Multi-Objective Optimization of Structural Parameters of an Ultra-High-Pressure Premixed Abrasive Waterjet Mixing Valve

The mixing valve is a key component of an ultra-high-pressure premixed abrasive waterjet system, in which the abrasive–water mixing uniformity plays a decisive role in determining the erosion and cutting performance of the jet. The geometric parameters of the mixing chamber inside the valve are therefore critical factors affecting this uniformity. In this study, the liquid–solid two-phase flow within the mixing chamber was numerically investigated using the Eulerian k–ε turbulence model coupled with the Fluent–Rocky DEM approach. Single-factor simulations were first conducted to identify the effective ranges of key structural parameters influencing the mixing performance. Subsequently, a response surface model was established to describe the relationship between the mixing efficiency (ME) and four critical chamber parameters, namely the throat diameter (TD), throat length (TL), abrasive inlet pipe diameter (AD), and the distance between the throat exit and the abrasive inlet pipe center (TE). Based on this model, the optimal structural parameters of the mixing chamber were determined. The results indicate that when TD = 4 mm, TL = 12 mm, AD = 10 mm, and TE = 7 mm, the simulated ME reaches 34.40% ± 0.49%, which is in close agreement with the predicted value of 34.57%. Experimental validation conducted on a premixed abrasive waterjet test rig shows that the mean absolute relative error between the simulated and measured ME values is 7.54%, which is below the 10% threshold, confirming the reliability and accuracy of the numerical model.