Numerical study on supercritical heat transfer of n-decane during pyrolysis in rectangular tubes

Lei, Zhiliang; He, Kuo; Qin, Hui; Bao, Zewei; Li, Xiangyuan

doi:10.1016/j.applthermaleng.2020.115002

Cited by 27 publications

(7 citation statements)

References 28 publications

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“…Furthermore, these cracking reaction models are embedded in commercial softwares such as ANSYS FLUENT, and this procedure is used to study the coupling of the cracking reaction, flow characteristics and heat transfer behavior. Ward et al (2004, 2005) proposed two chemical cracking mechanisms of one-step proportional product distribution (PPD), and these models were used by Bao et al (2014), Zhao et al (2018), Tao et al (2018a), Lei et al (2020) and Sun et al (2018a). Dahm et al (2004) suggested 1175 reactions and 175 species of n-dodecane using the EXGAS software.…”

Section: Introductionmentioning

confidence: 99%

Research status of supercritical aviation kerosene and a convection heat transfer considering thermal pyrolysis

Zhang

Xie

et al. 2022

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Purpose This paper aims to comprehensively clarify the research status of thermal transport of supercritical aviation kerosene, with particular interests in the effect of cracking on heat transfer. Design/methodology/approach A brief review of current research on supercritical aviation kerosene is presented in views of the surrogate model of hydrocarbon fuels, chemical cracking mechanism of hydrocarbon fuels, thermo-physical properties of hydrocarbon fuels, turbulence models, flow characteristics and thermal performances, which indicates that more efforts need to be directed into these topics. Therefore, supercritical thermal transport of n-decane is then computationally investigated in the condition of thermal pyrolysis, while the ASPEN HYSYS gives the properties of n-decane and pyrolysis products. In addition, the one-step chemical cracking mechanism and SST k-ω turbulence model are applied with relatively high precision. Findings The existing surrogate models of aviation kerosene are limited to a specific scope of application and their thermo-physical properties deviate from the experimental data. The turbulence models used to implement numerical simulation should be studied to further improve the prediction accuracy. The thermal-induced acceleration is driven by the drastic density change, which is caused by the production of small molecules. The wall temperature of the combustion chamber can be effectively reduced by this behavior, i.e. the phenomenon of heat transfer deterioration can be attenuated or suppressed by thermal pyrolysis. Originality/value The issues in numerical studies of supercritical aviation kerosene are clearly revealed, and the conjugation mechanism between thermal pyrolysis and convective heat transfer is initially presented.

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Section: Introductionmentioning

confidence: 99%

Research status of supercritical aviation kerosene and a convection heat transfer considering thermal pyrolysis

Zhang

Xie

et al. 2022

HFF

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“…Their result indicated that with increasing turbulence intensity, the radial distribution of conversion is more uniform. Lei et al 26 also applied this model to study the effect factors of convective heat transfer and then modified the Dittus−Boelter correlation, which is suitable for conversion less than 23% of rectangular tubes.…”

Section: Introductionmentioning

confidence: 99%

“…Ward et al , developed a one-step global model of 19 species for n-decane pyrolysis based on proportional product distribution (PPD). This model was applied to numerous studies. − Tao et al used this model to study the effect of n-decane thermal cracking under supercritical conditions on heat transfer characteristics and flow resistance and suggested that cracking can enhance heat transfer and improve heat transfer deterioration. Feng et al established a numerical model with the PPD chemical model to analyze the effect of turbulence on pyrolysis.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigations on the Molecular Reaction Model for Thermal Cracking of n-Decane at Supercritical Pressures

et al. 2022

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The pyrolysis of endothermic hydrocarbon fuel plays a vital role in regenerative cooling channels. Based on previous experiments and mechanism models of n-decane, and considering the impact of the secondary reaction at high conversion, the present work establishes a cracking reaction model of n-decane containing 16 species and 26 reactions. One-dimensional plug flow reactor simulation verifies that the model has high accuracy in predicting species distribution. The high-accuracy model is applied to the computational fluid dynamics (CFD) simulation of the supercritical cracking heat transfer, and compared with the results of a one-step global model as the chemistry model. The results show that the high-accuracy model is more accurate in terms of fuel conversion, temperature, and product distribution. Furthermore, the reasons for the difference of the two chemistry models in the CFD simulation are analyzed from the perspective of chemical kinetics. The new model generates more products of small molecules due to the consideration of secondary reactions. However, for the one-step model, it mainly cracked into large molecules even at high conversion. The product distribution affects the chemical endotherm and then the fuel temperature, which in turn affects the reaction rate and finally the conversion of the fuel. In addition, pyrolysis affects the properties of the fuel, which in turn affects the convective heat transfer. Among the several influencing factors of heat transfer, the correction factor of isobaric specific heat, which is the ratio of the specific heat of fluid to the average specific heat, can well reflect the changing trend of the convective heat transfer coefficient. The present work demonstrates the important role of the kinetic model in the simulation of the supercritical cracking heat transfer process, and the corresponding methods can be used in the design of regenerative cooling systems.

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“…For hypersonic flying vehicles, Endothermic hydrocarbon fuel has been widely considered to be used as the propellant and coolant for thermal protection 1‐4 . The fuel experiences thermal decomposition in the heat exchanger of flow channels to produce small hydrocarbon species and hydrogen 5‐7 .…”

Section: Introductionmentioning

confidence: 99%

Experimental study of ignition behaviors of pyrolysis gas of kerosene‐based endothermic hydrocarbon fuel

2021

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Summary The pyrolysis gas consisting of 29.4% CH4, 21.3% C2H4, 30.8% C2H6, and 18.5% C3H6 in mole fraction is presented, as the surrogate of the actual gaseous pyrolysis products. At the conditions of TC = 877.7‐963 K, PC = 3.22‐4.37 MPa, φ = 0.5 and 1.0, the ignition delays of pyrolysis gas/air (diluted with 52% Ar) have been measured. With TC or PC increasing, the ignition delay time decreases. The auto‐ignition of φ = 1.0 is faster than that of φ = 0.5. Furthermore, two widely used small hydrocarbons chemical mechanisms are validated with the measured results. The USC‐II mechanism can well predict experimental results at high‐T regimes, but fails at low‐T regimes. By sensitivity analysis of temperature, the two elementary reactions C2H6 + OH = C2H5 + H2O (negative sensitivity coefficient) and C3H6 + OH = aC3H5 + H2O (positive sensitivity coefficient) have been identified, which have higher reactivity at low‐T and lower reactivity at high‐T. Considering the extreme uncertainty of rate constants of C3H6 + OH = aC3H5 + H2O, the kinetic parameters have been modified for improving the predictions. The validated results indicate that the optimized mechanism improves predictions of the auto‐ignition behavior at low temperature regimes.

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Numerical study on supercritical heat transfer of n-decane during pyrolysis in rectangular tubes

Cited by 27 publications

References 28 publications

Research status of supercritical aviation kerosene and a convection heat transfer considering thermal pyrolysis

Research status of supercritical aviation kerosene and a convection heat transfer considering thermal pyrolysis

Numerical Investigations on the Molecular Reaction Model for Thermal Cracking of n-Decane at Supercritical Pressures

Experimental study of ignition behaviors of pyrolysis gas of kerosene‐based endothermic hydrocarbon fuel

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