A 6000 lbm jet is to be accelerated to 300 ft/s for take off from the deck of an

Question

A 6000 lbm jet is to be accelerated to 300 ft/s for take off from the deck of an aircraft carrier, using 90 lbm of high pressure steam in a piston-cylinder assembly below the deck. a) The ship's engineer calculates that 10,800 Btu of energy from the steam is needed to achieve takeoff. Check the calculation. b) Steam is available at 200 psia in the compressed state, and will end up as a saturated vapor at 1 atm in the expanded state. To what temperature must the compressed steam be superheated in order to send off the plane? (The expansion is rapid and can be assumed adiabatic) c) Perform an energy balance so as to derive a design equation that relates the specific internal energy of the steam to the takeoff velocity.

Explanation / Answer

a) Energy required   = 0.5 * 6000 * 300^2   = 270 * 10^6 lbm-ft or 10800 BTU

b)   At exit enthalpy = 1150.27 BTU / lbm

      Energy required = 10800 = 90 * ( h1 - 1150.27)

      h1 = 1270.27 BTU / lbm

      From steam tables we get

      T1 = 261 degree celsius   or 534 K

c) Energy balance = 90 * (U2 - U1)   = 0.5 * 6000 * v^2

                               change in internal energy = 33.33 * v^2

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.