Numerical simulation on the flow structure around the injection nozzles for pneumatic dimensional control systems

A numerical simulation on the airflow exiting from a nozzle in a pneumatic dimensional control system has been conducted using computational fluid dynamics code FLUENT (V. 4.3), which solves finite-difference equations. The important changes occurring in the velocity and pressure fields in the vicinity of the nozzle, as the air exiting from the nozzle and impinging on a flat plate, are the prime objectives of the present studies. Simulation studies were first focus on examining the flow characteristics of the system with the conventional nozzle geometry design. Some comparisons with the experimental results previously obtained by Crnojevic et al. (Crnojevic, C., Roy, G., Bettahar, A., and Florent, P., "The Influence or the Regulator Diameter and Injection Nozzle Geometry on the Flow Structure in Pneumatic Dimensional Control Systems," ASME J. Fluids Eng., 119, pp. 609-615) were also made. Further simulation studies were conducted with particular attention to a more efficient nozzle geometry. It was found that a divergent type of nozzle design could effectively eliminate the flow separation regions within the nozzle head. By allowing the divergent angle of the nozzle head (a) to vary (from zero to about 25 degrees), a more extensive and sensitive measurement range can be achieved at a given pressure regulator diameter to nozzle diameter ratio. © 2000 by ASME.