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Presented in this paper is part of an experimental series conducted at different altitudes to investigate the influence of altitude on the flammable liquids flash point. The BS-1 closed bomb apparatus is used to measure the flash points of two flammable liquids (dimethylacetylamide (DMA) and RP-5 Jet A) in a hypobaric chamber under the altitude change from 4860 km to the sea level. The experimental results show that the flash points of DMA and Jet A decrease linearly with the increase in altitude in the low altitude region below the corresponding critical altitudes but non-linearly above. The critical altitudes for DMA and RP-5 Jet A are found to be 3 km and 3.83 km respectively. When the altitude reaches or surpasses the critical altitude, the flash point decreases rapidly. In particular, the flash point of the DMA exhibits a peculiar sudden transition above the critical altitude.

Flash point and boiling point are the important physical property of the flammable liquids, and are important parameters to evaluate their combustion behavior. In this study, as series of measurement of two mono compound fuels (N-decane and N-hexanol) and two mixture compound fuels (0# diesel and Jet A) at different pressure were carried out by using the flash point (open-closed cup) and boiling point measuring apparatus in an altitude chamber at different sub-atmospheric pressures at 35 KPa, 45 KPa, 55 KPa, 65 KPa, 75 KPa, 85 KPa, 95 KPa and 101 KPa were conducted. Based on the theoretical formula between the flash point (TF) and the boiling point (TB) and the atmosphere pressure, the relationship between TB and TF has been derived. The experiment results and the theoretical formula all show that the flash point is in linear relationship with the boiling point. The results can provide a more scientific insight into the production, storage, transport and use of fuel and the safety design in aircraft fuel tank.