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A combination of optical and laser based methods have been employed for simultaneously studying fuel jet penetration and ignition behaviour of fuel jets inside the cylinder of a large marine two-stroke diesel engine during operation. Tests were performed on a four-cylinder Diesel engine with a bore diameter of 0.5 meter. Optical access was obtained through a custom designed engine cover. A double pulsed laser was employed for global illumination of the liquid fuel jet. For detection a dual camera set-up was employed, which allowed both simultaneous fuel jet and flame emission imaging, or dual frame fuel jet imaging for velocity measurements. From the data recorded the liquid penetration, jet cone angle, jet penetration velocity, ignition location, ignition time and flame lift-off could be extracted. Data was recorded for two different charge densities and temperatures, for two different atomizer designs, and for two different fuels.

In-cylinder flow velocity measurements using particle image velocimetry (PIV) have been performed for the first time in a full-size marine Diesel engine. The engine was a four cylinder two-stroke engine with a bore diameter of 0.5 meter and a stroke of 2.2 meter. For such engines uniflow scavenging is used, with fresh air entering through angled ports at the bottom of the cylinder to generate a swirling flow and burnt gases exiting through a centrally located exhaust valve at the top. For efficient design of this process and for validation of CFD models it is essential to obtain an experimental characterization of the flow inside a fully operational engine. Optical access was obtained through a custom designed engine cover, fitted with a number of optical ports into which sapphire windows were mounted. Both the laser and camera used for PIV were mounted directly onto the engine in order to minimize effects of vibrations on optical alignment.