Combustion air Metal cooling air Gas cooling air Figure 1-57. Airflow through a can-annular combustion chamber.  Figure 1-59. Combustion chamber louvers and holes. Figure 1-58. Annular combustion chamber with ceramic coating. Figure 1-60. Turbine inlet guide vanes. 1-47 The turbine transforms a portion of the kinetic (velocity)  energy of the exhaust gases into mechanical energy to drive the  gas generator compressor and accessories. The sole purpose  of the gas generator turbine is to absorb approximately 60  to 70 percent of the total pressure energy from the exhaust  gases. The exact amount of energy absorption at the turbine is  determined by the load the turbine is driving (i.e., compressor  size and type, number of accessories, and the load applied by  the other turbine stages). These turbine stages can be used to  drive a low-pressure compressor (fan), propeller, and shaft.  The turbine section of a gas turbine engine is located aft, or  After the combustion chamber has introduced the heat energy  into the mass airflow and delivered it evenly to the turbine  inlet nozzles, the nozzles must prepare the mass air flow to  drive the turbine rotor. The stationary vanes of the turbine  inlet nozzles are contoured and set at such an angle that they  form a number of small nozzles discharging gas at extremely  high speed; thus, the nozzle converts a varying portion of the  heat and pressure energy to velocity energy that can then be  converted to mechanical energy through the turbine blades. The turbine assembly consists of two basic elements: turbine  inlet guide vanes and turbine disk.  [Figures 1-60  and  1-61] The stator element is known by a variety of names, of which  turbine inlet nozzle vanes, turbine inlet guide vanes, and  nozzle diaphragm are three of the most commonly used.  The turbine inlet nozzle vanes are located directly aft of the  combustion chambers and immediately forward of the turbine  wheel. This is the highest or hottest temperature that comes  in contact with metal components in the engine. The turbine  inlet temperature must be controlled, or damage will occur  to the turbine inlet vanes. downstream, of the combustion chamber. Specifically, it is  directly behind the combustion chamber outlet. The basic components of an annular combustion chamber  are a housing and a liner, as in the can type. The liner  consists of an undivided circular shroud extending all the  way around the outside of the turbine shaft housing. The  chamber is constructed of heat-resistant materials, which  are sometimes coated with thermal barrier materials, such  as ceramic materials. The annular combustion chamber is  illustrated in  Figure 1-58 . Modern turbine engines usually  have an annular combustion chamber. As can be seen in  Figure 1-59 , the annular combustion chamber also uses  louvers and holes to prevent the flame from contacting the  side of the combustion chamber.  Turbine Section