The temperature trend of mass airflow from inlet to exhaust is described as:

• A. Increases from the inlet, through the compressor and the diffuser into the burner, and decreases through the turbine into the exhaust.
• B. Increases from the inlet, through the compressor and remains constant through the diffuser and increases at the burner, and decreases through the turbine into the exhaust.
• C. Remains constant at the inlet, increases from the compressor and the diffuser into the burner, and decreases through the turbine into the exhaust.
• D. Increases from the inlet and diffuser into the burner, and decreases through turbine into exhaust.

Answer: (A)

The temperature of the airflow generally rises as it passes through the compressor, then rises again in the burner, and finally falls as the hot gases expand through the turbine toward the exhaust. Air entering the engine is at ambient temperature; the compressor does work on it, converting mechanical energy into internal energy, so the static temperature increases. The diffuser ahead of the burner maintains the high pressure and the gas remains hot coming into the combustor, where fuel combustion adds a large amount of heat and drives the gas temperature even higher. Once the hot gases expand through the turbine, they do work on the turbine blades, which causes the gas to lose energy and cool down as it moves toward the exhaust. So the overall trend is an increase from inlet through the compressor and diffuser into the burner, followed by a decrease through the turbine to the exhaust.