Practical Fiber Delivered Laser Ignition Systems for Vehicles

Improved ignition methods are needed for advanced vehicle combustion systems, in particular those that allow reliable ignition of lean mixtures in gasoline engines at elevated pressures. Laser ignition is a candidate technology having the potential to address these needs. However, despite more than 40 years of laser ignition research, the technology is not yet in commercial use. A critical problem is the need for safe, reliable, and affordable laser delivery systems. The proposed effort is to test and develop new approaches for fiber optic delivery of the laser pulses to the engine. In this way, a single laser source can be multiplexed (shared) to multiple engine cylinders thereby allowing substantially less complex (and lower cost) systems as compared to laser-per-cylinder approaches (or approaches where a single pump laser is shared to gain elements on the individual cylinders). The need to reliably and safely deliver the high-power laser pulses through fiber optics strains the abilities of conventional optical fibers. The proposed research capitalizes on the most recent advances in high-power fiber delivery by investigating large clad fibers (that been recently been demonstrated for laser ignition by our team) as well as Kagome photonic bandgap fibers (that have recently been demonstrated for laser ignition by other researchers). In the proposed effort, we will perform bench top testing of these fibers to characterize and improve the delivered pulse energies and focused spark intensities. We will also test the improve configurations on a representative single-cylinder direct injection gasoline engine at Argonne National Laboratory. The engine tests will examine lean limits for both spark ignition and laser ignition, and compare the resulting engine performance (efficiency and emissions) to stoichiometric operation. Clearly, if viable approaches to laser ignition hardware can be demonstrated, there will be significant motivation for their commercialization. The project team has intellectual property in the area of high-power fiber delivery, and has strong linkages with engine and laser companies, thereby putting us in a strong position for the commercialization. In addition to laser ignition for vehicles, as is the focus of the current proposal, there is growing interest in the use of laser ignition for stationary gas engines as well as for ground based and aero- turbines, which would provide complementary markets. Accompanying support letters underscore the commercial interest in laser ignition.