text: energy to drive the propeller in addition to the 
  compressor and accessories. 
  
  maintain a nucleus of combustion in the com- 
  bustion chamber. 
  In rhe normal combustion 
  process, the speed of flame propagation is quite 
  low and, if the local velocities are too high at 
  the forward end of the combustion chamber, 
  is likely 
  poor combustion will 
  rhar the flame will blow out. The secondary 
  air-or cooling flow-is 
  introduced downstream 
  from the combustion nucleus to dilute the com- 
  bustion products and lower the discharge gas 
  temperature. 
  
  The combustion chamber delivers high en- 
  ergy combustion gases to the turbine section at 
  high pressure and tolerable temperature. The 
  turbine nozzle vanes are a row of stationary 
  blades immediately ahead of the rotating tur- 
  bine. These blades form the nozzles which 
  discharge the combustion gases as high ve- 
  In this 
  locity 
  manner, the high pressure energy of the com- 
  bustion gases is converted into kinetic energy 
  and a pressure and temperature drop takes 
  the turbine blades 
  place. The function of 
  operating in these jets is to develop a tangen- 
  tial force along the turbine wheel thus extract- 
  ing mechanical energy from the combustion 
  gases. This is illustrated in figure 2.8. 
  
  The  fuel nozzle must provide a 