Comparison of the Supersonic Length and Dynamic Pressure Characteristics of Discrete-Jet and Annular Close-Coupled Nozzles Used to Produce Fine Metal Powders

Published

June 1, 2000

Author(s)

Steven P. Mates, Stephen D. Ridder, Frank S. Biancaniello

Abstract

Demands for inexpensive fine metal powders for emerging P/M processing applications drive the need to maximize fine powder yields and improve the efficiency of the gas atomization method of powder production. High-speed visualization of gas-metal atomization indicate that a majority of the fine powder is produced via the disintegration of metal droplets over an extended distance within the long supersonic jet created by the coaxial gas nozzle. Because droplet breakup actively continues far from the nozzle tip, the length of the supersonic region of the gas jet strongly influences droplet breakup and the resulting particle size. Longer supersonic jets can project large dynamic pressures necessary to sustain droplet breakup far from the nozzle tip, thereby improving chances for thorough droplet atomization and a small average particle size. In this study, the supersonic length and dynamic pressure characteristics of four different converging-only close-coupled nozzles, including one annular and three discrete-jet designs, were examined to determine how nozzle geometry influences these attributes. Pitot pressure measurements revealed that nozzles which produce the longest supersonic jets and highest dynamic pressures are those that restrict the rate of mixing and entrainment of the jet by limiting the jet surface area in the initial mixing region just beyond the nozzle exit. The annular nozzle outperformed the discrete jet designs, all of which generate a greater initial jet surface area by virtue of their large nozzle exit perimeters. Among the discrete jet nozzles, those having a small inter-jet spacing and small jet ring diameter performed best.

Proceedings Title

Liquid Metal Atomization: Fundamentals and Practice, Annual Meeting and Symposium | | | TMS

Conference Dates

March 12-16, 2000

Conference Title

TMS Annual Meeting and Symposium

Pub Type

Conferences

Keywords

atomization, close-coupled nozzles, fine powder, nozzle design, supersonic jets

Citation

Mates, S. , Ridder, S. and Biancaniello, F. (2000), Comparison of the Supersonic Length and Dynamic Pressure Characteristics of Discrete-Jet and Annular Close-Coupled Nozzles Used to Produce Fine Metal Powders, Liquid Metal Atomization: Fundamentals and Practice, Annual Meeting and Symposium | | | TMS (Accessed April 19, 2024)