Project Details
Projekt
Fundamental Processes of Nanoparticle Synthesis in Spray Flames: Evaporation, Mixing, and Chemical Reactions
Applicant
Professorin Dr. Eva Gutheil
Subject Area
Fluid Mechanics
Term
since 2017
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 374463455
Nanoparticle synthesis in spray flames is characterized through evaporation, turbulent mixing, and chemical reactions. In contrast to a spray flame that is fed by a pure fuel, the precursor solution that is used in spray flame synthesis of nanoparticles strongly affects the entire system. In particular, the evaporation of the multicomponent droplets consisting of the precursor solution is difficult to access because of the lack of information of the physical properties of the precursor solution and the reactions that may occur inside the liquid. Particles may be formed directly inside the liquid droplet which is unwanted and microexplosion is observed which directly affect the entire process. These effects will be studied in this project by means of numerical simulations. Moreover, one-dimensional models resolving the gas phase will provide evidence of the reaction conditions in the wake of the droplet to provide information on the reaction conditions within the global system.The evaporated precursors influence the combustion behavior. In this project, the coupling of the chemical reactions and the evaporation is achieved through use of spray flamelet libraries in which the evaporation is accounted for in addition to the usual tabulation for pure gas combustion. In particular, partially premixed chemical reactions are considered using a mixture fraction and a chemical reaction progress variable which will be integrated into the turbulent spray combustion modeling of the precursor solution. Novel multiple solutions of laminar mono-disperse fuel-rich spray flames were found: the typical double reaction zone, where one of them resides on the spray side and the other one on the gas side of the configuration, and a new structure that shows a single reaction zone on the gas side, leading to separate evaporation and combustion zones that are strongly coupled: the evaporation zone feeds the gaseous fuel into the reaction zone which delivers the energy for spray evaporation. The latter scenario will be studied further in the context of the pulsation of the flame in the SpraySyn burner and the occurrence of microexplosion. These new structures will build a spray flamelet library for use in the simulation of the turbulent precursor spray flame.The interaction of the turbulent mixing, evaporation, and chemical reactions may be integrated into the turbulent simulation using joint probability density functions. The parameters mixture fraction, chemical reaction progress variable, evaporation rate, and enthalpy are used that characterize the spray flame where the evaporation of the precursor solution will be integrated. Parameter studies will give evidence of the influence of the initial conditions of nanoparticle synthesis in these flames. The sub-models which are developed in this project will enter the global simulation of the SpraySyn burner and transferred to the other project partners in the SPP.
DFG Programme
Priority Programmes
