Consider a turbojet powered airplane flying at a standard altitude of 30,000ft at a velocity of 500 mph. The turbojet engine itself has inlet and exit areas of 7 ft 2 and 4.5 ft2, respectively. The velocity and pressure of the exhaust gas at the exit are 1600 ft/s and 640 lb/ft2, respectively. Calculate the thrust of the turbojet. (Use the TSA value of pressure and density at the altitude of 30,000ft)

T  = 20.42 N

Explanation:

given data

standard altitude = 30,000 ft

velocity Ca = 500 mph = 0.4 m/s

inlet areas Aa = 7 ft² = 0.65 m²

exit areas Aj = 4.5 ft²  =  0.42 m²

velocity at exit Cj = 1600 ft/s = 487.68 m/s

pressure exit j = 640 lb/ft²   = 0.3 bar

solution

we get here thrust of the turbojet that is  express as

thrust of the turbojet T = Mg × Cj - Ma × Ca + ( j Aj - a Ag )   .............1

here Ma = Mg

Ma = a × Ca Aa = 0.042 kg/s

put value in equation 1 we get

T = 0.042 × (487.68 -0.14) + ( 0.3 ×  - 0.3 × 0.65 )  

T  = 20.42 N