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The Greening of Diesel - Page 2

Phillip Lundberg, a graduate student from Kokomo, Ind., demonstrates where urea would be introduced into the exhaust system of a diesel vehicle with a catalytic converter.

The other project overseen by Ramadan involves looking at how exhaust gases flow through a catalytic converter to better understand their flow characteristics and pressure drop. "When using a diesel system there is more concern about nitrogen oxides," said Ramadan. Exploring one way to reduce nitrogen oxides, or NOx, Phillip Lundberg a graduate student from Kokomo, Ind., will use a Computational Fluid Dynamics (CFD) model to determine the flow characteristics in exhaust systems and catalytic converters to eventually understand how to introduce urea into the exhaust system of a diesel vehicle with a catalytic converter.

"Diesel particulate filters (DPF) collect particles that create black smoke associated with diesel exhaust," Ramadan said, "NOX can be controlled by controlling temperature and by using a catalytic converter. However, catalytic converters don't work as well with diesel engines as with gasoline engines for reducing NOx.

"One reason is that diesel exhaust has a lower temperature and is usually the result of lean combustion. Catalytic converters work better at higher temperatures and with stoichiometric combustion. Moreover, diesel fuel contains sulfur that can poison the catalytic converter," he said. "The idea behind this project is to have a urea tank from which urea is injected as a liquid into the exhaust pipe ahead of the catalytic converter so it can evaporate and mix with the exhaust to create a chemical reaction that will reduce NOx," he added.

Urea is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula (NH2)2CO. It is also known as carbamide, especially in Europe. It was the first organic compound to be artificially synthesized from inorganic starting materials. It is found in mammalian and amphibian urine as well as in some fish.

Urea produces ammonia, which reacts with NOx to produce nitrogen and water. "We are looking at such issues as where to inject the urea into the exhaust system and what conditions are needed to perfect the process. Typical studies look at how to spray it, the spray pattern, droplet size, different locations in the exhaust for injection and how it all affects its distribution," he added.

Lundberg will perform mathematical simulations to simulate the physics of fluid flow and the chemical reactions that may occur upon the introduction of urea into the exhaust system. "If we can achieve the correct balance, we should only see nitrogen and water in the exhaust," said Ramadan.

To learn more about this project, contact Dr. Bassem Ramadan, professor of Mechanical Engineering, via email at bramadan@kettering.edu.

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