Solved Problem 6.13 - T700 Proposed Turbojet Conversion

Recall Solved Problem 6.11 in which we did an ideal thermodynamic analysis of the General Electric T700 helicopter gas turbine engine. During Fall Quarter 2008 Dr. Tom Scott (currently retired) presented an inspiring and animated demonstration of the cutaway T700 gas turbine engine as shown below:

During the talk he mentioned that one could unclamp and remove the power turbine at the rear and replace it with a nozzle to form a turbojet engine. This captured our imagination, hence we would like to do an initial ideal thermodynamic analysis of this conversion. Consider the schematic diagram of this conversion shown in the figure below:

Notice that the h-s diagram has retained the same shape and characteristics as that in Solved Problem 6.11 , with the only difference being that the change in enthalpy on the nozzle gives rise to a kinetic energy increase, rather than work output.

• On replacing the power turbine with an isentropic jet nozzle, determine the temperature (T ₅ ) and exhaust velocity (V ₅ - m/s). Given that the mass flow rate of the working gas through the system is 4.6 kg/s, determine the thrust force at the outlet of the nozzle (Thrust ₅ - lbf). [Note: 1 lbf (pound force) = 4.46 N]