new method of the instantaneous velocity of fluid.
The present invention is based on the fluid instantaneous velocity measurement mechanism of helmholtz instability, comprise transmission components, Helmholtz's oscillator, microphone 7 and noise spectrum analyzer 8, transmission components and Helmholtz's oscillator are threaded connection, microphone 7 to be arranged in through hole on Helmholtz's oscillator 15 and to communicate with vibration chamber 14, and microphone 7 is also connected with noise spectrum analyzer 8; Described transmission components is made up of flange 1 and velocity variation tube 2; Described Helmholtz's oscillator is made up of cavity 3, volume-adjustment dish 4, end cap 5 and screw rod 6.
Described velocity variation tube 2 welds with flange 1, and velocity variation tube 2 center holds B end to be provided with taper convergent runner 9, cylindrical cavity 10 and taper diffusion runner 11 successively along axis from A, the face of cylinder of velocity variation tube 2 is also provided with a threaded hole 13 be connected with cylindrical cavity 10, for being connected with Helmholtz's oscillator.
Described Helmholtz's cavity 3 is the right cylinder of hollow, upper end open, and lower end is provided with end cap 5, and on the wall of cavity 3, have a through hole 15, for placing microphone 7; Described volume-adjustment dish 4 and screw rod 6 are rigidly connected, and screw rod 6 through the center of end cap 5, and is threaded with end cap 5, to vibrate the volume in chamber 14 for regulating Helmholtz.
The present invention is based on the fluid instantaneous velocity measuring method of helmholtz instability, comprise the steps:
1, first device is needed to measure in the pipeline of flow velocity by flange access, start noise spectrum analyzer, then import the frequency signal that noise spectrum analyzer obtains into computing machine;
2, when the A of fluid from velocity variation tube holds with speed V 0when taper convergent runner flows through cylindrical cavity, speed is increased to V 1, fluid is held at the B of velocity variation tube after taper diffusion runner afterwards, and fluid velocity returns to initial speed V 0; When fluid is through cylindrical cavity, cause Helmholtz to vibrate the fluctuation of chamber internal gas pressure, producing frequency is the noise of f, and flow velocity V 1with frequency f, there is following relation:
f = S tan L ( L S / 2 d 1 ) 4 πd 1 · V 1 - - - ( 1 )
Wherein S = πfd 1 U c U c = V 1 t a n ( d 1 ) πd 1 f 2
In formula, f is noise frequency, and S is modulus, and L is that vibration chamber, chamber is long, d 1for vibration chamber diameter, V 1for cylindrical cavity fluid velocity inside, U cfor the convection velocity of whirlpool in fluid boundary layer;
3, calculated by above formula (1) in a computer after obtaining the frequency signal of noise, draw the flow velocity V of fluid at cylindrical cavity place 1, then by V 1substitute into the continuity equation (2) of following fluid, the initial velocity V of fluid can be obtained 0
πD 2 4 · V 0 = πd 2 4 · V 1 - - - ( 2 )
In formula, D is for treating fluid measured place pipe diameter, and d is the end diameter of taper convergent runner, V 0for rate of flow of fluid to be measured.
In addition, Helmholtz's oscillator is pulled down from velocity variation tube, and by Helmholtz's oscillator upper end open near jet beam; Frequency signal in noise spectrum analyzer, and is imported the noise transfer in chamber into computing machine calculates jet beam in air speed according to formula (1) by microphone further.
The present invention is a kind of based on the fluid instantaneous velocity measurement mechanism of helmholtz instability and the advantage of method is: utilize the vibrate dominant frequency of noise and the relation of flow velocity in chamber of Helmholtz just can obtain the flow velocity of fluid in real time, device is simple, cost is low, accuracy of measurement is high; This device not only can measure flow rate of liquid, also can measure air-flow velocity, and can distinguish the flow velocity of fluid in measuring channel and air, thus applied widely, and the measurement that the present invention is fluid instantaneous velocity provides a kind of new method.
Accompanying drawing explanation
Fig. 1 is the cut-open view of apparatus of the present invention.
Fig. 2 is the cut-open view of velocity variation tube.
Fig. 3 is the cut-open view of Helmholtz's oscillator.
In figure, 1 be flange, 2 for velocity variation tube, 3 for cavity, 4 for volume-adjustment dish, 5 for end cap, 6 for screw rod, 7 for microphone, 8 for noise spectrum analyzer, 9 for taper convergent runner, 10 for cylindrical cavity, 11 for taper diffusion runner, 12 for connecting hole, 13 for threaded hole, 14 for vibration chamber, 15 be through hole.
Embodiment
Below in conjunction with accompanying drawing, the present invention will be further described: as Figure 1-3, a kind of fluid instantaneous velocity measurement mechanism based on helmholtz instability, be made up of flange 1, velocity variation tube 2, Helmholtz's cavity 3, volume-adjustment dish 4, end cap 5, screw rod 6, microphone 7 and noise spectrum analyzer 8, described flange 1A and 1B is welded in the two ends of velocity variation tube 2 respectively, and the side a and b flow diameter of flange 1A and 1B middle through-hole diameter and velocity variation tube 2, all identical with treating fluid measured place pipe diameter.
Hold along axis from A B to hold in the middle part of described velocity variation tube 2 and be provided with taper convergent runner 9, cylindrical cavity 10 and taper diffusion runner 11 successively, the cone angle of described taper convergent runner 9 and taper diffusion runner 11 is 14 °; Described velocity variation tube 2 is provided with a threaded hole 13 on the wall just to cylindrical cavity 10, and for connecting Helmholtz's oscillator, and cylindrical cavity 10 is in communication with the outside by a connecting hole 12.
Described Helmholtz's cavity 3 is circular cylindrical cavity, and upper end is an opening, and bottom is threaded with end cap 5, and upper end is connected to velocity variation tube 2 by threaded hole 13, and the wall of Helmholtz's cavity 3 has a through hole 15.
Described volume-adjustment dish 4 is right cylinder, be placed in the inside of Helmholtz's cavity 3, and to vibrate chamber 14 with its formation one Helmholtz, the external cylindrical surface of volume-adjustment dish 4 and the inner cylinder face smooth contact of Helmholtz's cavity 3, and volume-adjustment dish 4 lower surface and screw rod 6 are rigidly connected.
Described screw rod 6 through the center of end cap 5, and is threaded connection.
Described microphone 7 is placed in the through hole 15 on Helmholtz's cavity 3 wall, and is connected with noise spectrum analyzer 8 by wire.
First function of the present invention is achieved in that needs to measure in the pipeline of flow velocity by flange 1 access by device, start noise spectrum analyzer 8 (if model is HS6288B), then import the frequency signal that noise spectrum analyzer 8 obtains into computing machine.When fluid is with speed V 0when taper convergent runner 9 flows through cylindrical cavity 10, speed is increased to V 1, fluid is held at the B of velocity variation tube 2 after taper diffusion runner 11 afterwards, and fluid velocity can return to initial speed V again 0.Because connecting hole 12 chamber 14 that cylindrical cavity 10 and Helmholtz to be vibrated is communicated with, when fluid is through cylindrical cavity 10, due to the Involving velocity of jet, Helmholtz will be caused to vibrate chamber 14 internal gas pressure fluctuation, thus to produce frequency be the noise of f, and flow velocity V 1with frequency f, there is following relation:
f = S tan L ( L S / 2 d 1 ) 4 πd 1 · V - - - ( 1 )
Wherein S = πfd 1 U c U c = V 1 t a n ( d 1 ) πd 1 f 2
Therefore calculated by above formula (1) in a computer after obtaining the frequency signal of noise, just can draw the flow velocity V of fluid at cylindrical cavity 10 place 1, then by V 1substitute into the continuity equation (2) of following fluid, the initial velocity V of fluid can be obtained 0.
πD 2 4 · V 0 = πd 2 4 · V 1 - - - ( 2 )
In device, the use of velocity variation tube 2 is to generate cylindrical cavity 10, thus makes connecting hole 12 and jet beam keep a slight distance, prevents because fluid (liquid) enters Helmholtz that the chamber 14 that vibrates affects frequency and the measurement result of noise.Because fluid is after taper diffusion runner 11, the speed of fluid returns to initial velocity, and thus convection cell is noiseless, measures accurately.On the other hand, because the vibrate chamber length in chamber 14 of Helmholtz can be regulated by screw rod 6, thus these apparatus and method rate of flow of fluid scope of being applicable to measuring is wide.When measuring, in order to improve measuring accuracy, the vibrate air in chamber 14 of Helmholtz need be made to reach resonance state as far as possible.Therefore, need adjusting screw(rod) 3, the noise frequency amplitude that microphone 7 is collected is the strongest, and the air namely now in chamber is in resonance state; Data after being processed by noise spectrum analyzer 8 are again imported computer into and are carried out calculating the instantaneous velocity that can obtain fluid.
Apparatus of the present invention can test tube inner fluid speed, when being liquid in pipeline, namely surveys flow rate of liquid; During for gas, then survey gas flow rate.Meanwhile, this device can survey non-tube fluid flow velocity (as sprayed into the fluid in air by nozzle, or the fluid in channel), and the chamber that Helmholtz vibrated is taken off, then by accent near fluid, in analysis cavity, noise frequency both can.

Claims (5)

1. the fluid instantaneous velocity measurement mechanism based on helmholtz instability, it is characterized in that: comprise transmission components, Helmholtz's oscillator, microphone (7) and noise spectrum analyzer (8), transmission components and Helmholtz's oscillator are threaded connection, communicate with vibration chamber (14) in the through hole (15) that microphone (7) is arranged on Helmholtz's oscillator, microphone (7) is also connected with noise spectrum analyzer (8); Described transmission components is made up of flange (1) and velocity variation tube (2); Described Helmholtz's oscillator is made up of cavity (3), volume-adjustment dish (4), end cap (5) and screw rod (6).
2. fluid instantaneous velocity measurement mechanism as claimed in claim 1, it is characterized in that: described velocity variation tube (2) welds with flange (1), and velocity variation tube (2) center holds B end to be provided with taper convergent runner (9), cylindrical cavity (10) and taper diffusion runner (11) successively along axis from A, the face of cylinder of velocity variation tube (2) is also provided with a threaded hole (13) be connected with cylindrical cavity (10), for being connected with Helmholtz's oscillator.
3. fluid instantaneous velocity measurement mechanism as claimed in claim 1, it is characterized in that: the right cylinder that described Helmholtz's cavity (3) is hollow, upper end open, lower end is provided with end cap (5), and on the wall of cavity (3), have a through hole (15), for placing microphone (7); Described volume-adjustment dish (4) and screw rod (6) are rigidly connected, screw rod (6) is through the center of end cap (5), and be threaded with end cap (5), to vibrate the volume of chamber (14) for regulating Helmholtz.
4. utilize the measuring method of the device described in any one of claim 1-3, it is characterized in that comprising the steps:
(1) first device is needed to measure in the pipeline of flow velocity by flange access, start noise spectrum analyzer, then import the frequency signal that noise spectrum analyzer obtains into computing machine;
(2) when the A of fluid from velocity variation tube holds with speed V 0when taper convergent runner flows through cylindrical cavity, speed is increased to V 1, fluid is held at the B of velocity variation tube after taper diffusion runner afterwards, and fluid velocity returns to initial speed V 0; When fluid is through cylindrical cavity, cause Helmholtz to vibrate the fluctuation of chamber internal gas pressure, producing frequency is the noise of f, and flow velocity V 1with frequency f, there is following relation:
f = S tan L ( L S / 2 d 1 ) 4 πd 1 · V 1 - - - ( 1 )
Wherein S = πfd 1 U c U c = V 1 t a n ( d 1 ) πd 1 f 2
In formula, f is noise frequency, and S is modulus, and L is that vibration chamber, chamber is long, d 1for vibration chamber diameter, V 1for cylindrical cavity fluid velocity inside, U cfor the convection velocity of whirlpool in fluid boundary layer;
(3) calculated by above formula (1) in a computer after obtaining the frequency signal of noise, draw the flow velocity V of fluid at cylindrical cavity place 1, then by V 1substitute into the continuity equation (2) of following fluid, the initial velocity V of fluid can be obtained 0
πD 2 4 · V 0 = πd 2 4 · V 1 - - - ( 2 )
In formula, D is for treating fluid measured place pipe diameter, and d is the end diameter of taper convergent runner, V 0for rate of flow of fluid to be measured.
5. measuring method as claimed in claim 4, is characterized in that: pulled down from velocity variation tube by Helmholtz's oscillator, and by Helmholtz's oscillator upper end open near jet beam; Frequency signal in noise spectrum analyzer, and is imported the noise transfer in chamber into computing machine calculates jet beam in air speed according to formula (1) by microphone further.
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Cited By (5)

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US10345800B2 (en) 2016-03-30 2019-07-09 3D Signals Ltd. Acoustic monitoring of machinery
CN111395963A (en) * 2020-03-13 2020-07-10 武汉大学 Water conservancy self-driven other-excitation pulse jet generating device and generating system
US10839076B2 (en) 2016-12-21 2020-11-17 3D Signals Ltd. Detection of cyber machinery attacks
US10916259B2 (en) 2019-01-06 2021-02-09 3D Signals Ltd. Extracting overall equipment effectiveness by analysis of a vibro-acoustic signal
CN113702660A (en) * 2021-10-27 2021-11-26 湖南江河机电自动化设备股份有限公司 Telemetering terminal for measuring hydrological data in river channel with relatively low convection speed

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Publication number Priority date Publication date Assignee Title
CN1587917A (en) * 2004-09-13 2005-03-02 浙江大学 Jet flow meter using vertical drain flow path and double outlet structure
US8468899B1 (en) * 2008-11-15 2013-06-25 A+ Manufacturing, Llc Wet natural gas sampling method and apparatus
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10345800B2 (en) 2016-03-30 2019-07-09 3D Signals Ltd. Acoustic monitoring of machinery
US10839076B2 (en) 2016-12-21 2020-11-17 3D Signals Ltd. Detection of cyber machinery attacks
US10916259B2 (en) 2019-01-06 2021-02-09 3D Signals Ltd. Extracting overall equipment effectiveness by analysis of a vibro-acoustic signal
CN111395963A (en) * 2020-03-13 2020-07-10 武汉大学 Water conservancy self-driven other-excitation pulse jet generating device and generating system
CN113702660A (en) * 2021-10-27 2021-11-26 湖南江河机电自动化设备股份有限公司 Telemetering terminal for measuring hydrological data in river channel with relatively low convection speed

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