Effects Of Hydrogen Donors And Coking-inhibitors On Pyrolytic Deposition Of Endothermic Fuels Under Supercritical Condition

In this thesis a set of reactor system which simulates the supercritical condition where fuel was used in hypersonic aircraft has been set up. The effect of additives on deposits was analyzed. Some parameters including reaction conversion/gas products mass fraction,weight of deposits, distribution of deposits and morphology of inner surface of reactor were measured. Three hydrogen donors, two coking-inhibitors and six composite additives were used to suppress baseline fuel pyrolytic deposition under supercritical condition and their effects were analyzed.Positive effects were obtained when BzOH, THN and THN/THNone are added into baseline fuel as hydrogen donors in 450℃～600℃. Among them THN/THNone binary donor is the most effective to increase the temperature by 43℃over baseline fuel on the same pyrolytic level. THN/THNone reduces the coke deposited by 42.44% compared to the case where no additive was present in n-dodecane at 550℃. The SEM results demonstrate that some morphologic change has happened on inner surface of reactor. The coke-layer becomes less compact and the diameter of granule is smeller.Coking-inhibitors work better than hydrogen donors to inhibit coke formating. Ph2Se2 is better which can reduce 63.41% and 52.12% carbon deposits to n-dodecane and RP-3, respectively. According to FTIR and XPS characterizations, some reaction between selenium and iron has taken place to produce mainly Fe₂Se₃ and a few Se when fuel decomposes under thermal stress.The composite additives exhibits a remarkable synergetic effect than hydrogen donor or coking-inhibitor. When mixtures of THN/THNone binary donor and Ph₂Se₂ as the additive, it presents a 77.56% and 76.97% reduction in deposit formation compared to n-dodecane and RP-3 with no additives, respectively.