Question 99Gas Turbine - 1st Asst/Chief

The correct answer is D) Power turbine cooling. In a marine gas turbine engine, the 9th stage bleed air is typically used for power turbine cooling. The power turbine is responsible for delivering the engine's output power, so it requires dedicated cooling to maintain optimal operating temperatures and prevent thermal damage. Directing the 9th stage bleed air to the power turbine is an effective way to provide this necessary cooling. The other answer choices are incorrect because they do not accurately describe the purpose of the 9th stage bleed air in this type of engine. Option A refers to compressor balance piston cavity pressurization, which is typically done using lower-stage bleed air. Option B describes high-pressure turbine nozzle cooling, which is a different function not associated with the 9th stage bleed. Option C relates to sump pressurization and cooling, which is also not the primary purpose of the 9th stage bleed air.