Ignition and Flameholding Characteristics of Laser Igniters in Supersonic Airstreams

An investigation on effects of a focused laser pulse for combustion enhancement characteristics was conducted for supersonic airstreams with a transverse hydrogen‐fuel injection. Numerical simulations using a time‐dependant Navier‐Stokes equation with finite‐rate chemistry were conducted to elucidate laser‐induced ignition and mixing enhancement characteristics. From the results, it was confirmed that, depending on the laser energy density and focal points, radicals, a shock wave, and shock‐induced local turbulences were being formed through the laser irradiation. Then recirculation zones with flamelets were induced. Moreover it was shown that these flamelets grew in moving upstream and downstream from the focal point up to 1 msec. From these results, it was shown that laser‐induced plasmas could be effective in both combustion reaction and mixing enhancements for the supersonic combustion.