The fuel-efficient diesel engine may face a bleak future unless engineers can dramatically reduce its particulate emissions to meet likely future regulations. Low-cost solutions, however, may emerge if engineers can rethink engine and fuels technologies in tandem, tailoring the fuel properties to the engine design and vice versa.
To help them achieve that match, MIT Energy Laboratory researchers are formulating a simulation tool that will predict the effects of changes in both engine design and fuel composition on emissions and efficiency. The simulation generates equations that describe chemical reactions occurring throughout the combustion chamber and links them to reflect the interdependency of chemical composition, flows and temperatures in adjacent regions.
The researchers are led by Assistant Professor William H. Green and Associate Professor Paul I. Barton, both of the Department of Chemical Engineering.
Representing all the molecular species in a combustor would require thousands of chemical models, so the simulation instead deals with "functional groups" -- groups of atoms that always act as a unit and are building blocks for many types of molecules.
Most important, the simulation uses "adaptive chemistry," a novel concept that uses the simplest possible chemical model to analyze a given region. Based on numerical analysis, the simulation determines which species and reactions are important in a region and which ones it can leave out. For example, why examine reactions involving fuel molecules in areas where no fuel remains? This approach simplifies the computational task without sacrificing accuracy.
While much work remains, the new simulation may one day reveal ways to fine-tune a variety of combustion devices and their fuels for cleaner operation, perhaps without major financial investment.
This research is funded by ABB Alstom Power, the US Department of Energy, and the US Environmental Protection Agency.
A version of this article appeared in MIT Tech Talk on October 25, 2000.