Preliminary Tests of a Burner for Ram-Jet Applications Page: 4 of 15
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NACA M No. L6K086 3
Mixing and efficient combustion.- An important part of any
combustion process is the proper mixing of fuel and air. When
a stream of gaseous fuel which has not been mixed with air is
ignited, there is a strong possibility that some of the fuel
may pass through the burner without being exposed to sufficient
air for combustion. Combustion in an atmosphere lacking in
sufficient oxygen results in the formation of free carbon, -hich
radiates a large amount of heat to the surroundings (as in a
yellow flame) and passes through as a waste of available energy.
Carbon monoxide also is formed, the reaction by which it is
formed having a low heat of combustion. It is important for
efficient combustion, therefore, to have all the fuel exposed
to sufficient air for cobustion. Greatly disturbing the air
to obtain this miing causes unnecessary losses, so that it is
most important to inject the fuel in such a manner that it will
became evenly distributed throughout the air. It might be
necessary, however, in a final burner design, to arrive at some
compromise between burner losses and rapid mixing.
DESCRIPTION OF BURNER AND TEST APPARATUS
A sketch of the cross section of the burner and inner passage
of the ram Jet is shown as figure 1. The burner consists of a
circular mixing duct surrounded by an annular igniter at the
trailing edge. The area of the mixing duct is one-eighth the
area enclosed by the inner passage of the rani jet, so that small
fractions of the total air can be burned and the air-fuel mixtures
are nearly stoichiometric.
Tests were made of a small burner 21 inches in diameter,
1 foot long, located in a tube of constant cross section 5 inches
in diameter and 7 feet long. This tube simulated the inner
passage of a ram jet and was mounted at the exit of a centrifugal
blower which served as the air supply. With this blower, an air
velocity of about 150 feet per second was available under conditions
of operation with maimum fuel flow. A static- and a total-
pressure tube were installed , inches ahead of the burner, and
static orifices were placed at intervals of 4 inches along the
inner passage of the ram jet to about 5 burner lengths downstream
from the burner.
Mixigprocess.- One of the main features of the burner tested
is that the fuel and air are mixed before ignition. Near the
leading edge of the burner gaseous fuel is injected into the air
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Huber, Paul W. Preliminary Tests of a Burner for Ram-Jet Applications, report, January 15, 1947; (https://digital.library.unt.edu/ark:/67531/metadc63915/m1/4/: accessed April 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.