When the nozzle operates with the maximum mass flow, the nozzle is said to be
Choked
Under-damping
Over-damping
None of these
Correct Answer :
A. Choked
Related Questions
Tertiary air is the air used to
Provide air around burners for obtaining optimum combustion
Transport and dry the coal
Cool the scanners
Convert CO (formed in lower zone of furnace) into CO₂ at higher zone.
Which of the following statement is correct for steam turbines as compared to reciprocating steam engines?
A steam turbine develops higher speeds
The efficiency of steam turbine is higher
The steam consumption is less
All of these
For water, at pressures below atmospheric;
Melting point rises slightly and boiling point drops markedly
Melting point rises markedly and boiling point drops markedly
Melting point drops slightly and boiling point drops markedly
Melting point drops slightly and boiling point drops slightly
Which of the following is a water tube boiler?
Lancashire boiler
Babcock and Wilcox boiler
Locomotive boiler
Cochran boiler
Which of the following statement is wrong?
The mechanical draught reduces the height of chimney.
The natural draught reduces the fuel consumption.
A balanced draught is a combination of induced and forced draught.
All of the above
There is always some steam left in the clearance space from the previous stroke. This steam left in the clearance space is called
Wet steam
Saturated steam
Superheated steam
Cushion steam
Which of the following coals has the highest calorific value?
Anthracite coal
Bituminous coal
Lignite
Peat
The efficiency of reaction turbine is maximum when (where α = Angle made by the absolute velocity V at inlet)
Vb = 0.5 V cosα
Vb = V cos α
Vb = 0.5 V² cosα
Vb = V² cosα
The critical pressure ratio for initially superheated steam is __________ as compared to initially dry saturated steam.
More
Less
Same
None of these
The missing quantity per stroke is equal to
Cylinder feed indicated mass of steam
Cylinder feed + indicated mass of steam
Mass of cushion steam + indicated mass of steam
Mass of cushion steam + cylinder feed
The diameter of a cylindrical shell of a Scotch marine boiler varies from
1.5 to 2 m
2.5 to 3.5 m
3.5 to 4.5 m
None of these
The ratio of the isentropic heat drop to the heat supplied, is called
Reheat factor
Stage efficiency
Internal efficiency
Rankine efficiency
By compounding the expansion of steam in two or more cylinders, the ratio of expansion
Does not change
Increases
Decreases
None of these
Caking coals are those which
Form lumps or masses of coke
Burn freely
Show little or no fusing action
Burn completely
The draught may be produced by a
Mechanical fan
Chimney
A steam jet
All of these
The critical pressure ratio is given by (where p₁ = Initial pressure of steam, and p₂ = Pressure of steam at throat or critical pressure)
p₁. p₂
p₁/p₂
p₂/p₁
p₁ + p₂
In a steam engine, superheated steam from the boiler is fed into the steam chest at a pressure of
10 atmospheres
20 atmospheres
30 atmospheres
40 atmospheres
The effect of friction on the flow of steam through a nozzle is to
Decrease the mass flow rate and to increase the wetness of steam
Increase the mass flow rate and to increase the exit temperature
Decrease the mass flow rate and to decrease the wetness of steam
Increase the exit temperature without any effect on mass flow rate
While steam expands in turbines, theoretically the entropy
Remains constant
Increases
Decreases
Behaves unpredictably
Natural water circulation, by convection in water tube boilers, with increase in pressure of boiler
Increases
Decreases
Remain unaffected
First increases and then decreases
Boiler stays are used to
Prevent flat surfaces under pressure from tearing apart
Take care of failure in shear
Take care of failure in compression
Provide support for boiler
The maximum steam pressure in a Locomotive boiler is limited to
0.18 MN/m²
1.8 MN/m²
18 MN/m²
180 MN/m²
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 fire tubes in a Locomotive boiler has _________ diameter.
4.75 mm
5.47 mm
7.45 mm
47.5 mm
The shell diameter of a Locomotive boiler is
1 m
1.5 m
2 m
2.5 m
The impulse turbine rotor efficiency will have a maximum value of 0.5 cos 2α, where α is the nozzle exit flow angle, if the
Blades are equiangular
Blade velocity coefficient is unity
Blades are equiangular and frictionless
Blade solidity is 0.65
A safety valve usually employed with stationary boilers is
Lever safety valve
Dead weight safety valve
High steam and low water safety valve
All of these
In which of the following boilers, the draught in furnace is increased by utilising exhaust steam from engine
Lancashire boiler
Locomotive boiler
Babcock and Wilcox boiler
Benson boiler
The selection of type and size of a steam boiler depends upon
The power required and working pressure
The geographical position of the power house
The fuel and water available
All of the above
For combustion of a fuel, following is essential
Correct fuel air ratio
Proper ignition temperature
O₂ to support combustion
All the three above