Abstract
Laser ignition (LI) has been shown to offer many potential benefits compared to spark ignition (SI) for improving the performance of internal combustion (IC) engines. This paper outlines progress made in recent research on laser ignited IC engines, discusses the potential advantages and control opportunities and considers the challenges faced and prospects for its future implementation. An experimental research effort has been underway at the University of Liverpool (UoL) to extend the stratified speed/load operating region of the gasoline direct injection (GDI) engine through LI research, for which an overview of some of the approaches, testing and results to date are presented. These indicate how LI can be used to improve control of the engine for: leaner operation, reductions in emissions, lower idle speed and improved combustion stability.
Highlights
It is widely accepted that the internal combustion (IC) engine will continue to be the main vehicle power plant over the two decades, before significant displacement by alternative technologies takes place
By collecting optical emission from the igniting laser spark through the optical plug, and analyzing cycle-by-cycle spectra, a linear correlation (R2 > 0.99) between spectral line intensity ratio and equivalence ratio was found, suggesting a potentially useful engine diagnostic method for cylinder-resolved equivalence ratio measurements. These results show that techniques such as laser-induced breakdown spectroscopy (LIBS), pattern recognition using photo detectors and advanced signal processing such as on-line principal component analysis (PCA) and neural networks could be investigated as the basis for real-time feedback control of combustion
Research to date on Laser ignition (LI) in engines has demonstrated improvements in combustion stability, as measured by coefficient of variation in IMEP (COVIMEP). These improvements can enable engines to be run under leaner conditions, with higher exhaust gas recirculation (EGR) concentrations, or at lower idle speeds without increasing the noise, vibration and harshness characteristics of a vehicle
Summary
It is widely accepted that the IC engine will continue to be the main vehicle power plant over the two decades, before significant displacement by alternative technologies takes place. SI restricts engine design, in new GDI engines, since the spark position is fixed by the cylinder head location of the plug, and the protruding electrode disturbs the cylinder geometry and may quench the combustion flame kernel. In this context, research into LI of IC engines seeks to examine its potential to improve combustion efficiency and stability compared to SI by igniting highly dilute air-fuel mixtures with comparatively low ignition energies and to initiate ignition away from the (cold) walls of the combustion chamber. The opportunities, challenges and prospects for future implementation of LI in generation IC engines are explored
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