도시가스 수직 배관 내 정지된 수소-메탄 혼합가스의 성층화 현상 연구

The stratification phenomena of still hydrogen (20%) and methane (80%) gas mixture in a vertical urban gas pipe have been investigated by simulating the flows based on a mixture model.
The stratification is accompanied with the natural convection by the buoyancy force. The hydrogen volume fraction in the upper sections of the pipe increases with time but the increasing rate gets smaller due to the weaker buoyancy force. The pipe with a smaller diameter exhibits a higher peak of hydrogen concentration. The size of vortices is proportional to the pipe diameter. The slip velocity between hydrogen and methane oscillates with a large amplitude at the earlier stage of stratification and then the amplitude decreases sharply. The slip velocity decreases with the diameter, making the stratification become slower. The length of pipe does not affect the stratification since the pipe is sufficiently long relative to the size of vortices.