A numerical study of the nozzle/diffuser micropump

This study numerically investigates the performance of micronozzle/diffuser pump subject to the influence of frequency, opening angle, geometric dimension, and amplitude. For the effect of geometric dimension, the effect of chamber length is far more important than that of chamber depth because it can provide much more effective pumping volume. It is found that the net flowrate of a micropump increased with pumping frequency and opening angle. However, a level-off phenomenon of the net flowrate versus amplitude is seen at amplitudes nearby 150-200 mu m and at an opening angle above 10 degrees. This phenomenon is associated with two factors that compensate with each other. One is the free jet flow from the outlet that overturns and blocks the flow from the inlet. The other is the reduction of the strength of jet flow at a larger amplitude owing to effective increase of cross-sectional area.