Clean Comeback
In the U.S., the diesel passenger car was known for its flaws. But diesel’s fuel-efficiency,performance, and improved exhaust treatment are raising demand
39°N/77°W There have been many Mercedes sedans in the life of Donna Kerr. The Realtor from Silver Spring, Maryland, currently owns two of the cars with stars. One is a 1970 Grand 600. The stretch limousine is slated to play a role in Kerr’s plans for an upscale restaurant, and is currently being restored for a price that would easily buy three Mercedes-Benz C-Class vehicles. Her “other” car is a Mercedes-Benz E 320 BLUETEC: the cleanest diesel vehicle on earth, and one that seldom needs a fill-up. For Kerr, the latter feature was decisive: “I hate stopping to pump gas.”
A new attitude
There was a time when the U.S., a nation of drivers, was awash in diesel. That was in the years immediately after the 1973 energy crisis. Along with the price of gasoline, diesel’s popularity soared. Nearly 90 percent of Mercedes-Benz models sold in the U.S. had compression-ignition engines. But with low sulfur fuel unavailable, diesels soon nearly vanished from the streets. What remained was an image that proved hard to shake: Diesel saves money by belching clouds of black exhaust from a vehicle that is both underpowered and noisy. But drivers familiar only with the diesels of 1973 have missed some major technological developments. Common-rail direct injection (CDI) allows diesel engines to achieve torque surpassing that of most gasoline engines. Maintenance-free particulate filters solve the soot problem. Meanwhile, over the last 15 years, Mercedes-Benz has reduced emissions of oxides of nitrogen by 75 percent.
On a par with gasoline engines
The latest technological paradigm shift won’t be so easy to ignore: BLUETEC reduces nitrogen oxides right down to the levels achieved by spark-ignition engines – while consuming 35 percent less fuel. Slowly but surely, the image transformation is gaining ground: Scientific American called BLUETEC one of the major scientific and technological innovations of 2006. Popular Science included it on the annual “Best of What’s New” list. And at the International Auto Show in New York in April, 2007, automotive journalists from around the world voted the Mercedes-Benz E 320 BLUETEC the “2007 World Green Car.” With emissions limits continuing to fall and oil prices climbing, diesel is poised for an American comeback: Market researchers expect diesel market share to climb from 3.4 percent to 15 percent by 2015. DaimlerChrysler, with its key role in creating and promoting the technology, stands to gain substantially as the palette of classic diesel models and BLUETEC versions is expanded to meet demand.
Innovation through exhaust treatment
Environmentally friendly emissions levels are achieved with a modular exhaust-scrubbing system. Two building blocks are an oxidation catalytic converter that serves to trap carbon monoxide, and a particulate filter that reduces soot particles by up to 98 percent, to barely detectable levels. A third element is the combination of a DeNOx storage catalytic converter and selective catalytic reduction. Nitrogen oxides accumulate in the DeNOx unit, but running the engine for a few seconds on an enriched ratio of fuel to air liberates the NOx as harmless nitrogen. Selective catalytic reduction (SCR) removes further NOx from the exhaust stream. “The real innovation of BLUETEC was combining several catalytic converters into a system that reduces all relevant pollutants,” Bernd Krutzsch says. The chemist heads up the Exhaust Gas Treatment department. His contributions to the development of BLUETEC won him the 2005 DaimlerChrysler Research Award. “Getting the rich-operation phase to work right was a challenge. A vehicle’s first reaction is to shake like a leaf and put out clouds of soot,” Bernd Lindemann remembers. The BLUETEC developer won a Research Award himself. “The first time we enriched the fuel-air mixture, it sounded like the pistons were going to take leave of the engine.” Many trials later, the transition had become so imperceptible that engineers were forced to install an acoustic signal for demonstration purposes. In other words: The driver is blissfully unaware of the engine’s operational strategies, and that’s the way it should be. | ||||||||||
Lowering sulfur levels in fuel
An even more effective way to put the kibosh on nitrogen oxides is BLUETEC with AdBlue. The technology has proven itself for two years in approximately 60,000 DaimlerChrysler trucks and buses. The principle: An aqueous solution of urea, AdBlue, is injected into the purified exhaust stream. In the SCR catalytic converter, the resulting ammonia helps convert up to 80 percent of the remaining NOx into nitrogen and water vapor. The technology will be available in passenger vehicles starting in 2008. That’s just what Margo Oge wants. The Director of the Office of Transportation and Air Quality at the U.S. Environmental Protection Agency (EPA) once remarked that the U.S. could save 1.4 million barrels of crude oil per day – as much as it imports from Saudi Arabia – by switching just one-third of its vans, pickups, and SUVs to diesel power. In line with that policy, she has lobbied for lower sulfur limits for diesel fuel – a deciding factor for the operation of modern, fuel-efficient vehicles. She got her way: Starting in October, 2006, ultra low sulfur diesel has been available at nearly every filling station offering diesel. “With ultra-low sulfur diesel fuels now a reality, the stage is set for light-duty diesels to make a major contribution toward lower oil use and lower carbon emissions,” Oge says. “Unfortunately,” she adds, “some Americans still have a negative image of diesel. It is important to educate our consumers that today’s clean diesel technologies have overcome these issues, and that the vehicles deserve recognition as a clean technology.”
Maryland to Maine
In Donna Kerr’s case, of course, no further education is necessary. Her Mercedes-Benz E 320 BLUETEC is so new that she hasn’t had time to estimate her own fuel consumption. But she volunteers the EPA figures: They tell her to expect 26 miles per gallon (9 liters per 100 kilometers) in city driving and 37 mpg (6.4 liters) on the highway. “We have a cottage in Maine,” she declares. The distance from her home in Maryland is 800 miles (nearly 1,300 kilometers). “And with a little luck, we get there on one tank.”
“Diesel passenger cars make an important contribution to reducing fuel consumption and CO2 emissions.” Margo Oge, Director, Office of Transportation and Air Quality U.S. Environmental Protection Agency
|
BLUETEC The facts on the new diesel exhaust treatment system USA “Eco-Alliance” is what the press called the cooperation between Mercedes-Benz, Jeep®, Audi, and Volkswagen to launch the environmentally friendly diesel technology BLUETEC in the U.S. market. DaimlerChrysler has already introduced the Mercedes-Benz E 320 BLUETEC. The shared branding benefits all participating companies by boosting recognition of diesel’s advantages in the hesitant U.S. market. Fuel Efficiency With a 224 horsepower V6 engine, the Mercedes-Benz E 320 BLUETEC gets 35 miles per gallon (6.7 liters/100 km), with a range of 800 miles (1200 kilometers). A Cleanest Car Automotive journalists from 22 countries voted the Mercedes-Benz E 320 BLUETEC 2007 the “World Green Car of the Year” for its low emissions. It is the only passenger car to meet strict U.S. BIN 8 emissions standards. Europe In Germany, Mercedes-Benz BLUETEC models could already be on the road: Ultra-low sulfur diesel is standard there. But the fuel is still not available throughout Europe. Availability in 15 European nations will be assured starting in 2008. Sulfur in fuel can damage the DeNOx storage catalytic converter. The launch of BLUETEC in Europe will begin in 2008 with the Mercedes-Benz E-Class. BLUETEC for Trucks In Europe, 60,000 trucks and buses are equipped with an additional BLUETEC component – the urea solution AdBlue. Its principle: Ammonia released in the SCR catalytic converter converts up to 80 percent of oxides of nitrogen into harmless nitrogen and water. The AdBlue dispenser at fueling stations resembles a fuel pump. BLUETEC with AdBlue will be available for passenger car models starting in 2008. BLUETEC Components of the E 320 cdi Oxidation catalytic converter, DeNOx storage catalytic converter, particulate filter, SCR catalytic converter – BLUETEC consists of several components in various combinations: The oxidation catalytic converter (1) and particulate filter (2) reduce emissions of carbon monoxide and soot. The newly developed DeNOx catalytic converter (3) collects nitrogen oxides, converting them into harmless nitrogen. The SCR (4) (selective catalytic reduction) catalytic converter reduces oxides of nitrogen still further. |
