AN EXPERIMENTAL AND ANALYTICAL STUDY OF THE INTERNAL FLUID DYNAMICS OF AN INK-JET PRINTHEAD (ORIFICE, RESONATOR, IMPEDANCE, OSCILLATING, ANEMOMETER).

摘要

An experimental and analytical study of the internal fluid dynamics of a drop-on-demand (DOD) ink-jet printhead has been conducted. The central idea of the project was to develop a large scale model with air as the working fluid in order to obtain fluid dynamics data relevant to the interior of a printhead. The analytical results are: (i) a model of an ink-jet printhead, (ii) a method for scaling up a printhead for experimental study with air as the working fluid, and (iii) a physically based interpretation of an ink-jet printhead as a piston driven Helmholtz resonator. An application of the model for the design of a DOD printhead was conducted. The analysis also illuminated the need for experimental information to characterize the orifice or nozzle area of the printhead.; The experimental task was focused on obtaining parameters to characterize the fluid dynamics of monochromatic sinusoidal zero mean flow through two orifices in series, the "Stemme" nozzle. In particular the dimensionless dependent variables R/(rho)SQRT.((omega)(nu)), (delta)/ 0.85d(,1), v(,0)/SQRT.((omega)(nu)), and v(,2)/v(,0) were correlated with the dimensionless independent variables; d(,2)/d(,1), t(,p)/d(,1) and P'/(rho)(omega)(nu) for the following ranges of parameters: 0.23 (LESSTHEQ) d(,2)/d(,1) (LESSTHEQ) 0.94, 0.4 (LESSTHEQ) t(,p)/d(,1) (LESSTHEQ) 2.6, and 660 (LESSTHEQ) P'/(rho)(omega)(nu) (LESSTHEQ) 4120; where (omega) is frequency, R is the resistance term which will characterize the nozzle damping, (delta) is the added mass term to characterize the nozzle mass attribute, d(,1) and d(,2) are the first and second orifice diameters, v(,0) and v(,2) are the velocity magnitudes out the first and second orifices, P' is the acoustic pressure across the two orifices, and t(,p) is the orifice spacing. Data was also obtained to show that for certain combinations of parameters, the double orifice nozzle will rectify an oscillating velocity. For the rectified case, a sinusoidal fluid velocity incident on the first orifice will produce a rectified sine wave fluid velocity out the second orifice.; The experimental study required a considerable methods development effort. The most significant result of this was a method for the calibration of a hot wire anemometer probe for the measurement of a zero mean sinusoidal reversing flow.