Propellant ---> burn ---> expand through nozzle (chem. energy) (thermal energy) (kinetic energy & momentum)
|Continuously:||a) Draw in air.|
|b) Compress it.|
|c) Add fuel and burn (convert chemical energy to thermal energy).|
|d) Expand through a turbine to drive compressor (extract work).|
|e.1) Then expand in a nozzle to convert thermal energy to kinetic energy & momentum (turbojet).|
|e.2) Or expand in a second turbine (extract work), use this to drive a shaft for a fan (turbofan), or a propeller (turboshaft). The fan or propeller impart k.e. & mom. to the air.|
Overall goal: take at Vo (flight speed), throw it out at Vo + DV
Figure 1.1 Schematics of typical military gas turbine engine: J57 turbojet with afterburning.
Figure 1.2 A typical high bypass-ratio turbofan (Adapted from Pratt & Whitney).
For more examples of real world powerplants, refer to Hill, P. and C. Peterson. Thermodynamics of Propulsion. 2nd Ed. Addison-Wesley, 1991.
The two performance parameters of greatest interest for a propulsion system are the force it produces (thrust, T), and the overall efficiency with which it uses energy to produce this force (hoverall). We will begin by looking at the production of thrust using the integral form of the momentum theorem. In the second lecture we will discuss the efficiency of propulsion systems.
Fluids + thermo + structures + dynamics + controls + chemistry + acoustics + …