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Which of these statements about an reaction turbine are correct or incorrect?

I. The pressure drops across the nozzle guide vanes
II. The pressure remains constant across the rotor blades

  • A
    I is incorrect, II is incorrect.
  • B
    I is correct, II is incorrect.
  • C
    I is correct, II is correct.
  • D
    I is incorrect, II is correct.

Refer to figure.

IMPULSE TURBINE
Nozzle guide vanes
(form convergent ducts – accelerate the gas)
Velocity increasesPressure decreases
Rotor BladesVelocity decreasesNo change in pressure
REACTION TURBINE
Nozzle guide vanes Pressure remains constant
Rotor Blades
(form convergent ducts – accelerate the gas, creating reaction force which drives the turbine)
Velocity increasesBoth temperature and pressure decrease

According to Rolls Royce, in a reaction turbine, the nozzle guide vanes simply direct the gas onto the turbine blades. Therefore, there is no change in speed or pressure across them, only a change in direction.

Therefore, correct option: INCORRECT, INCORRECT

IMPORTANT NOTE: Please note that we received initial feedback from students confirming that the correct answer was "correct, incorrect." Based on this, we believed that according to EASA, nozzle guide vanes formed slightly convergent ducts, resulting in pressure drops. However, we have received more recent feedback from Hungary and Slovakia, confirming that the correct answer is "incorrect, incorrect." It appears that EASA may have recently rectified this question to align with what we now believe to be the correct answer.

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