Additives to Increase Fuel Heat Sink Capacity

Nabity, James; Wickham, David; Hitch, Bradley D.; Engel, J.R.; Rooney, Sean

doi:10.2514/6.2002-3872

Cited by 8 publications

(7 citation statements)

References 4 publications

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“…This will add size, weight, and complexity to the heat exchanger, which, in turn, significantly increases the launching cost and degrades the aircraft performance. An attractive solution is to introduce an initiator as a soluble additive into the endothermic hydrocarbon fuels, through which the thermal cracking can be carried out at a lower temperature with the same cracking conversion level and the overall fuel heat sink can be significantly augmented. − …”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, alkylbenzenes could not be employed as initiators, because the aromatic hydrocarbons were restricted to a low content in the endothermic fuels: adding alkylbenzenes would cause a significant increase in coke deposition during the cracking process . Wickham and co-workers − made a great effort to study the role of initiators in accelerating the thermal cracking of endothermic fuels under supercritical conditions. Their experimental results clearly demonstrated that the adopted initiators were very effective in increasing the fuel heat sink capacities and lowering the thermal cracking temperatures of n -heptane and JP-7.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic Modeling of the Free-Radical Process during the Initiated Thermal Cracking of Normal Alkanes with 1-Nitropropane as an Initiator

Guan

Yang

et al. 2011

Ind. Eng. Chem. Res.

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To elucidate the accelerating effect of 1-nitropropane on the thermal cracking of normal alkanes, ab initio and density functional theory calculations were performed to investigate the elementary reactions involved in the initiated thermal cracking of a 1-nitropropane/n-heptane mixture. The kinetic parameters were evaluated on the basis of standard transition state theory (TST) or variational transition state theory (VTST) with Wigner tunneling correction. The activation energy for the C–N bond rupture of 1-nitropropane to produce primary n-propyl and nitro radicals is calculated to be 234–269 kJ/mol, while the bond dissociation energy of the C–C bond within the n-heptane molecule is predicted to be at least 335 kJ/mol. These calculated results demonstrate that the presence of 1-nitropropane makes the free radical formation become relatively easier compared with single n-heptane cracking. Furthermore, compared with the C–H bond cleavage and 1,3-H intramolecular transfer, the unstable n-propyl radical mainly follows the C–C bond cleavage pathway to produce ethylene and secondary ĊH3 radical. After formation of these free radicals, the H-abstraction of n-heptane with radicals occurs readily with considerably lower activation energy than the radical formation step to initiate the chain reaction. The analysis result indicates that the thermal cracking of n-heptane is accelerated mainly due to the change of the initial step from the C–C bond cleavage of n-heptane to the C–N bond rupture of 1-nitropropane.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetic Modeling of the Free-Radical Process during the Initiated Thermal Cracking of Normal Alkanes with 1-Nitropropane as an Initiator

Guan

Yang

et al. 2011

Ind. Eng. Chem. Res.

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“…70 At 600 °C and 35 bar pressure, the heptane conversion increased by about 1.7 times (from 7.5 to 12.5%) in the presence of 5.5 wt % triethylamine. Wickham et al 72,73 have examined the effect of diphenyl selenide (DPS) on the endothermic heat sink capacity of various fuels, namely, n-heptane, JP-7, n-decane, and Norpar-12. The addition of 4 wt % DPS enhanced the total heat sink capacity of n-heptane to a tune of around 17.5% and feed conversion from 5.4% to 32% at 570 °C and 38 bar pressure.…”

Section: Suitability Of Initiators To Enhance the Endothermicity Of H...mentioning

confidence: 99%

Heat Management in Supersonic/Hypersonic Vehicles Using Endothermic Fuel: Perspective and Challenges

et al. 2021

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In this study, an in-depth analysis has been performed on various technoengineering aspects of hydrocarbon cracking under supercritical conditions toward developing an endothermic fuel. The paper is segregated into several sections with specific emphasis. The major areas covered in this work include physicochemical characteristics of different endothermic fuels, supercritical pyrolysis of hydrocarbon fuels, phenomena of coking, and its suppression from an application viewpoint. The influence of various parameters (e.g., temperature, pressure, catalysts, space−time, etc.) on fuel conversion, endothermicity, and coke propensity has been emphasized in detail. The typical value of endothermic heat sink capacity for different fuels consisting of C 8 to C 15 hydrocarbons ranges from 500 to 1150 kJ/kg over temperature and pressure ranges of 550−750 °C and 25−55 bar, respectively. The effectiveness of various additives/initiators in improving endothermicity has been screened for wide ranges of temperature and pressure. Physicochemical properties like distillation characteristics, hydrocarbon composition, °API gravity, and sulfur content of different hydrocarbon fuels are compared in a single window. Most of the findings are abridged meticulously with relevant tables and plots. Toward the end, we have highlighted the critical issues/challenges on the experimental findings and prospective.

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“…Although they account for a little in the fuels, they could produce abundant active groups to combine with the fuels. For example, a kind of liquid initiator developed by the CIAM 14 has been found to quicken the reaction rate by 2-7 times in the range 500-600 C and decrease the starting temperature by approximately 100 C. Initiators developed by Wickham et al 50 also have a remarkable improvement on the heat sink of JP-7 and n-heptane. As for JP-7, the heat sink is found to increase by 23% in the range 400-550 C, and for n-heptane, this value is up to 49%.…”

Section: Thermal and Catalytic Crackingmentioning

confidence: 99%

“…65 However, Edwards 24 has divided the carbon into two types, one is the filamentous carbon while the other is the amorphous (condensation) carbon. The TDA Research Center has investigated the filamentous carbon thoroughly 50,67 and provided the order for the susceptibility of various metals and alloys to filamentous carbon. According to their results, metals which form unstable carbides such as iron and nickel are more susceptible to filamentous carbon formation while metals that do not form carbides (copper, for example) or metals that form stable carbides (titanium) have less tendency to catalyze filament formation.…”

Section: Coking Mitigationmentioning

confidence: 99%

Research status of active cooling of endothermic hydrocarbon fueled scramjet engine

Ning

Pan

Zhang

2012

Proceedings of the Institution of Mechanical Engineers, Part G:

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The active cooling with endothermic hydrocarbon fuel is proved to be a very effective approach for scramjet thermal protection. This article has summarized the research status of active cooling of endothermic hydrocarbon fueled scramjet engine from the following five aspects, cooling capacity and heat sink measurement, thermal and catalytic cracking, coking suppression, heat transfer characteristics, and injection, mixing, ignition, and combustion performance, and suggestions on the further study of active cooling of endothermic hydrocarbon fueled scramjets are put forward. The total heat sink of endothermic hydrocarbon fuel is found to be sufficient for scramjet cooling as the additional chemical heat sink is generated from cracking reactions, and catalytic cracking is proved to be better, because of its low cracking starting temperature, high conversion percentage, and good selectivity. As for coking mitigation, approaches are usually made from eliminating the oxygen dissolved in the fuel, reducing the amount of coking-foregoing substances, and doing some special treatments on the metal surface. The heat transfer of endothermic hydrocarbon fuels presents two enhancements. The first one is related to the variation of parameters near the critical point while the second one is a result of cracking reactions. The cracked products are proved to have better performance of injection, mixing, ignition, and combustion, and this is especially attractive for scramjets as effective mixing and stable ignition and combustion has always been difficult.

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Additives to Increase Fuel Heat Sink Capacity

Cited by 8 publications

References 4 publications

Kinetic Modeling of the Free-Radical Process during the Initiated Thermal Cracking of Normal Alkanes with 1-Nitropropane as an Initiator

Kinetic Modeling of the Free-Radical Process during the Initiated Thermal Cracking of Normal Alkanes with 1-Nitropropane as an Initiator

Heat Management in Supersonic/Hypersonic Vehicles Using Endothermic Fuel: Perspective and Challenges

Research status of active cooling of endothermic hydrocarbon fueled scramjet engine

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