Effect of pressure level on afterburner-wall temperatures Page: 4 of 25
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investigation. At the same time, because of its erratic nature, screech
could not be tolerated in a cooling investigation of the type that was
conducted. The flameholder screech shield therefore appeared to be a
good solution to the various requirements imposed.
Fuel for the afterburner was injected from 40 spray bars that were
mounted on the inner cone and directed the fuel normal to the gas stream.
The bars were arranged in two circumferential rows of 20 each at axial
distances of 26.5 and 29.5 inches upstream of the leading edge of the
flameholder. Spray bars at each of these axial positions were arranged
in pairs, one behind the other. The pairs were located in longitudinal
planes at 15 intervals around the circumference (four of these planes
were occupied by the diffuser inner-cone support struts). Details of the
fuel-spray-bar hole distribution are shown in figure 3.
Cooling system. - As shown in figure 1, about 38.5 inches of the
afterburner wall were jacketed to form an annular cooling-air passage.
Cooling air flowed through the annular passage from an annular header
and was discharged radially at the downstream end of the passage. Cooling
air was obtained from the laboratory compressed-air system and was di-
rected normal to the afterburner axis into the header at two diametrically
opposed points. The jacket and the header were insulated to prevent the
convective flow of heat from the cooling air into the test cell. Figure
4 shows the afterburner both before (fig. 4(a)) and after (fig. 4(b))
the installation of the jacket insulation. One of the header air inlets
is shown. Although the radial discharge slots for the cooling air are
shown equipped with valves in figure 4(a), the valves and chain-drive
mechanism were eventually abandoned and fixed discharge areas were used,
as shown in figure 4(b). The three rectangular openings or windows
through the jacket and aftehruner wall cho in figure 4 were origin lly
intended for direct measurement of radiation intensity. The windows were
never used during the experimental program, however, because the initial
results obtained indicated that luminous radiation was insignificant.
The significant geometrical characteristics of the cooling-air and
the afterburner gas-flow passages are shown in figure 5. The annular
cooling-air passage tapered from a depth of 0.88 inch at the upstream
end to 0.58 inch at the downstream end. Within this same length the
diameter of the afterburner gas flow passage tapered from 32.00 to 28.75
The engine and afterburner were installed in a test cell that ran at
approximately atmospheric pressure. High-pressure air from the laboratory
air-supply system was ducted past regulating valves to both the engine
inlet and the afterburner cooling system. A schematic diagram showing
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Shillito, Thomas B. & Smolak, George R. Effect of pressure level on afterburner-wall temperatures, report, June 11, 1958; (digital.library.unt.edu/ark:/67531/metadc52844/m1/4/: accessed November 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.