Abstract

When considering digital displacement machines, one of the key elements are the fast switching valves. However, the dynamic requirements and conflicting design objectives mean that designing these fast-switching valves is a complex process, which pushes the technology to the limit. Optimization approaches are therefore required just to find feasible and, secondly, optimal solutions. However, dynamic CFD simulation is required to accurately describe dynamic fluid effects as fluid stiction, -drag and -end damping. This limits the possibilities to use optimization approaches due to the computational burden imposed, the need for dynamic mesh generation, and the design parameterization. Hence, this paper investigates analytical approximations and the error size introduced by simplifying dynamic fluid friction effects into a lumped parameter form.

Specifically, the article presents a comprehensive parameter study of selected design parameters’ influence on the fluid forces in fast switching annulus valves, based on both analytical expressions and results derived from dynamic CFD simulations. The focus is primarily on describing the effects and size of the flow forces resulting from changes in parametric design parameters that influence the flow geometry. The results reveal a fair correlation between the fluid force predicted by the rapidly executable lumped model and the CFD model.

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