Unsteady and transient flow of compressible fluids in pipelines—a review of theoretical and some experimental studies

The importance of real-fluid behavior during the rapid decompression of dense natural gas mixtures has been investigated using existing one-dimensional models for real-fluid isentropic decompression (RID) and perfect-gas isentropic decompression (PID). The results show that the assumption of perfect-gas behavior may result in significant errors. In the case of ductile fracture propagation (DFP) analyses, the fracture-tip pressure level may be underestimated by more than 20 percent.



A real-fluid nonisentropic decompression (RND) model has been developed in order to investigate the importance of nonisentropic effects in DFP problems. The results indicate that nonisentropic effects may be neglected for pipe sizes above approximately 508 mm O.D.



On a etudie le phenomene de detente rapide de melanges de gaz naturels a l'aide de modeles unidimensionnels existangts pour la detente isentropique d'un fluide reel (RID) et la detente isentropique d'un gaz parfait (PID). Les resultats montrent que I'hypothese basee sur le modele du gaz parfait peut entrainer des erreurs importantes. Dans le cas des analyses de propagation de fracture ductile (DFP), le niveau de pression a l'extremite de la fracture peut etre sousestime de plus de 20 p. cent.



On a developpe un modele de detente non isentropique de fluide reel (RND) dans le but d'etudier I'importance des effect non isentropiques lors de la propagation de fractures ductiles. Les resultats montrent que les effets non isentropiques peuvent etre negliges pour des tuyaux dont le diametre exterieur depasse 508 mm.

The importance of real‐fluid behavior and nonisentropic effects in modeling decompression characteristics of pipeline fluids for application in ductile fracture propagation analysis

An efficient numerical simulation (CNGS-MOC), based on the method of characteristics for simulating full bore rupture of long pipelines containing two-phase hydrocarbons, was developed. The use of curved characteristics, in conjunction with a compound nested grid system, as well as a fast mathematical algorithm, lead to a significant reduction of CPU time, while improving accuracy. The model is validated extensively against field data including those obtained during the Piper Alpha tragedy, as well as the Isle of Grain depressurization tests. Its predictions are compared with those based on other mathematical models including PLAC, META-HEM, MSM-CS, as well as BLOWDOWN. Both CNGS-MOC and META-HEM produce reasonably accurate predictions with the remaining models assessed performing relatively poorly.

Fast numerical simulation for full bore rupture of pressurized pipelines

Calculation of the thermodynamic sound velocity in two-phase multicomponent fluids

Measurements of flow parameters and decompression wave speed following rupture of rich gas pipelines, and comparison with GASDECOM

The events following rupture of a pipeline containing gas at high pressure are very similar to those following rupture of the diaphragm in a simple shock tube. A description of the decompression wave resulting from such a rupture, and its rate of propagation in natural gases is the primary purpose of this paper. A computer program is written to calculate decompression wave velocities. The required thermodynamic properties are calculated using the Soave-Redlich-Kwong (SRK) equation of state and the results of computed wave velocities are presented and compared to values observed in the decompression zone of a shock tube.

T. K. Groves

Papers

Decompression wave velocities in natural gases in pipe lines