How do turbine nozzles convert energy in the gas flow?

Turbine nozzles play a crucial role in converting the energy within the gas flow by transforming the heat and pressure energy into kinetic energy, also referred to as velocity energy. This process occurs as the high-pressure, high-temperature gas passes through the nozzle's constricted section.

As the gas flows through the nozzle, its pressure decreases while its velocity increases. This conversion is essential for the operation of jet engines and gas turbines, where the high-speed exhaust produced from the nozzle is what drives the turbine blades, ultimately generating thrust or mechanical power. This efficient transformation of energy is a fundamental aspect of thermodynamics in aviation propulsion systems.

Given this context, the other options do not accurately describe the function of turbine nozzles. Cooling the gas to decrease its volume, compressing the gas for better ignition, and filtering impurities are not primary functions of the nozzles and do not contribute to the conversion of energy in a manner that supports the operation of turbine engines.