Euro 7 Engine and Aftertreatment Evolution for Ultra Low Emissions

Euro 7 vehicles, both light- and heavy-duty, will comply with the tightest emissions regulations ever seen in Europe. They will need to have very low emissions for a range of pollutants across a very wide range of operating conditions with a technology neutral approach, meaning that limits will be equally applied to all types of engines in the category. They will also have to maintain these very low levels for the full useful life of the vehicle. In order to achieve this goal significant improvements to both engine and aftertreatment hardware will be required.

Light-Duty Hardware Evolution for Euro 7

Most pollutant emissions from light-duty gasoline engines are well-controlled and engine evolution is mainly focused on improving efficiency in order to reduce carbon dioxide emissions. A significant change in the legislation is that Euro 7 particulate number (PN) limits will apply to all gasoline engines, whereas the current Euro 6 limits apply only to direct injection types. Fuel injection and combustion will improve with a continuing trend of higher injection pressures and smaller injector holes to improve fuel/air mixing. Aftertreatment hardware will also need to improve, and gasoline particulate filters (GPFs) will be used on all gasoline engines. Additionally, filters will need to be capable of providing exceptionally high filtration efficiencies right down to 10 nm in order to meet the new PN₁₀ limit.

Light-duty diesel vehicles are far less popular in Europe than they were a decade ago; however, they are still sold in large numbers and they will be vital to achieving manufacturer carbon dioxide (CO₂) targets. As with gasoline engines, injection technology will improve but with much higher injection pressures involved. The diesel particulate filter (DPF) is already a well-established aftertreatment technology but will need to be improved in order to meet lower limits and a wider range of particle size.

A bigger challenge will be controlling oxides of nitrogen (NO_X) at low temperatures. Currently the favored approach is a selective catalytic reduction (SCR) coating on the DPF substrate (often referred to as SCRF). The challenge will be keeping the catalyst hot enough at startup and low load operation. This will involve either “close coupling” (placing the catalyst close the engine to get the benefit of hotter exhaust gases), electrical heating (which needs a lot of electrical energy and therefore carries a CO₂ penalty) or a combination of the two.

Heavy-Duty Hardware Evolution for Euro 7

Heavy-duty diesel engines are very efficient power units and fuel consumption will continue to be improved in parallel with reduced pollutant emissions. Fuel injection pressures will increase further and the control of injection will be more precise than in previous engines. Cylinder deactivation may become widely adopted as a means of simultaneously improving efficiency and reducing NO_X.

For many years, heavy-duty vehicles have had to employ DPF and SCR technologies to address the challenge of simultaneous reductions in NO_X and particulates. This challenge will continue and increase, with testing for approval extended to low load / low temperature conditions including extended idling. The preferred solution is an improved version of the current combined oxidation catalyst / filter / SCR system with an additional, smaller close-coupled SCR unit to deal with low temperature NO_X emissions. In addition to close coupling this may need an electrical heater within the unit for very low temperature operation.

Summary

Euro 7 vehicles will be the cleanest ever seen on Europe’s roads. They will combine high efficiency with ultra-low emissions across all operating conditions. The engine technology will be taken to the next level and aftertreatment systems will be more complex to ensure clean operation under the very wide range of operating conditions in the legislation. Both light- and heavy-duty vehicles will be required to monitor emissions via the use of multiple sensors in the exhaust system. These sensors will be used to check that the emissions performance does not deteriorate unduly in service.

For these complex systems to work reliably over the life of the vehicle, regular and thorough maintenance will be needed and this will include the use of lubricants specifically designed for low-emission vehicles.