| Electromagnetic flow-meter is widely used in industry and agriculture for itsunique advantages. However, there is no proven technology to measure fluid flowwhen the pipe is not fully filled. Therefore, based on extensive domestic and foreignliterature, some key techniques of the electromagnetic flow-meter are studied in thispaper.The homogeneous degree of magnetic field is one of the important factors thataffect the precision of electromagnetic flow-meter measurement and convectionadaptability. Reasonable and effective evaluation index system has an importantinfluence on the determination of magnetic field uniformity. In the current design,uniformity problem is not considered or rough evaluation method is used, andrelatively recognized and unified evaluation system is not formed. In this paper,based on area weight deviation degree, established evaluation index system is builtand compared with the traditional evaluation index. And excitation structure of thesensor of traditional electromagnetic flow-meter is improved and optimized, andsensor field model is designed to meet the requirements of magnetic field uniformity.ANSYS software is used for numerical simulation and standard rate is used asmeasure index for comparing with traditional model, and the results show that theestablished new model is improved in magnetic field uniformity. Finally, the paperprovided the optimization simulation of the magnetic pole out length in the newmodel, and the optimal length is found out. A new approach for improving the fielduniformity of electromagnetic flow-meter is provided in this paper.In order to eliminate the impact of fluid state and liquid level on the non-fullpipe flow measurement, the paper further proposed a new structure of non-full pipeelectromagnetic flow sensor using long strip electrode. This square tube structure translates the asymmetrical flow into symmetrical when the pipe is not filled withliquid, and the measurement results only concern with the average flow velocityrather than with the fluid flow state. A pair of long strip electrodes are installed onthe inside of electromagnetic flow sensor, which can avoid the defects of traditionalpoint or long arc electrode for failing to detect the flow rate signal when the fluidlevel is too low, so that the electrode height has not influence on the measurementrange. This paper combines the measurement of flow rate and liquid level to measurethe volume flow of fluid when the pipe is not fully filled. The measurement principleof sensor is analyzed in detail. Then the key circuit and software flowchart ofmeasurement mechanism are designed. Finally, a prototype of electromagnetic flow-meter of unfilled pipes is built, and the field test results show that the proposedscheme is effective and feasible. |
PDF Full Text Request