Two-phase expanding mechanism and pressure response characteristic of boiling liquid expanding vapor explosion under rapid depressurization

Abstract

The two-phase flow evolution, internal pressure, and thermodynamics responses during a BLEVE (boiling liquid expanding vapor explosion) process with water are assessed. Various initial pressures ranging from 1.7 to 5.7 barg, liquid fills load and different pressure relief ways were tested. Results show that after the pneumatic valve was opened, the rise velocity of the bubble increased first, and then decreased until the rupture or collision of the bubbles. The countercurrent flow reversed to the mainstream was experimentally observed and inhibited the expansion flow to reduce the boiling intensity. Thus, as the initial pressure increased, the average rate of pressure rose first increased, then slightly decreased due to the competitive effects of expansion flow and countercurrent flow. The interactions between the rarefaction wave driven by a sudden opening of a valve and the medium degree of superheat, control the pressure response, and the delay of boiling can be classified into the rarefaction wave control region (dp/dt < 0) and the superheat degree control regime (dp/dt> 0). And the effect of the liquid fill level on the rate of pressure rise was not affected by the countercurrent flow. The boiling explosion after the crack formed was intensified with pressure relief action caused by a separate piece of equipment, due to the enhanced heterogeneous boiling on the inner wall.