| Endothermic hydrocarbon fuels are advanced liquid propellant developed to meet the active thermal protection requirements of hypersonic aircrafts,while undertaking cooling and propulsion functions.The oxidation stability of fuel is closely related to raw materials and processing technology.Its quality will directly affect storage period and pyrolysis application of fuel,so it is the key to research.In this paper,the oxidation stability of lab-made endothermic hydrocarbon fuel EHF-1 was evaluated from four aspects: autoxidation kinetics,metal compatibility,additives and storage period,which provided applicability basis for its application.The process of fuel autoxidation can be investigated from the perspective of reaction kinetics.The reaction kinetics was investigated to study the role of antioxidants in the autoxidation of fuels,the autoxidation kinetics of EHF-1 was investigated from aspects of temperature and dissolved oxygen by accelerated oxidation.The results showed that the reaction rate of antioxidant with oxygen was faster than that of alkanes and oxygen.Moreover,the inhibitory effect of BHT was enhanced with the increase of temperature and oxygen content,but it was still weaker than the promoting effect of them on fuel oxidation.On the whole,reducing temperature and oxygen content is crucial to improve the oxidation stability of fuels,and the effect of reducing the oxygen content below 50% is more significant.In order to provide theoretical basis for material selection of storage tanks,transportation pipelines and aircraft fuel system for endothermic hydrocarbon fuels,321 stainless steel,5052 aluminium alloys,DT4 iron and red copper were selected in this paper,and metal compatibility with EHF-1 was studied comprehensively.The results showed that the order of metals to accelerate oxidation of EHF-l is red copper > DT4 iron > 321 stainless steel > 5052 aluminum alloys.In addition,additive is the most economical and effective method to improve fuel performance,and it can inhibit fuel oxidation and improve oxidation stability.The actual effects of detergent dispersant,metal deactivator,coking inhibitor and thermal stability additive package on the fuel were studied in terms of basic properties,autoxidation products and thermal oxidation stability of EHF-1,which provided theoretical basis for selecting the type and content of additives for fuels.Storage period is a necessary oxidation stability index of fuel.In this paper,three methods are used to predict the storage period of EHF-1 at room temperature.Provided the theoretical basis for the actual storage of endothermic hydrocarbon fuels.Firstly,a mathematical model for predicting the storage period of EHF-1 was established based on hydroperoxide,which was produced by accelerating oxidation of fuel.In the second method,the residual amount of antioxidant after storage was taken as the detection index,and storage period of fuel was estimated by establishing the relationship between antioxidant consumption time and temperatures.The third method started with autoxidation kinetics,and combined kinetics coefficients of autoxidation at different temperatures with Arrhenius equation to derive the storage period of EHF-1 under isolated air at room temperature. |
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