Micronozzle/diffuser flow and its application in micro valveless pumps

The nozzle/diffuser flow with different Reynolds number ranges and conical angles is analyzed first. It is found that the flow coefficients of nozzle/diffuser xi(n) and xi(d) vary with angle with different trends for large (> 10(5)) and small (<50) Reynolds number ranges. The flow model of valveless pumps with nozzle/diffusers is proposed, and the relationship between nozzle/diffuser flow coefficients and the performance of the valveless pumps is investigated. In experiments, silicon nozzle/diffuser elements with conical angles of 5 degrees, 7.5 degrees and 10 degrees and a silicon micro valveless pump wafer are fabricated. The experimental xi(d,) xi(n) and xi(n)/xi(d), decrease with increasing nozzle/diffuser angles in the Re range (similar to 2000) of the experiment. The pumping direction of the fabricated valveless pump agrees with the nozzle/diffuser flow experiments and analysis. The pump works successfully with the output flow rate of 28 mu l/min under the input power of 50 mW and 500 Hz. (C) 1998 Elsevier Science S.A. All rights reserved.