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Understanding and predicting in-cylinder flow structures that occur within compression-ignition engines is vital if further optimisation of combustion systems is to be achieved. To enable this prediction, fully validated computational models of the complex turbulent flow-fields generated during the intake and compression process are needed. However, generating, analysing and interpreting experimental data to achieve this validation remains a complex challenge due to the variability that occurs from cycle to cycle. The flow-velocity data gathered in this study, obtained from a single-cylinder CI engine with optical access using high-speed PIV, demonstrates that significantly different structures are generated over different cycles, resulting in the mean flow failing to adequately reflect the typical flow produced in-cylinder.

This paper reports the findings from an experimental investigation of the engine cooling jacket filling process for a medium duty off-highway diesel engine to characterise the physical processes that lead to the occurrence of trapped air. The motivation for the project was to provide knowledge and data to aid the development of a computational design tool capable of predicting the amount and location of trapped air in a cooling circuit following a fill event. To quantify the coolant filling process, a transparent replica of a section of the cylinder head cooling core was manufactured from acrylic to allow the application of optical diagnostic techniques. Experimentation has characterised the coolant filling process through the use of three optical techniques. These include the two established methods of High-Speed Imaging and Particle Image Velocimetry (PIV), as well as a novel approach developed for tracking the liquid-air interface during the fill event.

It is widely accepted that engine combustion is fundamentally affected by the in-cylinder charge motion. Flow field structures present at the time and location of spark ignition are known to have a controlling effect on early flame development. Therefore, improved understanding of the variation in flow field structures local to the spark plug at the time of ignition is required. This study investigates the spatial and temporal development of flow field structures within the pent roof combustion chamber of a single cylinder, direct injection spark ignition (DISI) optical engine. High speed particle image velocimetry (HSPIV) has been used to quantify the flow field leading up to and following spark ignition. HSPIV data was recorded at a rate of 5 kHz, providing a temporal resolution of 1.8 crank angle degrees (CAD) between measurement fields and a spatial resolution of 512 by 512 pixels.