AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Sampling Temprature Effects on the Size Distribution of Paricles Emitted by a Two-Stroke Engine
Ricardo Morales Betancourt, YADERT CONTRERAS BARBOSA, Ana Paola Corredor, Joseph Herrera, Juan Camilo Vigoya, Universidad de los Andes
Abstract Number: 697 Working Group: Combustion
Abstract In this work we estimate the particle number and mass emissions produced by a 50 c.c two-stroke engine working with an oil-gasoline mixture as fuel. Exhaust gases were sampled and analyzed with an Electrical Low Pressure Impactor Dekati Mass Monitor (DMM-230) after dilution of the sample with a two stage ejection diluter. Two operating conditions were explored: Full Throttle engine load and at Idle. A new data inversion method was developed for the analysis of the raw data of the DMM-230. This new inversion method allows to calculate the number size distribution without the need of assuming a log-normal shape. The data inversion method is a modification of previous inversion algorithms (Mamakos et al., 2007). To interpret the effect of temperature on the size distribution of particles a sectional aerosol model was employed to simulate the transformations undergone by the aerosol size distribution in the sampling line. The TwO-Moment Aerosol Sectional (TOMAS) was used. Aerosol particles are assumed to be formed of five components, elemental carbon, water, sulfate, and two components of semi-volatile organic carbon. The two-component organic carbon model used here was used successfully to predict partitioning in other studies (Shrivasrava et al., 2006). To ensure reproducibility of the measurements, a total of 40 samples were carried out. In some of these samples heated diluted air was used to explore the effect of temperature on the size distribution. Results indicate that at higher sampling temperatures the characteristic fine mode of the 2-stroke engine exhaust emissions decreases in size, suggesting it is mainly composed of semi-volatile organics. At lower sampling temperatures, semi-volatile organics condense on the particles increasing the particle size. The measurements are consistent with the results obtained with the sectional aerosol model. Large values for the emission factors were observed, ranging from 120 to 250 grams per kilogram of fuel. Similar values were obtained with a carbon balance method.