The interest in lasers for engine ignition is the possibility of higher efficiency and reduction of pollutants compared with conventional spark plugs. The interest in this area is to understand the laser energy needed for breakdown and ignition in order to better design practical systems. To support such development, the laser induced breakdown of air is simulated by the use of a two-dimensional computational fluid-dynamic model for 10 and 46 ns laser pulses for several pressures and focal spot sizes. The simulation includes the laser propagation, multi-photon ionization, impact ionization, electrons heating and energy loss. The dependence of breakdown irradiance on pulse duration, ambient pressure, and dimensions of the focal region is investigated and compared with experimental results.

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