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The effect of diesel engine operating conditions on exhaust particle size distributions

Abstract Owing to the negative effects that aerosols have on human health, the interest in knowing the size and the amount of particulate matter emitted by diesel engines is increasing. The measurement of this kind of aerosol is mainly influenced by three parameters: the ambient conditions, the sampling method used to characterize the emissions together with the system used to determine the particle size distributions, and, finally, the physical and chemical characteristics of the aerosol, which are a direct consequence of those processes occurring in the engine (composition, size, and concentration of particles in the aerosol, amount of volatile organic compounds, sulphur compounds, and different residues coming from the additives used in fuels and lubricants, etc.). An experimental study has been developed which combines the use of a partial dilution minitunnel and a scanning mobility particle sizer. The aim is to study the influence that the engine operating conditions which the driver can control by using the throttle while driving a vehicle, i.e. the torque and engine speed, have on the particle size distribution and its statistical parameters, namely the mean diameter and total concentration. This study was carried out on a light-duty direct-injection diesel engine which is used currently on European roads. Four steady operation modes were tested, from the most emissions-significant zones of the engine map. Likewise, a complementary study has been developed for a better understanding of the combined effect of both fuel-to-air and exhaust gas recirculation (EGR) ratios. In this latter study the EGR was completely eliminated from the engine modes previously studied.