This paper investigates the influence of unresolved turbulent fluctuations on radiation heat transfer and formation of NO and soot in an n-dodecane spray flame (known as Spray A) under diesel engine conditions. The transported probability density function (TPDF) model – including the effect of turbulent fluctuations in temperature and composition – has been compared with the well-mixed (WM) model – neglecting these fluctuations – to separate and quantify the relative influence of turbulence-chemistry interactions (TCI), radiation heat transfer and turbulence-radiation interaction (TRI). Radiation is solved with the discrete ordinate method (DOM) including grey radiative properties from soot and gaseous species in the Reynolds-averaged Navier–Stokes (RANS) framework. At Spray A conditions (60 bar), the contribution to the Planck mean absorption coefficient from gas-phase species (mainly CO₂ and H₂O) was found to be comparable to the one of soot, this plays an important role for the radiation reabsorption in the periphery of the jet. Radiation was found to reduce the flame temperature by 10–20 K with a consequent reduction of the total NO mass by approximately 5–10%, with these reductions being comparable for both combustion models. However, neglecting turbulent fluctuations results in an increase of the NO mass by a factor of two. The effect of TRI on the emitted radiation was found to be modest (10% at most). The effect of radiation on soot formation was seen to be minor. Overall, it is concluded that under Spray A conditions the effect of radiation heat transfer does influence the NO formation but the effect of the combustion model is more important and needs further attention.

本文研究了在柴油发动机条件下，未解决的湍流波动对正十二烷喷雾火焰（称为喷雾A）中辐射传热以及NO和烟灰形成的影响。已将运输概率密度函数（TPDF）模型（包括温度和成分的湍流波动的影响）与充分混合（WM）模型（忽略了这些波动）进行了比较，以分离和量化湍流化学相互作用的相对影响（TCI），辐射热传递和湍流-辐射相互作用（TRI）。用离散纵坐标法（DOM）求解辐射，包括雷诺平均Navier–Stokes（RANS）框架中烟灰和气态物种的灰色辐射特性。在喷涂A条件下（60巴），₂和H ₂ O）被发现与烟灰具有可比性，这对于射流外围的辐射重吸收起着重要作用。发现辐射可将火焰温度降低10–20 K，从而使总NO质量降低约5–10％，这两种燃烧模式的降低幅度均相当。但是，忽略湍流波动会导致NO质量增加两倍。发现TRI对发射辐射的影响不大（最多10％）。辐射对烟灰形成的影响很小。总的来说，可以得出结论，在喷雾A条件下，辐射传热的影响确实会影响NO的形成，但是燃烧模型的影响更为重要，需要进一步关注。