作者: H Olguin , A Scholtissek , S Gonzalez , F Gonzalez , M Ihme
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摘要: In this paper, closure of the Scalar Dissipation Rate (SDR) in the Spray Flamelet Equations (SFE) is addressed. For this purpose, the gradient gξ of the mixture fraction ξ is used instead of the SDR itself. A transport equation for gξ is derived and transformed from physical into mixture fraction space. Moreover, the SFE of the species mass fractions and of gas temperature are re-derived in terms of gξ for consistency, where differential diffusion is considered. In the resulting set of equations, two different kinds of unclosed quantities appear: source terms due to momentum and energy exchange between the liquid phase and the gas phase and the spatial gradient of the product of the gas velocity and the gas density, â= d (ρuy)/dy. Closure of the latter is the focus of the present study. Numerical simulations of different counterflow ethanol/air flames in physical space are carried out using a well established detailed model, and the results are employed for the validation and analysis of the newly proposed set of SFE. In particular, a non-premixed gas flame is established as a base case and then perturbed by means of different monodisperse sprays injected from the air side of the configuration. Introducing a stream-like function, an expression for â is obtained. The validation confirms that the new set of SFE perfectly reproduces the counterflow structure when the correct profiles of the unclosed evaporation-related source terms are available. Moreover, the suitability of imposing a constant value for the closure of â is tested in terms of the ability of the SFE of properly predicting both gξ and the spray flamelet structure of the reference counterflow flames. Two …