Large Eddy Simulations of spray flames of biodiesel surrogate
(2022) 14th European Fluid Mechanics Conference — Location: Athens, Greece (13.September.2022)
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- Abstract
- The use of alternative fuels for engine applications has attracted a lot of attention due to increased concerns over the CO2 emissions generated by the combustion of fossil fuels. One promising example of such fuels is biodiesels for use in internal combustion engines, such as the Karanja Methyl Ester (KME). In this work, we report on numerical studies of spray combustion of a surrogate of KME via Large-Eddy Simulation. The surrogate fuel considered herein is a blend of n-dodecane (64.32%) and methyl butanoate (35.68%), which replicates the main characteristics of the actual gaseous KME biodiesel. The main objectives of this study is to investigate the properties of spray combustion of this surrogate and to compare them with those of standard diesel fuels. The computational setup follows closely the conditions of the reactive “Spray A” baseline defined by the Engine Combustion Network. Concerning the numerical methodology, we employ the Eulerian approach for the gaseous phase, coupled with Langrangian Particle Tracking for the motion of the liquid fuel droplets. For the breakup of the droplets we employ a modified version of the Taylor Analogy Breakup model that we presented recently1. Further, with regard to combustion modelling and turbulence-chemistry interaction, we employ the Flamelet-Generated Manifold (FGM) which is based on tabulated chemistry and in which the advancement of the reaction process and composition of the mixture is described in terms of certain control variables. Herein, we employ a new implementation of the FGM approach according to which the energy equation is cast in terms of the sensible enthalpy2. This allows the direct computation of the temperature and the temperature-dependent properties of the mixture, which results in significant computational savings. In this presentation we discuss our numerical predictions for key characteristics of the combustion process, such as ignition delay time, flame lift-off length and flame temperature, and compare them with those of surrogates of standard diesel fuel. Further, we present results for the concentrations of the following species: i) CH2O which is an indicator of the transition from low to high-temperature combustion, ii) OH which is an indicator of high-temperature combustion region, and iii) C2H2, which is a key soot precursor.
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Sula, C., Grosshans, H., & Papalexandris, M. (2022). Large Eddy Simulations of spray flames of biodiesel surrogate. 14th European Fluid Mechanics Conference, Athens, Greece. https://hdl.handle.net/2078.5/269396