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Abstract
A heavy-duty engine is homologated in a test cell. However, starting with Euro VI regulation, the in-service conformity is controlled with the engine installed in the vehicle using portable emission measurement systems (PEMS). In Europe, the application of solid particle number (SPN) PEMS started in 2021 for compression ignition (diesel) vehicles and in 2023 for positive ignition vehicles, thus including those operating with compressed natural gas (CNG). Even though today only particles with sizes > 23 nm are regulated, the Euro 7 proposal includes particles > 10 nm. There are not many studies on the accuracy of the SPN PEMS, especially for heavy-duty applications. In this study, PEMS measuring > 23 and >10 nm from two instrument manufacturers were compared with laboratory-grade instruments. The particle detector of one PEMS was a condensation particle counter (CPC), and of the other a the diffusion charger (DC). The results showed the robustness and good accuracy (40% or 1 × 1011 #/kWh) of the PEMS for ambient temperatures from −7 °C to 35 °C, active regeneration events, different fuels (Diesel B7, HVO, and CNG), different test cycles, cold start or hot engine operations, and high exhaust gas humidity content. Nevertheless, for the DC-based PEMS, sensitivity to pre-charged urea particles was identified, and for the CPC-based PEMS, sensitivity to pressure changes with one vehicle was nnoticed. Nevertheless, the results of this study confirm that the PEMS are accurate enough to measure even the stricter Euro 7 limits.
Highlights
The road freight transportation sector is central in the European Union (EU) for the economy and environment [1,2]
A big step forward was the introduction of portable emission measurement systems (PEMS), which made measurements of emissions possible without removing the engine from the vehicle [6]
Compared to previous PEMS assessment studies with light-duty [43] and heavy-duty vehicles [22], we extend with more engines and boundary conditions
Summary
The road freight transportation sector is central in the European Union (EU) for the economy and environment [1,2]. Exhaust emissions from vehicles have decreased significantly over the years due to the implementation of effective aftertreatment devices in response to the limits imposed by the different regulations [3–5]. For heavy-duty vehicles, engines are type-approved in test cells. This had the difficulty of removing the engine from in-use vehicles to control compliance over the lifetime of the engines. A big step forward was the introduction of portable emission measurement systems (PEMS), which made measurements of emissions possible without removing the engine from the vehicle [6]. In Europe, PEMS for gaseous pollutants were introduced with
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