Effect of multi-parameter optimization of water-laser coupling device and nozzle geometry on the stability of water-guided laser beam

The stability of the water jet flow used in water-guided laser processing plays a crucial role in determining the quality of the processing process. The present study aims to investigate the effect of water-laser coupling device and nozzle geometry on the stable length of a water-guided laser beam. A numerical model is developed to analyze the internal flow field within the coupling device. Computational fluid dynamics (CFD) simulations are employed to examine how variations in cone nozzle's length-to-diameter ratio, divergence angle, nozzle aperture, and inlet pressure that affect the flow characteristics of water jet. Subsequently, the Latin Hypercube experimental design method is employed to establish parameter samples and construct a Kriging approximation model for the stable length of water-guided laser beam. The Multiple Island Genetic Algorithm (MIGA) is utilized for global optimization of the approximation model, while CFD methods are employed to analyze and validate the optimization results. Finally, experimental verification was conducted to determine the stable length of water-guided laser beam generated by the optimized cone nozzle structure. The research findings demonstrate that the optimized nozzle structure can compensate for approximately 21 mm in the stable distance of water-guided laser beam under the pressure of 5.0 MPa. This study provides valuable guidance for enhancing the performance and engineering applications of laser micro-jet processing technology.