Ghai Sanjeev Kr, Ahmed Umair, Chakraborty Nilanjan, Klein Markus
School of Engineering, Newcastle University, Newcastle-upon-Tyne NE1 7RU, UK.
Department of Aerospace Engineering, University of the Bundeswehr Munich, 85577 Neubiberg, Germany.
Entropy (Basel). 2022 Mar 27;24(4):463. doi: 10.3390/e24040463.
The statistical behaviours of different entropy generation mechanisms in the head-on interaction of turbulent premixed flames with a chemically inert wall within turbulent boundary layers have been analysed using Direct Numerical Simulation data. The entropy generation characteristics in the case of head-on premixed flame interaction with an isothermal wall is compared to that for an adiabatic wall. It has been found that entropy generation due to chemical reaction, thermal diffusion and molecular mixing remain comparable when the flame is away from the wall for both wall boundary conditions. However, the wall boundary condition affects the entropy generation during flame-wall interaction. In the case of isothermal wall, the entropy generation due to chemical reaction vanishes because of flame quenching and the entropy generation due to thermal diffusion becomes the leading entropy generator at the wall. By contrast, the entropy generation due to thermal diffusion and molecular mixing decrease at the adiabatic wall because of the vanishing wall-normal components of the gradients of temperature and species mass/mole fractions. These differences have significant effects on the overall entropy generation rate during flame-wall interaction, which suggest that combustor wall cooling needs to be optimized from the point of view of structural integrity and thermodynamic irreversibility.
利用直接数值模拟数据，分析了湍流预混火焰在湍流边界层内与化学惰性壁面正碰相互作用中不同熵产生机制的统计行为。将预混火焰与等温壁面正碰相互作用情况下的熵产生特性与绝热壁面的情况进行了比较。研究发现，对于两种壁面边界条件，当火焰远离壁面时，化学反应、热扩散和分子混合引起的熵产生仍然相当。然而，壁面边界条件会影响火焰与壁面相互作用过程中的熵产生。在等温壁面的情况下，由于火焰熄灭，化学反应引起的熵产生消失，热扩散引起的熵产生成为壁面处主要的熵产生源。相比之下，在绝热壁面处，由于温度和物种质量/摩尔分数梯度的壁面法向分量消失，热扩散和分子混合引起的熵产生减少。这些差异对火焰与壁面相互作用过程中的总熵产生率有显著影响，这表明从结构完整性和热力学不可逆性的角度来看，燃烧室壁面冷却需要进行优化。
