| 1. |
- Antonini, Giulio, et al.
(författare)
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PEEC development road map 2007
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A road map for the long term development of the partial element equivalent circuit (PEEC) method is presented. Emerging areas are pointed out together with a solution strategy. Special attention is given to speed up approaches, mesh generation, and time domain stability. The purpose with the road map is to facilitate a unified development of the method into an electromagnetic modeling method suitable for incorporation in integrated analysis tools for engineers for electromagnetic compatibility and electromagnetic interference purpose.
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| 2. |
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| 3. |
- Berrebi, Jonathan, et al.
(författare)
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Detection of pulsating flows in an ultrasonic flow meter
- 2002
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Ingår i: Proceedings of the 8th International Symposium on District Heating and Cooling.
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Konferensbidrag (refereegranskat)abstract
- Transit-time ultrasonic flowmeters present advantages for district heating applications, since they are accurate, non-intrusive, and cheap. However, such flowmeters are sensitive to velocity profile variations since the flow rate is measured in the volume area between two ultrasonic transducers. Ultrasonic flowmeters are therefore sensitive to installation effects. Installation effects could be either static or dynamic. A pulsating flow is a dynamic installation effect. In the field, the diagnostic can only be performed with the measured flow rate. Flow measurements with and without pulsating flow have been recorded in a flow meter calibration facility. The detection of a pulsating flow can be made by using Hinich's harmogram. It is possible to detect harmonics that emerge from the noise by using the harmogram.
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| 4. |
- Berrebi, Jonathan, et al.
(författare)
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Detection of the error generated by a single elbow on an ultrasonic flow meter
- 2002
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Ingår i: ISA TECH/EXPO Technology Update Conference Proceedings. - : ISA - Instrumentation, Systems, and Automation Society. ; , s. 1268-1279
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Konferensbidrag (refereegranskat)abstract
- Ultrasonic flow meters are accurate and non-intrusive. However, one of their drawbacks is their sensitivity to installation effects especially when elbows or pulsating flows are found in front of the meter's inlet. Depending on the flow rate, such installations can create perturbations on the flow measurement. These perturbations cause an increase of the noise level as well as a possible error on the flow estimation. A technique using the noise level as a criterion for making a diagnostic of the error is presented. The perturbations are examined and compared to gaussian distributed signals. A basic method for detecting gaussian perturbations with equal means is described. The likelihood ratio is first computed in the general case. It is also computed making the assumption of uncorrelated signals. Receiver Operating Characteristics (R.O.C.) are plotted. The assumption of gaussian perturbations is then investigated. Optimal thresholds are proposed for both methods and for a large interval of flow rates (from 0.4 ml/s to 0,75 1/s). Probabilities of detection and of false alarm are evaluated for both methods. It is concluded that correct detection can be performed. The optimal threshold is to be chosen by the operator.
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| 5. |
- Berrebi, Jonathan, et al.
(författare)
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Reducing the flow measurement error caused by pulsations in flows
- 2004
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Ingår i: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; :5-6, s. 311-315
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Tidskriftsartikel (refereegranskat)abstract
- Different types of errors are generated by pulsations in flows. Among these errors is the sampling error due to a unadapted time-averaging of the flow rate. An improved model for pulsations in flows including harmonics is derived. The localization of the harmonics is performed by a detector. The period of the pulsations is estimated. It is then possible to reduce the sampling error by performing a correct averaging. The reduction of the sampling error is confirmed by simulations.
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| 6. |
- Berrebi, Jonathan, et al.
(författare)
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Ultrasonic flow metering errors due to pulsating flow
- 2004
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Ingår i: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; 15:3, s. 179-185
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Tidskriftsartikel (refereegranskat)abstract
- Transit-time ultrasonic flow meters present some advantages over other flow meters for district heating industries. They are both accurate and non-intrusive. It is well-known that ultrasonic flow meters are sensitive to installation effects. Installation effects could be static or dynamic. Among the possible dynamic installation effects is pulsating flow. The influence of pulsating flow on the prediction and the zero-crossing operations is investigated. Expressions are found for the prediction error and the zero-crossing error. The relative errors due to the prediction and the zero-crossing are plotted. The prediction error can reach dramatic values while the zero-crossing operation is hardly influenced by flow pulsations.
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| 7. |
- Borg, Johan, et al.
(författare)
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Reciprocal operation of ultrasonic transducers : experimental results
- 2006
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Ingår i: Proceedings. - Piscataway, NJ : IEEE Communications Society. - 1424402026 ; , s. 1013-1016
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Konferensbidrag (refereegranskat)abstract
- Ultrasonic transit-time flow-meters estimate fluid or gas flows from the difference in times of flight of upstream and downstream acoustic pulses. However, any delay differences arising from sources other than the flow to be measured will cause a troublesome "zero flow" offset error.In theory, the transducers used in the measurement system should not influence the zero flow error, as electroacoustic systems based on piezoelectric transducers have been shown to be reciprocal (when the media is stationary). However, care is required when designing the electrical interfaces for the piezoelectric transducers, if reciprocity in the system is to be utilized.This work presents technique and measurements that apply reciprocity to an ultrasonic transit-time flow-meter. Specialized electrical transducer interfaces with options to drive the transducers from either low or high impedance sources were used. Combined with a high-impedance receive mode these options made it possible to change the conditions for reciprocity in the system.We show reduced delay difference in 9 cases out of 10 when trying to utilize the reciprocal property compared to when we disregard it in favor for larger excitation energy. The delay improvements were accompanied by reduced differences between the center frequencies of the signals from the two paths.
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| 8. |
- 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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| 9. |
- Carlander, Carl, et al.
(författare)
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Temperature and installation effects on small commercial ultrasonic flow meters
- 2000
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Konferensbidrag (refereegranskat)abstract
- Experimental work has been performed on a selection of small ultrasonic flow meters for water. This work was accomplished in order to investigate the in fluence of temperature and flow profile disturbances on the performance of flow meters in district heating applications. The flow meters tested were all ultrasonic flow meters of sing-around type. The selection of flow meters contains in total seven meters of three different brands. All meters have a flow range from 0.015 m3/h to 1.5 m3/h. These meters are commonly used in heat meters in small district heating subscriber stations. The flow meters are presented without identification. All tests were performed in a flow meter calibration facility and in a flow range including the minimum and maximum flow of each flow meter. In the tests three different water tempera-tures and three different installations were investigated. Water temperatures of 20 °C, 50 °C and 70 °C were used. These temperatures are representative for district heating applications. The installations tested involved flow meters mounted with long straight pipes both up-and down-stream representing ideal conditions, a single elbow and a double elbow out of plane both generating disturbed flow profiles. All set-ups are in accordance with the flow meter specifications. The results demonstrate that both the change in temperature and the disturbed flow profiles introduce errors in the flow measurements. The change from 20 °C to 50 °C and 70 °C can cause a shift in meter performance larger than the specified maximum permissible error. Compared with the ideal installation the installations generating disturbed flow profiles cause errors up to more than 2 %. The errors due to temperature and installation effects have a bias to add when combined. This might lead to even larger errors.
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| 10. |
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