by Lew Harris By producing such a complete and thorough burning of the fuel in the cylinder that virtually no pollutants are formed, or
An automobile engine with 30 percent greater fuel efficiency than current models — but that also meets U.S. emission standards — is the goal of an engineering professor.
Robert W. Pitz, professor and chair of mechanical engineering, is attempting to develop the next generation of automobile engines by using advanced laser diagnostics to study the gasoline-combustion characteristics of direct injection gasoline engines.
“Five or 10 years from now, the predominant engine that automobile consumers buy may well have direct injection,” said Pitz, whose work is being supported by a federal Department of Energy grant. “Toyota, Mitsubishi and Nissan already make cars with direct injection engines that are being used in Japan, and Mitsubishi is marketing these cars in Europe.
“Gasoline is expensive there and the emissions standards aren’t as strict as ours. These engines give much better fuel economy in stop-and-start commuter driving, but they don’t meet U.S. emission standards.”
Conventional spark ignition motors deliver a pre-mix of fuel and air to be burned in the cylinder, Pitz said. In
direct injection engines, air comes in through intake valves and fuel is sprayed into the cylinder late in the compression stroke to greatly improve engine efficiency at both idle and urban driving conditions.
Pitz’s research will focus on ways to reduce or eliminate the pollutants produced by direct injection engines so that they will meet U.S. emission standards. He says that there are two ways to reduce automobile pollution:
By using a catalytic converter to remove pollutants before the emission exits the exhaust pipe.
Pitz will attempt to reduce pollution by superior burning in the cylinder.
With the help of Joseph A. Wehrmeyer, research associate professor, and graduate student Robin Osborne, a burner is being constructed at Vanderbilt that will simulate the kind of fuel-air stratification that is produced in a direct injection engine. The burner will have quartz windows so that Pitz can use his lasers to analyze flames and determine the chemical composition of pollutants.
“The analysis of stratified flames using lasers should lead to improved computer models of direct injection engines. The computer models could then be used by engine designers to optimize the design of the cylinders for the best clean-burning conditions,” Pitz said.
Understandably, U.S. auto makers like Ford, General Motors and Daimler-Chrysler are eager to develop direct injection engines that meet current emission standards. All of them are testing prototype direct injection engines. Pitz estimates that such engines, which require an expensive high-pressure fuel injector, will cost about $1,000 more than conventional motors.
The Department of Energy is interested in the energy conservation that could be realized with direct injection engines. The DOE is funding Pitz’s research with a three-year grant. He has sub-contracted a portion of the research to the University of Michigan and is collaborating with General Motors Research and Development Center.
Pitz received the National Science Foundation Presidential Young Investigator Award in 1987 in recognition of his achievements in combustion and laser diagnostics. He recently received a patent for a new method for unseeded velocity measurement for jet engines called ozone flow tagging. He has published more than 90 papers and received the AIAA award for the best paper in propellants and combustion in 1996.