In-Cylinder Diagnosis by Laser Tomography

A novel diagnostic method, termed laser tomography, is made feasible for application in automobile engine combustion studies, and sample results of temperature field measurements are presented. To investigate the potential of this method, data are taken in the visible region of the spectrum, where ‘coloring’ of the gas with potassium is required to overcome unsufficient spectral absorption. The research motor, a single-cylinder, BMW SI engine is controlled by a test stand. The tomographic method is based on the use of two known techniques: simultaneous measurement of the spectral absorption and emission data combined with tomographic recon-struction. Since optical access to the engine combustion chamber is limited, twelve laser beams are used for the probing, generated by beam splitters either from a single titan sapphire or dye laser. The beams are guided by novel optical sensors, which are miniaturized and equipped with fiber optic cables and lens systems to allow a defined imaging and probing. Three projections are used, each with four parallel laser beams. With this setup a volume of 24x24x1 mm³ is measured.