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3B2 POWER ENGINEER FINAL Newest Exam
Preparation With Complete Questions And Correct
Answers With Rationales Already Graded A+ Brand
New Version!!
QUESTION 1
When the exit pressure of a steam turbine nozzle is less than ________
times the inlet pressure, then a ________ nozzle will be used.
A) 0.757, convergent
B) 0.577, convergent-divergent
C) 0.757, convergent-divergent
D) 0.757, convergent
E) 0.577, convergent or convergent-divergent
Answer: B
Explanation: The critical pressure ratio for steam is approximately
0.577. When the exit pressure falls below this ratio relative to inlet
pressure, the steam achieves sonic velocity at the throat, necessitating a
convergent-divergent nozzle to efficiently expand the steam to
supersonic velocities and recover the energy. A convergent nozzle alone
would be insufficient and would result in significant losses.
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QUESTION 2
Turbine nozzles convert heat energy into which form of energy?
A) Potential energy
B) Enthalpy
C) Eddy currents
D) Kinetic energy
E) Pressure
Answer: D
Explanation: Turbine nozzles convert the heat energy (enthalpy) of the
steam into kinetic energy (velocity). The nozzle shape accelerates the
steam to high velocity, which then impacts the moving blades to
produce rotational mechanical energy.
QUESTION 3
What is the primary function of the moving blades (buckets) on a
turbine rotor?
A) To convert heat energy into kinetic energy
B) To convert kinetic energy of steam into mechanical energy
C) To reduce steam pressure only
D) To increase steam temperature
E) To condense exhaust steam
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Answer: B
Explanation: The moving blades on the rotor convert the kinetic energy
of the steam into mechanical rotational energy. As the high-velocity
steam passes through the moving blades, it changes direction and loses
velocity, transferring its momentum to the rotor.
QUESTION 4
Which type of steam turbine has a pressure drop across BOTH the
stationary and moving blades?
A) Impulse turbine
B) Velocity-compounded turbine
C) Reaction turbine
D) Pressure-compounded turbine
E) Extraction turbine
Answer: C
Explanation: The distinguishing feature of a reaction turbine is that the
pressure drops across both the fixed and moving blades. The moving
blades are nozzle-shaped, and the reaction principle causes the steam
to accelerate through them.
QUESTION 5
Labyrinth seals used on steam turbine shafts are typically made of
which materials?
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A) Cast iron only
B) Brass or stainless steel
C) Carbon steel
D) Copper alloys only
E) Rubber and polymers
Answer: B
Explanation: Labyrinth seals are typically made of brass or stainless
steel and are used on larger diameter turbine shafts. They are designed
to have small clearances but are not positive leak-proof seals; they
restrict leakage by creating a tortuous path for the steam.
QUESTION 6
What is the purpose of a dummy (balance) piston on a steam turbine?
A) To increase turbine speed
B) To counteract axial thrust
C) To reduce steam pressure
D) To improve sealing
E) To increase efficiency
Answer: B
Explanation: The dummy piston, also known as a balance piston, is
designed to counteract axial thrust generated by the pressure drop
3B2 POWER ENGINEER FINAL Newest Exam
Preparation With Complete Questions And Correct
Answers With Rationales Already Graded A+ Brand
New Version!!
QUESTION 1
When the exit pressure of a steam turbine nozzle is less than ________
times the inlet pressure, then a ________ nozzle will be used.
A) 0.757, convergent
B) 0.577, convergent-divergent
C) 0.757, convergent-divergent
D) 0.757, convergent
E) 0.577, convergent or convergent-divergent
Answer: B
Explanation: The critical pressure ratio for steam is approximately
0.577. When the exit pressure falls below this ratio relative to inlet
pressure, the steam achieves sonic velocity at the throat, necessitating a
convergent-divergent nozzle to efficiently expand the steam to
supersonic velocities and recover the energy. A convergent nozzle alone
would be insufficient and would result in significant losses.
,2|Page
QUESTION 2
Turbine nozzles convert heat energy into which form of energy?
A) Potential energy
B) Enthalpy
C) Eddy currents
D) Kinetic energy
E) Pressure
Answer: D
Explanation: Turbine nozzles convert the heat energy (enthalpy) of the
steam into kinetic energy (velocity). The nozzle shape accelerates the
steam to high velocity, which then impacts the moving blades to
produce rotational mechanical energy.
QUESTION 3
What is the primary function of the moving blades (buckets) on a
turbine rotor?
A) To convert heat energy into kinetic energy
B) To convert kinetic energy of steam into mechanical energy
C) To reduce steam pressure only
D) To increase steam temperature
E) To condense exhaust steam
,3|Page
Answer: B
Explanation: The moving blades on the rotor convert the kinetic energy
of the steam into mechanical rotational energy. As the high-velocity
steam passes through the moving blades, it changes direction and loses
velocity, transferring its momentum to the rotor.
QUESTION 4
Which type of steam turbine has a pressure drop across BOTH the
stationary and moving blades?
A) Impulse turbine
B) Velocity-compounded turbine
C) Reaction turbine
D) Pressure-compounded turbine
E) Extraction turbine
Answer: C
Explanation: The distinguishing feature of a reaction turbine is that the
pressure drops across both the fixed and moving blades. The moving
blades are nozzle-shaped, and the reaction principle causes the steam
to accelerate through them.
QUESTION 5
Labyrinth seals used on steam turbine shafts are typically made of
which materials?
, 4|Page
A) Cast iron only
B) Brass or stainless steel
C) Carbon steel
D) Copper alloys only
E) Rubber and polymers
Answer: B
Explanation: Labyrinth seals are typically made of brass or stainless
steel and are used on larger diameter turbine shafts. They are designed
to have small clearances but are not positive leak-proof seals; they
restrict leakage by creating a tortuous path for the steam.
QUESTION 6
What is the purpose of a dummy (balance) piston on a steam turbine?
A) To increase turbine speed
B) To counteract axial thrust
C) To reduce steam pressure
D) To improve sealing
E) To increase efficiency
Answer: B
Explanation: The dummy piston, also known as a balance piston, is
designed to counteract axial thrust generated by the pressure drop
