Study of influence of processing parameters on performance of micro-nozzles

Abstract

The inevitable milling-induced surface defects are overlooked in studies on micro-thruster performance optimization, resulting in a significant discrepancy between theoretical and actual flow fields that cannot directly guide engineering applications. This paper adopts a scheme of systematically varying tool type, radius, and stepover, and conducts a theoretical validation with a thrust deviation of merely 0.16%. On the basis of thrust data and velocity contours, the micro-nozzle aerodynamic performance under various machining parameters is comparatively analyzed. With attention paid to thrust magnitude and flow field stability, three tool types are evaluated in terms of overall performance. Results show that a critical stepover threshold of approximately 75 μm exists across all tool types, beyond which thrust degrades rapidly and nonlinearly. A 400 μm ball end mill radius maintains thrust above 1850 mN even at a 200 μm stepover, while smaller radii result in severe performance deterioration due to enhanced adverse pressure gradients. For chamfer end mills, a steep 60° chamfer sustains thrust above 1820 mN at 200 μm stepover, whereas shallow 15° chamfers cause thrust to drop below 1750 mN. Among the three cutter types, the ball end mill yields the best overall performance, delivering approximately 2% higher average thrust than the flat end mill and the chamfer end mill, while also exhibiting superior flow stability with the smallest thrust standard deviation.