Page 223 - The Jet Engine

Thrust distribution

24. Assuming that an afterburner jet pipe and
propelling nozzle are fitted to the engine used in the
previous calculations, and the new conditions at the
propelling nozzle are as follows-

OUTLET Area (A) = 455 sq.in.
Pressure (P) = 5 lb. per sq.in.
(gauge)
Velocity (v ) = 2,404 ft. per sec.
J
Mass flow (W) = 157 lb. per sec.
The thrust

= ( A x P ) + WV J − 16 , 745
g
157 x , 2 404
= ( 455 x ) 5 + − 16 , 745
32
= 14,069 - 16,745
= 2,676 lb. acting in a rearward direction.

Therefore, compared with the previous calculation in
para. 17, it will be seen that the negative thrust is
reduced from -5,587 lb. to -2,676 lb.; the overall
positive thrust is thus increased by 2,911 lb; which is
equivalent to a thrust increase of more than 25 per
cent.
system are reheated to provide additional thrust. The
effect of afterburning is to increase the volume of the 25. To arrive at the total thrust of the engine with
exhaust gases, thus producing a higher exit velocity afterburning the calculations in para. 20 should use
at the propelling nozzle. the above figures.

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