Compressors increase the pressure of air before it enters the combustor for combustion. The compressor gets more air in the engine, and in general the more air that is put in the engine the more power will be produced. The energy released by the combustor is proportional to the mass of the air that enters the engine, so the compressor is an important part of the engine. The main kinds of compressors that have been used with gas turbines include centrifugal flow, and axial flow compressors 。