Article title: Generation and characterization of diesel engine combustion emissions from petroleum diesel and soybean biodiesel fuels and application for inhalation exposure studies
Authors: Mutlu E., Nash D. G., King C., Krantz T. Q., Preston W. T., Kooter I. M., Higuchi M., DeMarini D. M., Linak W. P., & Gilmour M. I.
Journal: Inhalation Toxicology
Bibliometrics: Volume 27, Number 11, pages 515 - 532
DOI: http://dx.doi.org/10.3109/08958378.2015.1076910
In our published papers examining the chemistry and emission factors of soy biodiesel, we calculated particulate matter (PM), organic pollutant species, and mutagenicity emission rates (mg/h), mutagenicity emission factors, and DNA adduct emission factors based on fuel consumption (mg/kg fuel), thermal energy released (mg/MJth), and electrical energy produced (mg/MJe). To make these calculations, we used hot-wire anemometer measurements of the engine air-inlet flow rates, determined corresponding engine exhaust-flow rates, and related these with measured pollutant-emission concentrations. However, while analyzing data from a new study using the same methods and experimental equipment, we discovered errors in the original anemometer measurements that caused our reported emission rates and emission factors to be too large by a factor of 2.56. Because this correction factor is a constant throughout the study, the relative values and comparisons in our published papers are unchanged, as are the conclusions.
Measured engine inlet flow rates reported by Mutlu et al. (2015) ranged from 70.2 to 75.0 m3/h. Corrected values from our subsequent canola and waste vegetable oil study ranged from 27.1 to 28.8 m3/h. We have confirmed these corrected values by calculations of engine volumetric flows based on the fixed displacement (320 cm3); constant operating speed (3600 rpm); an assumed volumetric efficiency (80%); and the understanding that for 4-stroke engines, air intake occurs every other downstroke. Based on these input parameters, we have shown that the calculated engine air-inlet flow rate was 27.7 m3/h. We also confirmed this value using several online calculators and the same input parameters. Comparison of this calculated flow with the corrected values measured from our recent study suggests that the assumed volumetric efficiency was approximately correct. Because the emission characteristics, compositions, and concentrations are related directly to emission rates and the various emission factors through the emission volumetric flow rates, the values for these various parameters were reported incorrectly large by a factor directly proportional to the ratio of these flow rates. Although the absolute values are smaller, the relative values have not changed any discussion points or conclusions.
To correct the data reported in Mutlu et al. (2015), divide the following values by 2.56:
Table 1, column 2 (engine air inlet flow rate, m3/h), column 3 (exhaust flow rate, m3/h)
Table 4, column 5 (PM mass emission rate, mg/h), column 6 (PM mass emission factor mg/kg fuel), column 7 (PM mass emission factor, mg/MJth), column 8 (PM mass emission factor, mg/MJe)
Tables 6-10, columns 3, 5, 7, 9 (µg/MJth)
Tables 11-14, columns 3, 5, 7, 9, 11 (µg/MJth)