Experiment And Theoretical Study On Ignition Characteristics Of Typical Aviation Combustible Liquids Under Atmospheric And Reduced Pressure

Flash point and autoignition temperature(AIT)are primary properties used to determine the potential for fire and explosion hazard of fuels.The combination of increasing flight demand and fuel costs and pressure to reduce emissions has pushed the aviation industry under considerable strain.One of the best options to achieve green development is to focus on sustainable alternative aviation fuels to replace conventional fossil aviation fuels.Literature on autoignition behavior of aviation fuels focuses on the combustion mechanism of engines and the autoignition experiments at atmospheric pressure.However,conditions in these tests differ greatly from those of interest for accidental thermal ignition events in aircraft,which typically occur at relatively low pressure(<1 atm).Research on the flash point and AIT of aviation fossil fuels and alcohol alternative fuels under atmospheric and reduced pressure has scientific value and practical significance for the safe application of aviation fuels and the development of sustainable fuels,and the fire safety design and verification in the aviation field.In order to study flash point variation of hydrocarbon-alcohol fuel blends,n-dodecane,pxylene,and commercial fuels(kerosene,diesel)blending with long chain alcohols(n-butanol,n-hexanol,n-octanol)were selected.The results show that the flash point of petroleum-based fuels blending with long chain alcohols is close to or lower than the low flash point components in large concentration ranges.Liaw-UNIFAC model for the flash point prediction of complex mixture was reduced to that for binary mixture,with the introduction of average molecular structure of petroleum fuels in the activity coefficient model.The deviations between the predicted values of Liaw-UNIFAC model and experimental data were mostly within 2℃.The graphical user interface software was designed,developed,and programmed for automatic flash point calculation under various pressures.The software methods were introduced,as well as the procedure to calculate the flash point fuel blends under low pressure.The software was verified by experimental data.The flash point study is of practical value for the safe application aviation fuel blends.To study AIT variation of aviation fuel under reduced pressures(20-101kPa),five alkanes(n-heptane,n-octane,n-decane,n-dodecane,and n-hexadecane),three alcohols(ethanol,nbutanol,and n-hexanol),aviation kerosene(RP-3),and aviation lubricating oil(Mobil Jet Oil II)were selected.In addition,the AITs of five fuels were measured in a large-scale reaction vessel under low pressure.The experiment results show that AITs of different fuels typically exhibit consistent variation over a wide pressure range.The AIT prediction model was developed based on the Semenov chain ignition theory,which contains two main influencing factors of pressure and reactor scale.Experimental AIT data under various pressures in the reaction flask was used for the regression of model parameters of each fuel.The predicted results are consistent with the experimental AIT variation,however,the predictive results in larger reaction vessel are generally lower than the experimental values.The study on the AIT variation of aviation fuel is of scientific value for more in-depth and comprehensive understanding of the factors affecting AIT,and the phenomenon and nature of autoignition process.