LO2 Tank Research Articles

Thermal analysis of coupled vapor-cooling-shield insulation for liquid hydrogen-oxygen pair storage

The long-term storage of liquid hydrogen (LH2)-liquid oxygen (LO2) pair with extremely low heat leakage is essential for future deep space exploration. Vapor-cooled shield (VCS) is considered an effective insulation structure that can significantly reduce the heat penetration into the LH2 tanks, however it is relatively ineffective for the LO2 tanks. Novel coupled VCS insulation schemes for LH2-LO2 bundled tanks were proposed to achieve optimal performance not only for the LH2 but also for the LO2 tanks. A thermodynamic model had been developed and validated by experiments. The optimal VCS location, the temperature profile within the insulation, the heat leakage reduction contributed by the VCS, and the thermal performance versus scheme structural mass had been parametrically investigated. A comparison indicated that the proposed single integrated shield configuration can reduce the heat flux of the LH2 and the LO2 tanks by 64.0% and 54.8%, respectively compared with the non-VCS structure. In addition, the results also confirmed that zero boil-off storage of LO2 can be achieved by only utilizing the exhausted hydrogen vapor, with no need for an extra cryocooler.

Coupling optimization of composite insulation and vapor-cooled shield for on-orbit cryogenic storage tank

The long-term storage of cryogenic propellants on orbit under thermal and pressure control is a promising enabling technology for future space exploration. Composite insulation composed of polyurethane foam (Foam), variable density multilayer insulation (VD-MLI), and a vapor-cooled shield (VCS) is considered as an effective passive thermal control method for such missions. This paper presents a theoretical model that considers three heat transfer mechanisms simultaneously within the VD-MLI and convective heat transfer inside the VCS, to predict and optimize the thermal performance of the insulation combination. The model is validated by experimental data. The influences of VCS position and warm boundary temperature (heat flux) on the thermal insulation performance are investigated for LH2, LN2, LO2, and LCH4 tanks. The temperature profiles within the insulation material with or without VCS are compared. In addition, the contributions from the VCS to reduce the heat flux into the tank are evaluated. The conclusions are valuable for the optimal design of future composite insulation with Foam/VCS/VD-MLI for cryogenic storage tanks on orbit.

Investigation on pressurization behaviors of two-side-insulated cryogenic tank during discharge

Reducing pressurant gas requirement is of importance to the design of pressurization systems. In the present paper, a two-side-insulated tank, in which both of interior and outside surfaces of the tank wall are covered by insulation layers, is proposed, and a computational fluid dynamic (CFD) approach is introduced to investigate its thermal behaviors and pressurization performance. The pressurant gas requirement, temperature distributions, and energy distributions within the tank system are obtained and analyzed. The results show that the inner insulation layer can remarkably reduce the gas requirement during the liquid discharge period. For the event of pressuring a liquid oxygen (LO2) tank with 300K helium gas, a decrease in gas requirement of 16% could be reached by using a 3-mm-thickness foam layer at the tank interior surface. For the event of pressuring a liquid hydrogen (LH2) tank with 300K hydrogen gas, the same thickness foam layer produces a decrease of 14.2% in gas requirement. Moreover, the effect of inner insulation layer in reducing gas requirement is more significant with the increase of inlet gas temperature. When 600K helium gas is used to pressure the LO2 tank, a decrease of 23.2% in gas requirement is reached by only a 1-mm-thickness foam layer in comparison with the tank without inner layer. The effect of inner insulation layer in reducing gas requirement is mainly because the energy distribution, occupied by ullage, wall, inner insulation layer and liquid propellant, is changed. Since the character of low thermal conductivity for the insulation material, there is a significant temperature drop within the insulation layer by which the heat transfer from ullage to insulation layer is reduced apparently, resulting in more energy left in ullage to provide pressurization effect. However, the gas-to-liquid heat transfer is also enhanced due to the warmer ullage caused by the introduction of inner insulation layer, which suppresses the energy proportion rise in the ullage region. In general, the introduction of inner insulation layer can distinctly reduce the pressurant gas requirement in the pressurized discharge process of cryogenic tanks, and the two-side-insulated tank technique may be an alternative technique in the design of pressurization system.

Transient thermal and pressurization performance of LO2 tank during helium pressurization combined with outside aerodynamic heating

A computational fluid dynamic (CFD) model, which can simultaneously account for the heat exchanges inside the tank and outside aerodynamic heating, is constructed to investigate the transient thermal and pressurization performance of cryogenic tank during discharge. Besides the fluid and tank wall regions, the foam region is also considered as the computational domain. Reference enthalpy method is used to account for the outside aerodynamic heating effect. The predictive ability of the CFD model is evaluated on the basis of the comparisons between its results and experimental data and a good agreement is obtained. Then the model is used to predict a pressurized discharge event, and the thermal and pressurization behaviors are obtained and analyzed. The results show that outside aerodynamic heating cannot penetrate the foam layer to facilitate the pressurization performance. Conversely, a certain proportion of energy might be transferred from heated tank wall to foam layer, which exert a negative effect on the pressurization behaviors. The aerodynamic heating effect may not be accounted for in the CFD simulation of a foam-insulated tank, if the thermal performance at outer surface of the tank is not particularly concerned. Generally, this paper supplies an effective way to predict pressurization performance and expresses valid results of the thermal performance inside and outside the cryogenic tank during discharge. It is also stated that the CFD model has a better accuracy in predicting pressurization characteristics.

Nonlinear Behavior of Space Shuttle Superlightweight Tank Under Booster Ascent Loads

Results of linear-bifurcation and nonlinear analyses of the Space Shuttle superlightweight (SLWT) external liquid-oxygen (LO2) tank for an important early booster ascent loading condition are presented. These results for thin-walled linear elastic shells that are subjected to combined mechanical and thermal loads illustrate an important type of response mode that may be encountered in the design of other liquid-fuel launch vehicles. Linear-bifurcation analyses are presented that predict several nearly equal eigenvalues that correspond to local buckling modes in the forward ogive section of the LO 2 tank. In contrast, the nonlinear response phenomenon is shown to consist of short-wavelength bending deformations in the forward-ogive and barrel sections of the LO2 tank that grow in amplitude in a stable manner with increasing load. Imperfection sensitivity analyses are presented that show that the presence of several nearly equal eigenvalues does not lead to a premature general instability mode for the forward-ogive section. For the linear-bifurcation and nonlinear analyses, the results show that accurate predictions of the response of the shell generally require a large-scale, high-e delity, e nite element model, and that a design based on a linear-bifurcation buckling analysis and a buckling-load knockdown factor is overly conservative. Results are presented that show that the SLWT LO 2 tank can support loads in excess of approximately 2.6 timesthevaluesof theoperationalloads considered. In addition, results are presented that show that local bending deformations may cause failure of the thermal protection system (TPS) at load levels less than the load level corresponding to structural collapse. Results are presented that can be used to estimate the load level at which TPS failure is likely to occur.