Pressure Drop of Annular Flow Channel Electromagnetic Pump Examined Using Divided Flow Channel Model

It has been reported that operating an annular flow channel electromagnetic pump (EMP) near the peak of the head pressure and flow rate curve sometimes suffers a drop of head pressure. This phenomenon was attributed to nonuniform distribution of inlet flow or magnetic field, but its mechanism has not been clarified. For fear of this undesired head pressure drop, current EMP design is sometimes too conservative in that the rated efficiency is set low compared with experimentally achieved values. Understanding this phenomenon clearly, therefore, will prospectively make possible more proper design. We modeled the annular channel with parallel divided channels to examine the response of the EMP for distributed inlet flow. For each of the divided channels, the equation of fluid motion is numerically solved including the pressure from the external flow loop. Since the time constant of the pressure from the external loop is slow compared with that of the divided channels, decreased flow in some divided channels can undergo reversed pressure and become unstable in certain cases. Transient behaviors, such as the total head pressure and the flow rate of the EMP, were examined, and conditions of this pressure drop occurrence were clarified, making possible more proper EMP design.