Detailed numerical simulation of the auto-ignition of liquid fuel droplets

摘要

One and two dimensional numerical simulations of the auto-ignition process of single droplets of methanol and n-heptane in air are presented. Detailed models are used to simulate the transport processes as well as the chemical kinetics. Efficient numerical methods are implemented to reduce the computing time. The influence of different ambient parameters on the ignition process is investigated. The ambient gas temperature turns out to be the physical parameter with the largest influence on the ignition delay time. With increasing ambient temperature the ignition delay time decreases. Furthermore, the ignition delay time decreases with increasing pressure following a power law. Two dimensional simulations show the almost exponential dependence of the ignition delay time on the velocity of a gas counterflow. If the counterflow is too strong, the flame is extinguished. Furthermore, the location of ignition is strongly affected by the counterflow velocity.