Date of Graduation
Statler College of Engineering and Mineral Resources
Mechanical and Aerospace Engineering
Heavy-duty on-road diesel engines currently sold in the United States are subjected to emission certification over the Federal Test Procedure and Supplemental Emissions Test in an engine test cell as well as in-use testing in real world environments using portable emissions measurement systems (PEMS). The current method for analyzing in-use emissions is based on the Not-To-Exceed (NTE) region of engine operation. With this method, emissions are reported only when the engine is operating in the NTE region for a minimum of thirty seconds. The downfall to this method is that any engine operation outside of this region is neglected. An alternative method for measuring in-use emissions is based on a work approach previously proposed by Shade. This method integrates power produced by the engine over time to create work windows; the integration duration can be defined using a pre-specified work level. One such work level could be the work that the engine was exercised over during the Federal Test Procedure. The emissions produced during this window are then summed and divided by the work to produce brake specific emission levels for each window. By basing this analysis on work produced by the engine instead of time an engine spends in a certain region of operation, almost no point of engine operation is neglected and the majority of all emissions produced during the test are accounted for.;A study using in-use compliance data from seven vehicles representing diverse vocations was used to compare the currently implemented NTE method of in-use emissions measurement and a proposed work-based window method for measuring brake specific emissions of CO, CO2, NOx, THC, and PM emissions. Analysis of this data showed that without any exclusions applied to either method, the work-window method resulted in an average percent difference of 162% higher CO, 12% higher CO2, 94% higher NOx, and 186% higher THC emissions when compared to the average NTE results. Average PM results from the work-window method, however, showed a 122% lower level than the NTE method. Due to limitations associated with the NTE method, it was determined that the work-based window method may still provide better representation of actual in-use emissions despite the higher calculated brake specific emission levels.
Music, Nathan, "Comparison of a Work-Based Window Method to NTE Method for Reporting In-Use Emissions" (2011). Graduate Theses, Dissertations, and Problem Reports. 4759.