In this study, a numerical investigation is presented to characterize the geometry effects on the transient behaviors of a micro diffuser pump. Four parameters of the dynamic diffuser pump, half-angle, depth, length, and excitation frequency, are considered. A time-dependent sinusoidal pressure with fixed pressure amplitude (200 Pa) is applied at the inlet as the boundary condition. The results from the numerical analysis have been quantified in terms of average volumetric flow rate. Despite the corresponding low Reynolds numbers (Re < 10), circulation is observed for all tested half-angles. When the direction of pressure gradient switches, fluid flows against the pressure gradient and triggers flow separation near wall. The vortex then migrates from wall toward the center of diffuser with time. For 5° ≤ θ ≤ 35°, diffusers with larger half-angles show better rectification effects. For θ gt; 35°, net flow rate is nearly independent of half-angle. Shorter and deeper diffuser results in larger net flow rate regardless of its half-angle. The increase of the excitation frequency diminishes the flow rectification in micro diffuser.
Numerical investigation of injector geometry effects on fuel stratification in a GCI engine