Flow analysis and nozzle-shape optimization for the cold-gas dynamic-spray process

Abstract

An isentropic, one-dimensional model is used to analyse the dynamics of dilute two-phase (feed powder particles plus the carrier gas) flow during the cold-spray process. While the physical foundation of the model is quite straightforward, the solution for the model can be obtained only numerically. The results obtained show that there is a particle-velocity-dependent, carrier-gas-invariant optimal value of the relative gas/particle Mach number that maximizes the drag force acting on feed powder particles and, hence, maximizes the acceleration of the particles. Furthermore, it is found that if the cold-spray nozzle is designed in such a way that at each axial location the acceleration of the particles is maximized, a significant increase in the average velocity of the particles at the nozzle exit can be obtained. For the optimum design of the nozzle, helium as the carrier gas is found to give rise to a substantially higher exit velocity of the particles than air. All these findings are in good agreement with experimental observations.

An Investigation on Temperature Distribution Within the Substrate and Nozzle Wall in Cold Spraying by Numerical and Experimental Methods

“…The existing studies on this field mainly focused on two aspects including the optimal design of the CS nozzle (Ref [5][6][7][8][9][10][11][12] and the investigation on the parameters influencing the gas flow and particle acceleration ( . Notwithstanding these findings, several important problems still need to be further studied, such as the heat exchange between the hot gas and the adjacent solid bodies, e.g., spray nozzle and substrate, in CS.…”

Finite Element Modeling and Analysis of Powder Stream in Low Pressure Cold Spray Process

“…Grujicic et al [11] were able to employ a one-dimensional model to predict the particle velocity at nozzle exit and particle behavior upon impact with a substrate during CGDS. One-dimensional models generally used to analyze the dynamics of dilute two-phase (feed-powder particles suspended in a carrier gas) flow during the cold-gas dynamicspray process; require the use of numerical procedures to obtain solutions for the governing equations.…”

“…(11) and (12) in Eqs. (6), (8), (10) results in the following finite element equations: (a) Continuity equation: Z X e q g oa T ox j :c:dx ¼ 0 ð13Þ…”

Study of the particles deformation of nickel coatings obtained by the cold gas-dynamic low pressure spraying technology

“…Данная модель используется с целью определения температуры поверхности контактного вза-имодействия напыляемых частиц и оценки возможно-сти плавления материала в зоне высоких напряжений, предела текучести материала частиц при деформации, энергетического баланса между кинетической энергией частицы и ее пластической работой, выполняемой при деформации вместе с выявлением влияния пластикации материалов для холодного напыления. В модели при-няты следующие допущения [5,6,[8][9][10][11][12][13][14][15]:…”