Experimental investigation of thrust augmentation of a turbojet engine at zero ram by means of tail-pipe burning Page: 4 of 37
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NACA RM No. ESJ21
Static thrust, pounds ........ .......... .. 4000
Rotor speed, rpm . . . . . . . . . . . . . . .......... 7700
Tail-pipe gas temperature, .................. 1660
For all tests, JP-l fuel was used in the engine and AN-F-22 fuel was
used in the tail-pipe burner.
Engine installation. - The general arrangement of the installation
of the engine with the standard tail pipe is shown in figure 1. A
spherical "clam-shell" type adjustable-area exhaust nozzle having a
discharge-area range from 224 to 283 square inches was installed at
the end of a 30-inch long tail pipe. This short tail pipe, which has
an inside diameter of 21 inches, was installed to provide for discharge
of the exhaust gas outside the test cell. The engine was mounted on
a swinging framework suspended from the ceiling of the test cell and
the engine thrust was balanced and measured with an air-pressure dia-
phragm (fig. 1). An inlet-air nozzle, fitted with an exit diffuser,
was used to determine the air flow. The engine speed and fuel flows
were measured with standard instrumentation.
Tail-pipe burner. - Several different types of tail-pipe burner
were investigated; the complete assembly of the engine with the burner
that incorporated the most satisfactory design features is shown in
figure 2. This burner is simple in construction, consisting essen-
tially of an enlarged tail pipe, which incorporates fuel-spray nozzles
and a flame holder. A sketch of the tail-pipe burner showing the
details of construction is shown in figure 3; a photograph of the
burner assembly removed from the engine is shown in figure 4.
The burner shell consists of a 6-foot section of straight duct
made out of one-sixteenth inch thick Inconel and has an inside diameter
of 25- inches. The burner is attached to the engine by means of an
annulr diffuser section having an outlet-to-inlet area ratio of 1.5
and a short adapter section, which is bolted to the turbine-discharge
flange (fig. 3). The annular diffuser is formed by an inner cone,
similar to but slightly shorter than the standard turbine-discharge
inner cone, and an outer duct. An adjustable-area exhaust nozzle
similar to that used in the standard tail pipe and with a discharge-
area range from 265 to 397 square inches is fitted to the discharge
of the tail-pipe burner.
As shown in figure 3, the fuel was introduced into the tail-pipe
burner through two rings of spray nozzles, an upstream ring and a
downstream ring. The upstream spray-nozzle ring protrudes about one-
eighth inch from the surface of the turbine-discharge inner cone near
the turbine discharge and consists of twenty 40-gallon-per-hour
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Lundin, Bruce T.; Dowman, Harry W. & Gabriel, David S. Experimental investigation of thrust augmentation of a turbojet engine at zero ram by means of tail-pipe burning, report, January 6, 1947; (digital.library.unt.edu/ark:/67531/metadc58109/m1/4/: accessed May 25, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.