Staying within the limit

Latest EU emissions regulations affect the automotive industry

The European Union has recently introduced Euro 6 regulations for diesel engines. While these regulations may seem a long line in a list of directives, they are relevant for the entire automotive industry. Here we look at how developments of diesel particulate filters (DPFs) are increasingly important in reducing the levels of harmful emissions.

Since Euro 1 in 1993, the EU has regulated what comes out of the exhaust of a diesel engine. It particularly monitors levels of nitrogen oxide (NOx) and particulate matter (PM), commonly known as soot.

As a result, engine manufacturers have invested a great deal of time and money trying to work within these regulations. DPFs were developed in order to work alongside selective catalytic reduction (SCR) or exhaust gas recirculation (EGR) devices, as these remove particulate matter (PM) from the exhaust gas of a diesel engine. From Euro 5 in 2009, these became a legal requirement for all new diesel vehicles.

PM is a particular target for the EU as it is extremely harmful to the environment and to the population, particularly in built up areas. PM penetrates into the sensitive regions of the respiratory system and can cause cancer or respiratory illnesses. From an environmental point of view, PM is one of the leading causes of global warming. Black carbon, one of the strongest light-absorbing components of PM has a 20 year Global Warming Potential. That's 4000 times higher than that of carbon dioxide. It’s therefore easy to see why the EU is keen to reduce the levels of PM in the air.

The new regulations target ultrafine PM of 0.1 microns, which are 50 times smaller than a human hair. This is a 66 percent drop in the levels permitted in Euro 5. Due to these new regulations, there is expected to be a growth in demand for DPF servicing. Under the Euro 6 regulations, all emissions management systems have to be durable for 700,000 km or seven years for the largest vehicles.

While DPFs can be extremely effective and can remove up to 95 percent of harmful PM emissions, they can be quite temperamental and will only work under the right conditions. There are two modes for DPFs to work. Under passive regeneration, they trap soot particles and burn them off during the regeneration process, with temperatures reaching over 550 Celsius. However, this is only possible when the vehicle reaches the optimal temperature, typically when driven on longer journeys and at higher speeds.

Active regeneration occurs when soot levels in the filter reach a set limit of 45 percent. The vehicle's engine management computer will initiate a post-combustion fuel injection to increase the exhaust temperature and to trigger regeneration. However, the cycle can only complete when the vehicle is driven for over ten minutes at speeds of over 60 kmph.

If the vehicle is only driven in short bursts or in stop-start traffic, the cycle will not complete. The extra fuel, which has been injected into the cylinders for the process will not burn off, oil quality will deteriorate and the oil level will rise. If this continues to levels of 75 percent of soot in the filter, warning lights will appear on the dashboard and forced regeneration will take place, significantly reducing engine performance. Once the levels reach 85 percent, it’s too late. The entire DPF system would have to be cleaned or replaced at considerable cost.

It’s becoming clear that due to the dramatic drop in permitted PM emissions, a traditional DPF system alone is simply no longer enough. This is on top of the fact that many DPF systems fail due to unsuitable conditions and a lower temperature is needed to maintain adequate levels of PM. This is where additives can help.

Fuel additives can reduce the temperature at which soot burns off in DPF systems from around 550 to 400 degrees Celsius. This means that the PM can be burnt off even when in slow traffic, meeting regulations and reducing the risk of failure of the DPF system.

Fuel additives that reduce active regeneration also have a beneficial impact on engine performance as dirt takes longer to build up. Drivers and fleet managers will typically experience increased service life, lower fuel consumption, improvements to vehicle torque and power delivery, lower risks of fuel blow-by and reduced overall system pressure.

Although the strict regulations of Euro 6 may seem to be a nightmare for the automotive industry, research and development are the way round it. NCH’s DPF protect solution is an example of this. The product works to lower the temperature needed for regeneration, meaning that vehicles can comply with the regulations but it also reduces the rate of DPF system failure, especially when vehicles are driven around urban areas.

There is no doubt that the regulations are necessary and here to stay. Rather than resting on our laurels, the industry should respond by innovating and developing new technologies in order to meet the new requirements and look forward to future progress.