02/15/2002
Structural Biology Research Advances Combustion Science
The Science
Synchrotron x-radiography and a fast x-ray detector were used to record the time evolution of the transient fuel sprays from a high-pressure injector. A succession of 5.1-microsecond radiographs captured the propagation of the spray-induced shock waves in a gaseous medium and revealed the complex nature of the spray hydrodynamics. The monochromatic x-radiographs also allow quantitative analysis of the shock waves that has been difficult if not impossible with optical imaging. Under injection conditions similar to those found in operating engines, the fuel jets can exceed supersonic speeds and result in gaseous shock waves.
Summary
A new detector developed in the BER Structural Biology Instrumentation Research program is leading to understanding of the dynamics of fuel sprays in diesel and gasoline engines. The new device, known as a Pixel Array Detector (PAD), is being developed at Cornell University in order to increase the speed of obtaining data sets in protein crystallography experiments at synchrotron light sources. The goal is to obtain complete images in microseconds instead of in a second as the current detectors require. This would allow completion of experiments with fragile protein crystals before they break down in the intense x-ray beam. A PAD module has now been used to image the change over microsecond time periods of the fuel spray from a diesel engine fuel injector. Studies were carried out at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL) and at the Cornell High Energy Synchrotron Source (CHESS) at Cornell University. The images obtained with the PAD show development of a supersonic shock wave as the leading edge of the spray reaches speeds well above the speed of sound in the medium very soon after injection. The results are reported in the February 15, 2002, issue of Science. The online version of the article includes an animated sequence of x-radiographic images of the shock wave.
BER Program Manager
Amy Swain
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]
Funding
The Cornell group is directed by Physics Professor Sol Gruner, who is also Director of CHESS, and is funded by the Office of Biological & Environmental Research. The ANL group is lead by Jin Wang at the APS and receives funding from the Office of Basic Energy Sciences and DOE’s FreedomCAR Program.
References
MacPhee, A. G., M. W. Tate, C. F. Powell, Y. Yue, M. J. Renzi, A. Ercan, S. Narayanan, E. Fontes, J. Walther, J. Schaller, S. M. Gruner, and J. Wang. 2002. “X-Ray Imaging of Shock Waves Generated by High-Pressure Fuel Sprays,” Science 295. DOI:10.1126/science.1068149.