Morphological characteristics and flashing mechanism of superheated liquid jets released from rectangular breaches

The leakage of liquefied gases such as liquefied hydrocarbons and liquid chlorine is usually accompanied by an intense phase transition that results in two-phase release. This two-phase release will lead to fire, explosion, toxic diffusion and other major dangerous accidents, seriously endangering the safety of personnel and ecological environment, resulting in inestimable losses. To deepen the understanding of such accidents, a 20L tank was used to simulate the accidental release of superheated liquid and study its accident behavior. This work simulated different breaches by using different shapes of nozzles with equal cross-sectional area and more focused on rectangular nozzles. Besides, the influence of initial temperature (110–130 °C) and pressure (6–16 bar) was also taken into account. A high-speed camera was used to record the external morphological characteristics of the superheated liquid jets released from the nozzles. The jet angle and half-width were extracted as the quantitative characterization of the external morphology by threshold processing algorithm. The results revealed that the rectangular nozzle jet (RNJ) has a different external morphology from the circular nozzle jet (CNJ) due to the presence of vortex and axis-switching phenomena. Aspect ratio plays an important role in the determination of external morphology of the RNJ and there is a critical aspect ratio AR = 3. In addition, this study also demonstrates that the rectangular nozzle has a different flashing mechanism from the circular nozzle, which is the underlying reason for the different external morphologies. In summary, compared to the traditional circular breach, rectangular breach has a significant promotion effect on the jet flashing, and the industrial medium released from the slit breach will have a greater impact range, resulting in more serious consequences of accidents.