Uncertainties in Shock-Tube and Flame Speed Measurements at Extreme Conditions
Thursday, March 22, 11AM – 12PM
Eric L. Petersen
Discrepancies between shock-tube data and model/RCM results have been observed for methane, propane, and fuel blends with up to C4 alkanes at temperatures below 1100 K. This discrepancy can in part be attributed to a significant rise in pressure (and correspondingly temperature) before main ignition behind the reflected shock wave. This early, significant increase in pressure is not predicted by the chemical kinetics and is suspected to be due to early reactions in this facility and others alike, as evidenced by the accompanying appearance of excited intermediates such as OH and CH. While the origin of this early reaction and subsequent pressure rise is not known at this time, it appears for the cases presented herein that it is not the result of a facility-induced pressure rise due to boundary layer interactions. Nonetheless, when the measured pressure rise is taken into account, the discrepancies between the shock-tube data and the model results are rectified. The pre-ignition pressure (and thus temperature) increase greatly accelerates the chemical kinetics in the gas mixture behind the reflected shock wave in a shock tube, leading to the earlier-than-expected strong ignition. At elevated pressures and for very fast flame speeds such as in hydrogen-based mixtures, uncertainties in flame speed measurements can come from several sources, including thermo-diffusive instabilities, stretch effects, and precision in the actual measurement. Some recent flame speed measurements in methane- and hydrogen-based fuel blends are presented, with emphasis on the accuracy of the experimental technique. An overview of the overall research activities in the speaker’s laboratory will also be given.
Eric Petersen Bio Dr. Petersen is presently an Associate Professor and Holder of the Leland T. Jordan Career Development Professorship in the Department of Mechanical Engineering at Texas A&M University. He received his Ph.D. in Mechanical Engineering from Stanford University (1998), his M.S. in Mechanical Engineering from the University of Florida (1990), and his B.S. in Mechanical Engineering from the University of Central Florida (1988). After receiving his M.S. degree, he worked for three years as an Analytical Engineer in the combustion group at Pratt & Whitney, Government Engines & Space Propulsion in West Palm Beach, Florida (1990-’93), where he performed fluid and thermal analyses and experiments in support of advanced gas turbine and rocket combustor technologies. Dr. Petersen was a staff scientist at The Aerospace Corporation in the Propulsion Science Department from 1997 to 2001. During his period at Aerospace, Dr. Petersen was also an instructor in the Mechanical and Aerospace Engineering department at the University of California, Irvine. Dr. Petersen has been at Texas A&M since January 2008. Prior to his current position at TAMU, Dr. Petersen was an Assistant and then Associate Professor in the Mechanical, Materials and Aerospace Engineering department at the University of Central Florida (2001-07). His research has been in the fields of gas dynamics, propulsion, combustion, shock wave physics and chemistry, chemical kinetics, optical diagnostics and spectroscopy, combustion instability, fluid mechanics, aerosol science, materials synthesis, and rocket combustion. He has authored over 200 papers and reports in these areas.
Hosted by Noel Clemens, Bob Moser