Venturi Diode

Valve-Less Rectification Pumps, Fig. 5 Typical valve-less microfluidic single-action pump. The fluid motion, caused by the diaphragm deformations, is rectifled (as explained in Fig. 6) by the Venturi diodes that replace - though not very efficiently - the membrane valves from Figs. 3 and 4... 

A typical present-day valve-less micropump may correspond to the example presented in Fig. 5. There is again the displacement by deformation of the compliant membrane, but the rectification is made by the fluidic suction and delivery valves, formed by cavities in the solid body of the pump. The valves shown in Fig. 5 are the Venturi diodes, currently very popular. Their rectification effect is based on the dissimilarity of the flow in the two opposite directions, as... 

Valve-Less Rectification Pumps, Fig. 21 An example of a planar version single-action pump made by one-sided etching in a metal plate. It is driven by alternating air pressure acting on the liquid surface in the displacement cavity. Rectification by convergent-divergent Venturi diodes... 

Better performance and, because of the short and simple path, high-frequency range are characteristic of the venturi diode, consisting of a nozzle and a diffuser placed in series. Under various other names [5], it is currently among the most popular among the no-moving-part rectifiers (Figs. 10 and 11). An application of the use of a two-Venturi rectifier circuit in a flow control actuator for gen-... 

Valve-Less Redilicalioii Pumps, Rgure 11 Single-action pump with the Venturi diode rectifier. This is currently the most common type of valve-less pumps used in microtluidics... 

Extreme diodity values as high as X> =20 have been demonstrated in some of the best vortex diodes, based on centrifugal effects in rotating fluid (while with the Venturi and labyrinth diodes it is considered a success if the diodity reaches T> 1.6). Unfortunately, the vortex spin-up and spin-down times are so long that pumps using vortex diodes have to be switched between the OPEN and CLOSED regimes after quite long... 

Tippetts [7] to discover the importance of the three-terminal Venturi devices (Fig. 20) known as reverse flow diverters (RFD). The two Venturi-type diodes shown in Fig. 21 (a planar version of Fig. 5, standard nowadays), may be replaced by more efficient though less well known RFD pumps according to Figs. 22 (single-phase)... 

Valve-Less RecWicadon Pumps, Rgure 12 Sunrey of the jet-lype diodes, (a) A standard jet pump may exhibit a reasonabie rectification effecl (b) The Waikden two-phase fuii-wave rectifier was deveioped from a jet pump with two parallel primary nozzies , actuaiiy better performing when shaped as diffusers, (c) Tippetfs analysis of the long-nosed symmetric Waikden rectifier found it actually consists of three three-terminal devices, (d) The three-terminal Venturi, sometimes known as RFD device... 

Valve-Less Rectification Pumps, Figure 10 Rectification effect in the Venturi (convergent-divergent) diode is based on the larger energetic loss by dissipating kinetic energy of the narrower jet... 

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