Analyses of Cryogenic Propellant Tank Pressurization based upon Experiments and Numerical Simulations
The active-pressurization of cryogenic propellant tanks for the launcher application was analyzed in this study. Therefore, ground experiments, numerical simulations and analytical studies were performed with the following important results: In order to minimize the required pressurant gas mass, a higher pressurant gas temperature is advantageous or the application of helium as pressurant gas. Numerical simulations of the pressurant gas mass using Flow-3D show good agreement to the experimental results. The dominating heat transfer during pressurization appears from the injected pressurant gas to the axial tank walls and the predominant way of phase change during the active-pressurization phase depends on the type of the pressurant gas. After the end of the pressurization phase, a significant pressure drop occurs. A theoretical model is presented for the analytical determination of this pressure drop.
Experimental and Numerical Investigation of Stratification and Self pressurization in a High Pressure Liquid Nitrogen Storage Tank
ABSTRACT This paper discusses the evolution of stratification and self-pressurization in a cryogenic storage tank. The heat ingress due to the large temperature difference between ambient and cryogen leads to thermal stratification and self-pressurization. The prediction of the thermodynamic state of cryogen is required for the successful execution of any space mission. An experimental cryogenic test tank which is a combination of an evacuated vacuum jacket and multilayered insulation has been designed, fabricated and is used for stratification studies using liquid nitrogen as the model propellant. Stratification at two conditions were tested; ‘venting’ and ‘non-venting’. During venting condition, only saturated boiling occurs, and the degree of thermal stratification is very less. Whereas during non-venting condition, there is a significant amount of thermal stratification and the degree of thermal stratification increases with working pressure. For a deeper understanding of the phenomenon and better prediction of the state of cryogen, a numerical model had been developed and validated with the experimental result. A stratification parameter has been used to quantify the degree of stratification for both “venting” and “non-venting” conditions. The model developed can be used for accurate prediction of the state of cryogen.
THE PERFORMANCE OF STEADY DETONATION ENGINES
Propulsion systems driven by steady normal detonations are studied. The practical di‐culties associated with stabilizing a detonation wave are highlighted. The requirement on the freestream total enthalpy is considered in parallel with efiects such as condensation or auto-ignition of the fuel-air mixture and limitations associated with fuel sensitivity to detonation. A criterion for detonation stabilization is formulated and applied to an analytical treatment of a detonation ramjet and a detonation turbojet, which are the respective analogs of the ramjet and the turbojet using detonative combustion. The performance of these engines is evaluated and compared to the ideal ramjet and turbojet models for hydrogen and JP10. A limitation is placed on the maximum total temperature allowed in the combustor, based on material considerations. The results show that steady detonation engines have a small thrust-producing range, due to the requirements for detonation stabilization. Their performance is always lower than that of the conventional ramjet and turbojet because of the total pressure loss across the detonation.