The engine of cryogenic liquid rocket is required for fully precooling by natural circulation before launching

and the return flow location of the circulation loop plays an important part in field distribution of tank.In the present investigation

the physical field of tank with different return flow locations was simulated numerically based on computational fluid dynamics(CFD) technique

the distributions of temperature and velocity fields were depicted

the effect of the return flow location on thermal stratification was analyzed.It is found that the return location at 2 meter above the bottom header is optimal

where the volume and depth of subcooled liquid oxygen in tank have the most values

thus providing an important theoretical support to the design of rocket propulsion system.