Residual surface topology modeling and simulation analysis for micro-machined nozzle

The performance of the micro nozzle is determined primarily by its machined surface topology. A circular cross-section micro-Laval nozzle is modeled and studied by using numerical simulation in this paper. The geometry of residual height and residual area of machined nozzle surface with flat-end milling cutter and ball-end milling cutter are created. It is found that the ball end milling cutter with large diameter is better than the flat one for nozzle finishing operations. The nozzle velocity performance is also revealed in this research. When residual height increased from 0.6 μm to 9.6 μm for nozzle with throat diameter less than 2 mm, the maximum outlet velocity of nozzle reduced gradually. The maximum outlet velocity of nozzle remains stable for the nozzle with throat diameter greater than 2 mm. The results show that the maximum outlet velocity of nozzle significantly reduces with throat diameter decreasing under constant residual height. Based on the analysis about velocity boundary layer, when residual height changing from 0.6 μm to 9.6 μm, the nozzle with throat diameter is 1 mm, has the boundary layer thickness ranging from 5% to 14% of outlet radius.