| 1. |
- Carlander, Carl, et al.
(författare)
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Installation effects on an ultrasonic flow meter with implications for self diagnostics
- 2000
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Ingår i: Flow Measurement and Instrumentation. - 0955-5986 .- 1873-6998. ; 11:2, s. 109-122
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Tidskriftsartikel (refereegranskat)abstract
- A small ultrasonic flow meter for water was exposed to five different test configurations, a reference experiment, a single elbow, a double elbow out of plane, a reduction in pipe diameter and a pulsating flow experiment. All tests were performed in a flow calibration facility ranging over Reynolds number from 25 to 110 000. The experiments with the four installation effects were compared with a reference experiment. The error and the change in standard deviation compared to the reference experiment were calculated. The standard deviation serve as a measure of the noise level of the flow meter. The results show that all disturbances generated errors in the flow measurement. The maximum errors were mainly in the range of 2–4% of flow rate, but at very low flow rates the pulsating flow caused larger errors. In most of the flow range there were no or smaller errors. All installation effects also generated an increase in the noise level. The different pipe configurations increased the standard deviation up to more than 100%. The pulsating flow induced even higher enlargements in the noise level. The errors and the increase in the standard deviation are present in about the same flow ranges. The results demonstrate not only that the installation effects tested introduce errors in the flow measurements but also that these effects can be detected from the noise level in the data. The noise level was determined from the standard deviation. This could be interpreted as that the disturbances amplify the turbulence intensity. Thus the standard deviation can be used as a measure of the turbulence. The presence of a disturbance could be recognised by comparing the magnitude of the noise level in the present data with a reference level valid for the measured flow rate. A procedure like this could possibly be performed by the meter itself in operation.
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| 2. |
- Carlson, Johan, et al.
(författare)
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Ultrasonic speckle correlation imaging of 2D particle velocity profiles in multiphase flows
- 2003
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Ingår i: Flow Measurement and Instrumentation. - 0955-5986 .- 1873-6998. ; 14:4-5, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional ultrasonic speckle correlation velocimetry (USV) is a new technique that allows imaging of moving scattering media, at a high frame-rate. In this paper we apply the technique to determine two-dimensional particle velocity profiles of multiphase flows. Experiments are realized with suspensions of Sonazoid (medical contrast agent) and Magnetite (Fe3O4) in water. All measurements are performed in a vertical pipe with the flow moving downwards. The two-dimensional particle velocity profiles are then compared with a reference liquid volume flow velocity. As expected from theory, the heavier Magnetite particles have slightly higher velocity than the liquid, whereas the contrast agent simply follows the liquid motion. The proposed technique can be used in combination with other techniques to measure the mass flow of the solid phase, in solid/liquid multiphase flow. This is generally more interesting than measuring the bulk mass or volume flow.
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| 3. |
- Delsing, Jerker
(författare)
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The zero-flow performance of a sing-around ultrasonic flowmeter
- 1991
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Ingår i: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; 2:4, s. 205-208
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Tidskriftsartikel (refereegranskat)abstract
- Zero-flow performance was tested on a new sing-around flowmeter. Design considerations were made to correct for the influences of speed of sound and use was made of reciprocity. The meter was tested from 1 000 to 20 000 sing-around loops, the loop period being approximately 64 μs. To investigate averaging phenomena, 1-100 primary velocity values were averaged to form one value. The temperature range tested was 2-45°C, with measurements at 5°C intervals. The measurements show a zero-flow stability of better than ±0.6 mms-1 (± 1lh-1 for 25 mm diameter pipe) over the entire temperature range. The standard deviation at each temperature tested was less than 0.45 mm s-1. This implies that flow velocities as low as 6 cm s-1 (100 lh-1, 25 mm diameter pipe) could be measured with an accuracy of better than ±1%. The tests were made with water, but equivalent results are expected for other liquids as well as gases.
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| 4. |
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| 5. |
- Håkansson, Evert, et al.
(författare)
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Effects of flow disturbances on an ultrasonic gas flowmeter
- 1992
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Ingår i: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; 3:4, s. 227-233
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Tidskriftsartikel (refereegranskat)abstract
- A series of tests are carried out to assess the effects of flow disturbance on a small dimension ultrasonic gas flowmeter. Flow disturbances generated by cone couplings, and single and double elbows are investigated. Measurements with a 100 D straight pipe upstream with a smooth connection to the meter body are used as a reference. Our measurements show that the symmetrical disturbance produced by a cone coupling at a 12 D distance from the transducer path does not impair the performance of the flowmeter. An asymmetrical disturbance, such as a single or a double elbow at the same distance, seems generally to give an underestimation of the flow velocity, resulting in reading errors of -1% or worse. Measurements with straight pipes of 10 D, 20 D, 40 D and 80 D between the disturbance and the flowmeter have also been made showing that 10 D can cause an overestimation of flow velocity. Increasing the length of the straight pipe generally decreases the error. More than 80 D straight pipe between the disturbance and the flowmeter is required to give a result within ±1% of reference conditions. The angle between the elbow plane and the transducer plane is changed from 0 to 315° in 45° steps. The meter error is plotted as a function of inlet angle, showing a clear relationship between these values.
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| 6. |
- Håkansson, Evert, et al.
(författare)
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Effects of pulsating flow on an ultrasonic gas flow meter
- 1994
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Ingår i: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; 5:2, s. 93-101
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Tidskriftsartikel (refereegranskat)abstract
- A series of tests was carried out to assess the effects of pulsating flow on a small-dimension ultrasonic gas flowmeter. Three different parameters were investigated: pulsation amplitude, pulsation frequency and mean flow velocity. The measurements were carried out in air using a 100D straight pipe upstream of the ultrasonic gas flowmeter. The performance of the flowmeter was tested at mean flow rates from 1.2 to 9.6 m s-1, using four different pulsation frequencies (2, 5, 10 and 20 Hz) with pulsation amplitudes from 0 to ≈70% r.m.s. Our measurements reveal three major phenomena affecting the ultrasonic flowmeter performance. (1) Sampling phenomena, i.e. aliasing: it is shown that a mismatch between the setting of the sampling parameters in the flowmeter and the frequency of the pulsations can result in large positive and negative errors due to aliasing. (2) Errors due to changes of the flow profile caused by an imaginary high Reynolds number due to the pulsating flow: it is shown that these errors are proportional to the pulsation amplitude and inversely proportional to the pulsation frequency. Further, the error caused by a change in the flow profile generally appears in the laminar and transition areas. (3) Non-linearities when averaging very high or low flow velocities, respectively: very large pulsation amplitudes result in instantaneous flow velocities, sometimes exceeding both the maximum and the minimum limits of the calibrated range of the meter. For the ultrasonic meter tested, this results in large negative errors due to non-linearities on the extremes of the error curve of the meter.
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| 7. |
- Nilsson, Ulf R. C.
(författare)
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New method for finding inaccurate gas flow meters using billing data : finding faulty meters using billing data
- 1998
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Ingår i: Flow Measurement and Instrumentation. - 0955-5986 .- 1873-6998. ; 9:4, s. 237-242
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Tidskriftsartikel (refereegranskat)abstract
- A method that uses billing readings to find inaccurate meters is presented. This method uses these readings to form an individual load index (LI), which is primarily affected by the climate rather than the customer's individual behaviour. Meters used in installations where the gas is used in industrial processes are therefore excluded since the consumption is not affected by the climate. The individual LI is compared with an average LI, and meters that differ from the average LI are examined. The method was tested on the gas distribution network in the city of Lund, which consists of approximately 1500 meters. Based on the results obtained so far, the LI method will be a useful aid in tracking down faulty meters. However, laboratory tests of a large number of meters selected by the LI method are still needed. Extrapolation of the results indicates that at least 1% of the installed meters have substantial errors
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| 8. |
- Nilsson, Ulf RC, et al.
(författare)
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In situ detection of inaccurate gas flow meters using a fingerprint technique
- 1998
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Ingår i: Flow Measurement and Instrumentation. - 0955-5986 .- 1873-6998. ; 9:3, s. 143-152
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Tidskriftsartikel (refereegranskat)abstract
- This work describes an in situ method for the testing of mechanical flow meters. The method was developed on diaphragm gas meters, but can be applied to most mechanically-based flow meters. The proposed fingerprint method analyses the behaviour of the meter during a work cycle. The result from the analysis is a ''fingerprint'' of the meter, in which mechanical errors in the meter can be detected. This is explained by the mechanical connection between the sensing mechanism and the mechanical output from the meter. An error analysis of a diaphragm meter was carried out to deduce the type of errors that are likely to occur in such meters. The most severe malfunctions are leakage, internal friction and liquid in the meter. These errors can either lead to measuring errors or can cause the meter to cease functioning. The fingerprint method has been tested on meters with simulated errors and on used meters taken from the gas grid in Lund. The fingerprint method can correctly diagnose errors such as leakage, increased friction and liquid in the meter.
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| 9. |
- Svensson, Bernt, et al.
(författare)
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Application of ultrasonic clamp-on flow meters for in situ tests of billing meters in district heating systems
- 1998
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Ingår i: Flow Measurement and Instrumentation. - 0955-5986 .- 1873-6998. ; 9:1, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- Three methods of using ultrasonic flow meters for the purpose of testing small- and medium-sized billing flow meters in district heating subscriber stations in situ were investigated. Four subscriber stations, six billing flow meters, and three ultrasonic clamp-on meters were part of the investigation. The obtained results show that clamp-on meters have measurement accuracy problems on the ordinary steel piping in the subscriber stations. When using well defined pipes mounted in series with the billing flow meters the results are clearly better; provided that the flow rates exceed a Reynolds number of approximately 10 000. In this flow region, billing flow meter deviations >±5% can be detected. A flow rate below this Reynolds number renders the method less reliable. The useful flow range is extended when using calibration data from the clamp-on meter to correct the measured data, making it possible to determine deviations >±10% in flow rates below a Reynolds number of 10 000. The investigation also showed that not all clamp-on meters are suited for this type of in situ test.
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| 10. |
- Baidar, Binaya, et al.
(författare)
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Sensitivity of the Winter-Kennedy method to different guide vane openings on an axial machine
- 2019
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Ingår i: Flow Measurement and Instrumentation. - : Elsevier. - 0955-5986 .- 1873-6998. ; 68
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Tidskriftsartikel (refereegranskat)abstract
- This work studies the effects of guide vane openings (GVOs) on the Winter-Kennedy (WK) flow measurement method using CFD. The dependence of the WK coefficient with GVOs and its physical mechanism are presented. Although the WK method is reported to be sensitive to different factors including GVO, it is still unclear to which extent the GVO can be changed without modifying the WK coefficient significantly and the mechanism leading to such modification, if any. A numerical model of a Kaplan model turbine with a semi-spiral casing is developed and used to such purpose. Previously conducted experiments on the model turbine are used to validate the numerical results. The magnitude and behavior of the secondary flow are investigated together with the WK coefficients. The GVO is found to have an impact on the WK method, and the impact increases with the GVOs as the flow structure change. A suitable location to minimize the impact of the GVO is suggested. Furthermore, the theoretical WK constant with a suitable location and configuration are also presented; this can be useful in the absence of the measured WK coefficient.
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