The gaseous and particulate matter exhaust emissions produced by internal combustion engine (ICE) powered vehicles are detrimental to human and environmental health. To reduce harmful exhaust emissions, manufacturers implement various exhaust aftertreatment systems with minimal impact on the performance of an engine. Automotive emission testing began in the late 20th century and has become increasingly stringent as a result of urban air quality and global climate targets. In its infancy, automotive emission testing imposed that new vehicles must pass a laboratory-based (rolling road) type approval (TA) protocol only. However, these early tests became widely criticised as inaccurate and not symbolic of real-driving conditions and patterns. Therefore, in 2015 (Europe), a significant protocol advancement was imposed on ICE vehicle manufacturers in the form of Real Driving Emission (RDE) testing. RDE tests, with the use of portable emission measuring systems (PEMS), now incorporate numerous driving styles and weather conditions on a variety of real public roads including urban, rural and motorway sections.
Since the European Commission imposes regulated RDE testing, the PEMS equipment used for the new vehicle TA process must also be regulated. Regulatory-approved PEMS technology is guided by industry-standard measurement techniques and is essential for test uniformity and data conformity for all RDE testing across Europe. Furthermore, ICE vehicle manufacturers need regular access to their own private PEMS devices for vehicle research and development purposes and preparation for the RDE TA process. However, European regulatory approved PEMS are expensive (~£150,000 per device). Therefore, this research aimed to design, construct and evaluate a low-cost portable emission measuring system (LCPEMS) (including software platform) for indicative RDE testing of light-duty vehicles (LDV).
To achieve a LCPEMS, some regulatory approved technologies were used (where commercially possible), as well as some low-cost technology alternatives. This work also designed and constructed an exhaust sampling manifold to connect to a test vehicle. The LCPEMS was used with the exhaust sampling manifold to measure emission characteristics of a test vehicle under a variety of conditions and RDE drive cycles were performed on real, public roads. A software platform was also programmed to acquire, interpret, visualize and record test data.
This work yielded mixed levels of success and the research aims were partially met. Particulate matter (number concentration) measurement in commercial PEMS is scientifically complex and requires additional ancillary technologies, therefore a low-cost alternative was deemed to be beyond the scope of this work. Furthermore, testing found that the exhaust flow sensing arrangement was completely unsuitable and the carbon monoxide (CO) sensor in the LCPEMS was considered somewhat unfit for the application. However, the other LCPEMS sensors for; oxides of nitrogen (NOx), oxygen (O2), carbon dioxide (CO2) and exhaust gas temperature, as well as the LCPEMS gas pumping arrangement, exhaust sampling manifold and software platform were all determined to be suitable for indicative RDE testing of LDVs. This work established a feasible LCPEMS prototype with a clear understanding of further development requirements.
Matthew is an MRes student under the supervision of Dr Gavin Phillips, Department od Mathematical and Physical Sciences, University of Chester.