Researchers seek clean fuel injection car engine

Robert W. Pitz, professor and chair of mechanical engineering, is using laser diagnostics to study the combustion characteristics in direct injection petrol-fuelled engines.

“Five or 10 years from now, the predominant engine that automobile consumers buy may well have direct injection,” Pitz said. Toyota, Mitsubishi and Nissan already make cars with direct injection engines that are being used in Japan and Europe. “These engines give much better fuel economy in stop-start commuter driving, but they don’t meet US emission standards,” 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 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 US emission standards.

Pitz says that there are two ways to reduce automobile pollution: Produce such a complete and thorough burning of the fuel in the cylinder that virtually no pollutants are formed or use 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 research associate professor Joseph A. Wehrmeyer 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 analyse 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 optimise the design of the cylinders for the best clean-burning conditions,” Pitz said.

US carmakers like Ford, General Motors and Daimler-Chrysler are anxious 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 US Department of Energy is interested in the energy conservation that could be realised with direct injection engines. The DOE is funding Pitz’s research with a three-year grant.