TY - CONF
T1 - Ignition and flame propagation enhancement by dual-pulsed laser-induced breakdown
AU - Wermer, Lydia
AU - Lefkowitz, Joseph K.
AU - Ombrello, Timothy
AU - Im, Seongkyun
N1 - Funding Information:
This work was supported by the AFRL Summer Faculty Fellowship Program. Lydia Wermer was supported by U.S. National Science Foundation Graduate Research Fellowship Program (Grant No. DGE-1106756).
Funding Information:
Figure 5: (a) Schlieren images and (b) flame area of single LIB with 25 mJ energy and DPLIB with an energy combination of 10/15 mJ for an equivalence ratio of 0.55. 4. Conclusion The ignition probability and flame growth rate were enhanced by DPLIB depending on the equivalence ratio and time interval between pulses. Below the lean flammability limit, dt < 100 ns caused enhancement because of the enlarged breakdown surface area. Above the lean flammability limit, DPLIB with time intervals close to the ignition delay has enhanced flame growth rate from the interaction between pulses along with other mechanisms from the second LIB. 5. Acknowledgements This work was supported by the AFRL Summer Faculty Fellowship Program. Lydia Wermer was supported by U.S. National Science Foundation Graduate Research Fellowship Program (Grant No. DGE-1106756). 6. References
Publisher Copyright:
© 2017 Eastern States Section of the Combustion Institute. All rights reserved.
PY - 2017
Y1 - 2017
N2 - Ignition probability and flame growth rates of single and dual-pulse laser-induced breakdown were experimentally investigated in a turbulent premixed methane-air flow to examine enhancement by dual-pulse at fuel-lean conditions. The ignition and flame propagation was visualized with high-speed schlieren imaging. Successful ignition was confirmed by CO2 filtered infrared imaging. Experiments were performed in a 3.8 cm by 3.8 cm square cross-section wind tunnel with a bulk velocity 10 m/s, equivalence ratios of 0.45 to 0.6 and total laser energy of 25 mJ per pulse. Ignition probability enhancement by dual-pulsed laser-induced breakdown with time intervals in the tens of nanosecond ranges occurred in premixed flows with equivalence ratios of 0.45 to 0.5 where pulse-to-pulse energy coupling enlarged the spark area and increased the available ignition energy. Dual-pulsed laser-induced breakdown with time intervals between pulses of hundreds of microseconds had increased flame growth rates in premixed flows with equivalence ratios 0.5 to 0.6 where conditions were sufficient for the first breakdown to ignite the mixture before arrival of the second breakdown. The hot plume induced by the second breakdown interacted with the ignition kernel induced by the first breakdown increasing the flame surface area and the flame growth rate.
AB - Ignition probability and flame growth rates of single and dual-pulse laser-induced breakdown were experimentally investigated in a turbulent premixed methane-air flow to examine enhancement by dual-pulse at fuel-lean conditions. The ignition and flame propagation was visualized with high-speed schlieren imaging. Successful ignition was confirmed by CO2 filtered infrared imaging. Experiments were performed in a 3.8 cm by 3.8 cm square cross-section wind tunnel with a bulk velocity 10 m/s, equivalence ratios of 0.45 to 0.6 and total laser energy of 25 mJ per pulse. Ignition probability enhancement by dual-pulsed laser-induced breakdown with time intervals in the tens of nanosecond ranges occurred in premixed flows with equivalence ratios of 0.45 to 0.5 where pulse-to-pulse energy coupling enlarged the spark area and increased the available ignition energy. Dual-pulsed laser-induced breakdown with time intervals between pulses of hundreds of microseconds had increased flame growth rates in premixed flows with equivalence ratios 0.5 to 0.6 where conditions were sufficient for the first breakdown to ignite the mixture before arrival of the second breakdown. The hot plume induced by the second breakdown interacted with the ignition kernel induced by the first breakdown increasing the flame surface area and the flame growth rate.
KW - Ignition
KW - Laser-induced breakdown
KW - Lean mixture
KW - Schlieren imaging
UR - http://www.scopus.com/inward/record.url?scp=85048993241&partnerID=8YFLogxK
M3 - Paper
AN - SCOPUS:85048993241
T2 - 10th U.S. National Combustion Meeting
Y2 - 23 April 2017 through 26 April 2017
ER -