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2 Journal of KONES

2 2010

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Optical diagnostics of the cyclic variation in the kernel development and abnormal combustion: SI boosted engine

Gallardo-Ruiz J. M., Ballais R., Merola S. S., Sementa P., Tornatore C.

Journal of KONES

2010

Vol. 17, No. 2

103-111

The combustion stability of a spark ignition engine significantly influences its performances. The cyclic variation is generally evaluated by the fluctuation of in-cylinder peak pressure which changes in both magnitude and position measured from TDC. In this work the cyclic variation of combustion process were analysed as function of crank angles. The different SI engine process phases were investigated. The pressure related data were correlated with cycle resolved visualization measurements. The cycle resolved digital imaging was applied to follow the kernel inception and growth and to study the flame front propagation until the exhaust phase. A custom numerical post-detection procedure was applied to correlate the optical data from the integral luminous signal measured in the combustion chamber with the pressure related parameters .The flame kernel and the abnormal combustion due to the fuel deposits burning resulted particular relevant for the cycle-to-cycle variations. Optical measurements outlined better than pressure related analysis the role of the early andfinal stages of the combustion process. The experiments were performed in a 400 cm3 single cylinder, port fuel injection, four-stroke spark ignition engine. The engine was optical accessible with the same geometrical parameters as a 1600 cm3 passenger car engine. The head and the injection system of a commercial engine mounted on a passenger car were used. Standard EURO IV gasoline was used

Optical diagnostics of the cycle-to-cycle variation in the kernel development and abnormal combustion: SI small engine

Ballais, Gallardo-Ruiz J. M., Merola S. S., Sementa P., Tornatore C.

Journal of KONES

2010

Vol. 17, No. 2

17-25

The combustion stability and more in details the cyclic variability significantly influences the performance and the pollutant emissions of a spark ignition engine. In this work, an experimental research activity was carried out to investigate the influence of the different combustion phases on the cycle-to-cycle variation. In particular the flame kernel development and the fuel deposits burning were investigated by in-cylinder pressure measurements and optical investigations. Engine cycle resolved visualization was applied to characterize the spatial evolution of the flame front from the spark ignition until the exhaust phase. A numerical custom post-detection procedure was used to correlate the optical data with the pressure related parameters during the combustion process. The simultaneous use of optical diagnostics and pressure related analysis demonstrated the fundamental role of the first stage and late phase of the combustion on the spark ignition engine process. Flame kernel and diffusion controlled flame due to fuel deposits burning dominated the cyclic variability of in-cylinder combustion. The experiments were realized in a 250 cm3 single cylinder, port fuel injection, four-stroke spark ignition engine. The engine was optically accessible and it was equipped with the head, injection system and exhaust device of a commercial engine mounted on small motorcycles and scooters. Standard EURO IVgasoline was used.