This study focuses on supercritical octane flow simulation with pyrolysis reactions in a heated circular pipe to determine the multicomponent effects of changes in thermophysical properties. The reaction rate of n-octane for pyrolysis was estimated by a zeroth-dimensional simulation of hydrocarbon pyrolysis. The resulting mole fractions of the decomposed components were compared with the experimental data. The mole fraction results were then used to develop three thermophysical property models for the mixture of unreacted n-octane and decomposed hydrocarbons, i.e., 1-, 4-, and 12-component models. In the supercritical octane flow simulations, the multicomponent thermophysical properties of each component model were determined using the polynomial equations in the Reference Fluid Thermodynamic and Transport Properties Database. The conventional $k-\omega \text{ SST}$ model and $k-\omega \text{SST}+M_{\tau }$ model served as the Reynolds-averaged Navier–Stokes turbulence models. In cases with a low wall temperature, the outlet temperatures in all component models were consistent with the experimental data, in which pyrolysis did not occur. In cases with a high wall temperature above 973 K, the density change and production of kinetic energy affected the turbulent thermal diffusivity in the heated pipe. In cases where the multicomponent effects of thermophysical properties and turbulence were considered, the numerical method reproduced a reasonable outlet temperature and conversion rate, whereas the experimental results were underestimated in all the other cases. These numerical results indicate that the accurate prediction of density changes and the production of turbulent kinetic energy are the key issues in reproducing thermal fluid flows of supercritical hydrocarbons with pyrolysis reactions in uniform wall temperature cases.

本研究的重点是在加热的圆形管道中使用热解反应进行超临界辛烷值流动模拟，以确定热物理性质变化的多组分效应。正辛烷热解的反应速率通过烃热解的零维模拟来估计。将分解组分的所得摩尔分数与实验数据进行比较。然后使用摩尔分数结果为未反应的正辛烷和分解的烃的混合物开发三个热物理特性模型，即 1-、4- 和 12-组分模型。在超临界辛烷值流动模拟中，每个组分模型的多组分热物理特性是使用参考流体热力学和传输特性数据库中的多项式方程确定的。常规的$克-\omega \text{ 不锈钢}$ 模型和 $克-\omega \text{不锈钢}+{米}_{\tau }$模型作为雷诺平均 Navier-Stokes 湍流模型。在壁温较低的情况下，所有组件模型的出口温度与实验数据一致，未发生热解。在壁温高于 973 K 的情况下，密度变化和动能的产生影响了受热管中的湍流热扩散率。在考虑热物理特性和湍流的多分量效应的情况下，数值方法再现了合理的出口温度和转化率，而在所有其他情况下实验结果都被低估了。