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Laser Ignition of an IC Test Engine using an Nd: YAG Laser and the Effect of Key Laser Parameters on Engine Combustion Performance
E. Dodd, J. Mullett, S. Carroll, G. Dearden, A.T. Shenton, K.G. Watkins, G. Triantos and S. Keen

The use of laser energy to ignite gas and liquid based fuel-air mixtures has been the subject of a number of studies and laboratory experiments at a fundamental level over the past 30 years. Yet, the practical implementation of this laser application has still to be fully realised in a commercial automotive application. Laser Ignition (LI), as a replacement for Spark Ignition (SI) in the internal combustion (IC) engines of automotive vehicles, offers several potential advantages including extending lean burn capability, reducing the cyclic variants between combustion cycles and reducing the overall ignition package costs, weight and energy requirements. The continued development of increasingly compact and efficient laser sources and new associated laser beam delivery techniques have provided the basis for significant steps forward in research towards practical proof-of-concept demonstration of LI in engines for automotive vehicles. This paper reports on some results of research recently undertaken in the Department of Engineering, University of Liverpool, in which a Q-switched Nd:YAG laser operating at 1064 nm wavelength has been used to successfully ignite and run (for extended periods) one cylinder of a 4-cylinder internal combustion (IC) test engine. The variation of several laser parameters and their effect on the engine performance are reported; namely, pulse energies of 5–20 mJ, pulse lengths of 6–15 ns and focused beam waist diameters at the combustion point of 40–100•m. The engine performance was measured in terms of changes in Coefficient of Variant (COV) in both Indicated Mean Effective Pressure (IMEP) and the Peak Cylinder Pressure Position (PPP). Further experiments on the focal position of laser ignition were undertaken.

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