Investigation of the flow characteristics within a micronozzle/diffuser

TLDR: In this paper, the authors present an analysis of the performance of micronozzle/diffusers and report on the fabrication and testing of a micronoezzel/diffuser.

Abstract: In this paper, we present an analysis of the performance of micronozzle/diffusers and we report on the fabrication and testing of a micronozzle/diffuser. We have found that the pressure loss coefficient for the nozzle/diffuser decreases with the Reynolds number. At a given Reynolds number, the pressure loss coefficient for the nozzle is higher than that of the diffuser due to a considerable difference in the momentum change. We find that the nozzle/diffuser length has little influence on the pressure loss coefficient. At a fixed volumetric flow rate, we encounter a 'minimum' phenomenon of the pressure loss coefficient versus nozzle/diffuser depth. This is related to the interactions of velocity change and friction factor. In this work, we find good agreement between the measured data and the predicted results, except for a diffuser having an opening angle of 20°. This is because of the presence of flow separation. The departure of this case from the prediction is due to the separation phenomenon in a diffuser with a larger angle.