What creates the high-pressure exhaust gases in a gas turbine engine?

The high-pressure exhaust gases in a gas turbine engine are predominantly created by the ignition of fuel in the combustor. When fuel is injected into the combustion chamber, it mixes with the compressed air that has been heated by the compressor. Once the fuel ignites, a significant amount of energy is released in the form of heat, which causes the temperature and pressure of the combustion gases to rise sharply.

This rapid increase in temperature results in a corresponding increase in pressure, which is critical for ensuring the gases can expand and flow through the turbine section of the engine. As the high-pressure exhaust gases pass through the turbine, they drive the turbine blades, which are connected to the compressor, thus enabling continuous operation of the engine.

Other options, while related to various aspects of engine function, do not directly contribute to the creation of high-pressure exhaust gases in the same way. The cooling of air and the lowering of air temperature would tend to reduce pressure and energy available for combustion rather than increase it. The operation of the compressor helps to increase the pressure of the air before combustion, but it is the ignition of the fuel that ultimately generates the high-pressure exhaust needed to propel the engine effectively.