Thermal Engineering Multiple Choice Questions on “Classification of Steam Turbines”.
1. Steam turbine produces useful work in the form of rotation of turbine shaft, by extracting thermal energy from pressurized steam.
a) True
b) False
Answer: a
Clarification: Steam turbines are one of the most important prime movers for power generation. In a steam turbine the potential energy of the steam is transformed into kinetic energy and it is then it is transformed into the mechanical energy of rotation of the turbine shaft.
2. According to the number of pressure stages, steam turbines are classified into _____
a) single cylinder and multi-cylinder
b) single stage and multi-stage
c) mono stage and multi-stage
d) axial and radial
Answer: b
Clarification: On the basis of number of stages, steam turbines are classified into single stage and multi stage turbines. Single stage turbines have only one pressure stage but can have multiple velocity stages. They are used for small power capacities like driving centrifugal compressors or blowers etc. Multistage turbine is a combination of impulse and reaction turbines and they are made for a wide range of power capacities.
3. According to the direction of steam flow, steam turbines are classified into _____
a) axial and radial
b) uniaxial and multi-axial
c) upstream and downstream
d) forward and backward
Answer: a
Clarification: According to the direction of steam flow, turbines are classified into axial and radial turbines. In case of axial turbine, the direction of steam flow is parallel to the axis of the turbine. In radial turbines steam flow direction is perpendicular to the axis of turbine.
4. Turbines with separate rotor shafts for each cylinder placed parallel to each other are known as _____
a) multi-rotor turbines
b) multiaxial turbines
c) single-cylinder turbines
d) multi-utility turbine
Answer: b
Clarification: Multiaxial turbines are multi-cylinder turbines with separate rotor shafts for each cylinder placed parallel to each other. Multi-cylinder turbines in which the rotors are mounted on one shaft and coupled to a single generator are known as single-shaft turbines.
5. On the basis of method of governing, steam turbines are classified into turbines with _____
a) diffuser governing and nozzle governing
b) throttle governing and nozzle governing
c) impulse governing and reaction governing
d) throttle governing and diffuser governing
Answer: b
Clarification: In case of turbines with throttle governing, fresh steam enters through one or more simultaneously operated throttle valves. in turbines with nozzle governing, fresh steam enters through two or more consecutively opening regulators.
6. Which of the following is NOT a valid type of steam turbines, based on heat drop process?
a) Condensing turbines with generator
b) Back pressure turbines
c) Topping turbines
d) Supercritical turbines
Answer: d
Clarification: According to heat drop process, steam turbines are classified into mixed pressure turbines, low pressure turbines, back pressure turbines, topping turbines, back pressure turbines with steam extraction from intermediate stages at specific pressure, condensing turbines with generator, condensing turbines with one or two intermediate stage extractions at specific pressures.
7. Which of the following statement regarding condensing turbines with generators is TRUE?
a) Exhaust steam is supplied to intermediate stages
b) Steam is not extracted from intermediate stages
c) The latent heat of exhaust steam during condensation is utilized in feed water heating
d) Steam at a pressure less than atmospheric is directed to a condenser