ARGONNE, Ill. - Researchers at Argonne National Laboratory have captured a view of the tiny plumes of fuel that spray from injector nozzles in car and truck engines.
It is not a pretty sight.
Injectors don't disperse fuel the way their designers thought they would, researchers say. The result is fuel combustion that is less complete, and, therefore, less efficient and more polluting.
Despite the findings, the Argonne researchers are overjoyed. They call their fuel spray images a breakthrough that will change models of what happens inside engines.
And, although they aren't able to say how much their findings might improve engine performance, they are convinced better injectors will be designed.
`It's like spit'
For diesel engines and direct-injection gasoline-powered engines, fuel injector performance is critical. But fuel spray has not been well understood because 'it's like spit,' said Roy Cuenca. He is an engineer with the Center for Transportation Research in Argonne's Energy Systems Division and a leader in spray research.
The method Argonne used to get a better look at spray dispersion sounds like the scientific equivalent of using a sledgehammer to kill a flea, but it worked.
Argonne has a particle accelerator - a racetrack-sized machine that scientists use to study the nature of matter - to find out what makes up atoms and molecules, for example.
But the pragmatic Argonne researchers found another use for the ultra high-energy X-rays the accelerator creates when it bends speeding electrons. They captured images, unprecedented in detail, of the fuel droplets in the millisecond after they are sprayed from an injector.
'This is the first time we've shown this to the world,' said Johnson after a presentation to Automotive News.
Automotive companies are interested in the research, they are just reluctant to say current injectors aren't doing the job.
'Everybody wants to make their injectors even better,' Johnson said.
No sale, so far
Robert Bosch GmbH and Delphi Automotive Systems Corp. have offered to buy rights to the information, but the lab has declined to sell its findings. The lab wants to complete the research, and then determine if it should be made available to all auto companies.
Bosch did contribute equipment and has collaborated on the research, lab officials said.
Jin Wang, the Argonne physicist who led the X-ray effort, said spray research has gone on for decades, and many methods have been developed to study spray, but Argonne's experiments show previous methods are inadequate.
The most common was optical imaging. It produced a kind of external photograph of the spray. X-rays penetrate throughout the spray mass, Wang said.
'The experiment is really easy. It's not too much different from your dental X-ray or your chest X-ray,' he said. But in this case 'you need to take a picture of everything in a millisecond.'
With the optical method, a plume of fuel may appear to be well formed and evenly diffused, but with the more detailed and multidimensional view provided by X-rays, the same plume can be seen to be a hollow cone, Wang said.
Cuenca said of the findings, 'We think it's a home run.'