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<p>To address the challenges associated with machining the ultra-smooth surfaces of calcium fluoride (CaF<sub>2</sub>) crystals, this paper investigates the effect of negative-pressure structure on the jet polishing performance of rotating nozzles, with ultraviolet (UV)-assisted nanoparticle colloid adopted as the polishing process, aimed at improving the stability of the flow field in the machining zone to achieve superior workpiece surface quality. A negative-pressure rotating nozzle was designed in this study. Through computational fluid dynamics (CFD) analysis, the flow field characteristics (including velocity, pressure, and turbulence intensity) of the negative-pressure rotating nozzle were compared with those of a conventional rotating nozzle, and the flow field optimization mechanism was elaborated from the perspectives of wall shear stress and particle impact behavior. Furthermore, the influences of key process parameters including inlet pressure, outlet negative pressure and jet distance on the flow field characteristics were systematically explored. Simulation results indicate that the negative-pressure rotating nozzle effectively suppresses turbulent diffusion; its exit turbulence intensity (15.5) is significantly lower than that of the conventional rotating nozzle (20.9), while exhibiting stronger jet vorticity and a more stable flow field. Polishing experiments were conducted, and the effects on the surface topography and roughness of CaF<sub>2</sub> crystals were evaluated using atomic force microscopy (AFM). The experimental results showed that after polishing with this nozzle, the surface roughness Sa of the CaF<sub>2</sub> workpiece decreased from an initial value of 1.92&#xa0;nm to 1.36&#xa0;nm. The maximum peak-to-valley height Sz on the workpiece surface was significantly reduced from 457&#xa0;nm to 33&#xa0;nm. Under the same process parameters, the negative-pressure structure improves polishing uniformity by stabilizing the jet flow field. Compared with the conventional rotating nozzle, it yields comparable arithmetic mean roughness Sa, but significantly reduces the maximum peak-to-valley height Sz and delivers better surface flatness.</p>

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The effect of negative-pressure structure on the jet machining performance of rotating nozzles

  • 期刊论文

  • 发表日期：

    2026年8月1日

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  • Xingwu Ma,
  • Huilong Zhao,
  • Junfeng An,
  • Xinyao Du,
  • Zhijie Qin,
  • Xiaozong Song

摘要

To address the challenges associated with machining the ultra-smooth surfaces of calcium fluoride (CaF2) crystals, this paper investigates the effect of negative-pressure structure on the jet polishing performance of rotating nozzles, with ultraviolet (UV)-assisted nanoparticle colloid adopted as the polishing process, aimed at improving the stability of the flow field in the machining zone to achieve superior workpiece surface quality. A negative-pressure rotating nozzle was designed in this study. Through computational fluid dynamics (CFD) analysis, the flow field characteristics (including velocity, pressure, and turbulence intensity) of the negative-pressure rotating nozzle were compared with those of a conventional rotating nozzle, and the flow field optimization mechanism was elaborated from the perspectives of wall shear stress and particle impact behavior. Furthermore, the influences of key process parameters including inlet pressure, outlet negative pressure and jet distance on the flow field characteristics were systematically explored. Simulation results indicate that the negative-pressure rotating nozzle effectively suppresses turbulent diffusion; its exit turbulence intensity (15.5) is significantly lower than that of the conventional rotating nozzle (20.9), while exhibiting stronger jet vorticity and a more stable flow field. Polishing experiments were conducted, and the effects on the surface topography and roughness of CaF2 crystals were evaluated using atomic force microscopy (AFM). The experimental results showed that after polishing with this nozzle, the surface roughness Sa of the CaF2 workpiece decreased from an initial value of 1.92 nm to 1.36 nm. The maximum peak-to-valley height Sz on the workpiece surface was significantly reduced from 457 nm to 33 nm. Under the same process parameters, the negative-pressure structure improves polishing uniformity by stabilizing the jet flow field. Compared with the conventional rotating nozzle, it yields comparable arithmetic mean roughness Sa, but significantly reduces the maximum peak-to-valley height Sz and delivers better surface flatness.