%0 Generic
%A Urzica, Daniela
%D 2010
%F heidok:11461
%K CH4/LOx , spray combustion , cryogenic enriched oxygen , counterflow configuration , laminar flame
%R 10.11588/heidok.00011461
%T Numerical Investigation of Droplet Vaporization and CH4/Air, CH4/O2 and CH4/LOXCounterflowing Spray Flames for Elevated Pressure
%U https://archiv.ub.uni-heidelberg.de/volltextserver/11461/
%X Study and optimization of the physical and chemical processes that are involved in many applications in science and engineering are worthwhile, to ensure the stability and efficiency of their performance. Examples are combustion process in direct injection engines, gas turbine combustors, and liquid rocket propulsion systems.  First step in understanding a spray must naturally be the understanding of its basic constituents: i.e. single droplets. Hence, it is important to develop good numerical models that can predict and simulate the process of evaporation of a single droplet accurately. Thus, computational investigation of the evaporation of water droplets induced by an infrared laser beam is performed. In particular, a single spherical droplet is considered, which is suspended on horizontal and vertical glass fibers in air under atmospheric pressure. The droplet heating and evaporation are induced by a pulsed CO2 laser. The fuels in liquid rocket propulsion systems, methane and kerosene, are being discussed as alternative fuels to hydrogen because of their high energy content. Methane has some advantages compared to kerosene because of its cleaner burning characteristics. The present study contributes to an improved understanding of methane/air, methane/oxygen and methane/LOX (liquid oxygen) combustion compared to the hydrogen/oxygen system. A numerical investigation of laminar CH4/air and CH4/O2 flames is performed, where different mixtures of nitrogen and oxygen in the oxidizer stream are studied. Moreover, liquid oxygen spray flames with carrier gas methane against an oxygen stream are investigated in the counterflow configuration. The obtained results may be used in (spray) flamelet library or computations of flamelet generated manifolds in turbulent combustion. The mathematical model is based on the two-dimensional conservation equations, which are transformed into one-dimensional equations using a similarity transformation. The numerical simulation concerns the axi-symmetric configuration with an adaptive grid for the gas phase. Detailed models of all relevant processes are employed; in particular, a detailed chemical reaction mechanism is used, which comprises 35 species involving 294 elementary reactions. The chemical reaction scheme presented in this work was developed in [1]. The thermodynamic data for CH4 and O2 between 100 and 300 K are implemented for normal and elevated pressures for use in computations of cryogenic CH4/LOX combustion. For the CH4/air laminar flame, the present results are compared with results from literature to verify the mathematical model, chemical mechanism and the numerical scheme. The CH4/O2 flame is studied for elevated pressures up to 2 MPa. Both extinction strain rates and the scalar dissipation rates at stoichiometric conditions are evaluated for use in future turbulent flamelet computations. It is shown that oxygen dilution, pressure, and strain rate have a pronounced effect on flame structures, which becomes evident by studying the effects of liquid oxygen compared to gaseous oxygen on flame structure. The combustion of CH4/LOX with preceding evaporation of liquid oxygen under cryogenic conditions has displayed a significant effect of the liquid phase on gas temperature. Moreover, the spray flame is broadened with increase of initial droplet size.