Development of an Emissions Monitoring Methodology Using On-Board NOx Sensors and Revision to Current In-Use Emissions Regulatory Protocols

摘要

Measurement of in-use emissions from heavy-duty (HD) vehicles under real-world operation has been widely performed by using portable emissions measurement system (PEMS). PEMS serve as an accurate and lightweight emissions measurement system to evaluate in-use emissions from HD vehicles. However, emissions measurement using PEMS instrumentation can be time consuming and labor intensive. Advantage of utilizing already existing on-board sensors such that they can potentially provide an alternative measurement methodology to the PEMS. A successful implementation of an on-board NOx sensor-based methodology for assessing in-use NOx emissions will allow for a cost-effective and simplified approach to monitor real-world, NOx emission rates. The technology of on-board NOx sensors is in its initial stages to be used to monitor in-use NOx emissions and the ability of the sensor to measure NO x concentration during selective catalytic reduction (SCR) activity period is of concern. Furthermore, the on-board NOx sensors are also subject to various cross-sensitivity and durability concerns.;The primary objective of this dissertation is to compare the on-board NOx sensor response and accuracy against laboratory grade instrumentation that include PEMS using Non-Dispersive Ultra-Violent (NDUV) and Fourier transform infrared spectroscopy (FTIR) measurement to assess the measurement thresholds of on-board NOx sensors. The study compares the cross-sensitivity of the NOx sensors to ammonia (NH3) concentration in the exhaust. NH3 slip from SCR is believed to interfere with NO x measurements using Zirconium oxide sensors and this study will discuss NH3-NOx cross sensitivity on on-board NO x sensors during real-world HD vehicle activity. Results from this study will compare on-board NOx sensor measurement capabilities and they will be assessed at different power levels related to different SCR conversion efficiency and different NOx concentration levels related to measurements obtained from a laboratory grade emissions measurement system FTIR. The secondary objective of this work is to explore and modify boundary conditions for the Not-to-exceed (NTE) and (Work-based window) WBW regulatory protocols due to deficiencies of current protocols in appropriately characterizing regulated emissions especially during the port drayage and urban activity, characterized by low-load engine operation. Thus, new revised regulatory protocols for a wide range of driving activity are needed for an accurate characterization of in-use NOx emissions.