<DOC>
<DOCNO>
1072
</DOCNO>
<TITLE>
ignition and combustion in a laminar mixing zone .
</TITLE>
<AUTHOR>
marble,f. and adamson,t.c.
</AUTHOR>
<BIBLIO>
jet prop. 24, 1954, 85.
</BIBLIO>
<TEXT>
  the analytic investigation of laminar combustion
processes which are essentially two- or three-dimensional
present some mathematical difficulties .  there are, however,
several examples of two-dimensional flame propagation
which involve transverse velocities that are small in
comparison with that in the principal direction of flow .
such examples occur in the problem of flame quenching
by a cool surface, flame stabilization on a heated flat plate,
combustion in laminar mixing zones, etc .  in these cases
the problem may be simplified by employing what is
known in fluid mechanics as the boundary-layer approximation,
since it was applied first by prandtl in his treatment
of the viscous flow over a flat plate .  physically it
consists in recognizing that if the transverse velocity is
small, the variations of flow properties along the direction
of main flow are small in comparison with those in a
direction normal to the main flow .  the analytic description
of the problem simplifies accordingly .  the present
analysis considers the ignition and combustion in the
laminar mixing zone between two parallel moving gas
streams .  one stream consists of a cool combustible mixture,
the second is hot combustion products .  the two
streams come into contact at a given point and a laminar
mixing process follows in which the velocity distribution is
modified by viscosity, and the temperature and composition
distributions by conduction, diffusion, and chemical
reaction .  the decomposition of the combustible stream
is assumed to follow first-order reaction kinetics with
temperature dependence according to the arrhenius law .
for a given initial velocity, composition, and temperature
distribution, the questions to be answered are ..  (1) does
the combustible material ignite,. and (2) how far downstream
of the initial contact point does the flame appear
and what is the detailed process of development .  since
the hot stream is of infinite extent, it is found that ignition
always takes place at some point of the stream .  however,
when the temperature of the hot stream drops below a
certain value, the distance required for ignition increases
so enormously that it essentially does not occur in a
physical apparatus of finite dimension .  the complete
development of the laminar flame front is computed using
an approximation similar to the integral technique introduced
by von karman into boundary layer theory .
</TEXT>
</DOC>
