Jet Flow Field Analysis of Convergent‐Divergent Nozzle for Hydraulic Perforation for Natural Gas Hydrates

ABSTRACT The nozzle is a critical component of hydraulic sandblasting perforation tool used in hydrate reservoir stimulation, with its jet performance significantly influencing the penetration depth. The cavitation effect generated by convergent‐divergent nozzle contributes to enhance jet performance. Thus, it exhibits better jet performance compared to conventional conical straight nozzle. In this study, the mixture multiphase flow model, the RNG k‐ε model and the Schnerr‐Sauer cavitation model are employed to numerically simulate the flow field of the convergent‐divergent nozzle. When the outlet diameter and inlet velocity are fixed, the cavitation effect of nozzle and the influence of various structural parameters on jet performance are analyzed. Based on single‐factor and orthogonal experimental analyses with axial velocity and vapor volume fraction as evaluation indices, the geometric structure of the convergent‐divergent nozzle is preliminarily optimized as follows: contraction segment length = 16 mm, contraction angle = 30°, cylindrical segment length‐diameter ratio = 1, diffusion segment length = 12 mm, and diffusion angle = 20°.