Experimental And Simulation Study On Direct Cryogenic Helium Pressurization System In Kerosene Tank

The pressurization system is an important part of carrier rocket,its structure and form have great influence on carrying capacity and stability of the rocket.The common methods of pressurization system include fuel gas pressurization,self-generation pressurization and gas cylinder pressurization.Among these methods,gas cylinder pressurization is widely used due to its good compatibility and flexible design.Meanwhile,helium is often use as the pressurized gas due to its low density and low boiling point,which is not easy to condense.The pressurization which use cryogenic helium as the medium is called cryogenic helium pressurization.The cryogenic helium pressurization system is widely used in liquid hydrogen/liquid oxygen and liquid oxygen/kerosene rockets.At present,due to the requirements of heating the cryogenic helium to the roomtemperature or high temperature,heat exchangers are often needed to be installed in the cryogenic helium pressurization system,which make the system has a more complex structure and bigger mass.If the principle and structure can be optimized,and omit some needless parts,the structure mass of liquid rocket can be reduced well,and the carrying capacity of rocket can be improved effectively.In this paper,the structure optimization design of cryogenic helium pressurization system of the liquid oxygen/kerosene rocket is carried out.Meanwhile,to verify the practical effect of the optimization scheme and explore relevant laws,experimental research and simulation analysis are carried out for the scheme.The specific research contents and conclusions are as follows:(1)For liquid oxygen/kerosene rocket,the scheme of direct cryogenic helium pressurization system in kerosene tank is put forward.In this scheme,the cryogenic helium bottles are stored in the oxygen tank,and the cryogenic helium will be directly send into the liquid area of kerosene tank during pressurization.The cryogenic can be heated by the kerosene directly without heat exchanger.In this way,the significant pressurization effect can be achieved,and the heat exchanger can be saved.Furthermore,the structure mass is reduced.(2)Based on the scheme of direct cryogenic helium pressurization system,a ground experimental system was developed and built.The normal temperature helium was cooled by liquid nitrogen to obtain cryogenic helium,which can simulate the helium in the liquid oxygen temperature on rocket.Meanwhile,a scale tank model in the ground experimental system was built to simulate the kerosene tank in rocket.The cold helium gas was send into the kerosene tank for pressurization and drainage,and the experimental data during this process was obtained to evaluate the actual pressurization effect of the scheme,and the law of pressurization was analyzed.(3)Based on the experimental system,experiments ware carried out with different pressurization gas inlet positions,diffuser forms,pressurized gas medium and drained medium,and the influence of these factors on pressurization was analyze.Through experiments,a fact is established that the pressurized gas has a stronger pressurizing ability when it is send into the liquid area.About 33.1% of helium can be saved under the same condition.However,it is more difficult to stabilize the pressure and drainage flow.The similarity between helium and nitrogen,kerosene and water is analyzed through experiments.In addition,it is confirmed that under many working conditions,the phenomenon of liquid freezing and bubbles entering the drainage pipeline did not occur.(4)A numerical model was built,and the influence of drainage flow on pressurization was analyzed.For pressurization in the liquid area,since the pressurized gas is fully heated,it’s temperature is close to the liquid,so its consumption rate is stable,and is not affected by the drainage flow.For the pressurization in the ullage area,the larger drainage flow results in lower ullage temperature and higher gas consumption rate.The relationship between the gas consumption rate and the drainage flow is approximately linear.Through the above research,the optimization methods of cryogenic helium pressurization system in the kerosene tank are expounded.The main factors which affect the pressurization effect is revealed,and its functional rule,which enriches the theoretical cognition and technical scheme of cryogenic helium pressurization system,and provides reference and help for carrying out the scheme on real rocket in the future.