Progress in Modeling Pressurization in Propellant Tanks

Abstract

Summary The pressure of propellant and oxidizer tanks has to be maintained within a narrow margin and is critical to the proper functioning of the liquid propulsion system. Several control mechanisms such as venting and spray bars are specifically deployed in the tankage to ensure that the pressure in the tank is restricted to the design margins. In this paper a suite of predictive tools have been developed that can aid in the design and management of propellant tanks. The analysis tools comprise of a multi-node lumped parameter code, a multi-phase CFD code, and a hybrid procedure that utilizes CFD in conjunction with a lumped parameter based internal boundary between the ullage and the liquid. Each tool is specifically tailored towards a certain class of tank pressurization problems: for example the multi-node lumped parameter approach is particularly suited for long duration space tank applications, while the CFD approach is applicable to short duration injection based pressurization problems where mixing is the dominant physical mechanism. In long duration cases, where injection or venting based control systems can significantly alter the flow in the tank the hybrid approach is more appealing. A series of test cases from different regimes of tank pressurization were considered in this paper with the three approaches. The first simulation was based on the Saturn AS-203 self-pressurization fuel tank experiment in a low gravity environment. The complete duration of the test was analyzed with the multi-node lumped parameter code with average heat loads through the tank walls and the