Measuring and testing – Volume or rate of flow – By measuring vibrations or acoustic energy
Patent
1993-08-20
1996-05-07
Chilcot, Richard
Measuring and testing
Volume or rate of flow
By measuring vibrations or acoustic energy
7386125, G01F 100
Patent
active
055135358
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a method of acoustic flow measurement for measurement of the flow velocities of gases and/or of quantities that can be derived from same, in which method long-wave sound is transmitted into a measurement pipe and the sound signals passing in the gas flow downstream and upstream are detected by means of two sound detectors placed in connection with the measurement pipe at a specified distance from one another, the flow velocity of the gas that flows in the measurement pipe being determined by making use of polarity correlation of said signals, and in which method the frequency of the sound that is transmitted into the measurement pipe is scanned between a certain minimum and maximum frequency.
Further, the invention concerns a device for measurement of the flow velocities of gases and/or of quantities that can be derived from same, such as volumetric flow and/or mass flow, which device comprises a measurement pipe, in which the gas flow to be measured runs, which device comprises loudspeakers as the transmitters of the sound signals and microphones as the sound detectors, which microphones are placed in connection with the measurement pipe between said loudspeakers at a certain known distance from one another, which device comprises a frequency-scanned signal generator or generators, by whose means frequency-scanned electric signals are fed to said loudspeakers, and which device comprises a polarity correlator, into which the signals received from said microphones are fed.
From the FI Patent No. 76,885 of the Technical Research Centre of Finland (Valion tutkimuskeskus VTT), a method and a device of acoustic flow measurement are known for measurement of the flow velocities, volumetric flows, and/or mass flows of gases, liquids, and/or multi-phase suspensions in a pipe or in an equivalent wave tube by making use of acoustic waves passing downstream and upstream. In this prior-an method and device, the wide-band acoustic signal coming from the sound sources is made to pass in the measurement pipe or equivalent wave tube in the plane-wave mode both downstream and upstream, and the flow velocity is determined on the basis of the sound travel times obtained from the maxima and/or the minima of the correlation functions of the measured sound signals and on the basis of the mutual distance between the measurement points.
In one technical solution described in said FI patent, the sound is fed into the measurement pipe in the form of frequency scanning, and the travel time of sound is determined from the signals of the microphones placed at the ends of the measurement distance by means of a polarity correlator. From the travel times measured downstream and upstream, it is possible to measure both the average flow velocity and the sound speed in a medium at rest with high accuracy. Moreover, if necessary, from the flow velocity and from the cross-sectional area of the pipe, it is possible to calculate the volumetric flow rate, and from that further the mass flow rate by combining the results of pressure and temperature measurements.
Practical experiments have established that the method and the device of said FI patent operate in the desired way provided that the sound level of the frequency scanning signals transmitted into the pipe is at least of the same level as the interference noise occurring in the pipe. In the presence of a strong background noise, the desired sound signal is superposed on the signal produced by the noise, in which case the state of the comparator circuit present at the input of the polarity correlator cannot be varied in the desired way, which phenomenon will be described in more detail later with reference to the accompanying FIG. 3. Besides the noise in the environment, the connections of the microphones and the loudspeakers needed in the measurement method and device to the measurement pipe produce turbulence in the gas flow, which, as is well known, produces a noise of a relatively wide spectrum. Also, other discontinuities in the flow duct, such as valves, flow thr
REFERENCES:
patent: Re28686 (1976-01-01), Coulthard
patent: 2826912 (1958-03-01), Kritz
patent: 3568661 (1971-03-01), Franklin
patent: 3819919 (1974-06-01), McGunigle
patent: 3844170 (1974-10-01), Critten
patent: 4019038 (1977-04-01), Critten et al.
patent: 4312238 (1982-01-01), Rey
patent: 4787252 (1988-11-01), Jacobson et al.
patent: 4975645 (1990-12-01), Lucas
patent: 5220923 (1993-06-01), Hagiwara et al.
patent: 5226328 (1993-07-01), Petroff et al.
"Ultrasonic cross-correlation flowmeters," Ultrasonics (Mar., 1973), by Coulthard, J.
Hiismaki Pekka
K.ang.ll Leif
Knuuttila Matti
Koukkari Sauli
Mayranen Tarmo
Biegel Ronald L.
Chilcot Richard
Instrumenttitehdas Kytola Oy
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