Laser-Stimulated Ignition in a Homogeneous Charge Compression Ignition Engine

A laser-induced spark was generated inside the combustion chamber of a reciprocating engine running in Homogeneous Charge Compression Ignition (HCCI) mode to investigate the influence of the plasma on combustion performance. For a fuel consisting of 90% natural gas and 10% isooctane, the advance of combustion due to the plasma was found to be strong up to air excess ratios of λ = 2.3 and to cease completely above λ = 2.7. Combustion timing was advanced with increasing advance of plasma timing to a certain extent. The laser was able to sustain HCCI combustion even at much lower inlet temperatures than normally required without plasma. Inlet temperature changes of more than 10 °C could not eliminate laser stimulated HCCI combustion. A potential application of laser stimulated ignition is as a means to actively control HCCI combustion timing.