A roar fills the small room in MIT’s Building 31 as a car engine, minus the car, revs loudly. Outside the room-one of 12 test cells in the Sloan Automotive Laboratory-a student watches as a computer collects data on the engine, whose spark-plug-free design might one day earn it some room under the hood.
The engine employs a technique called homogeneous charge compress ignition, which gives it a less complicated design than a gasoline engine but the efficiency of a diesel engine. The engine maintains a much higher ratio of air to fuel than an ordinary car’s, heats the mixture through compression, and causes the fuel to ignite spontaneously, without a spark. The result is faster and more efficient combustion and a 10-fold reduction in the amount of pollution the engine emits.“Here’s a major new idea that has the possibility of having an enormous impact on the industry,” says Professor John Heywood, director of the laboratory. “I’m not going to guarantee it goes into production five or 10 years from now, but it’s on a path to doing that.”
Another novel idea for a more efficient engine uses a device called a plasmatron, invented at the MIT Plasma Science and Fusion Center. The device shoots an arc of electricity through a mixture of air and hydrocarbon fuel, converting it to hydrogen and carbon monoxide. Hydrogen burns much faster than gasoline, and again brings the engine’s efficiency close to that of a diesel engine without running as roughly as diesels do under some conditions.
But while the Sloan Lab looks at these experimental variations on the old internal-combustion engine, its main thrust is to develop a theoretical understanding of how engines work, and then use that understanding to build computer models that designers can turn into better commercial engines.
“People sort of feel that once a technology is developed, it’s developed. But it’s not developed fully,” Heywood says. Engineers can build a working engine without a theoretical understanding of everything that’s happening inside it. But lacking that understanding, they may not come up with the very best engine, he says.