Numerical evaluation of an additively manufactured uniform fractal flow mixer

Abstract

The uniform distribution and mixing of fluids is a common functional requirement in a range of process intensified fluid handling applications. Traditional manufacturing processes have limited the design and performance of flow distributors and mixers. However, the maturing of additive manufacturing (AM) has increased the range of manufacturable geometries, enabling the construction of novel high-performance flow distribution devices. An additively manufactured fractal flow mixer was designed using the concept of self-similar bifurcating channels that symmetrically bifurcates a flow into multiple channels, achieving flow uniformity through a series of sequential stages. After four stages of bifurcation, a y-junction on each channel was introduced before the outlet, mixing the flow from two modules. Computational fluid dynamics (CFD) simulations were carried out to characterise the hydrodynamics and mixing performance of the newly designed mixer over a range of operating conditions and for mixing two gases. Effect of inlet Reynolds numbers (Re) and flow ratio was studied, the maximum relative standard deviation (RSD) was found to be ∼8%, and majority of the flow was uniformly mixed with a distribution index close to unity. The fractal flow mixer was successfully manufactured using vat photopolymerisation (VP) and laser powder bed fusion (L-PBF) techniques without any supports.