Numerical Calculation of Particles Velocity under the Compressible Fluid in Fine Particle Bombardments(Machine Elements, Design and Manufacturing)

Abstract

Surface modification by fine particle bombardment is mainly influenced by the velocity and diameter of a particle as well as the material properties. In this study, numerical calculation of particles velocity through a convergent nozzle is conducted by considering air as a compressible fluid. Because the axial flow of the convergent nozzle was much more dominant than that of a flat nozzle, the modeling of particle bombardment was accomplished based on a one dimensional isentropic fluid flow. The apparatus presupposed here is a direct pressure-type shot peening machine in which the air inside the nozzle expands and accelerates to the critical speed. Then, the particle accelerates by drag received from air, and the particle velocity increases up to the air velocity. The results of our numerical calculations show the particle velocity obtained from our numerical calculations values is close to that of the experimentally measured values. This demonstrates that our simple and easy model is reasonably accurate and can be used to give insight into the mechanism and selection of optimum drive parameters such as size and material properties of the particles used in the shot peening process.