Through turbine rotor blades, the pressure changes as described. Which statement is correct?

• A. Increases, temperature increases, velocity decreases.
• B. Decreases, temperature and velocity decreases.
• C. Remains constant, temperature increases.
• D. Increases, temperature decreases, velocity increases.

Answer: (B)

Through turbine rotor blades, energy is extracted from the hot gas to drive the shaft. This energy transfer causes the gas to expand and do work, so its static pressure falls. The enthalpy lost as the gas does work shows up as a lower gas temperature. The rotor blades also slow the flow to transfer that energy, so the gas velocity leaving the rotor is reduced. So, pressure decreases, temperature decreases, and velocity decreases, which matches the described behavior.