Performance of compact mobile emissions monitoring system for real-time on-board emissions measurement
Date of Graduation
Statler College of Engineering and Mineral Resources
Mechanical and Aerospace Engineering
The objective of this study was to evaluate the performance of the Compact Mobile Emissions Monitoring System (CMEMS) in an engine dynamometer test cell equipped with laboratory grade analyzers, and under real-world testing conditions. The CMEMS was evaluated in the test cell with the engine operating under transient (FTP) and steady state conditions and results were compared with laboratory data.;In response to the Consent Decrees, which were entered into by some of the heavy duty engine manufactures and the United States, several in-use portable emissions measurement systems (PEMS) have been developed, and some of them are commercially available. However, most of these systems are based upon an impractical design that requires one or more "boxes" to be placed in the cab of the test vehicle, with heated analyzers and sample handling systems, an exhaust flow rate measurement system installed on the tailpipe, and heated sample lines. Such systems place a taxing power demand on the engine. They are bulky and heavy, and the deskew times contribute to measurement uncertainties.;In response to the "lessons learned" from the use of WVU's Mobile Emissions Measuring System (MEMS), WVU has developed compact MEMS, which addresses the concerns associated with currently available PEMS, including the MEMS. The unique feature of the CMEMS is that it is a single unit with all components incorporated in the single 34" x 8" x 8" container, which is mounted on the exhaust stack.;Compared to the MEMS, the Compact Emissions Monitoring System weighs 60lb, which is 70lb less than the MEMS. CMEMS consists of a CO2 analyzer, NOx sensor and the control unit to measure CO2 and NOx emissions from a vehicle. CMEMS uses solid state nondispersive infrared detector BE-150 for measuring CO2 emissions. CMEMS has a built in Data Acquisition System. On the other hand, even though the Engine Control Module (ECM) uses a CAN (Controller Area Network) to serial adaptor, the ECU was not probed with the current set-up of the CMEMS.;The engine was tested over the steady-state cycles, federal heavy-duty certification cycle and simulated on-road cycle. Mass emissions rates measured by CMEMS differed from laboratory generated results by 6.2% for CO2 and by 5.7% for NOx over the steady-state cycle. Over the FTP transient cycle, the differences observed were -8.3% for CO2 and 11.1% for NOx. Significantly lower percentage differences were recorded while testing CMEMS over the on-road cycle: 1.4 and 2.9% for CO2 and NOx emissions respectively. Under real-world conditions, the CMEMS had a maximum error percentage of 7.7% for CO2 and 8% for NOx, in comparison to the MEMS.;CMEMS in its current configuration was unable to maintain the required temperature for the chiller, under real world testing. Lack of ventilation and heat dissipation problems were accountable for temperature problems, hence the erroneous CO2 reading by CMEMS. Further both BE-150 and MEXA-720, the NOx analyzer, were sensitive for vibration. Therefore, rugged road conditions too account for bad NOx and CO2 readings. Compact layout of CMEMS made trouble shoot time consuming when problems occurred.;It should be noted that, to the best authors' knowledge, this is the first attempt to develop an engine emissions measuring system directly attached on the tail pipe of a heavy-duty truck. Further considerations and work will be needed when redesigning the system in order to get better engine emissions data.
Jayasinghe, Chandima S., "Performance of compact mobile emissions monitoring system for real-time on-board emissions measurement" (2007). Graduate Theses, Dissertations, and Problem Reports. 1830.