Tomographic imaging of the liquid and vapour fuel distributions in a single-cylinder direct-injection gasoline engine

This article reports the application of optical tomography and chemical species tomography to the characterisation of the in-cylinder mixture preparation process in a gasoline, direct-injection, single-cylinder, motored research engine. An array of 32 near-infrared beams is transmitted in a horizontal plane across the cylinder bore near the top of the cylinder, through a circular quartz annulus. A novel approach to enable the optical alignment of the transmitting and receiving optics is utilised. The engine is operated at a stoichiometric condition at 1200 r/min, with negative valve overlap timing. Two tomographic measurement schemes (optical attenuation and chemically specific absorption) were used to acquire data on the spatial and temporal distribution of fuel throughout the engine cycle. Optimised data pre-processing methods are described for maximal beam count and data reliability. The presence of fuel during the intake stroke was detected by the optical beam attenuation due to scattering from the li...