The axial-flow compressor’s advantages are: The axial-flow compressor’s disadvantages are: The location of the combustion section is directly between  the compressor and the turbine sections. The combustion  chambers are always arranged coaxially with the compressor  and turbine regardless of type, since the chambers must be in a  through-flow position to function efficiently. All combustion  chambers contain the same basic elements: There are currently three basic types of combustion chambers,  variations within type being in detail only. These types are: The can-type combustion chamber is typical of the type  used on turboshaft and APUs.  [Figure 1-52]  Each of the  The diffuser is the divergent section of the engine after the  compressor and before the combustion section. It has the  all-important function of reducing high-velocity compressor  discharge air to increased pressure at a slower velocity. This  prepares the air for entry into the flame burning area of the  combustion section at a lower velocity so that the flame of  combustion can burn continuously. If the air passed through  the flame area at a high velocity, it could extinguish the flame. The combustion section houses the combustion process,  which raises the temperature of the air passing through the  engine. This process releases energy contained in the air/ fuel mixture. The major part of this energy is required at the  turbine or turbine stages to drive the compressor. About ²⁄ ³  of  the energy is used to drive the gas generator compressor. The  remaining energy passes through the remaining turbine stages  that absorb more of the energy to drive the fan, output shaft,  or propeller. Only the pure turbojet allows the air to create  all the thrust or propulsion by exiting the rear of the engine  in the form of a high-velocity jet. These other engine types  have some jet velocity out the rear of the engine but most  of the thrust or power is generated by the additional turbine  stages driving a large fan, propeller, or helicopter rotor blades. The primary function of the combustion section is, of course,  to burn the fuel/air mixture, thereby adding heat energy to  the air. To do this efficiently, the combustion chamber must: Figure 1-52. Can-type combustion chamber. 1-44 •  Provide the means for proper mixing of the fuel and  air to assure good combustion, •  Burn this mixture efficiently, 1.  Can type 2.  Can-annular type 3.  Annular type 5. Fuel drainage system to drain off unburned fuel after  engine shutdown 4.  Some means for initial ignition 3.  Fuel injection system 2.  Perforated inner liner 1. Casing •  Good efficiencies over only narrow rotational speed range, •  Difficulty of manufacture and high cost, •  Relatively high weight, and •  High starting power requirements (partially overcome  by split compressors). •  Increased pressure rise by increasing number of stages,  with negligible losses.  •  Straight-through flow, allowing high ram efficiency;  and •  Small frontal area for given airflow; •  High peak efficiencies; •  Cool the hot combustion products to a temperature  that the turbine inlet guide vanes/blades can withstand  under operating conditions, and •  Deliver the hot gases to the turbine section. Diffuser Combustion Section