The combustion chamber has the difficult task of burning large quantities of fuel, supplied through the fuel burners, with extensive volumes of air, supplied by the compressor, and releasing the heat in such a manner that the air is expanded and accelerated to give a smooth stream of uniformly heated gas at all conditions required by the turbine. This task must be accomplished with the minimum loss in pressure and with the maximum heat release for the limited space available.
The amount of fuel added to the air will depend upon the maximum temperature rise required and, as this is limited by the materials from which the turbine blades and nozzles are made, the rise must be in the range of 700 to 1,200 deg.C. Because the air is already heated by the work done during compression, the temperature rise required at the combustion chamber may be between 500 and 800 deg.C. Since the gas temperature required at the turbine varies with engine speed, and in the case of the turbo-prop engine upon the power required, the combustion chamber must also be capable of maintaining stable and efficient combustion over a wide range of engine operating conditions.
Efficient combustion has become more and more important because of the rapid increase in commercial aircraft traffic and the consequent increase in atmospheric pollution, which is seen by the general public as exhaust smoke.