Annular field-focusing capacitance sensor for visualization of the two phase flows

In this work, the construction of a field-focusing capacitance sensor geometry in the pipeline for monitoring the multiphase flow of non-conductive materials is presented. With a built-in cone, the annular flew field is formed. The sensor geometry has the electrodes around the built-in cone and the inner wall of the tube for forming the field-focusing capacitance measurement form in annular field. Two typical sensitivity maps for the annular field-focusing geometry were calculated with a finite element approach and some typical situation with the sensitivity feature are discussed. Using the multiplexed excitation and parallel measurement scheme, the capacitance of the fluid in the sub-region which defined by the field-focusing sensor in the annular pipe is measured. The prototype sensor is formed by 16 by 16 electrodes, presenting a total of 256 sub-domain capacitance measurements. The annular field flow images can be obtained from the raw measurement data directly. Three annular field two phase flow types are used to carry out simulation experiments and the imaging capability is tested.