Worried about the adverse health effects of diesel exhaust in general, and diesel soot in particular, the European Commission’s new Stage V regulations will further reduce allowable limits on criteria emissions and place limit values on particulate number, often referred to as PN. For engines between 19 and 560 kW (25 to 750 hp), PN cannot exceed 1x10¹² per kW·h.
“Stage V also extends the range of machines required to comply,” said Fabricio Cardoso of Integer Research. Both smaller engines below 56 kW (75 hp) and larger engines above 560 kW would be regulated. “It also extends to new sets of railroad, agricultural, mining, and construction equipment as well as snowmobiles, ATVs, and mobile power generators that were not addressed in Stage IV,” he said.
Integer Research tracks, among other commodities, the worldwide sales of the chemical compound urea used in selective catalytic reduction (SCR) devices. This fluid is sometimes known as AdBlue as well as diesel exhaust fluid, or DEF.
“The big change with Stage V is the particulate number limits. It is really trying to encourage the use of DPFs [diesel particulate filters],” said Mike Kenhard, Chief Engineer for AVL Powertrain Engineering. “DPFs are the message behind the legislation.”
The good news for many engine providers, according to Kenhard, is that they already have those DPF solutions available. “For most people, implementing it means applying the technology and learning from other existing products or they already have it implemented,” he said.
The real challenges for engine makers in meeting a future Stage V is in the smaller engine categories, according to Kenhard. He noted that these typically do not command the price to justify additional aftertreatment equipment in the same way as larger horsepower engines. “56-kW engines and below is where it becomes very challenging,” he said.
Added to these challenges is the fact that OEMs today are interested in selling to multiple global markets. Increasingly fragmented emissions requirements are challenging them in offering a certified product for each market.
“When a country is considering introducing non-road engine emission standards, one of the simplest steps towards harmonization is for that country to adopt an existing globally recognized emission level,” explained Oliver Lythgoe, Perkins Product Marketing Manager. For example, a country may adopt a Stage IIIA/Tier 3 equivalent, rather than inventing their own.
The key to adopting such a standard is matching it to the supporting infrastructure that the country can provide. “While many countries want to make emissions improvements, progress can only be achieved at the same pace as other factors in the market such as the availability of good quality ultra-low sulphur diesel. Same with diesel exhaust fluid,” explained Lythgoe. “However, as appropriate emissions-related infrastructure continues to develop around the world, we could see global emissions standards move toward convergence over the next 10 to 20 years.”
Even meeting Stage IV/Tier 4F today requires careful consideration, and no foreseeable way of controlling pollutants without aftertreatment in the larger engines. “Above 56 kW, some form of selective catalytic reduction is really the only practical means of achieving NOx targets. Alternatives have been explored, but the effects on machine performance would not be acceptable,” said Lythgoe. He advocates a systems approach.
“One thing that OEMs can do for engines in the 56 to 75 kW (75 to 100 hp) range is to work with Perkins on machine integration. In many cases it will be possible to reduce the engine power requirement to below 56 kW, thus reducing machine cost and installation complexity,” said Lythgoe.