Abstract
HAJI, or Hydrogen Assisted Jet Ignition, is an ignition system which uses a hot gaseous jet to initiate and stabilise combustion. Advantages include reduced cyclic variability and a lean limit of lambda A5.0. This allows efficiency improvements in excess of 25% and low emissions, particularly of NOx. Combustion analysis based on the fractal dimensions of the propagating flame fronts, obtained from flame images, support the hypothesis of enhancement of flame speeds through the presence of active chemical species. However, the relative contributions of turbulence and active species to the mechanisms of combustion enhancement are not yet well defined. HAJI ignition has also been simulated with a comprehensive three dimensional combustion code, KIVA3. The simulations have been calibrated against flame photographs and heat release data. The results provide evidence of the influence that turbulence, chemistry and geometry have on flame growth and propagation.