方形通道内超临界碳氢燃料传热恶化数值研究

Numerical Study on Heat Transfer Deterioration of Supercritical Hydrocarbon Fuel in Square Channels

为了深入理解火箭发动机再生冷却过程中碳氢燃料的流动传热规律,采用RNG k-ε湍流模型结合增强壁面处理方法对非对称受热(上壁面外侧加热)方形冷却通道内超临界压力甲烷的对流换热进行了数值研究。重点考察了加热壁面内侧的传热恶化以及由传热恶化和固壁热传导共同作用引起的热流异常传递现象,拟合得到了传热恶化的临界热流密度和起始内壁温关系式、加热侧内壁面和侧壁面内侧平均热流密度的预测关系式。结果表明:当外壁热流密度和质量流速比值高于0.288 k J/kg时,近壁流体流动加速诱发了加热侧内壁面的传热恶化;同时,固体区域温度畸变导致加热侧内壁面热流密度减小,热流更多地向侧壁面内侧传导。运行压力越低,该现象越显著。

In order to deeply understand the flow and heat transfer characteristics of hydrocarbon fuels in the regenerative cooling process of rocket engines,a numerical study on convective heat transfer of supercritical methane in square cooling channels with asymmetric heating imposed on the top exterior channel surface was conducted based on the RNG k-ε turbulence model with enhanced wall treatment. The heat transfer deterioration at the internal heating wall,and the abnormal heat flux transmission phenomenon due to the combined effects of heat transfer deterioration and wall heat conduction,were investigated in detail. The empirical corrections for critical heat flux and initial internal-wall temperature of heat transfer deterioration have been successfully obtained. Furthermore,the expressions for averaged heat flux predictions at the top and side internal walls have also been effectively established. Results indicate that when the ratio of exterior wall heat flux and mass flux is higher than 0.288 k J/kg,the flow acceleration effect occurs in the near-wall region at the internal heating wall,and thus leads to a significant heat transfer deterioration phenomenon. Meanwhile,the heat flux decreases at the internal heating wall,and more heat flux transmits to the side internal wall surface,resulting from the temperature distortion in the solid region. This phenomenon is more obvious with the decrease of pressure.