Traceable uncertainty of exhaust flow meters embedded in portable emission measurement systems
Abstract
Exhaust flow meters (EFM) measure the amount of exhaust gas during type approval tests of diesel and petrol fuelled vehicles. They are embedded in portable emissions measurement systems (PEMS), together with analysers which measure pollutants in the exhaust gas. The European Union adopted Real Driving Emissions legislation in 2016 - 2018 in which real-driving emission tests using PEMS are a requirement for type approvalof vehicles. SI-traceable calibration of the exhaust flow meter and analysers in PEMS for real driving conditions is a challenging task. Currently a conformity factor is employed to acknowledge the fact that the calibration of PEMS components in accurately controlled laboratory conditions does not consider all factors contributing to overall PEMS uncertainty in a real-driving type approval test. The EFM uncertainty is a dominant uncertainty component in PEMS measurements. A need exists for traceable quantitative uncertainty characterization not limited to transients in the exhaust flow, flow pulsations, gas composition, temperature, and drift of the flow meter. As part of the European Metrology Programme for Innovation and Research (EMPIR) research project 19ENV09 “MetroPEMS”, this paper (I) presents a generic uncertainty analysis of the EFM using state-of-the-art knowledge, and (II) presents first measurement results of quantitative and (partly) traceable assessment of factors contributing to the overall uncertainty of the EFM. While some experimental results show that the EFM matches legislative accuracy requirements, other experiments indicate that this is not generically proven for all possible on-road conditions in which the PEMS are used.
Event details
- Event
- FLOMEKO 2022
- Technical Committee
- TC9
- lich@nim.ac.cn
- Place
- Chongqing, CHINA
- Time
- 1 November 2022 - 4 November 2022
- Website
- http://flomeko2022.msmk.tech/c/index.html