Anatomy and SSSF Analysis of Ideal Turbo Jet Engine P M V Subbarao Professor Mechanical Engineering Department Features of A True Flying Machine Muscles ….

Anatomy of A Jet Engine V ac V jet

Ideal Turbo Jet Cycle T p s s 2 6 : Jet 2

Anatomy of A Jet Engine : Intake s = constant T: Increasing p: Increasing V ac V jet

Inlet : Steady State Stead Flow Conservation of mass First Law :  

No heat transfer and no work transfer : A Pure Passive compressor : No Change in potential energy. Assume gas as an ideal and calorically perfect. Kinetic energy that can produce enthalpy and hence temperature rise and vice versa.

More fundamentally, Temperature (Static Temperature) is a measure of microscopic kinetic energy. Dynamic Temperature is a measure of macroscopic kinetic energy. Define: Total Temperature = Static Temperature + Dynamic Temperature

A fluid at rest (zero macroscopic kinetic energy) can convert its internal energy or enthalpy into kinetic energy, provided: It is above absolute zero pressure and temperature. A moving fluid (finite macroscopic kinetic energy) can convert its kinetic energy into internal energy or enthalpy. Maximum possible conversion corresponds to fluid coming to rest.

Measure of An ActionMeasure of Hardware Measure of benefits at zero running cost Measure of capital cost An Inlet of A Jet engine is a passive compressor, i.e. zero running cost

Measure of Compression An ideal intake device is an isentropic compressor with zero power input. At design condition:

Maximum Possible Compression An inlet device with zero exit velocity will produce maximum compression. At design condition:

Control Volumes Can never Afford to Generate Maximum Compression Total Pressure and Total Temperature are just reference measures…..

Anatomy of A Jet Engine : Compressor s = constant T : increasing p : increasing V ac V jet

Compressor : Steady State Stead Flow Process First Law :   Conservation of mass

No heat transfer, change in potential energies is negligible

A compressor of A Jet engine is an active device, i.e. there exist capital and running cost. If so, why is this? Do I get more befit than the expenditure? Does it also compensate extra capital cost too?

Measure of Extra Life Generation Isentropic active compression

Anatomy of A Jet Engine: Combustion Chamber s : increasing T: increasing p : constant??? V ac V jet

3 – 4 : Isobaric Heat addition   No work transfer and change in potential energies is negligible

3 – 4 : Ideal Combustor   No work transfer and change in potential energies is negligible & adiabatic combustion

How much fuel should be added to get High fuel economy? How to get a compact jet engine ?

Anatomy of A Jet Engine:Turbine s = constant T : decreasing p : decreasing V ac V jet

Turbine : SSSF Process : No heat transfer. Change in potential energies is negligible 4 5 T

Turbine is to produce just enough power. The vigor of Jet:

Anatomy of A Jet Engine : Nozzle s = constant T : Decreasing P: decreasing V ac V jet

Nozzle : Steady State Stead Flow  

Anatomy of An Ideal Jet Engine s = constant T 0 = constant P 0 = constant s = constant T 0 = increasing P 0 = increasing s = increasing T 0 = increasing P 0 = constant s = constant T 0 = decreasing P 0 = decreasing s = constant T 0 = constant P 0 = constant

Ideal Turbo Jet Cycle T0T0 1, ,6 s

p0p0 s 1, ,6