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首页> 外文期刊>International Journal of Heat and Mass Transfer >Large eddy simulations and analyses of hydrocarbon fuel heat transfer in vertical upward flows at supercritical pressures
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Large eddy simulations and analyses of hydrocarbon fuel heat transfer in vertical upward flows at supercritical pressures

机译：超临界压力下垂直向上流动中烃燃料热传递的大涡流模拟及分析

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摘要

Gravity and/or flight acceleration would lead to significant buoyancy effect on heat transfer of a hydrocarbon fuel in the propulsion system. Urge eddy simulations have been conducted to study upward flows and heat transfer of n-decane in a vertical tube at supercritical pressures. Detailed data analyses indicate that the fluid flow and heat transfer process with buoyancy effect can be divided into three stages. In the first stage, owing to the relatively low inlet Reynolds number, flow and heat transfer are initially in the laminar state. Large density reduction under strong heating at a supercritical pressure leads to flow acceleration, which is mainly due to buoyancy and helps improve heat transfer. Further downstream, buoyant acceleration results in an M shaped velocity profile, which promotes the shear production of turbulence. Turbulence is also strongly generated by buoyant production at this stage. In addition, viscous dissipation decreases at high temperature. These factors eventually cause turbulence transition. Heat transfer is thus significantly enhanced, and the wall temperature is drastically reduced. Comparing to the cases of forced convection, buoyancy could promote or delay turbulence transition under different surface heat fluxes. In the third stage, fluid flows and heat transfer enter the fully developed turbulence region, which is maintained mainly by the shear production mechanism. Numerical analyses herein would provide fundamental understanding of buoyancy effect on supercritical-pressure heat transfer of hydrocarbon fuel in the regenerative enine cooling application.
机译：重力和/或飞行加速将导致对推进系统中烃燃料的传热显着的浮力影响。已经进行了催潮模拟，以在超临界压力下在垂直管中研究N-癸烷的向上流动和传热。详细的数据分析表明，流体流动和传热过程具有浮力效应可以分为三个阶段。在第一阶段，由于相对较低的入口雷诺数，流动和传热最初在层状状态下。在超临界压力下强加热下的强密度降低导致流动加速，这主要是由于浮力，有助于改善传热。进一步下游，浮力加速度导致M形速度曲线，这促进了湍流的剪切产生。在该阶段，浮力生产也强烈产生湍流。此外，粘性耗散在高温下降低。这些因素最终导致湍流过渡。因此显着提高了传热，壁温急剧减少。与强制对流情况相比，浮力可以在不同的表面热通量下促进或延迟湍流过渡。在第三阶段，流体流动和传热进入完全开发的湍流区域，该区域主要由剪切生产机制保持。本文的数值分析将为再生烯冷却施用中烃燃料超临界压力传热的浮力影响的基本理解提供了对浮力效应的基本理解。

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