What function do turbine nozzle diaphragms serve in a gas turbine engine?

Turbine nozzle diaphragms play a crucial role in the performance of a gas turbine engine by increasing the velocity of heated gases. When the high-temperature gases that result from combustion exit the combustion chamber, they pass through the nozzle diaphragms. These diaphragms are designed to restrict the flow area, which results in an increase in the gas velocity as it expands through the nozzle.

As the gases accelerate, they utilize the energy from their thermal state, converting it into kinetic energy. This high-velocity jet of gases is then directed towards the turbine blades, causing them to spin. This spinning motion is what ultimately converts thermal energy into mechanical energy, driving the engine's output. By increasing the velocity of the gases, nozzle diaphragms enhance the efficiency of the engine's turbine section, contributing to overall engine performance.

The other options, while related to gas turbine function, do not accurately define the primary role of the nozzle diaphragms within the engine system.