Diesel engines are powerful and generally significantly more efficient than gasoline engines, but they have their challenges like soot and nitrogen oxide emissions. Automakers have gone to great lengths to optimize diesel engines while mitigating those emissions in meaningful and cost-effective ways. It’s not an easy challenge.
“We can generally clean up emissions for a gasoline engine with a three-way catalyst,” says Ronald Grover, staff researcher at General Motors Research and Development. “The problem with diesel is that when you operate lean, you can’t use the conventional three-way catalysts to clean up all the emissions suitably, so you have to add a lot of complexity to the after-treatment system.”
That has prompted a research program to improve combustion models for diesel passenger car engines using the Titan supercomputer at the U.S. Department of Energy’s Oak Ridge National Laboratory. A 27-petaflop Cray XK7 supercomputer with a hybrid CPU–GPU architecture, Titan is the nation’s most powerful computer for open scientific research. The ultimate goal is to accelerate innovative engine designs capable of meeting ever-stricter emissions standards.
The GM team’s goal is to better simulate what happens in the engine, making use of the Titan to increase the complexity of the chemistry in their combustion models, compare the results of Titan simulations with GM experimental data to measure accuracy, and identify other areas for improvement in the combustion model. ORNL’s goal is to help the GM team improve the accuracy of the combustion model, an exercise that could benefit other combustion research down the road.
“Usually a company will go through a vehicle development process from end-to-end that could take 4 or 5 years,” says Grover. “If you could develop the powertrain faster, then you could get cars to market faster and more reliably.”