Fundamental flame velocities of pure hydrocarbons 2: alkadienes Page: 4 of 14
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NACA f E50B25
to the flame tube. The volumetric rate of flow divided by the cross-
sectional area of the flame tube is a mean value of the gas veloc-
ity Ug. An empirical relation between the gas velocity and the linear
flame velocity was experimentally established (reference 1) and was
Used to calculate the gas velocity
Ug = 0.236 Uo - 10.47 (2)
The surface area of the flame Af was determined by photographing
the flame and calculating the area from the photographs by the method
of Coward and Hartwell as modified by the authors (reference I). The
flame surface area was found to have a constant value for every hydro-
carbon type and concentration.
The reproducibility of the experimental procedure was confirmed
by the periodic testing of n-pentane during the investigation of the
alkadienes. At no time did the linear flame velocity for n-pentane
deviate more than 2 percent from its original value (reference 1). At
least three determinations of the linear flame velocity were made for
each mixture concentration studied. The flame velocities reported
herein are average values and have a precision of. 2 percent.
RESULTS AND DISCUSSION
The flame-velocity data together with the source and estimated
purity of all the hydrocarbons considered in this investigation are
summarized in table I.
The fundamental flame velocity of three series of hydrocarbons
with 4, 5, .and 6 carbon atoms in the straight chain is presented as
a function of hydrocarbon concentration (expressed as fraction of
stoichiometric) in figures 1, 2, and 3, respectively. In general,
the maximum flame velocity occurs in mixtures containing 10 to 30 per-
cent excess fuel. In figure 4 the maximum flame velocity for each
individual hydrocarbon is cross-plotted from figures 1 to 3 against
the number of carbon atoms in the straight chain. Addition of a
second double bond to an alkene increases the flame velocity; the
extent depends on the molecular weight of the alkene and on whether
the resulting alkadiene has an isolated, conjugated, or cumulative
double-bond system. The maximum flame velocities of 1,3-butadiene
and 1,2-butadiene are approximately 26 and 34 percent greater, respec-
tively, than that of 1-butene (reference 1); the flame velocity of
1,2-butadiene is the same as 1-butyne (reference 1). The maximum
flame velocities of ci 1,3-pentadiene, trans 1,3-pentadiene, and
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Levine, Oscar; Wong, Edgar L. & Gerstein, Melvin. Fundamental flame velocities of pure hydrocarbons 2: alkadienes, report, November 3, 1950; (https://digital.library.unt.edu/ark:/67531/metadc58618/m1/4/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.