Design and Bench-Top Testing of Multiplexed Fiber Delivered Laser Ignition System for Natural Gas Engines

Past research has demonstrated the feasibility of using optical sparks for engine ignition, and has shown potential benefits associated with reduced cyclic variability and increased rate of cylinder pressure rise, thus extending the lean operating limit of natural gas engines. This contribution details the design and bench-top testing of a fiber-optic delivery system for ignition of natural gas engines. The system is designed for use on a Caterpillar G3516C engine and is comprised of a single Nd:YAG laser as the energy source, a multiplexer for switching the beam between cylinders, fiber optics to deliver the laser pulses to individual cylinders, and optical plugs to couple the beam into the cylinders. The optical fibers are a critical component of the system and discussion of use of both solid core silica fibers and cyclic olefin polymer-coated silver hollow fibers is included. The multiplexer design is presented and optical testing of the multiplexed fiber delivery on the bench-top is reported. Design considerations for engine integration are introduced.