Modal analysis of in-use emissions from heavy-duty diesel engines: on-board measurement

This paper reports the results of modal analysis performed to determine the episodic nature of events and emissions for engine operation within the not-to-exceed (NTE) zone, for each of the selected routes. West Virginia University developed a portable emissions measurement device called the mobile emissions measurement system to obtain engine operating conditions, vehicle speed, and in-use brake-specific emissions of CO2 and NOx from heavy-duty vehicles, tested on specific routes, which included a mix of highway and city driving patterns. The contribution of each mode to variations in emissions rates h as been documented. The average brake-specific emissions of NOx and CO2 show a strong dependence oil the driving modes and were the highest when the engine operated in the cruise mode. The amounts of time that the engine spends in the NTE region and also over continuous 30 s windows of NTE operation for the different routes were calculated. Results indicate that longer operation in the NTE region produced higher brake-specific emissions of NOx compared with their shorter operating counterparts. The primary implication of this work is that emission control strategies and policies should be focused on the mode of operation of the vehicle during oil-road operation, in addition to existing procedures.