ID#: 92
Abstract Title: Modeling the Ignition of Sprays
Session Title: Ignition Phenomena
Session Date: 7/31/01
Session Start Time: 8:30 AM
Contributing Author: Correa, C.D.
Organization: IWR, Univerisity of Heidelberg
Country: Germany
Authors: Chrys Correa, Berthold Schramm, Juergen Warnatz
Short Abstract: The ignition of sprays is important for many industrial processes, such as the autoignition in diesel engines. The characteristic ignition delay time due to radical chain reactions can be described using detailed reaction mechanisms. The use of such detailed mechanisms in the simulation of 3-D instationary processes is too computationally expensive due to the large number of species, radicals and reactions involved. In this paper, a simplified ignition model will be presented which is based on a detailed reaction mechanism. Itis assumed that the complete radical pool formation can be represented by a single species acting as a progress variable, and therefore a conservation equation needs to be solved only for that species. This species should have a very low concentration during the ignition delay time and show a sharp increase in concentration during ignition. The concentration of this species should show a monotonic behavior. In this work, CO was chosen as the representative species. In order to compute the reaction rate of CO, trajectories in homogeneous reactors were traced for different mixture fractions (z), pressures (p) and temperatures (T), and the reaction rates of CO (rCO) was tabulated as a function of z, p, T and the CO concentration (CCO). In turbulent flows, the reaction rate needs to be integrated over a probability density function (pdf). Here, statistical independence of the variables was assumed and a presumed pdf method was used. This ignition model was implemented in a standard engine code (KIVA III) and used to predict the ignition delay time and the position of ignition.