Abstract: As a key focus of airworthiness safety, the fuel tank's flammability is a crucial factor affecting flight safety. To investigate the flammability of the central fuel tank of a certain aircraft under specific flight envelopes without adopting flammability reduction measures (FRM), considering the fuel consumption during the flight, a heat transfer model and a two-phase flow model of the central fuel tank were established. A three-dimensional simulation of the fuel temperature heat transfer process was conducted, and the simulation data were compared with flight test data to verify the accuracy of the model and the credibility of the simulation results. The flammability exposure time of the fuel tank was calculated based on the flammable temperature limit of RP-3 fuel, and the flammability of the fuselage fuel tank was assessed in accordance with the flammability exposure time specified by relevant airworthiness standards. The results show that the error between the simulated fuel temperature data and the flight test data is small, and the maximum relative error is not more than 10.24%, indicating high reliability. Under the selected flight phase time calculation domain, the flammability exposure time of the fuselage fuel tank is 76.7%, posing an extremely high flammability risk. Therefore, monitoring the fuel temperature and adopting FRM for the fuselage fuel tank are crucial.

Key words: fuselage fuel tank, heat transfer model, two-phase flow model, three-dimensional simulation, flammability assessment