Experimental and Error Analysis Investigation into Dilution Factor Equations 2007-01-0310

As emission regulations become increasingly strict, the need for more accurate sampling systems becomes essential. When calculating emissions from a dilution system, a correction is made to remove the effects of contaminants in the dilution air. The dilution air correction was explored to determine why this correction is needed, when this correction is important, and what methods are available for calculating the dilution factor (DF). An experimental and error analysis investigation into the standard and recently proposed methods for calculating the DF was conducted. Five steady state modes were run on a 1992 Detroit Diesel engine series 60 and the DF from eleven different equations were investigated. The effects of an inaccurate dilution air correction on calculated fuel flow from a carbon balance and the mass emissions was analyzed. The dilution air correction was shown to be important only for hydrocarbons, particulate matter (PM), and CO₂. Only at idle was the dilution air correction of CO₂ emissions significant. The propagation of error of the dilution factor by direct measurement of the exhaust flow and tunnel flow was found to have the lowest error. Fuel flow based on a carbon balance with no dilution air correction was shown to be the most accurate method (within 2.4% of the direct flow measurement) at high loads and the least accurate at idle.