Numerical Analysis and Optimal CFD Model Verification of Piezoelectric Inkjet Printhead

Flow dynamics accurate prediction is critical for the early-stage design and performance optimization of the piezoelectric (PZT) printhead. To achieve this, the Computational Fluid Dynamics (CFD) method has been widely used. However, for accurate fluid simulation of the PZT printhead, the optimal parameters settings still need to be clarified, which will be discussed in full in this paper. The modelling work is divided into two sub-parts, namely, a three-dimensional (3-D) modelling for the ink chamber and a two-dimensional (2-D) modelling for the nozzle-air domain. Simulations of the 3-D ink chamber were carried out firstly, thereby the transient mass flow rate of the ink outflow from the chamber could be obtained, which will be set as the inlet boundary condition of the 2-D nozzle-air simulations. To ensure accuracy and convergence of 2-D simulations, independence tests of the mesh grid and time step were performed, where the Fine level mesh density and 1e-8 s time step were identified as the optimal choice. And this combination was adopted in the transient simulations of the droplet ejection process. For the model validation purpose, an experimental test rig was developed, and comparisons between the simulations and experimental tests show a good agreement, verifying the accuracy of the developed model. In addition, to validate the feasibility of the developed model, the effect of the ink viscosity on the droplet ejection process was tested, and the results were consistent with those produced by published literature, confirming the feasibility of the CFD model developed in this paper.