Structure and Extinction of Low Strain Rate Non-Premixed Flames by an Agent in Microgravity.
Structure and Extinction of Low Strain Rate Non-Premixed
Flames by an Agent in Microgravity.
(8058 K)
Hamins, A.; Bundy, M.; Oh, C. B.; Fuss, S. P.; Logue, J.
NISTIR 7445; 181 p. September 2007.
Keywords:
nonpremixed flames; microgravity; flame structure; flame
extinction; extinction; diffusion flames; fire
suppression; experiments; nitrogen; carbon dioxide;
propane; high temperature; FT-IR
Abstract:
This final report describes the study that has been
supported through the National Aeronautics and Space
Administration (NASA) microgravity grants program from
February 2004 through March 2007. This work was a
continuation of a NASA microgravity grant that was
active from February 1999 through September 2003. The
work has used computations and measurements to
investigate the structure and suppression of low strain
rate non-premixed flames. This final report, on the
latest grant, includes a summary of the work done on the
contract and a list of publications. The work during
this grant period focused on both measurements and
calculations and included the following: (*) Continued
development of the two-dimensional simulation with
finite rate chemistry. These publications are provided
in Appendices 1 and 2. These calculations considered
extinction of methane-air diffusion flames with N2 added
to the fuel stream. The work compares calculations with
our earlier measurements made in normal gravity and in
microgravity using the NASA 2.2 s drop tower, (*)
Two-dimensional calculations were completed .that
considered the extinction of methane-air diffusion
flames with CO2 added to the fuel stream in normal and
microgravity. This study is provided in Appendix 3. The
computations were compared to the N2 addition results,
(*) Flame extinction studies on the normal gravity
extinction of propane were conducted. The results of
this study are provided in Appendix 4, (*) Finally,
spectroscopic measurements were conducted on key flame
intermediates to support detailed modeling of radiative
exchange in near-extinction flames. Wakasuki et al.
developed a method to estimate the temperature
dependence of absorption coefficients through an
extrapolation algorithm. This publication is provided in
Appendix 5. Spectroscopic measurements are important to
understand the mechanisms of extinction associated with
flames being suppressed by agents. CF3Br (Halon 1301) is
one of the most important suppressants and has been used
on space platforms for many years. Suppression
studies often use CF3BR as a reference or baseline in
considering the effectiveness of alternative agents. As
part of this study, Fourier Transform Infrared
Spectroscopy (FTIR) measurements were made on CF3Br at
elevated temperatures. Those measurements are reported
in Appendix 6. Appendix 7 presents similar spectral
measurements and analysis for propane, heptane and
propylene. The seven manuscripts mentioned above are
included as appendices in this final report. The
remainder of the report presents an overview of the work
and the main findings of the project. Detailed
information on each of the topics can be found in the
appendices.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899