Laser Ignition and Diagnosis.

About

Technology Due to the large cylinder pressure and mixture density desired in modern engines, traditional spark ignition systems must operate at high voltage levels. As a result, dielectric breakdown (unwanted sparking) and electrode erosion frequently plague modern gas engines and are a limiting factor in the operational envelope of modern gas engines. Optical sparks suffer from neither of these shortcomings and thus may have significant advantages for improved engine operation. In certain cases, optical sparks can also afford performance benefits associated with extension of maintenance intervals as well as changes in the lean limit, coefficient of variation of pressure, pollutant emissions and other parameters. Laser ignition has been shown to be a particularly effective way of igniting lean mixtures. In fact, it is fairly easy to create a spark by using "open path" laser delivery. The open path method implies that the laser beam propagates through the ambient air and is steered to the desired location by mirrors. Although simple and effective, this system is not practical for most industrial applications. Thus, there is a need for the development of an alternative optical delivery system. Researchers in the Department of Mechanical Engineering at Colorado State University have developed laser-based ignition systems based on state-of-the-art optical fibers and sophisticated new delivery strategies. It is generally challenging to use optical fibers to deliver laser pulses in a way that allows one to focus the exit (output) pulse to form a spark in the gas-phase. The required breakdown intensity is typically approximately 100-300 GW/cm2. Light intensities of this magnitude require an exit pulse with a sufficient combination of optical power and beam quality (the latter in order to focus the light to a small spatial dimension). To meet this challenge, researchers at Colorado State University have employed state-of-the-art optical fibers and creative new delivery strategies. With four issued U.S. patents, these researchers are at the forefront of this exciting field.