Georgios Bikas

Kinetic modelling of n-decane combustion and autoignition

Abstract A chemical kinetic mechanism for the combustion of n -decane has been compiled and validated for a wide range of combustion regimes. Validation has been performed by using experimental measurements on a premixed flame of n -decane, O 2 and N 2 , stabilized at 1 atm on a flat-flame burner, as well as from shock-tube ignition experiments, from jet-stirred reactor experiments and from a freely propagating premixed flame. The reaction mechanism features ∼600 reactions and 67 species. The oxidation of C 1 -C 2 -species and the description of the hydrogen-oxygen system is similar to that of well-established mechanisms for lower hydrocarbons. Special attention is directed towards an accurate description of species relevant to pollutant formation. The low-temperature oxidation mechanism is lumped from similar mechanisms in the recent literature to account for every type of reaction appearing in this combustion regime, e.g., thermal decomposition of alkanes, H-atom abstraction, alkyl radical isomerization, and β-decomposition for the high temperature range, and a few additional reactions at low temperatures. The transition between low and high temperatures with a negative temperature dependence is excellently reproduced.

Simulation of combustion in direct injection diesel engines using a eulerian particle flamelet model

An overview of flamelet modeling for turbulent non-premixed combustion is given. A short review of previous contributions to simulations of direct injection (DI) diesel engine combustion using the representative interactive flamelet concept is presented. A surrogate fuel consisting of 70% (liquid volume) n -decane and 30% α -methylnaphthalene is experimentally compared to real diesel fuel. The similarity of their physical and chemical properties is shown to result in a very similar combustion process for both fuels. The mathematical derivation for the Eulerian particle flamelet model is outlined. A strategy based on physical arguments is described for subdividing the computational domain and assigning these domains to different flamelet histories associated with Eulerian marker particles. For each of these marker particles, a transport equation has to be solved. Experiments conducted with an Audi DI diesel engine equipped with a piezo injector and running with diesel fuel are compared to simulations using the surrogate fuel. The use of multiple flamelets, each having a different history, significantly improves the description of the ignition phase, leading to a better prediction of pressure, heat release, and exhaust emissions such as soot and NO x . The effect of the number of flamelet particles on the predictions is discussed.