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The objective of this work is to improve the understanding of variables like dilution and sampling conditions that contribute to particle-based emission measurements by assessing and comparing the nucleation tendency of diesel aerosols when diluted with a porous wall dilutor or an air ejector in a laboratory setting. An air-ejector dilutor and typical dilution conditions were used to establish the baseline sensitivity to dilution conditions for the given engine operating condition. A porous tube dilutor was designed and special attention was given to integrating the dilutor with the exhaust pipe and residence time chamber. Results from this system were compared with the ejector dilutor. Exhaust aerosols were generated by a Deere 4045 diesel engine running at low speed (1400 rpm) and low load (50 Nm, ~10% of rated). Primary dilution parameters that were varied included dilution air temperature (25 and 47°C) and dilution ratio (5, 14, and 55).

The focus of this work was the physical characterization of exhaust aerosol from the University of Minnesota Formula SAE team's engine. This was done using two competition fuels, 100 octane race fuel and E85. Three engine conditions were evaluated: 6000 RPM 75% throttle, 8000 RPM 50% throttle, and 8000 RPM 100% throttle. Dilute emissions were characterized using a Scanning Mobility Particle Sizer (SMPS) and a Condensation Particle Counter (CPC). E85 fuel produced more power and had lower particulate matter emissions at all test conditions, but more fuel was consumed.