Page 221 - The Jet Engine

Thrust distribution

The thrust The thrust

= ( A x P ) + WV J − 14 , 326 = ( A x P ) + WV J − 16 , 745
g g
153 x 643 153 x , 1 917
= ( 651 x 21 ) + − 14 , 326 = ( 332 x ) 6 + − 16 , 745
32 32
= 16,745 - 14,326 = 11,158 - 16,745

= 2,419 lb. of thrust in a forward direction. = 5,587lb. acting in a rearward direction.

It is emphasized that these are basic calculations
and such factors as the effect of air offtakes have
been ignored.
18. Based on the individual calculations, the sum of
the forward or positive loads is 57,836 lb. and the
sum of the rearward or negative loads is 46,678 lb.
Thus, the resultant (gross or total) thrust is 11,158 lb.
Engine
19. It will be of interest to calculate the thrust of the
engine by considering the engine as a whole, as the
resultant thrust should be equal to the sum of the
individual gas loads previously calculated.
Propelling nozzle
17. The conditions at the inlet to the propelling 20. Although the momentum change of the gas
nozzle are the same as the conditions at the jet pipe stream produces most of the thrust developed by the
outlet, i.e. 16,745 lb.
WV
J
Therefore, given that the propelling nozzle-- engine (momentum thrust = ), an additional
OUTLET Area (A) = 332 sq.in. g
Pressure (P) = 6 lb. per sq.in. thrust is produced when the engine operates with the
(gauge) propelling nozzle in a 'choked' condition (Part 6). This
Velocity (v J ) = 1,917 ft. per sec. thrust results from the aerodynamic forces which are
Mass flow (W) = 153 lb. per sec. created by the gas stream and exert a pressure

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