Study On Thermal Stability Of Model Hydrocarbon Fuels

As a new kind of flammable coolant, the endothermic hydrocarbon fuel was proposed in order to solve the thermal management problem of the hypersonic vehicles. The thermal oxidation stability, heat sink and mixed-fuel of model hydrocarbon fuels were studied in the present work. The results obtained may offer important information for the development of endothermic hydrocarbon fuel.A dynamic experimental apparatus was designed for the study of model hydrocarbon fuels according to the actual test condition. It can be used to evaluate the thermal oxidation stability, heat sink and cracking properties of endothermic hydrocarbon fuel. As the model fuels, the n-octane,n-nonane, n-decane, cyclohexane, JP-10and1,2,3,4-tetrahydronaphthalene were studied on the dynamic experimental apparatus.The effects of temperature and reaction time on the total acid number and existent gum of fuels were studied. Results show that total acid number rises with increasing thermal oxidation reaction time. While with increasing the reaction temperature, the total acid number goes through a maximum then decreases. The experimental results also show that temperature plays an important role on the accumulation of existent gum, which becomes to deposit remarkably with temperature increasing.The heat sinks of six model fuels have been measured under the conditions with the temperature range from100℃to650℃,and the pressure of3.5MPa. Under the experimental conditions, the heat sink is sensitive to temperature.It increases rapidly under high temperature for the chemical reaction of fuels. In addition, we study the thermal stability of model fuels under high temperature. It is concluded that with the increasing of temperature, the decomposition conversions and yields of gas increase. The gaseous products for thermal cracking of fuels mainly contain methane, ethane, propane, ethylene, propylene, and the liquid products include alkanes, olefins, aromatic hydrocarbons and so on. It is found that the coke deposits become to appear at the distance from tube entrance of60～70cm, and reach a maximum at about85cm from the tube entrance.The densities and viscosities are determined over the whole composition range for the binary mixtures of n-octane, n-nonane and n-decane with1,2,3,4-tetrahydronaphthalene. Based on these measured data, the excess molar volume and viscosity deviation values are calculated. We also study the heat sink and thermal stability of the blended fuels of1,2,3,4-tetrahydronaphthalene/n-decane. It can be seen that with increasing of the content of1,2,3,4-tetrahydronaphthalene.the heat sink decrease. Results also show that the conversion of blended fuel decrease with the increasing the content of1,2,3,4-tetrahydronaphthalene.The thermal stability of blended fuel is enhanced with the addition of1,2,3,4-tetrahydronaphthalene.