Additives to Increase Fuel Heat Sink Capacity in a Fuel/Air Heat Exchanger

Wickham, David; Engel, Jeffery; Rooney, Sean; Hitch, Bradley D.

doi:10.2514/6.2005-3916

Cited by 6 publications

(13 citation statements)

References 3 publications

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“…As evidence, it was observed that in a given cracking period of 20 min, the Dod conversion was so low at 400 °C that could not be detected, but it increased from 2.5% at 420 °C, even to 22% at 455 °C, which may considerably depress the promoting effect of initiative additives. Wickham et al , also reported the similar results in their supercritical cracking experiments of JP-7 and Norpar-12 with 4 wt % initiator. They found that the chemical heat sink improvement attributed to the cracking of JP-7 and Norpar-12 at 475 °C was very small below 10 Btu/lb; it increased to ca.…”

Section: Resultssupporting

confidence: 54%

“…According to Yu and Eser, and Wickham et al, , the following simple first-order kinetics for the thermal cracking of straight-chain alkanes were used to determine the corresponding rate constants k = 1 t ln 1 1 − X where X was the conversion of Dod, k was the apparent first-order rate constant (h −1 ), and t was the reaction time (h).…”

Section: Resultsmentioning

confidence: 99%

“…Wickham et al investigated the promoting effect of an initiator in the thermal cracking of heptane under supercritical condition, and observed that only 2 wt % initiator accelerated the cracking rate of heptane up to 200% with the similar reaction mechanism and product distribution as the thermal cracking under supercritical conditions (773.15 K, 6.8 MPa). Wickham et al , further applied laboratory bench-scale and pilot-scale calorimetric tests to directly measure heat sink capacity of JP-7 and model compound n -decane with or without initiator, and found that the initiator improved the heat sink (from 25 to 550 °C under 550 psi) from 766 to 849 Btu/lb for n -decane, from 732 Btu/lb to 791 Btu/lb for JP-7 fuel at liquid hourly space velocity (LHSV) of 1000 h −1 . Those work confirmed the feasibility of applying initiator as an effective additive to improve heat sink of jet fuel under supercritical condition.…”

Section: Introductionmentioning

confidence: 99%

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Supercritical Thermal Cracking of N-Dodecane in Presence of Several Initiative Additives: Products Distribution and Kinetics

et al. 2008

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Supercritical initiative-thermal cracking of a jet fuel model compound, n-dodecane, was studied in presence of several initiative additives, such as1-nitropropane (NP), triethylamine (TEA), and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane (TEMPO) in view of improving heat sink of jet fuel. It was found that remarkable promoting effect of the initiative additives on the cracking rates, compared with the thermal cracking of pure n-dodecane, were observed up to 20-150% in the following order: NP > TEMPO > TEA. Comparisons of products distributions from the thermal cracking of n-dodecane with and without initiators indicated that initiators type had a slight effect on the gas products selectivity, but a non-negligible effect on liquid products distributions. Apparent first-order kinetics was used to describe the supercritical initiative-thermal cracking of n-dodecane, and the apparent cracking activation energy of pure n-dodecane were 256.56 kJ/mol, which decreased to 185.80 kJ/mol by NP, 196.05 kJ/mol by TEMPO, and 242.83 kJ/mol by TEA. Attempts were also made to explain the observed experimental results with proposed reaction mechanisms for the thermal cracking of pure initiators.

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Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Supercritical Thermal Cracking of N-Dodecane in Presence of Several Initiative Additives: Products Distribution and Kinetics

et al. 2008

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“…In recent years, many studies have been performed in this particular area. The improvement effect of initiators on the heat sink capacity − and conversion rate ,− of fuel were studied experimentally. These previous experimental results demonstrated that initiators could improve the heat sink capacity and greatly accelerate the reaction rate of jet fuel.…”

Section: Introductionmentioning

confidence: 99%

“…Recent experimental conditions for the initiated pyrolysis of hydrocarbon fuels are summarized in Table . It can be observed that a nonflow reactor − ,, and a low flow rate with a large-diameter flow reactor − ,,,, were adopted during studies on homogeneous initiators. However, this setup is quite different from the operational conditions of the practical cooling channels in advanced aircraft.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on Pyrolysis of n-Decane Initiated by Nitropropane under Supercritical Pressure in a Miniature Tube

Jia

Zhou

et al. 2019

Energy Fuels

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Adding an initiator is an effective method of promoting hydrocarbon pyrolysis and improving the heat sink of fuels. Nitropropane was proposed as an initiator with good performance, owing to its lower reaction activation energy for C–N bond cleavage. To study the effects of this initiator on hydrocarbon pyrolysis, a miniature tube reactor that can simulate a real heating procedure in an aeroengine was used to investigate the n-decane pyrolysis with and without nitropropane under experimental supercritical conditions. The results demonstrate that the nitropropane initiator promotes the pyrolysis of fuel as it flows through a tube with a large length–diameter ratio within a certain temperature range. The initial decomposition temperature of n-decane is reduced by approximately 100 K, and the increase in the conversion leads to a higher heat sink for n-decane, which can result in decreases in the fuel and reactor temperatures under the same heating condition and within the effective temperature range. A stronger promoting effect can be achieved by increasing the concentration of the nitropropane initiator. The variation laws for the n-decane pyrolysis reaction rate along the flow reactor are changed by the initiator, the presence of nitropropane greatly accelerates the pyrolysis reaction of fuel at a lower temperature, and the opposite tendency appears as the fuel temperature increases, which is caused by the consumption of the initiator. In addition, the selectivity of methane, propane, and alkenes, especially ethylene, increases because of the propyl radical generated by the C–N dissociation of nitropropane before the initiator is consumed.

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Experimental and Modeling Investigation on the Pyrolysis of n-Decane Initiated by Nitropropane. Part I: 1-Nitropropane

et al. 2023

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Initiators can accelerate the pyrolysis of hydrocarbon fuels, thereby reducing the required reaction temperature in the hypersonic vehicle heat exchanger/reactor. Nitro-alkanes are considered as efficient initiators due to their lower energy barrier of the C–N bond cleavage reaction. To research the mechanism of the initiation effect of nitro-alkanes on the decomposition of hydrocarbon fuel, synchrotron radiation vacuum ultraviolet photoionization-mass spectrometry (SVUV-PIMS) was employed to experimentally study the pyrolysis of n-C10H22, 1-C3H7NO2, and their binary mixtures in a flow tube under pressures of 30 and 760 Torr. The species identified and measured in the experiments included alkanes, alkenes, dialkenes, alkynes, nitrogen oxides, benzene, and free radicals, which revealed the mechanism of n-decane and 1-C3H7NO2 pyrolysis, as well as the interactions of the two fuels. Experiments show that the presence of 1-C3H7NO2 reduces the initial decomposition temperature of n-C10H22, and the increased pressures could achieve a stronger promoting effect on the conversion of n-C10H22. A detailed kinetic model containing 1769 reactions and 278 species was established and validated based on the mole fraction distributions of n-C10H22, major pyrolysis species, and important intermediates measured in pure fuel and initiated pyrolysis. The kinetic model can accurately predict the experimental data, and the mechanism of 1-C3H7NO2-initiated pyrolysis of n-C10H22 is analyzed with the model. The effect of 1-C3H7NO2 on the consumption of n-C10H22 and selectivity of cracked products is highlighted.

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Additives to Increase Fuel Heat Sink Capacity in a Fuel/Air Heat Exchanger

Cited by 6 publications

References 3 publications

Supercritical Thermal Cracking of N-Dodecane in Presence of Several Initiative Additives: Products Distribution and Kinetics

Supercritical Thermal Cracking of N-Dodecane in Presence of Several Initiative Additives: Products Distribution and Kinetics

Experimental Investigation on Pyrolysis of n-Decane Initiated by Nitropropane under Supercritical Pressure in a Miniature Tube

Experimental and Modeling Investigation on the Pyrolysis of n-Decane Initiated by Nitropropane. Part I: 1-Nitropropane

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