2010: A Look Ahead
The engines of the future must meet increasingly stringent environmental standards
By Paul Abelson
The EPA 2007 engines are barely on the road, and attention is quickly turning to the next round of emissions regulations: 2010. Early 2007 test engines seemed to operate quite well. However, the extra heat rejected through the radiator and into the under-hood spaces was tough on accessories and components. Fleets involved in development reported at the Fall Technology and Maintenance Council (TMC) meeting that while the engines operated well, there were problems with other parts such as fan belts, belt tensioners, power steering and alternators. Also, the diesel particulate filters (DPFs) add a great deal of heat, especially when they regenerate (burn soot at temperatures between 1100 and 1200 degrees F). Cab temperatures have escalated.
While there will be several new engines introduced on or before 2010, many makers will use the same platforms that are in use today. Some will probably be introduced earlier than 2010. That will let the engine builders, truck manufacturers and truck operators gain experience before the tighter regulations come into effect. A new 12.9 liter engine is on the way from Paccar. International will soon begin production of their new MaxxForce engines, and Detroit Diesel recently unveiled their future platform, the DD15. Caterpillar, Cummins, Mack and Volvo will stay with the Class 8 engine platforms now in production. The Volvo family, Mack and Volvo, introduced new engines for 2007. They have a common platform, but differ in detail to meet each brand’s specific market needs.
Engineers have faced a dilemma since the first EPA-mandated emissions limits took effect. There are two major groupings of pollutants, particulate matter (PM) and oxides of nitrogen (NOx). PM includes all non-gaseous matter: soot and unburned hydrocarbon fuel (HC). NOx are created in the diesel combustion process. The strategy that gets rid of one increases the other. High heat completely burns fuel and minimizes soot formation. But that heat combined with pressure inside the cylinder causes oxygen and nitrogen to combine to form NOx, respiratory irritants and precursors to smog. Burn cooler to reduce NOx, and PM will increase.
Regulations alternated between which family of pollutants were to get the most attention. Measured in grams per horsepower-hour (g/hp-hr), NOx combined with non-methane hydrocarbons have to improve from 2.5 to 0.2 through 2009. In 2010, NOx must be reduced to 0.2 grams. PM, already at 0.01 grams, must stay at that “not to exceed” value.
PM is being managed with diesel particulate filters (DPFs), the large, expensive devices that trap solids in porous ceramic, then burn them to convert them to carbon dioxide. Every engine builder uses DPFs today and will continue to do so for 2010. By filtering solids out of the exhaust after combustion, engine makers could concentrate on reducing NOx formation during combustion.
The question has been how to control NOx. When allowable NOx was cut roughly in half for engines introduced in October 2002, most makers opted for cooled exhaust gas recirculation (EGR), a method of adding inert exhaust to lower the burn temperature inside the combustion chamber. Caterpillar did it with two-stage turbocharging, while the others used variable geometry turbochargers. All engine makers used higher fuel injection pressures and advanced electronics to control multi-stage pulsed injection.
For 2010 and beyond, some engine makers believe the best way to control NOx is through a chemical process called selective catalytic reduction (SCR). A liquid, urea, is carried on board. The urea is sprayed into the exhaust over a catalyst. It is converted to ammonia that reacts with the NOx, reducing it to elemental nitrogen and oxygen, the major components of air.
Other engine makers, notably Cummins and International, recently announced that they would meet the NOx standard without requiring SCR. Both companies believe the marketplace — you — will not want to have to deal with a second fluid to be added when refueling. Further, they believe the added weight and complexity of the SCR system will be negative factors when you select an engine supplier. SCR, they estimate, can add up to $10,000 to a truck.
SCR’s proponents, engine makers with European roots, believe the system offers advantages that outweigh its disadvantages. Daimler, Volvo and Paccar all have several years experience with SCR in Europe, so the systems are well developed and reliable. If SCR is not used, greater percentages of EGR must be used, adding more soot to the exhaust. That will necessitate more fuel-burning regeneration. Urea is less expensive than diesel fuel and extends fuel economy. SCR’s proponents claim better fuel economy using SCR, which can pay for any added purchase cost. In the United States, Detroit Diesel (Daimler), Mack and Volvo all announced they would use SCR. Caterpillar and Paccar have not committed to either strategy.
What will all this mean to you? It’s probably too soon to make predictions. The Cummins diesel used in Dodge pickups already meets 2010 standards, but the Indiana engine maker announced it will be using SCR in other light and medium duty engines.
When we get closer to 2010, we’ll be reporting on test engines that will soon be out for evaluation. Some early development models may be on the highways already. ‘Til then, sit tight and stay informed.