The transient thermal behavior in the cryogenic oxidizer tank for the liquid propulsion system of the KSLV-I satellite launching space vehicle is theoretically investigated for the pressurization process by gaseous helium injection followed by the readiness check stage. The numerical model is established using the transient mass and energy conservation of oxygen/helium mixtures both in ullage and liquid regions. At the liquid-gas interface, various modes of heat and mass transfer are considered, including the liquid evaporation and the helium absorption. The present study focuses on the effects of the increasing pressurization level on some of important properties that should be considered in the propulsion system design, such as tank pressure, ullage gas temperature, and evaporation of liquid oxygen. Particularly, the tank pressure drop after the pressurization is investigated in the proposed design of propulsion system. Also, the effect of the initial loading of liquid oxygen in the oxidizer tank is studied and discussed. As for the helium absorption into the liquid region, its mass is negligibly small and it should not be the concern in design and operation of the oxidizer tank system.

In this study, analysis of the overspray fogging process, which consists of inlet fogging and wet compression processes in gas turbine cycle, is carried out with a non-equilibrium analytical modeling based on liquid droplet evaporation. The transient behaviors of droplet diameter and air temperature are examined. Special attention is paid to the effects of system parameters such as pressure ratio, water injection ratio, and initial droplet diameter on the process performances, including evaporation time of droplets, compressor outlet temperature, and compression work. Process performances are also estimated under the condition of critical water injection ratio above which complete evaporation of injected water droplets within a compressor is not possible. The analytical results indicate that the overspray fogging process has a potential of lowering compressor outlet temperature and saving significant compression work when compared to dry compression, and this technique is more effective for a higher pressure ratio and smaller size of injected water droplet.

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