Analysis of leakage characteristics and leakage point diameter prediction in supercritical CO2 pipeline

Abstract

This study systematically investigates supercritical CO₂ pipeline leakage dynamics using an integrated experimental platform. Real-time multi-sensor monitoring and high-speed photography reveal continuous phase transitions during leakage, with pressure and temperature exhibiting three distinct stages: stable phase, rapid decline phase, and slow stabilization phase. The Joule-Thomson effect dominates temperature variations, with cooling intensity scaling proportionally to flow velocity. The leakage orifice size significantly influences leakage dynamics: orifices lead to exponentially increasing pressure drops. A relationship between orifice diameter (D) and pressure drop (△P) is established. Jet development is categorized into three stages—slow growth, rapid expansion, and stabilization. Leakage orifice significantly affects jet outlet velocity; at an orifice of 1 mm, velocity changes from 6 m/s to 20 m/s in a short time, and larger orifices exacerbate this change. Variations in leakage orifice diameter exert a more pronounced influence on the jet expansion angle (θ_c). When the orifice diameter increases from 0.5 mm to 3 mm, θ_c rises from 16.365° to 40.965°. In contrast, the core contraction angle (θ_d) demonstrates higher sensitivity to pressure fluctuations: as pressure increases from 8.7 MPa to 9.31 MPa, θ_d increases from 4.844° to 8.615°. These findings provide critical data support for safety design, risk assessment, and emergency response strategies of supercritical CO₂ pipelines.