Status of the Air Force HyTech Program

Boudreau, A H

doi:10.2514/6.2003-6947

Cited by 16 publications

(5 citation statements)

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“…For example, very early reports by Lander and Nixon suggested that dehydrogenation of naphthenes (cyclic paraffins) to form H 2 and aromatic compounds over Pt/Al 2 O 3 can double the amount of heat removed by the thermal heat capacity of the fuel. Since that time, interest in endothermic reforming for cooling purposes has increased, leading to a large number of publications − and patents, , especially for applications to scramjet engines.…”

Section: Introductionmentioning

confidence: 99%

Endothermic Reforming of n-Hexane on Metal (Pt, Ga) Containing H-ZSM-5 at High Pressures

Yeh

Yü

Luo

et al. 2015

Ind. Eng. Chem. Res.

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The supercritical, high-pressure reaction of n-hexane over H-ZSM-5, with and without the addition of Pt and Ga, has been studied for application to endothermic reforming in scramjet engines. The endothermicities of the reactions were determined from the product distributions. For unpromoted H-ZSM-5, the product distribution indicated that the endothermicity is low and decreases with increasing pressure. The addition of Ga to H-ZSM-5 has a relatively small effect on n-hexane conversion but significantly increases the endothermicity of the reaction by increasing the selectivity to form small aromatics. The H(Ga)-ZSM-5 catalyst showed no deactivation for at least 5 h at 633 K and 137 bar of n-hexane. By contrast, the addition of Pt had a minor effect on both the rate and the reaction endothermicity.

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Section: Introductionmentioning

confidence: 99%

Endothermic Reforming of n-Hexane on Metal (Pt, Ga) Containing H-ZSM-5 at High Pressures

Yeh

Yü

Luo

et al. 2015

Ind. Eng. Chem. Res.

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“…The US Air Force has initiated a program to investigate scramjet engines since 1995, 12 namely the HyTech (Hypersonic Technology Program), which led to X-51, the first hydrocarbon scramjet flown in the world. Ground demonstration engine (GDE) 13 has been used to assess the engine's thermal structural characteristics.…”

Section: Cooling Capacity and Heat Sink Measurementmentioning

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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“…As one of the most promising technologies in the field of spaceflight, scramjets have attracted more and more attention in recent years. But at the excessive speed of >5 Mach , the scramjet technology faces the serious challenge of heat management. − Traditional passive cooling methods are not capable of cooling the scramjet, especially for the extremely severe heat environment of the combustion chamber. In order to effectively reduce the heat load of the combustion chamber, active cooling was proposed in recent years as an innovative cooling method, which adopted methods of not only physical heat adsorption but also chemical heat adsorption to cool the scramjet. , As a key index of active cooling, the heat transfer characteristics of hydrocarbon fuel are badly in need of further investigation especially in the high-temperature region.…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Investigation of the Pyrolysis Effect on Heat Transfer Characteristics for n-Decane in the Horizon Mini-Channel

et al. 2019

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In order to better understand the heat transfer process with the pyrolysis of hydrocarbon fuel, the pyrolysis effect on heat transfer characteristics in the mini-channel was comprehensively investigated in this work. First, the heat transfer characteristics were experimentally measured, and the thermophysical properties of fuel were calculated according to the species distribution. Then, the heat transfer and thermophysical properties in an ideal condition (no pyrolysis in the same heat flux) were simulated by a numerical method. By comparing the experimental results with the simulation results, it could be found that pyrolysis can significantly inhibit the rising of fuel temperature up to 332 K. Meanwhile, pyrolysis can significantly decrease the density, increase the viscosity and thermal conductivity, and keep the specific heat capacity approximately at a constant. Then, the variation of thermal properties can decrease the Reynold number and Prandtl number, thus impairing the heat transfer performance. However, while pyrolysis occurs from a mild degree to a deep degree, the heat transfer will be enhanced. This phenomenon may be caused by the dramatic difference of pyrolysis in the radial direction. At the same time, in the high-temperature region, the percentages of the chemical heat sink in the total heat sink are all over 50%. Especially in these low mass flux conditions, the percentages of chemical heat sink can be up to 65%. According to the results of this work, both the negative and positive effect of pyrolysis should be taken into consideration in cooling structure design.

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Status of the Air Force HyTech Program

Cited by 16 publications

References 0 publications

Endothermic Reforming of n-Hexane on Metal (Pt, Ga) Containing H-ZSM-5 at High Pressures

Endothermic Reforming of n-Hexane on Metal (Pt, Ga) Containing H-ZSM-5 at High Pressures

Research status of active cooling of endothermic hydrocarbon fueled scramjet engine

A Comprehensive Investigation of the Pyrolysis Effect on Heat Transfer Characteristics for n-Decane in the Horizon Mini-Channel

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