Analyses for turbojet thrust augmentation with fuel-rich afterburning of hydrogen, diborane, and hydrazine Page: 3 of 23
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2 S-- NACA RM E57D22
Reference I shows that thrust-increases with diborane flow up to a
fuel-air ratio of 1.3 times the stoichiometric value; the rate of change
of thrust-with fuel-air ratio at the stoichiometric point indicates that
hydrogen-rich afterburning will also augment thrust. Further, reference
1 confirms the futility of rich combustion with hydrocarbons.
The ideal fuel for rich afterburning would be a dense one with a high
heat of combustion. It would decompose when heated, releasing energy
and forming low-molecular-weight products. Hydrazine is a fairly dense
liquid that has a positive heat of formation and yields products with
low molecular weights. These properties make hydrazine a good prospect
for fuel-rich afterburning even though it has a low heat of combustion.
This report presents net thrusts computed for hydrogen, diborane,
and hydrazine with fuel-air ratios from stoichiometric values to 0.5.
Net thrusts for fuel-rich afterburning are compared with those for
stoichiometric combustion of the turbojet fuel and air augmented with a
220-second specific-impulse rocket. Conditions were selected to repre-
sent fuel-rich afterburning during
(1) Takeoff with any of four turbojet engines having compressor
pressure ratios from 5.2 to 12 and turbine-outlet total tempera-
tures from 15100 to 20620 R
(2) Flight at Mach 2 and au altitude of 55,000 feet with a turbojet
engine having a compressor pressure ratio of 8.4 and a turbine-
outlet total temperature of 20620 R (sea-level-static ratings).
These turbojet engines are described in reference 2. Three of the
engines are similar to existing models; the turbojet engine with a 20620 R
turbine-outlet temperature is an advanced design with a cooled turbine
(engine D of table I).
The conditions and fuels for these studies were selected to repre-
sent takeoff-and flight of turbojet engines with fuel-rich afterburning.
Some afterburner-inlet conditions for various turbojet-engine operating
points are given in table I, which was taken from reference 2. The
results of this work extend those of reference 2.
Fuels and Operating Conditions
Net thrusts and exhaust-nozzle-exit areas were computed for fuel-
rich combustion of the following liquids: hydrogen at 20.390 K, diborane
at 180.630 K, and hydrazine at 298.160 K. The conditions chosen for
these studies are
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Morris, James F. Analyses for turbojet thrust augmentation with fuel-rich afterburning of hydrogen, diborane, and hydrazine, report, June 18, 1957; (digital.library.unt.edu/ark:/67531/metadc63662/m1/3/: accessed November 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.