Fluid-dynamic investigation and optical characterization of particulate to reduce Diesel emissions

This paper reports recent studies on air motion in a new combustion chamber geometry that reduces the exhaust emission and an on-line optical characterization of the particulate emitted at the exhaust for a development of an after treatment device. A direct injection (d.i.), heavy-duty, single cylinder diesel engine with an optical access, operating at 1000 rpm under motored conditions, was used. Laser Doppler Anemometry (LDA) measurements of cycle resolved instantaneous tangential velocity, performed in different locations of the conventional straight sided and new generation of re-entrant combustion chamber, were reported. The mean motion and turbulence intensity were computed, during the compression stroke, using a filtering procedure of LDA data. In addition, simultaneous multiwavelength scattering and extinction measurement from the near ultra-violet (u.v.) to visible were carried out at the exhaust of a d.i. diesel engine operating at 2200 and 3000 rpm. Size, concentration, optical properties and mass of particulate were evaluated versus different engine parameters. A good agreement was observed on comparing the data with those obtained by conventional techniques.