text: The function of the t&pipe or exhaust no?& 
  is to discharge the exhaust gases to the atmos- 
  phere at the highest possible velocity to pro- 
  duce the greatest momentum change and thrust. 
  If a majority of the expansion occurs through 
  the turbine section, there remains only to con- 
  duct the exhaust gases rearward with a mini- 
  mum energy loss. However, 
  if the turbine 
  operates against a noticeable back pressure, the 
  nozzle must convert the remaining pressure 
  energy into exhaust gas velocity. Under ideal 
  conditions, the nozzle would expand the flow 
  to the ambient static pressure at the exhaust 
  and the area distribution 
  in the nozzle must 
  provide these conditions. When the ratio af 
  exhaust gas pressure to ambient pressure is 
  relatively low and incapable of producing sonic 
  flow, a converging nozzle provides the expan- 
  sion. The exit area must be of proper size to 
  If the exit 
  bring about proper exit conditions. 
  Figure 2.9 provides illustration of the func- 
  tion of the various engine components and the 
  changes in static pressure, temperature, and 
  velocity through the engine. The conditions 
  at the inlet provide the initial properties of the 
  engine airflow. The compressor section fur- 
  nishes the compression pressure rise with a 
  certain unavoidable but undesirable increase in 
  temperature. High pressure air delivered to 
  combustion chamber receives heat from the 
  combustion of fuel and experiences a rise in 
  temperature. The fuel flow is limited so that 
  the turbine inlet temperature is within 
  limits 
  which can be tolerated by the turbine structure. 
  The combustion takes place at relatively con- 
  stant pressure and initially 
  low velocity. Heat 
  addition then causes large increases in gas vol- 
  ume and flow velocity. 