NASA Scientific and Technical Aerospace Reports

We have recorded time-resolved LII signals from a laminar ethylene diffusion flame over a wide range of laser fluences
at 532 nm. We have performed these experiments using an injection-seeded NdYAG laser with a pulse duration of 7 ns. The
beam was spatially filtered and imaged into the flame to provide a homogeneous spatial profile. These data were used to aid
in the development of a model, which will be used to test the validity of the LII technique under varying environmental
conditions. The new model describes the heating of soot particles during the laser pulse and the subsequent cooling of the
particles by radiative emission, sublimation, and conduction. The model additionally includes particle heating by oxidation,
accounts for the likelihood of particle annealing, and incorporates a mechanism for nonthermal photodesorption, which is
required for good agreement with our experimental results. In order to investigate the fast photodesorption mechanism in more
detail, we have recorded LII temporal profiles using a regeneratively amplified Nd:YAG laser with a pulse duration of 70 ps
to heat the particles and a streak camera with a temporal resolution of -65 ps to collect the signal. Preliminary results confirm
earlier indications of a fast mechanism leading to signal decay rates of much less than a nanosecond. Parameters to which the
model is sensitive include the initial soot temperature, the temperature of the ambient gas, and the partial pressure of oxygen.
In order to narrow the model uncertainties, we have developed a source of soot that allows us to determine and control these
parameters. Soot produced by a burner is extracted, diluted, and cooled in a flow tube, which is equipped with a Scanning
Mobility Particle Sizer (SMPS) for characterization of the aggregates.
NTIS
Diesel Engines; Soot; Combustion Products
20040111175 Lawrence Livermore National Lab., Livermore, CA
Detailed Chemical Kinetic Reaction Mechanisms for Combustion of Isomers of Heptane
Westbrook, C. K.; Pitz, W. J.; Curran, H. C.; Boercker, J.; Kunrath, E.; Mar. 26, 2001; In English
Report No.(s): DE2003-15005667; UCRL-JC-143290; No Copyright; Avail: National Technical Information Service (NTIS)
Detailed chemical kinetic reaction mechanisms are developed for all nine chemical isomers of heptane (C(sub 7)H(sub
16)), following techniques and models developed previously for other smaller alkane hydrocarbon species. These reaction
mechanisms are tested at high temperatures by computing shock tube ignition delay times and at lower temperatures by
simulating ignition in a rapid compression machine. Although the corresponding experiments have not been reported in the
literature for most of these isomers of heptane, intercomparisons between the computed results for these isomers and
comparisons with available experimental results for other alkane fuels are used to validate the reaction mechanisms as much
as possible. Differences in the overall reaction rates of these fuels are discussed in terms of differences in their molecular
structure and the resulting variations in rates of important elementary reactions. Reaction mechanisms in this study are works
in progress and the results reported here are subject to change, based on model improvements and corrections of errors not
yet discovered.
NTIS
Combustion; Error Analysis; Hydrocarbons; Isomers; Heptanes
20040111517 Air Univ., Maxwell AFB, AL
Airpower as a Tool of Foreign Policy, Two Case Studies of Airpower’s Use: The Philippines in 1941 and Berlin in 1948
Therianos, Janet A.; May 1993; 80 pp.; In English
Report No.(s): AD-A425508; No Copyright; Avail: CASI; A05, Hardcopy
The purpose of this work is to provide insight for the operational air planner who must determine the circumstances under
which airpower can be an effective tool of foreign policy. With insight into this issue, both the air strategist and diplomat may
be better equipped to evaluate the appropriateness of using airpower in international relations. To accomplish this purpose, this
paper provides an analysis of two specific cases in which USA political leadership called upon airpower to further foreign
policy goals without resorting to war. The first case study centers around the decision to place B-17s on the Philippine Islands
in October of 1941. The second case study focuses on the use of airpower during the Berlin Blockade of 1948-1949. Both case
studies use a framework for analysis that examines the interrelationships between political, material, and military influences
on the ultimate operational air plan. Future students who may wish to pursue expanded studies of these or other cases may
capitalize on this framework to pursue those studies.
DTIC
Foreign Policy; International Relations; Philippines
20040111571 Massachusetts Inst. of Tech., Cambridge, MA
Fully Coupled Dynamic Analysis of a Floating Wind Turbine System
Withee, Jon E.; Jun. 2004; 151 pp.; In English
Report No.(s): AD-A425623; No Copyright; Avail: CASI; A08, Hardcopy
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