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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

COUPLING PROCESS ANALYSIS ON THE FLOW AND HEAT TRANSFER OF HYDROCARBON FUEL WITH PYROLYSIS AND PYROLYTIC COKING UNDER SUPERCRITICAL PRESSURES

Chaofan Zhao
School of Energy and Power Engineering Beihang University Beijing 100191, China

Xizhu Hu
School of Energy and Power Engineering Beihang University Beijing 100191, China; College of Aeronautical Engineering, Civil Aviation University of China Tianjin 300300, China

Jianqin Zhu
School of Energy and Power Engineering Beihang University Beijing 100191, China

Zhi Tao
National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics The Collaborative Innovation Center for Advanced Aero-Engine of China Beihang University Beijing 100191, China

Hongwei Wu
School of Engineering and Technology, University of Hertfordshire STRI 1E115, College Lane Campus, Hatfield, AL10 9AB, United Kingdom

DOI: 10.1615/IHTC16.cms.023866
pages 2061-2074


KEY WORDS: Numerical simulation and super-computing, Gas turbine, supercritical, hydrocarbon fuel, pyrolysis, coking

Abstract

The regenerative cooling technology has become the most effective method to reduce the high-temperature of the scramjet engine. With physical and chemical heat sink, the endothermic hydrocarbon fuel has excellent performance in the regenerate cooling system of the scramjet engine which operates under the extremely high temperature. The pyrolytic reactions not only absorb a large amount of heat, but also produce some kinds of coking precursors, mainly alkenes and aromatics. Because of the coking precursors and the coking reactions, a lot of coke would be generated on the wall and exert strong impact on the heat transfer, as the conductivity of the coke is much lower than that of the metal wall. Meanwhile, the surface coking changes the geometric parameters of the cooling tube, which leads to the flow field variations with the thickening coking layer. So, it is needed to find out the interaction between these variations. In this paper, a one-dimensional (1D) model has been developed to calculate the flow and heat transfer parameters distributions of the pyrolytically reacted RP-3 along the regenerative cooling tube with the pyrolytic coking. The 24-step pyrolytic reaction model and the coking kinetic model are applied to predict the pyrolysis and pyrolytic coking process of RP-3, with accurate computations of the physical properties of fluid mixture which undergo drastic variations during the trans critical process. Comparisons between the current predictions and the open published experimental data are carried out and good agreement is achieved. Calculations on the coupling relationships between the flow, heat transfer, pyrolysis and pyrolytic coking within 20 min in the circular tube have been conducted. And the temperature of the outer tube wall rises rapidly owing to the increasing thermal resistance of the coke layer. Moreover, the flow velocity becomes faster during the narrowing process of the tube caused by surface coking. The results in this paper have significant reference value in the design of the regenerative cooling system.

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