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Simulations and experimental studies of diffuser/nozzle pumps

An investigation of diffuser/nozzle micropumps is presented. Numerical simulations are done using CFD program ANSYS/Flotran. The simulations show when the opening angel is small, the flow in the diffuser/nozzle is steady, the mass flow is increasing with the adding opening angle. But when the opening angel continues increasing, the pressure grads will be bigger than zero. It means that the static pressure is gradually going up along the diverging direction. The fluid near the wall stops flowing because the velocity decreases rapidly and the dynamic pressure is not big enough to overcome the increasing of the static pressure. Finally the fluid flows reversely from the backward position of higher pressure area, this makes the separation flow of fluid, the diffuser is full of reverse fluid. And this results in the dropping of mass flow at last. The simulations also show that the performance of diffuser with a round inlet is better than that with a sharp inlet. The mass flow of micropumps with different opening angles, different inlets are measured. The experimental results agree well with the simulations.