Answer:
In air-breathing propulsion engines, the most significant source of excess enthalpy available to drive a propeller, fan or produce jet momentum downstream of the high pressure turbine is the compression of the air. When the air is compressed, its temperature and pressure increase. This increase in temperature and pressure results in an increase in the enthalpy of the air. The high enthalpy air can then be used to drive a propeller, fan, or produce jet momentum.
The other sources of excess enthalpy in air-breathing propulsion engines are the combustion of the fuel and the expansion of the exhaust gases. However, the compression of the air is the most significant source of excess enthalpy because it occurs at a much higher pressure than the combustion of the fuel or the expansion of the exhaust gases.
Step-by-step explanation: