Study On Heat Transfer Stratification Characteristics Of Aircraft Fuel Tank

With the continuous improvement of aircraft performance,the demand for fuel performance is higher and higher,and the proportion of fuel tank in the aircraft is increasing.Under the aerodynamic heating,the fuel in the fuel tank will be stratified under the action of gravity,resulting in the uneven temperature distribution in the fuel tank,which is easy to cause local fuel overheating.Therefore,in this paper,the following work is carried out according to the thermal stratification characteristics of a fuel tank.Firstly,the ground simulation test of heat transfer in the fuel tank was designed and carried out.The experimental results show that the thermal stratification in the fuel tank is obvious,and the temperature difference between the top and the bottom is large,up to 47 ℃.In the case of half tank,the temperature difference of working fluid is small,and the maximum temperature difference is less than 2 ℃.When the external working fluid flows in,the thermal stratification structure inside the fuel tank will be destroyed directly,and the temperature inside the fuel tank will be evenly distributed.The numerical simulation model of the fuel tank is established,and the reliability of the simulation results is verified by comparing with the experimental results.The results show that the high temperature working fluid mainly moves along the wall towards the top of the fuel tank,and the area of the top is small,so it is easy to gather the high temperature working fluid.The flow field in the lower part of the fuel tank is dominated by vortices,which inhibits the thermal stratification and makes the temperature distribution more uniform.In the half tank state,the top area of the liquid level is larger,so the temperature difference in the central area is relatively small.Under the effect of the inflow of external working fluid,the fuel tank has a strong mixing,the whole flow field is occupied by the vortex,and the thermal stratification structure is completely destroyed.According to the structure of the fuel tank,different improvement schemes are put forward.It can be found that the baffle structure installed on the 45 ° height of the fuel tank wall can effectively prevent the high-temperature working fluid from moving to the top of the fuel tank,and the average temperature rise of the top working fluid decreases by 14%.Because the different shape of pipe has little effect on the mixing of most areas in the tank,changing the pipe shape will only produce a temperature difference of no more than 2 ℃ on the top of the tank.