Numerical optimization of three-cavity magneto mercury reciprocating (MMR) micropump

The operation of the three-cavity magneto mercury reciprocating (MMR) micropump, whose prototype were presented in an earlier companion paper, was numerically explored. In the three-cavity MMR micropump, three mercury slugs are moved by a periodic Lorentz force with a phase difference in three separate cavities. A consecutive motion of the slugs in their cavities transfer air from the inlet to the outlet. Two-dimensional OpenFOAM simulations were carried out to explore the influence of electric current excitation phase difference and back-pressure. The numerical simulations predicted the MMR micropump (with no valve) with a phase difference of 90∘ and 120∘ produces a mean pumping flow rate of 2.7 and 6.1 mL/min at a back-pressure of 10 Pa and maintains a maximum back-pressure of 17.8 and 20 Pa, respectively. However, it was found that there was a reverse flow at large back-pressures with an excitation phase difference of 90∘. The numerical results showed that employing a diffuser/nozzle valve with a length of 5 mm and an angle of 10∘ improves the mean flow rate of the micropump with a phase difference of 90∘ at a back-pressure of 10 Pa by 140% from 2.7 to 6.5 mL/min, and its maximum back-pressure by 125% from 17.8 to 40 Pa.

本研究对三腔磁汞往复式（magneto mercury reciprocating, MMR）微泵的运行特性开展了数值探究，该泵的原型机已在前期相关配套论文中予以展示。在该三腔MMR微泵中，三个汞柱分别位于三个独立腔体中，由存在相位差的周期性洛伦兹力驱动运动。汞柱在腔体内的连续运动可实现空气从泵入口到出口的输送。本研究采用二维OpenFOAM仿真方法，探究了电流激励相位差与背压对该泵运行特性的影响。数值仿真结果表明，无阀MMR微泵在相位差为90°与120°时，于10 Pa背压下的平均泵送流量分别为2.7 mL/min与6.1 mL/min，对应的最大承载背压分别为17.8 Pa与20 Pa。但研究发现，当激励相位差为90°且背压较高时，泵内会出现逆流现象。数值结果还显示，在泵内加装长度为5 mm、夹角为10°的扩压/喷嘴式阀后，相位差为90°的MMR微泵在10 Pa背压下的平均流量可提升140%（从2.7 mL/min升至6.5 mL/min），最大承载背压可提升125%（从17.8 Pa升至40 Pa）。