Towards an optimization of turbulence effects on heat and mass transfer in evaporating and reacting gas turbine sprays

ABSTRACT In this paper, the way towards an optimization of turbulence effects on heat and mass transfer in evaporating and reacting GT-sprays is outlined. It is based on an accurate consideration of coupling between turbulence and turbulence modulation, swirl intensity and non-equilibrium effects during the vaporization. This is achieved by including a physically consistent modelling of turbulence modulation phenomena that allows to better retrieve mass and heat transport effects on the droplet surface, and therefore improves the prediction of processes, like evaporation and combustion, which in turn affect the turbulence. For this purpose, an Euler-Lagrangian method in conjunction with advanced models has been used in RANScontext and applied to the numerical study of a single gas turbine combustor configuration. a) To quantify, to control or to optimize the effects of turbulence along with the swirl intensity effects, a mixing parameter has been introduced. b) Under reacting conditions, it is shown how the evaporation characteristics, mixing rate and combustion process are influenced by turbulence. In particular, the turbulence modulation modifies the evaporation rate, which in turn influences the mixing and the species concentration distribution. It is demonstrated that this effect can not be neglected far from the nozzle for low swirl intensities (Sw.Nu.<1) and close to the nozzle for high swirl number intensities. All these findings can well be used to optimize turbulence effects in evaporating and reacting sprays. INTRODUCTION The success of some promising approaches, such as the LPP-or the RQL-concept strategies, that can help to limit gas turbine emissions, depends on a suitable homogeneity of the air-fuel mixture in the reaction zone. To achieve this goal by means of numerical simulations, an accurate determination of droplet and vapour spatial distribution and a reliable control of the interaction between the evaporating and reacting spray with the surrounding turbulent gas flow are prerequisite. As pointed out in [1, 2] a considerable amount of works have been done including diverse parameter studies (e. g. [1-5, 8-15, 20-25, 34]. However, there are relatively few experimental and numerical results devoted to the effects of turbulence characteristics on spray combustio