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WorksheetsSTEAM TURBINES
Total questions: 50
Worksheet time: 38mins
The pressure compounded impulse turbine as compared to velocity compounded turbine require __________ number of stages.
Same
Less
More
None of these
In an impulse turbine.......
The steam is expanded in nozzles only and there is a pressure drop and heat drop
The steam is expanded both in fixed and moving blades continuously
The steam is expanded in moving blades only
The pressure and temperature of steam remains constant
The person's reaction turbine has........
Only moving blades
Only fixed blades
Identical moving and fixed blades
Fixed and moving blades of different shape
The stage efficiency (ηs)is given by ( where ηb=blading efficiency and ηn =nozzle efficiency )........
ηb/ηn
ηn/ηb
ηb.ηn
ηn/ηb
The reheating of steam in a turbine........
Increases the work done through the turbine
Increases the efficiency of the turbine
Reduces wear on the blades
All of the above
The thermal efficiency of a steam turbine is......than that of steam engine
Lower
Higher
Same
None of the above
Da-laval turbines are mostly used.......
Where low speeds are required
For small power purposes and and low speeds
For small power purposes and and high speeds
For large power purposes
The degree of reaction is defined as the ratio........
Heat drop in the fixed blades to the heat drop in the moving blades
Heat drop in the moving blades to the heat drop in the fixed blades
Heat drop in the moving blades to the total heat drop in the fixed blades
Heat drop in the fixed blades to the total heat drop in the moving blades
The maximum efficiency of a Da-Lavel turbine is (where α= nozzle angle)........
Sin^2α
Cos^2 α
Tan^2 α
Cot^2 α
The ratio of isentropic heat drop to the heat supplied is called........
Rankine efficiency
Stage efficiency
Reheat factor
Internal efficiency
Steam turbine is........combustion thermal prime mover
Internal
External
Both internal and external
None of the above
There is enthalpy drop only in.......blades in case of an impulse steam turbine
Fixed
Rotating
Moving
All of the above
The efficiency of steam turbine may be improved by........
Reheating of steam
Regenerative feed heating
Binary vapour plants
Any of the above
The ratio of work done on the blades per kg of steam to the energy supplied to the blades is called........
Gross or stage efficiency
Diagram or blading efficiency
Nozzle efficiency
Mechanical efficiency
In a reaction turbine........
The steam is allowed to expand in the nozzle, where it gives a high velocity before it enters the moving blades
The expansion of steam takes place partly in the fixed blades and partly in the moving blades
The steam is expanded from a high pressure to a condenser pressure in one or more nozzles
The pressure and temperature of steam remains constant
The action of steam in a steam turbine is......
Static
Dynamic
Static and dynamic
Neither static nor dynamic
The ratio of total useful heat drop to the total isentropic heat drop is called.......
Internal efficiency
Rankine efficiency
Stage efficiency
Efficiency ratio
The person's reaction turbine, the degree of reaction is........
20%
30%
40%
50%
In impulse turbine, when friction is neglected, the relative velocity of steam at outlet tip of the blade is.......the relative velocity of steam at inlet tip of the blade
Equal to
Less than
Greater than
None of the above
The blade friction in the impulse turbine reduces the velocity of steam by......while it passes over the blades
10% to 15%
15% to 20%
20% to 30%
30% to 40%
In a reaction turbine, when the degree of reaction is zero, then there is......
No heat drop in the moving blades
No heat drop in the fixed blades
Maximum heat drop in the moving blades
Maximum heat drop in the fixed blades
Efficiency of Rankine cycle can be increased by
Decreasing initial steam pressure and temperature
Increasing exhaust pressure
Decreasing exhausts pressure
Increasing the expansion ratio
In an impulse turbine
The steam is expanded in nozzles only and there is a pressure drop and heat drop
The steam is expanded both in fixed and moving blades continuously
The steam is expanded in moving blades only
The pressure and temperature of steam remains constant
The blade friction in the impulse turbine reduces the velocity of steam by __________ while it passes over the blades.
10 to 15%
15 to 20%
20 to 30%
30 to 40%
In impulse turbines, when friction is neglected, the relative velocity of steam at outlet tip of the blade is _________ the relative velocity of steam at inlet tip of the blade.
Equal to
Less than
Greater than
None of these
Steam turbines are used for
Large marine propulsion
Electric power generation
Direct drive of fans, compressors, pumps
All of these
A single stage impulse turbine with a diameter of 1.2 m runs at 3000 rpm If the blade speed ratio is 0.42, then the inlet velocity of steam will be
79 m/s
188 m/s
450 m/s
900 m/s
For a Parson's reaction turbine, if α₁ and α₂ are fixed blade angles at inlet and exit respectively and β₁ and β₂ are the moving blade angles at entrance and exit respectively, then
α₁ = α₂ and β₁ = β₂
α₁ = β₁ and α₂= β₂
α₁ < β₁ and α₂ > β₂
α₁ = β₂ and β₁ = α₂
In a reaction turbine when the degree of reaction is zero, then there is
No heat drop in moving blades
No heat drop in fixed blades
Maximum heat drop in moving blades
Maximum heat drop in fixed blades
Parson's reaction turbine is a __________ reaction turbine.
40 percent
50 percent
60 percent
70 percent
A compound steam engine in which the high pressure and low pressure cylinders have common piston rod, is called
Receiver type compound engine
Tandem type compound engine
Woolf type compound engine
None of these
In a reaction turbine, when steam flows through the fixed blades
Pressure increases while velocity decreases
Pressure decreases while velocity increases
Pressure and velocity both decreases
Pressure and velocity both increases
The relative efficiency is defined as the
Ratio of thermal efficiency to Rankine efficiency
Ratio of brake power to the indicated power
Ratio of heat equivalent to indicated power to the energy supplied in steam
Product of thermal efficiency and Rankine efficiency
The purpose of governing in steam turbines is to
Maintain the speed of the turbine
Reduce the effective heat drop
Reheat the steam and improve its quality
Completely balance against end thrust
The ratio of the work-done on the blades per kg of steam to the total energy supplied per stage per kg of steam is called
Blading efficiency
Nozzle efficiency
Stage efficiency
Mechanical efficiency
In a 50% reaction turbine stage, tangential component of absolute velocity at rotor inlet is 537 m/s and the blade velocity is 454 m/s. The power output in kW of steam will be
302 kW
260 kW
282 kW
296 kW
In an ideal impulse turbine, the
Absolute velocity at the inlet of moving blade is equal to that at the outlet
Relative velocity at the inlet of the moving blade is equal to that at the outlet
Axial velocity at inlet is equal to that at the outlet
Whirl velocity at inlet is equal to that at the outlet
A throttle governed steam engine develops 15 kW with 280 kg per hour of steam and 35 kW with 520 kg per hour of steam. The steam consumption in kg per hour when developing 20 kW will be nearly
150 kg/h
210 kg/h
280 kg/h
340 kg/h
An impulse turbine as compared to a reaction turbine, for a given power has _________ row of blades.
Equal
Less
More
None of these
The action of steam in a steam turbine is
Static
Dynamic
Static and dynamic
Neither static nor dynamic
De-Laval turbines are mostly used
Where low speeds are required
For small power purposes and low speeds
For large power purposes
For small power purposes and high speeds
Blading efficiency is also known as
Stage efficiency
Diagram efficiency
Nozzle efficiency
None of these
Steam turbines may be classified according to
Direction of steam flow
Number of stages
Mode of steam action
All of these
In a compound steam engine, the first stage of expansion is carried out in a high pressure cylinder whereas the last expansion is completed in low pressure cylinder. The diameter of high pressure cylinder is _________ the low pressure cylinder.
Equal to
Less than
More than
None of these
In an impulse reaction turbine, the pressure drops gradually and continuously over
Fixed blades
Moving blades
Both fixed and moving blades
None of these
The pressure compounded impulse turbine as compared to velocity compounded turbine require __________ number of stages.
Same
Less
More
None of these
Degree of reaction is defined as the ratio of
Heat drop in fixed blades to the heat drop in moving blades
Heat drop in moving blades to the heat drop in fixed blades
Heat drop in moving blades to the heat drop in fixed blades plus heat drop in moving blades
Heat drop in fixed blades plus heat drop in moving blades to the heat drop in moving blades
The isentropic enthalpy drop in moving blade is two-third of the isentropic enthalpy drop in fixed blades of a turbine. The degree of reaction will be
0.4
0.56
0.67
1.67
A turbine is said to have an axial discharge when the steam leaves the blade tip at _________ to the direction of the blade motion.
60°
90°
180°
270°
A steam turbine, in which a part of the steam after partial expansion, is used for process heating and the remaining steam is further expanded for power generation, is known as
Back pressure turbine
Pass out turbine
Low pressure turbine
Impulse turbine
