Study on cavitation flow characteristics of orifice plate-elbow structure in liquefied natural gas receiving station

In liquefied natural gas (LNG) receiving stations, the combined structure of the orifice plate throttling device and elbow becomes a high-incidence area of cavitation damage due to intense pressure gradient and flow field distortion, which seriously threatens the safe operation of the pipeline system. In this study, a numerical model based on the mixture model and large eddy simulation is developed to investigate the coupling mechanism between the condensation shock wave and reentrant jet caused by the cryogenic properties of LNG. Combined with the thermodynamically modified Tait equation and the Schnerr–Sauer cavitation model, the LNG cavitation flow characteristics and the pipe wall damage mechanism are studied in depth. It was found that the orifice plate throttling effect led to the formation of a significant pressure drop of 10–11 MPa downstream, inducing gas–liquid two-phase separation and periodic cavitation phenomena. The centrifugal force in the area of the elbow produces a localized high-pressure zone of 4–5 MPa, which is highly consistent with the measured failure location. By analyzing the four-stage evolution process of cavitation (incipient-developing-contracting-periodic collapse), the mechanism of cavity shedding under the joint action of reentrant jet and condensation shock wave is revealed, and the “supersonic” regional phenomenon unique to cryogenic cavitation is found. The research results can provide a theoretical basis for improving fluid flow stability, optimizing orifice design, and solving elbow failure problems in LNG receiving stations, thus reducing the risk of perforation failure of pipeline elbows and improving the safety and reliability of the system.