|
|
|
|
| NIRE Annual Report | 
| 1998 |
Numerical Analysis of the LPG DispersionSystem Safety DivisionSafety Engineering Department |
|---|
Objectives
Recently, propane is planned to be supplied in various forms. The accidental release of propane, if used widely as residential fuel, is potential hazard especially in densely populated areas. There is a need to research on the gas behaviour in various complicated diffusion fields.
Numerical analysis for the diffusion of dense gas around fixed block(s) has been performed. As the dense gas, propane is leaked from a pipe diffused into the flows around cubic block(s). For the calculations, we used the program code PHOENICS ver.2.1.2. We calculated the gas concentration distribution, as influenced by the obstacles, and the number and arrangement of the block(s) were changed. We applied the Lam-Bremhorst's Low-Reynolds number turbulence model (L-B model). To take buoyancy into account, we calculated the density in each cell as a function of the gas concentration. The simulation results are compared with the experimental concentration measured in the wind tunnel.
Results
We calculated the propane concentration contours on the floor plane using models for three block configurations. The concentration distributions for each case are shown in Fig.1 for the x-z (horizontal, on the floor) plane. The range of propane concentration figures is 5.39×10-6 to 60 [LEL%]. The shapes of the contour lines in the numerical calculation results are very similar to those of the wind tunnel experiments for all three cases.
Studying the contour in x-z plane, characteristic results were obtained. In the no block condition, the contour figure shows fork- shape shown in the top of Fig.1. According to our wind tunnel experiments, a pair of large eddies on x-z plane was observed. On a plane vertical to the main flow direction, the eddies are generated by the gravitation of the dense gas itself and its flow direction is from outside to inside of the gas cloud. Since the fork shaped concentration profile was able to be predicted, for example, it is thought that computer simulation can be applied to dense gas dispersion phenomena to study fine scale behaviour.
Selected Publications
1) Numerical Analysis of the Dense Gas Dispersion around Cubic Obstacles, Journal of NIRE, 5, No.3, 53-61, 1996. 2) Release and Dispersion of Liquefied Petroleum Gas, Journal of NIRE, 5, No.3, 35-41, 1996. 3) Simulation for the diffusion of High Density Gas around Blocks, Journal of Computational Fluid Dynamics & its applications, 9, No.3, 308-325, 1996.