Laser Spark Ignition Modeling

Laser spark phenomena are studied in air and ammonia-oxygen mixtures by the use of a two-dimensional, axially-symmetric, time-accurate computational fluid dynamic model. The initial laser spark temperature distribution is generated to simulate a post-breakdown profile that is consistent with theoretical, experimental, and computational investigations for a nominal 10-ns optical breakdown laser pulse. Thermodynamic properties of various species are extended to 35,000 K to cover the range of the initial temperature distribution. The developed computational model includes a kinetics mechanism that implements plasma equilibrium kinetics in ionized regions.

The computational model time-accurately predicts species concentrations, free electron number density decay, blast wave formation and propagation, vortex formations, temperature profiles, ignition kernel dynamics, flame front formation and propagation, and flow field interactions of laser spark decay in various non-combustible and combustible gaseous mixtures. The computationally predicted fluid phenomena are shown to agree with various flow patterns characteristic of laser spark decay by direct comparison with experimental records.