Compression response and shock-wave behavior of liquid nitrogen caused by energy injection in an enclosed pipeline

Abstract

In a cryogenic liquid medium, shock waves will be formed by the expansion of compressed gas that has been vaporized due to the injection of a large amount of energy. This may severely threaten the reliability of high-Tc superconducting (HTS) apparatus. Several studies have documented the destructive forces of evaporating nitrogen produced by arc energy. However, the properties of and propagation mechanisms relating to pressure waves in liquid nitrogen have yet to be understood. The aim of this study was to clarify the evolution of pressure waves within an enclosed pipeline and reveal the effects of several factors such as the pipe size and the injected energy on the shock-wave impact using explosion dynamics simulations. The results provide evidence for the strengthening of shock waves due to multiple reflection and superposition. In addition, analysis of the pressure impulse and effective strain reveals that, in the case of moderate injected energy, the overall shape of the inside wall of the pipe will remain unchanged except at the points closest to the explosion center; in contrast, the ends of the pipeline may suffer from more severe deformation. Finally, the calculations suggest that the shock-wave impact increases almost linearly with the injected energy, and in logarithmic coordinates, the pressure is inversely proportional to the explosion distance. These findings provide a better understanding of the characteristics and propagation patterns of shock waves in liquid nitrogen, and they lay a foundation for evaluating the safety of HTS cables and energy pipelines.