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Exhaust Emissions and Energy Consumption to be Reduced in Heavy-duty Vehicles



VTT Technical Research Centre of Finland is investigating the emissions and energy consumption of heavy-duty vehicles, and how to influence them. The goal is to reduce both emissions and fuel consumption, while also investigating retrofitted exhaust gas purifiers and their actual performance. During the study, a city bus with Euro 3 level emissions could be modified to Euro 5 level with a retrofitted exhaust gas purifier. The nitrous oxide emission-reducing SCR system from Proventia Emission Control Oy is being piloted in a bus belonging to Koskilinjat Oy, part of the Koiviston Auto Group in Oulu.

The project is a HDENIQ heavy-duty vehicle research project forming part of the TransEco research programme. Several parties are participating in the project, including one purifier manufacturer, Proventia Emission Control, and some transport operators, including Koiviston Auto. Last autumn, the project studied how clean a Euro 3 level city bus can be made, when SCR (Selective Catalytic Reduction) and DPF (Diesel Particulate Filter) exhaust aftertreatment systems are installed on it. In practice, the old Euro 3 bus from the early 2000s could be modified so that its emissions match those of the latest city buses. This means that the existing bus fleet does not necessarily need to be constantly replaced. The retrofitted SCR-DPF system is a so-called separate system, i.e., it is not connected to the vehicle’s engine control.

The next phase in the project is to optimise the engine control system so that, in addition to emissions, fuel consumption could also be reduced. The engine is optimised for high nitrous oxide emissions and low fuel consumption by modifying the fuel injection timing. The high nitrous oxide emissions are then treated in an SCR catalyzer, and the particulate emissions are reduced to Euro 5 level using equipment that is as simple as possible. This allows the fuel consumption to be reduced by around 5% in some vehicles, and exhaust gas emissions reduced to Euro 5 level at lower cost than with the SCR+DPF-system.

The exhaust gas emission levels used in Europe are Euro 1 to 5. For heavy-duty vehicles, the engines are approved as components separate from the vehicle, not as entire vehicles as is the case with passenger cars. This causes problems with regard to exhaust gas emissions, especially in city bus traffic, as the engine approval does not reflect actual driving situations, and emissions may be very high in reality. VTT’s heavy-duty vehicle chassis dynamometer enables the simulation of actual driving situations and the acquirement of emission results in these.

DPF = Diesel Particulate Filter (filter for filtering diesel particulates from exhaust emissions)
pDPF = Partial Diesel Particulate Filter, a so-called open filter (works like a DPF but at a lower purification efficiency)
SCR = Selective Catalytic Reduction (reduces nitrous oxide emissions catalytically utilising the Adblue urea solution)

Emission limit values for heavy-duty vehicles