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

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

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

Correct option: CORRECT, INCORRECT

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