Search

In this study, we investigate and propose an improved theoretical method to more accurately predict the performance of a field-emission electric propulsion (FEEP) thruster with its complex configuration. We identify critical flaws in the previous theoretical methods and derive corrected equations. Additionally, we define and implement the overall half angle of the Taylor cone to account for variations in the Taylor cone's half angle depending on the applied voltage. Next, we also establish an improved method of the electric filed simulation in a three-dimensional domain to accurately predict a trajectory of extracted ions and a resulting spatial beam distribution of the FEEP thruster by incorporating a configuration of the Taylor cone with the estimated overall half angle from the results of the present theoretical method. Through comparison with the experimental measurements, we found that the present improved methods for theoretical and electric field simulations can yield more accurate predictions than those of the previous methods, especially for higher V and Iem regimes, which correspond to the actual operating conditions of the FEEP thruster. Consequently, we anticipate that the proposed methods can enhance the reliability and efficiency of the design process by accurately predicting performance when developing the new FEEP thruster with its non-symmetric complex configuration to match specific thrust or spatial beam requirements. [ABSTRACT FROM AUTHOR]

A two-dimensional numerical model for a cylindrical piezoelectric inkjet was developed to analyze the ink droplet formation and meniscus behavior, considering the ink compressibility. The propagation of the acoustic pressure wave, which was generated by the piezo actuator, could be simulated by considering the compressibility of the ink. The volume of fluid method was employed for multiphase flow, while the dynamic mesh method was used to implement the piezo actuation. In this study, the key operational parameters of operating voltage, compressibility of working fluid, dwell time of waveform, contact angle, and restrictor dimensions were varied to conduct a comprehensive parametric analysis. The underlying mechanism governing droplet formation could be identified through the analysis of the propagation of successive acoustic pressure waves. Furthermore, the volume fraction and mass flow rate results were used to analyze the jetting performances quantitatively and qualitatively. The mass flow rate results were used to determine the implicit effect of physical properties, such as the viscosity and surface tension, through momentum analysis. The developed model including ink compressibility accurately predicted the behavior of the inkjet jetting and the meniscus motion. In addition, it allows visualization of the internal flow structure and optimization of operating conditions to increase the stability and productivity of inkjet printing. [ABSTRACT FROM AUTHOR]

To obtain uniform and high-resolution jetting, the drop-on-demand inkjet can be operated with various physical properties of inks. To determine how supply pressure control affects the stability of the jetting, an experimental study was conducted on eight model inks in a range of Z number (1 < Z < 17). The velocity and volume of drop were measured by a visualization method to analyze the performance of piezoelectric inkjet head. Increasing negative supply pressure reduced both velocity and volume. The decline of volume was uniform regardless of driving voltage, whereas the decline of velocity increased with decreasing driving voltage. The printability diagram of Z–We was derived to analyze the jetting behavior according to the ink properties, such as viscosity and surface tension, and operating conditions, such as driving voltage and supply pressure. For dimensionless numbers, Z and We, the surface tension term can be compensated by the supplementary Laplace pressure force generated by the supply pressure. In the printability diagram of the modified Z* and We*, the suppression of the satellite drop formation by negative supply pressure can be identified as a shift from the outer to the inner stable region. The critical aspect ratio at the pinch-off was estimated from the Taylor–Culick analysis of the liquid filament breakup. The damping time of residual vibration was measured according to the supply pressure within the printable range. We conclude that control of the supply pressure with slight droplet velocity and volume reduction can improve the printing stability and frequency. [ABSTRACT FROM AUTHOR]