CFD-Based Flow Field Analysis of the Triple Diaphragm Pump

As a core fluid device, the triplex diaphragm hose pump is prone to unstable operation owing to its complex internal flow field. In this study, a dynamic mesh technique is established as the core of the numerical model. The periodic flexural deformation of the hose wall is prescribed through a user-defined function (UDF) with a Gaussian distribution, which drives the mesh motion and realizes the one-way fluid–structure interaction (FSI) between the hose and the fluid; the opening and closing of the ball valve is simulated by the dynamic mesh combined with the gap model and the six-degree-of-freedom (6DOF) solver, realizing the two-way FSI between the valve and the fluid. The results reveal intense turbulence (with a turbulent kinetic energy of 0.1–0.5 m2/s2) at the valve gaps and vortices downstream of the valves. Owing to the positional effects, the three pump heads exhibit uneven flow distribution: within 1 s (two working cycles), the cumulative conveyed masses of pumps a, b, and c are 0.02258, 0.02299, and 0.02283 kg, respectively, differing by up to about 1.8%. The parametric analysis shows that a smaller inlet manifold diameter enlarges the flow-rate differences among the pump heads: as the diameter increases from 25 mm to 100 mm, the mean manifold velocity decreases from about 2.91 m/s to 0.66 m/s and the system pulsation rate δq1 decreases from 0.408 to 0.280, while the improvement tends to become marginal beyond approximately 100 mm. Furthermore, as the hose deformation amplitude increases from 0.006 m to 0.020 m, the mean manifold velocity increases linearly from 0.299 m/s to 0.993 m/s, while the normalized pulsation rate δq1 decreases from 0.309 to 0.139. These findings provide a quantitative basis for the design and performance control of the triplex diaphragm hose pump.