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Researchers at West Virginia University have long studied emissions from diesel vehicles to provide independent data about emissions performance both in the laboratory and on the road, as well as provide technology demonstration, other research and design support.
The most recent study from WVU’s Center for Alternative Fuels, Engines and Emissions measured oxides of nitrogen emissions, or NOx, from five Fiat Chrysler vehicles in real-world and laboratory tests.
“This type of testing – the combination of real-world and laboratory – allows us to learn more about the challenges that vehicle manufacturers face to produce cars with low emissions that also satisfy consumer expectations of performance,” said Dan Carder, director of the center. “These are opportunities to gather data and other information that can help both manufacturers and regulators find solutions, improve technology and provide better air quality.”
In 2016, Carder, Marc Besch, research assistant professor of mechanical and aerospace engineering in the Statler College of Engineering and Mineral Resources, Sri Hari Chalagalla, an engineer at CAFEE, and a team of engineers and technicians tested the vehicles – two Jeep Grand Cherokees and three Dodge Ram 1500 pickup trucks.
The team conducted on-road emissions testing, in which vehicles were equipped with a scaled-down version of traditional laboratory equipment called a portable emissions measurement system, or PEMS. The equipment is the size of a mini refrigerator and is powered by a generator.
This “mobile lab” fits in the back of the vehicle and samples and analyzes its exhaust while it is being driven on the road, allowing researchers to study the performance of the vehicle’s cleaning technologies in real-world driving conditions.
CAFEE’s testing covered a variety of road and ambient conditions, traffic patterns and terrain over two routes – an urban and a highway route – in the Morgantown, West Virginia, area.
“Testing vehicles on the road allows you to collect data from diverse driving conditions,” Besch said. “You can see how the vehicle technologies perform with different loads, vehicle speeds, ambient temperatures, etc.”
Additionally, CAFEE engineers tested the vehicles in their lab. There, a vehicle is placed on a light-duty chassis dynamometer, which functions as a large treadmill.
The instrument allows the vehicle to be driven through a test that closely simulates the route that was driven on the road. The study used the same mobile lab equipment used on the road to analyze the vehicles’ exhaust in the laboratory.
The testing showed that compared to in-laboratory tests, route averages of NOx emissions exceeded government standards by a factor of 3 to 20 during on-road driving.
“There are currently no U.S. standards for in-use emissions testing of light-duty vehicles, so an absolute comparison between real-world and laboratory isn’t possible,” Carder said. “But we would not expect laboratory performance under all real-world conditions.”
“When looking at results averaged over a trip, we would not be surprised to find deviations of 3 to 4 times between on-road and lab conditions. Results that show an increase by a factor of 20 indicate different emissions control strategies, but the scope of our research doesn’t include whether those strategies have previously been negotiated between automakers and regulators or not.”
Carder goes on to say that data from CAFEE research will be used by the center to help refine existing vehicle technologies and define technology advancements for the future. Additionally, CAFEE uses data from its research and other independent research organizations, to identify possible gaps between regulatory certification and compliance standards and real-world performance.
“Clean diesel is not a myth,” Carder said. “When I started in this field more than 25 years ago, the heavy-duty standard for NOx was 6.0 g/bhp-hr, and we are now working on 0.02 g/bh-hr. As an industry, we have made a difference, and we will continue to do so.”
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