CN201688869U - Double-blunt-body vortex street flowmeter based on self-adaptive FFT power spectrum analysis - Google Patents
Double-blunt-body vortex street flowmeter based on self-adaptive FFT power spectrum analysis Download PDFInfo
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- CN201688869U CN201688869U CN2010201059029U CN201020105902U CN201688869U CN 201688869 U CN201688869 U CN 201688869U CN 2010201059029 U CN2010201059029 U CN 2010201059029U CN 201020105902 U CN201020105902 U CN 201020105902U CN 201688869 U CN201688869 U CN 201688869U
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Abstract
The utility model discloses a double-blunt-body vortex street flowmeter based on self-adaptive FFT power spectrum analysis. Two blunt bodies with non-streamlined sections are mounted inside a pipeline, and two sensors are mounted at symmetric positions on two sides of a rear blunt body and respectively connected with a secondary instrument via lines. A karman vortex street generated by fluid on a downstream of a front blunt body falls off in a cyclic staggering manner, and a more stable secondary karman vortex street with stronger vibration is obtained after the karman vortex street flows through the rear blunt body and then is secondarily excited, so that metering of the flowmeter is reduced. After vibration signals measured by the two sensors are processed by a self-adaptive FFT power spectrum analysis signal processing module, effective vibration pulse signals after noise removal are provided for the secondary instrument. The double-blunt-body vortex street flowmeter avoids lost steps and false triggering existed in traditional analogue signal processing, realizes searching for sampling frequencies in a self-adaptive mode, improves frequency resolution in low frequency, improves flowmeter measuring precision and lowers metering lower limits.
Description
Technical field
The utility model relates to a kind of device of measuring fluid flow, especially relates to a kind of two bluff body vortex shedding flow meters based on the self-adapting FFT power spectrumanalysis.
Background technology
When fluid is flowed through the blunt form bluff body, can form Karman vortex street in the downstream of bluff body, follow alternately coming off of vortex, can cause the vibration of fluid in the downstream of bluff body, within the specific limits, the frequency of fluid oscillation is directly proportional with flow rate of fluid.Utilize the vortex shedding flow meter of this principle development to obtain using more widely at home and abroad.
The principal character of existing vortex shedding flow meter is that the bluff body that xsect is a blunt form is installed in runner, in bluff body or its downstream installation and measuring element, utilize secondary instrument that sensor is come off or the vibration signal of fluid is handled to vortex, and be converted to the flow of fluid by instrument coefficient.There is two large problems in existing vortex shedding flow meter: 1, measurable flux lower limit is higher.The frequency that vortex comes off is relevant with Strouhal number (Strouhal Number), concern as follows: (f is the frequency that stable vortex comes off to f=(v/d) St, St is a Strouhal number, v is the flow velocity of detected fluid, d is that the post of bluff body is wide), studies show that Strouhal number is the function of Reynolds number in the certain flow scope, the flow velocity of detected fluid and the frequency that vortex comes off satisfy proportional relation at this moment, but Reynolds number hour, fluid oscillation is very faint, signal to noise ratio (S/N ratio) can not satisfy the detection requirement, and the metering lower limit of therefore existing vortex shedding flow meter generally is taken at about reynolds number Re=2000, has greatly limited the measures range of flowmeter.2, interference free performance is poor, and especially when flow small vibration frequency was low, noise caused the primary transducer output signal-noise ratio not good enough, is difficult to detect effective vibration signal, influences metering performance.Vortex shedding flow meter is the measurement that utilizes fluid self vibration realizing fluid, and treat that the pressure fluctuation or extraneous vibration source and the noise source that exist in the examining system also can cause the vibration for the treatment of fluid in the examining system, the vibration signal that these are external, or change vortex vibration frequency, or directly enter secondary instrument, cause error in dipping.Yet traditional analog signal processing is generally realized by hardware circuit, be the signal that records of flow sensor after the amplification of oversampling circuit, filtering, amplitude limit, shaping, pulse signal is sent into microprocessor count, thus the instantaneous and integrated flow of acquisition measured medium.Use the hardware circuit calculated rate, real-time is good, but vibration interference sensitivity to external world, mechanical vibration and flow field are disturbed signal amplitude are altered a great deal, and may cause false triggering or lose the step phenomenon, cause measuring error, and in the little low-frequency range of flow, this problem is particularly outstanding.Therefore, people are generally by the regulation lower-cut-off frequency, and the restriction range is head it off recently, but just improved the lower limit of flowmeter metering like this, cause range ratio less.In the last few years, people began to attempt to replace hardware circuit to solve the problems referred to above with digital signal processing.Digital Signal Processing has flexibly, accurately, outstanding advantage such as strong interference immunity, speed be fast, these all are that analog signal processing technology is incomparable.At present, the digital signal processing method that is used for fluid oscillation formula flowmeter mainly contains cross-correlation method, Zymography, Wavelet Transform etc.Wherein use more be spectrum analysis method, it can extract the predominant frequency of effective vibration signal from the signal that contains noise.Yet, all adopt single sample frequency in the existing FFT power spectrum analysis method, because signal frequency the unknown, sample frequency is set at 2 times of maximum flow respective signal frequency values generally according to Shannon's theorems.Simultaneously,, need adopt low-power scm to carry out the FFT power spectrumanalysis again for satisfying the battery powered requirement of flowmeter, but not the bigger DSP of power consumption, the single-chip microcomputer finite storage space has limited sampling number.Therefore, though existing digital signal processing method efficiently solves the anti-noise problem, improved the weight by flow renaturation, but limited by the single-chip microcomputer finite storage space, bigger sample frequency, lower sampling number will make frequency resolution can't reach requirement when hanging down flow velocity, thereby cause measuring error, cause flowmeter low discharge measurement performance still unsatisfactory.
Summary of the invention
It is lower that the purpose of this utility model provides the measurement flux lower limit, a kind of two bluff body vortex shedding flow meters based on the self-adapting FFT power spectrumanalysis that interference free performance is high.
The technical scheme that its technical matters that solves the utility model adopts is:
It comprises pipeline, preceding bluff body, back bluff body, two sensors and flowmeter secondary instrument the utility model, it is the preceding bluff body and the back bluff body of blunt form that the cross section is housed in pipeline, in bluff body symmetria bilateralis position, back the first sensor and second sensor is housed respectively.Two sensors are sent into signal self-adapting FFT power spectrumanalysis signal processing module respectively by circuit and are handled, and the effective vibratory impulse signal that will remove again behind the noise is received the flowmeter secondary instrument.
Be 0.6DN～1.5DN apart between bluff body and the back bluff body end face before described, wherein DN is the diameter of pipeline, and two its shape of cross sections of bluff body are
Shape,
Shape,
Shape or
Shape.
Described two sensors are piezoelectric transducer or capacitance type sensor.
The described primary transducer output signal S1 that is made up of two sensors is divided into two-way, one road signal pre-amplification circuit, filtering circuit, amplitude limiter circuit, the shaping circuit in self-adapting FFT power spectrumanalysis signal processing module is successively finished analog signal processing, primary transducer output signal S1 single-chip microcomputer direct and in the self-adapting FFT power spectrumanalysis signal processing module in another road is connected, and effective vibratory impulse signal S3 of output is connected with the secondary instrument that is used for flow rate calculation.
The beneficial effect that the utlity model has is:
1, utilize two bluff body unitized constructions of optimizing to cause the overlapping phenomenon of vortex, can obtain stable more, the stronger fluid oscillation signal of vibration, under the identical situation of Reynolds number, descended 2～4 times with the fluid-velocity survey lower limit of the linear corresponding relation of vibration frequency, significantly enlarged by the comparable existing vortex shedding flow meter of measurement range based on two bluff body vortex shedding flow meters of self-adapting FFT power spectrumanalysis of this principle design.
2, after the signal process self-adapting FFT power spectrumanalysis signal processing module processing that sensor measurement arrives, obtain effective vibratory impulse signal, avoided losing of hardware circuit analog signal processing existence to go on foot and the false triggering phenomenon, and overcome the drawback that traditional single sample frequency FFT power spectrum analysis method can not be applicable to low-and high-frequency metering simultaneously, seek rational sample frequency in adaptive mode, frequency resolution when having improved low frequency can effectively be improved the flow measurement accuracy of measurement and reduce the metering lower limit.
Description of drawings
Below in conjunction with drawings and Examples the utility model is further specified.
Fig. 1 is a structured flowchart of the present utility model.
Fig. 2 is self-adapting FFT power spectrumanalysis signal processing module structure and a signal flow graph among Fig. 1.
Fig. 3 is a various bluff body cross-sectional view of the present utility model.
Among the figure: 1. pipeline, 2. before bluff body, 3. back bluff body, 4. sensor, 5. sensor, 6. outlet line, 7. self-adapting FFT power spectrumanalysis signal processing module, 8. flowmeter secondary instrument, 7.1. pre-amplification circuit, 7.2. filtering circuit, 7.3. amplitude limiter circuit, 7.4. shaping circuit, 7.5. single-chip microcomputer, S1. primary transducer output signal, signal after the S2. analog signal processing, the effective vibratory impulse signal of S3..
Embodiment
Below in conjunction with drawings and Examples the utility model is further specified.
As shown in Figure 1, the utility model comprises pipeline 1, preceding bluff body 2, back bluff body 3, two sensors 4,5 and flowmeter secondary instrument 8, it is the preceding bluff body 2 and the back bluff body 3 of blunt form that the cross section is housed in pipeline 1, in bluff body 3 symmetria bilateralis positions, back the first sensor 4 and second sensor 5 is housed respectively.Two sensors are sent into signal self-adapting FFT power spectrumanalysis signal processing module 7 respectively by circuit 6 and are handled, and the effective vibratory impulse signal that will remove again behind the noise is received flowmeter secondary instrument 8.
As shown in Figure 2, signal processing module 7 is between flowmeter primary transducer 1 and flowmeter secondary instrument 8, with the primary transducer output signal S1 that has noise is input, and the effective vibratory impulse S3 after the output denoising offers flowmeter secondary instrument 3 and is used for flow rate calculation.The signal processing module 2 inner modes that adopt analog signal processing to combine with digital signal processing.Primary transducer output signal S1 divides two-way entering signal processing module 2, wherein one the tunnel carries out simulation process through the hardware circuit is made up of pre-amplification circuit 7.1, filtering circuit 7.2, amplitude limiter circuit 7.3 and shaping circuit 7.4, and signal S2 enters single-chip microcomputer 7.5 after the analog signal processing at last.There is DSP program single-chip microcomputer 7.5 inside, and signal frequency are divided into several frequency ranges, have provided the suitable sample frequency value of each frequency band signals.Single-chip microcomputer 7.5 is according to signal S2 anticipation signal frequency range after the analog signal processing, and according to the selected suitable sample frequency value of frequency range of living in.Simultaneously, another road primary transducer output signal S1 is directly guided to the A/D input port of single-chip microcomputer 7.5, single-chip microcomputer 7.5 is sampled to primary transducer output signal S1 with selected sample frequency, and realize digital signal processing in FFT power spectrumanalysis mode, obtain accurately effectively vibration signal frequency.Finally, single-chip microcomputer 7.5 outputs effective vibratory impulse S3 give flowmeter secondary instrument 8, is used for calculated flow rate.
As Fig. 1, shown in Figure 3, at a distance of being 0.6DN～1.5DN, wherein DN is the diameter of pipeline 1 between described preceding bluff body 2 and back bluff body 3 end faces, and the shape of cross section of two blunt form bluff bodies is
Shape,
Shape,
Shape or
Shape.Optimum distance between preceding bluff body 2 and back bluff body 3 end faces is by bluff body before changing 2 and back bluff body 3 end distance experimental verification gained results.
Described two sensors are piezoelectric film sensor.
Principle of work of the present utility model is as follows:
It is two bluff bodies of blunt form that xsect is housed in pipeline, in the symmetria bilateralis position of back bluff body two sensors is housed, and two sensors is connected with secondary instrument by circuit respectively.The Karman vortex street that the cycle staggering that is produced in preceding bluff body downstream by fluid comes off is inspired secondly under the bluff body effect of back and obtains stable more, the stronger secondary Karman vortex street of vibration, to reduce the metering lower limit of flowmeter.After the vibration signal that two sensors measures is handled through self-adapting FFT power spectrumanalysis signal processing module, offer the effective vibratory impulse signal after secondary instrument is removed noise, avoided losing of traditional analog signal Processing existence to go on foot and the false triggering phenomenon, and realize that adaptive mode seeks sample frequency, frequency resolution when having improved low frequency is improved the flow measurement accuracy of measurement and is reduced the metering lower limit.
Claims (4)
1. two bluff body vortex shedding flow meters based on the self-adapting FFT power spectrumanalysis, comprise pipeline (1), preceding bluff body (2), back bluff body (3), two sensors (4,5) and flowmeter secondary instrument (8), it is the preceding bluff body (2) and the back bluff body (3) of blunt form that the cross section is housed in pipeline (1), in bluff body (3) symmetria bilateralis position, back first sensor (4) and second sensor (5) are housed respectively, it is characterized in that: two sensors are sent into signal self-adapting FFT power spectrumanalysis signal processing module (7) respectively by circuit (6) and are handled, and the effective vibratory impulse signal that will remove again behind the noise is received flowmeter secondary instrument (8).
2. a kind of two bluff body vortex shedding flow meters based on the self-adapting FFT power spectrumanalysis according to claim 1 is characterized in that: at a distance of being 0.6DN～1.5DN, wherein DN is the diameter of pipeline (1) between preceding bluff body (2) and back bluff body (3) end face.
3. a kind of two bluff body vortex shedding flow meters based on the self-adapting FFT power spectrumanalysis according to claim 1, it is characterized in that: described two sensors (4,5) are piezoelectric transducer or capacitance type sensor.
4. a kind of two bluff body vortex shedding flow meters according to claim 1 based on the self-adapting FFT power spectrumanalysis, it is characterized in that: described by two sensors (4,5) the primary transducer output signal S1 of Zu Chenging is divided into two-way, one road signal is the pre-amplification circuit (7.1) in self-adapting FFT power spectrumanalysis signal processing module (7) successively, filtering circuit (7.2), amplitude limiter circuit (7.3), shaping circuit (7.4) is finished analog signal processing, primary transducer output signal S 1 single-chip microcomputer (7.5) direct and in the self-adapting FFT power spectrumanalysis signal processing module (7) in another road is connected, and effective vibratory impulse signal S3 of output is connected with the secondary instrument that is used for flow rate calculation (8).
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| Application Number | Priority Date | Filing Date | Title |
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| CN2010201059029U CN201688869U (en) | 2010-01-26 | 2010-01-26 | Double-blunt-body vortex street flowmeter based on self-adaptive FFT power spectrum analysis |
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| CN2010201059029U CN201688869U (en) | 2010-01-26 | 2010-01-26 | Double-blunt-body vortex street flowmeter based on self-adaptive FFT power spectrum analysis |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102322904A (en) * | 2011-06-11 | 2012-01-18 | 杭州电子科技大学 | Vortex shedding flow meter based on self-adaptive fast Fourier transformation |
| CN112654842A (en) * | 2018-08-30 | 2021-04-13 | 微动公司 | Non-invasive sensor for vortex flowmeter |
| CN113551721A (en) * | 2020-04-23 | 2021-10-26 | 中国石油化工股份有限公司 | Vortex street flowmeter and flow detection method thereof |
-
2010
- 2010-01-26 CN CN2010201059029U patent/CN201688869U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102322904A (en) * | 2011-06-11 | 2012-01-18 | 杭州电子科技大学 | Vortex shedding flow meter based on self-adaptive fast Fourier transformation |
| CN112654842A (en) * | 2018-08-30 | 2021-04-13 | 微动公司 | Non-invasive sensor for vortex flowmeter |
| CN113551721A (en) * | 2020-04-23 | 2021-10-26 | 中国石油化工股份有限公司 | Vortex street flowmeter and flow detection method thereof |
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| Date | Code | Title | Description |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20101229 Termination date: 20170126 |