The effect of fluid temperature on basic characteristics about liquid nitrogen cavitating flows

Cryogenic fluid is used for a propellant of liquid rockets and for a coolant of superconducting systems. Cavitation is easily caused by a variation of the shape of pipes, many obstacles and heat inclusion in cryogenic apparatuses. They get into troubles like unstable flows, flow beatings, performance decrements and destructions of the apparatuses. However, the study of cryogenic cavitating flows is not so enough because of the difficulties of experimental techniques and the characteristics. In this study, a visualized experiment about cryogenic cavitating flows passing through a convergent-divergent nozzle installed in a horizontal pipe was carried out to clarify the basic flow characteristics. As a result, the characteristics of cavitating flows at the boiling temperature under the atmospheric pressure were different from those at the lower temperature. At the boiling point under atmospheric pressure (T=77K), cavitating flows were more stable and the pressure oscillation at the transient region was small. However, at lower temperature (T=69K), cavitating flows occurred intermittently and the pressure increases abruptly whenever cavitation appears.