TransForum Vol. 9, No. 2

TTRDC Now Equipped with “X-ray Vision”

Mechanical engineer Alan Kastengren examines a diesel injection nozzle used in Argonne’s X-ray fuel spray research.

Engineers at Argonne’s Transportation Technology Research and Development Center (TTRDC) now have another invaluable research tool at their disposal—regular access to the brightest X-ray beams in the Western Hemisphere.

In March 2009, TTRDC researchers began conducting research at their new permanent beamline at Argonne’s Advanced Photon Source (APS), a national synchrotron X-ray research facility funded by the U.S. Department of Energy (DOE). The TTRDC was able to secure this research space with funding from the DOE’s Office of Vehicle Technologies and Office of Basic Energy Sciences.

The powerful X-ray beams created by the APS can penetrate materials to reveal details that cannot otherwise be seen. Currently, Argonne transportation researchers are using this tool to peer inside liquid sprays from fuel injectors for diesel engines.

"The physics of sprays are still not very well understood,” said Christopher Powell, an engine research scientist at Argonne. "With the X-ray beam, you can measure exactly how much fuel is in the spray at any given time.” With a greater understanding of fuel spray composition, researchers have the ability to manipulate sprays to improve fuel efficiency and reduce harmful emissions.

"The way in which the fuel is distributed has the biggest impact on fuel efficiency. It’s one of the few variables you have to play with in a diesel engine,” Powell said.

TTRDC researchers have been using the APS to study fuel injectors and sprays for the past decade. However, their research time was limited to about six weeks per year. Now they can perform X-ray studies year-round.

“The biggest advantage of having a permanent space here is that it gives us easy access to this unique tool and allows us to expand our collaborations with industrial partners,” Powell said.

Industry Excitement

Over the last 10 years, Robert Bosch GmbH, the world’s leading producer of fuel injection equipment, has collaborated with Argonne on a wide variety of injection research projects. Bosch researcher Philippe Leick believes that Argonne’s spray research can help improve engine development by providing a more detailed understanding of the fuel injection system. This is a crucial component for diesel engines, as the atomization of the fuel jet and its subsequent propagation, evaporation and combustion are strongly affected by the nozzle and injector designs.

"Compared to other experimental techniques, which only scratch the surface of the diesel spray, X-ray radiography is unique because it shows us what is going on inside the spray,” Leick said.

"Argonne is in an exceptional position among research laboratories because it offers both the extremely bright synchrotron X-ray source needed for these experiments and has a team of highly qualified, experienced engineers and physicists dedicated to engine research,” he added.

David L. S. Hung, currently an associate professor of mechanical engineering at Michigan State University and previously a technical fellow at Visteon Corporation, has been collaborating with Argonne researchers at the APS since 2004 to investigate fuel injector spray characteristics. He said the facility has helped reveal critical fuel atomization phenomena such as the fuel breakup and evolution of emerging jets from high turbulence injection nozzles.

"The contributions of this collaborative effort have made a significant impact to the automotive fuel injector industry by allowing engineers and researchers to design cleaner and better fuel injectors and to meet the demands of more challenging fuels such as bioderived and alternative fuels,” Hung said.

First Research Project

Engine research engineer Christopher Powell fits a specially designed X-ray pressure window to a high-pressure chamber used in diesel spray research.

Powell said the objective of the work is to improve computational models of sprays and engines, and to help engine and injection manufacturers make more efficient automobiles.

Sandia researchers have already completed visible light imaging and combustion measurements on the same injector, so there is a wealth of data to work with. The University of Wisconsin will use the results to develop new and improved computational models.

Powell said these improved models could save automakers a lot of time and money by streamlining the engine design process, which currently relies heavily on trial and error.

The initial APS experiments are not complete yet, but Powell expects the collaborative project to be finished sometime later this year.

Looking Ahead

Other projects are already looming on the horizon for TTRDC’s new research space. Plans include using the X-rays to explore injectors that are used in Argonne’s continuing research into low-temperature combustion. This project will use injectors and operating conditions that match those being used in Argonne’s engine research lab, with the goal of linking the structure of sprays with engine performance and emissions.

Argonne will also team with Sandia as part of the Engine Combustion Network. Sandia is distributing 10 identical injectors to research organizations around the world to compile a broad data set on one injector. Upon completion the data will be made freely available on the Web.

October 2009