# Mechanical Engineering :Steam online Test

For a parson’s reaction turbine, are fixed blade angles at inlet and exit respectively and are the moving blade angles at entrance and exit respectively. Then
and 

< and >

Which is the false statement in connection with a parson’s reaction turbine
Both fixed and moving blades are identical
The velocity diagram is symmetrical about a vertical centre line
The relative velocity of steam either remains constant or reduces slightly when the steam glides over moving blades
The turbine has 50% degree of reaction
/
Curtis turbine
De laval turbine
Parson turbine
In parson’s reaction turbine, the maximum blading efficiency is obtained when

cos
cos2

Where is the blade speed ratio and is the nozzle angle
In parson’s reaction turbine, the maximum rate of doing work per kg of steam per second equals
0.5 Cb2
Cb2
2 Cb2
4 Cb2
Where Cb is the blade speed
The maximum value of diagram efficiency for parson’s reaction turbine is given by________
Ljungstorm turbine is
Velocity compounded impulse turbine
Single rotor reaction turbine
Tangential flow reaction turbine
Which of the following turbines has all the blades revolving?
Parson’s turbine
Rateau turbine
Ljungstorm turbine
De-laval turbine
The outward radial flow turbine in which there are two rotors rotating in opposite directions is known as
Contilever turbine
Ljungstrom turbine
Pass-out turbine
Match list I (turbines) with list II (classification) and select the correct answer using the codes given below the lists: List IList IIparson’s de laval rateu curtis1.pressure compounded 2.reaction 3.simple impulse 4.velocity compounded
(A,3), (B,2), (C,1), (D,4)
(A,2), (B,3), (C,1), (D,4)
(A,2), (B,3), (C,4), (D,1)
(A,3), (B,2), (C,4), (D,1)
A curtis state, a rateau stage and a 50% reaction stage in a steam turbine are examples of
Different types of impulse stages
Different types of reaction stages
A simple impulse stage, a velocity compounded impulse stage and a reaction stage
A velocity compounded impulse stage, a simple impulse stage and a reaction stage
Match list I (different turbine stages) with list II (turbines) and select the correct answer using the codes given below the lists: List IList II50% reaction stage two stage velocity compounded turbine single stage impulse two stage pressure compounded turbinerateau parson curtis de laval hero
(A,5), (B,1), (C,2), (D,3)
(A,5), (B,3), (C,2), (D,1)
(A,2), (B,3), (C,4), (D,1)
(A,3), (B,1), (C,4), (D,2)
Which of the following statements are correct? 1.impulse turbine rotor blades are thick at the centre 2.rateau turbine is more efficient than Curtis turbine 3.blade velocity coefficient for an impulse turbine is of the order of 60% Select the correct answer using the codes given below:
1, 2 and 3
1 and 2
1 and 3
2 and 3
The correct sequence of the given steam turbine in the ascending order of the efficiency at their design points is
Rateau,de laval,parson’s, curtis
Curtis, de-laval, rateau, parson’s
De-laval, curtis, rateau, parson’s
Parson’s, curtis, rateau, de-laval
Mark the wrong statement
Impulse blades area of the plate or profile type and are symmetrical
The steam velocity and the blade speed for a reaction turbine are more than those for an impulse turbine
For a reaction turbine, the efficiency curve is reasonably flat in the region of maximum value of diagram efficiency
The number of stages for a reaction turbine are much greater than those for an impulse turbine of the same power
In steam terminology, diaphragm refers to
Separating wall between rotors carrying nozzles
Ring of guide blades between rotors
Partition between low and high pressure sides
Flange connecting the turbine exit to the condenser
In a single stage impulse wheel, the residual velocity loss expressed as a percentage of isentropic heat drop is about
2-4%
5-8%
10-12%
15-20%
High moisture content in the last stages of a turbine leads to
Low thermal efficiency of plant
Better efficiency of condensing unit
Unbalanced rotor
Reheat cycle is essential in a steam power plant to
Utilize the heat of flue gases
Heat the feed water on its way to boiler
Increase the plant efficiency
Restrict the moisture content in the low pressure stages of turbine within the limits of 10-12%
Which aspect is not true in the context of reheat cycle for a steam turbine?
There is increase in specific steam consumption
Steam has less moisture content in the low pressure stages of the turbine
Within certain limits, there is slight improvement in thermal efficiency
Use justified only in plants with high capacity
The reheat cycle power plant is mainly adopted to
Improve thermal efficiency
Decrease the moisture content in low pressure stages to safe value
Decrease the capacity of condenser
Recover the waste heat of boiler
In a steam power plant, feed water heater is a heat exchanger to preheat feed water by
Live steam from the generator
Hot air from the air preheater
Hot flue gases coming out of the boiler furnace
Extracting steam from the turbine
The term bleeding in a steam turbine refers to
Leakage of steam
Steam doing no useful work
Steam extracted for preheating feed water
Removal of wet steam in the low pressure stages of turbine
The percentage of steam bled at certain section of the turbine and subsequently using it for heating the feed water being supplied to the boiler is about
5%
8%
12%
20%
In the regenerative arrangement, the vapour extracted or bled from turbine is used for
Preheating of air
Preheating of fuel
Heating feed water being supplied to boiler
Reheating steam to be supplied to low pressure stages of the turbine
Which aspect is not true in the context of bleeding?
Increase in thermodynamic efficiency of plant
Increase in work output from turbine
Reduction in thermal stresses in the boiler
Complicated and less flexible system
A regenerative steam cycle renders
Increased work output per unit mass of steam
Decreased work output per unit mass of steam
Increased thermal efficiency
Decreased work output per unit mass of steam as well as increased thermal efficiency
Consider an actual regenerative rankine cycle with one open feed water heater. For each kg steam entering the turbine, m kg of steam with specific enthalpy h1 is bled from the turbine. If the specific enthalpy of liquid water entering the heater is h2, then specific enthalpy h3 of saturated liquid leaving the heater is equal to
mh1-(h2-h1)
h1-m(h2-h1)
h2-m(h2-h1)
mh2-(h2-h1)
For a given set of operating pressure limits of a rankine cycle, the highest efficiency occurs for
Saturated cycle
Superheated cycle
Reheat cycle
Regenerative cycle
The isentropic enthalpy drop in moving blade is two-thirds of the isentropic enthalpy is fixed blades of a turbine. The degree of reaction will be
0.4
0.6
0.66
1.66
In an impulse reaction turbine stage, the heat drops in fixed and moving blades are 15 kJ/kg and 30 kJ/kg respectively. The degree of reaction for this stage will be
1/3
½
2/4
¾
The ratio of cumulative enthalpy drop to isentropic enthalpy drop is known as
Overall efficiency
Degree of reaction
Gross stage efficiency
Reheat factor
The value of reheat factor varies from
1.02 to 1.06
1.1 to 1.5
1.5 to 2.0
0.5 to 1.0
The overall efficiency ,stage efficiency  and the reheat factor R are correlated by the edentity
R
1/R

R2
The average state of steam during its expansion in a multi-stage turbine is shown by
Willan’s line
Wilson line
Line of condition
Saturated curve
Goverening of steam turbines can be done by the following: nozzle control throttle control providing additional valve and passage The correct answer will be
1, 2 and 3
1 and 2
2 and 3
1 and 3
Indicate the method commonly used for the governing of steam turbines
Throttle governing
Cut off governing
Nozzle control governing
By-pass governing
Which of the followings is the least efficient method of governing steam-turbines?
Throttle governing
By-pass governing
Nozzle control governing
Combined nozzle and by-pass governing
Efficiency of a nozzle governed turbine is affected mainly by losses due to
Throttling
Interstage pressure drop
Condensation in last stages
Consider the following statements regarding the nozzle governing of steam turbines working nozzles receive steam at full pressure high efficiency is maintained at full loads stage efficiency suffers due to partial admission in practice,each nozzle of the first stage is governed individually Which of these statements are correct?
1, 2 and 3
2, 3 and 4
1, 3 and 4
1, 2 and 4
The operating pressure range of a pass out turbines is
10-20bar
20-30bar
30-50bar
50-80bar
In a back pressure turbin, the steam exhaust is
Below atmospheric pressure
At atmospheric pressure
Above atmospheric pressure
Discharge of steam can be at any pressure
In thermal power plants, the deaerator is used mainly to
Remove air from condenser
Increase feed water temperature
Reduce steam pressure
Remove dissolved gases from feed water
Which aspect may or may not be true regarding the advantage gained by using a condenser in a steam power plant?
Expansion of steam to a lower back pressure
Increase in available enthalpy drop and consequently more work output
Reduction in steam consumption per kW-hour
Fuel economy and safety from thermal stresses in the boiler shell
Which one of the followings is a wrong statement?
The employment of condenser permits the expansion of steam to a pressure lower than atmospheric pressure
The thermodynamic efficiency of a condensing steam turbine unit is higher than that of a non-condensing one
The vacuum in a condenser is a function of both absolute pressure and the barometric pressure
The ratio of actual vacuum in the condenser to ideal vacuum is called condenser efficiency
Which aspect is not true in the context of a jet condenser?
More intimate mixing of steamand cooling water
Air extraction pump requires high power
Requires considerable space for erection
Equipment simple and low in cost
The maximum limit of vacuum attained in a jet condenser is about
55 cm of Hg
60 cm of Hg
65 cm of Hg
70 cm of Hg
All of the following statements about surface condenser are correct,except
High vacuum can be attained and greater plant efficiency is achieved
Condensate can be salvaged and used for boiler feed
High capital and maintenance cost
Maximum chances of losing vacuum
Suitable for high capacity units
In a surface used in steam power station, under cooling of condensate is undersirable as this would
Not absorb the gases in steam
Reduce efficiency of the steam
Increase the cooling water requirements
Increase the thermal stresses in the condenser
/
(A,4), (B,5), (C,2), (D,1), (E,3)
(A,2), (B,3), (C,1), (D,4)
(A,2), (B,3), (C,4), (D,1)
(A,3), (B,2), (C,4), (D,1)
Description:

paper has 50 questions which are required to be finished in an hours time approximately.

By: fazzu
737 days 2 hours 58 minutes ago

good questions

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