To address restart challenges in heavy oil‑water ring pipelines caused by water ring instability,an experimental study was conducted using a laboratory‑scale restart loop system with four conventional heavy oils. The research investigated flow pattern evolution and pressure drop characteristics during pipeline restart under constant water velocity,analyzing effects of oil holdup (Ho),oil viscosity (μo),shutdown duration (tst),and water velocity (Ucl). An exponential decay model was established to describe time‑dependent restart pressure drop. Results reveal four distinct flow pattern phases during constant‑flow restart: water shear stripping of oil layer,oil droplet/cluster migration,wall‑adherent film formation and film detachment. The pressure drop exhibits initial peak followed by decay and equilibrium stages,with model predictions showing excellent agreement (goodness‑of‑fit values approaching 1).Within tested ranges (Ho=0.26~0.76,μo=1.055 3~3.02 Pa·s,tst=0.5~1.0 h,Ucl=0.25~1.01 m/s),maximum restart pressure drop increases with Ho,μo,tst,and Ucl (up to 30.38 kPa),while restart duration extends with Ho,μo,and tst but shortens with Ucl (up to 3 616.78 s).This study provides theoretical and practical guidance for optimizing pipeline restart operations.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |