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Multiple choice question for engineering

Set 1

1. Fuels are classified as primary and secondary fuel based on the __________
a) Capacity to burn
b) Availability
c) State
d) Occurrence

View Answer

Answer: d [Reason:] Based on the occurrence, fuels are classified as primary fuels and secondary fuels. A primary fuel is available in nature E.g., wood, peat, lignite, natural gas, petroleum etc. A primary fuel is also called as a natural fuel. A secondary fuel is not available in nature, but it is prepared from primary fuel by artificial means e.g. gasoline, diesel, coke gas, blast furnace gas, kerosene etc. A secondary fuel is also known as an artificial fuel.

2. Which fuel is partially carbonized and is considered as primary stage in coal formation?
a) Coal bitumen
b) Anthracite
c) Peat
d) Lignite

View Answer

Answer: c [Reason:] Peat is partially carbonized and decomposed material formed mainly due the transformation of buried vegetation. It is considered as the primary stage in the formation of the coal. It is spongy substance with high moisture content (upto 80%). Hence it has to be dried before use. In dry form it has a calorific value of about 14560 KJ/kg. It consists of 58% C; 6.3% H2; 30.8% O2; 0.9% N2and 4% ash.

3. Which fuel is called secondary stage in the formation of coal?
a) Lignite
b) Bituminous coal
c) Peat
d) Anthracite

View Answer

Answer: a [Reason:] Lignite is the secondary stage in the formation of coal. It is brown in color and hence known as brown coal. It is used as a low grade fuel especially for domestic use and also as a boiler fuel. It is the intermediate stage between bituminous coal and peat. It has a calorific value of about 12500kJ/kg. It consists of 66% C; 5% H2; 20% O2; 1% N2; 1% S and 3.5% ash and other incombustibles.

4. Which fuel is commonly available in both caking and Non-caking forms?
a) Lignite
b) Bituminous coal
c) Peat
d) Anthracite

View Answer

Answer: b [Reason:] Bituminous coal is the most commonly used form of coal. It is available in both caking and non-caking forms. It burns with a yellow flame. It has calorific value of about 32000kJ/kg. It consists of 81%C; 5%H2; 8% O2; 1.5% N2; 1% S; and 3.5% ash. Caking bituminous coal softens and forms a pasty mass if heated at higher temperature. This coal is used to manufacture coke. Non-caking bituminous coal doesn’t soften on heating and hence it is used in steam power plants.

5. Which fuel is the final stage in formation of coal?
a) Bituminous coal
b) Anthracite coal
c) Peat
d) Lignite

View Answer

Answer: b [Reason:] Anthracite coal is called final stage of transformation of buried vegetation into coal. It is non-caking and has highest calorific value of about 35500kJ/kg. It burns at high temperature and is smokeless. It consists of 91% C; 3% H2; 2.5% O2; 0.5% N2; 0.5% S and 2.5% ash. It is also used as a boiler fuel.

6. Which form of fuel is used as domestic form of fuel?
a) Wood
b) Bituminous Coal
c) Dung cake
d) Anthracite coal

View Answer

Answer: a [Reason:] wood is mainly used as a domestic fuel. It has low calorific value of about 10500kJ/kg. It consists of about 48.5% C; 6% H2; 1.5% of ash; 43.5% O2 and 0.5% N2. Wood fuel is used in different forms such as firewood, charcoal, chips, sheets, pellets and sawdust. The particular form used depends upon factors such as source, quantity, quality and application.

7. What is the main purpose of demineralization treatment plant?
a) To remove deposits made on tube
b) To reduce scaling on tube
c) To remove salts
d) To filter the boiler water

View Answer

Answer: c [Reason:] The salts (calcium and magnesium) of hard water have to be removed to overcome all types of effects caused by water on tubes. Demineralization treatment plant generally consists of cat- ion, anion and mixed bed exchangers. These ions are recombined with water to form pure water. Very pure mineralized water becomes highly corrosive once it absorbs oxygen.

8. What type of gear mechanism is provided to rotate the turbine generator shaft?
a) Mutilated gear mechanism
b) Ratchet gear mechanism
c) Barring gear mechanism
d) Planetary gear mechanism

View Answer

Answer: c [Reason:] Barring gear is the mechanism provided to rotate the turbine generator shaft at a very low speed after unit stoppages. Once the steam inlet valve is closed, the turbine comes down towards standstill. When it stops completely, there is a tendency for turbine shaft to deflect or bend if allowed to remain in same position for too long.

9. Which gas cooling is used in large generator units of steam plant?
a) Sulfur dioxide
b) Hydrogen
c) Carbon dioxide
d) Nitrogen

View Answer

Answer: b [Reason:] Hydrogen gas cooling is used for large generator units in steam plant. Because it has the highest heat transfer coefficient of any known heat transfer coefficient of any gas and for its low viscosity which reduces wind-age losses. This system requires special handling during start up, with air in the generator enclosure first displaced by carbon dioxide before filling with hydrogen. This ensures that the highly flammable hydrogen does not mix with oxygen in air.

Set 2

1. What type of boiler is a Lamont boiler?
a) Forced circulation
b) Natural circulation
c) Over-through
d) Positive forced circulation

View Answer

Answer: a [Reason:] A Lamont boiler is a forced circulation water tube boiler. In which the boiler water is circulated through an external pump through long closely spaced tubes of small diameters. The mechanical pump is employed to get an adequate and positive circulation in steam and hot water boilers.

2. What is called as the heart of the Lamont boiler?
a) Water drum
b) Centrifugal pump
c) Furnace
d) Blower

View Answer

Answer: b [Reason:] A centrifugal pump which forms the heart of the Lamont boiler is responsible to circulate water within the boiler system. It receives water from the drum and delivers it to the distribution header. The numbers of headers may differ in numbers and depends on the size and design of each boiler.

3. Through what is feed water from hot-well is passed through, before entering steam and water drum in Lamont boiler?
a) Evaporator tubes
b) Economizer
c) Distributer header
d) Circulating pump

View Answer

Answer: b [Reason:] Feed water from the hot well is passed through the economizer tubes before entering the steam and water drum. During its flow through the economizer tubes, water gains maximum sensible heat from the flue gases escaping to the exhaust.

4. In what form are the boiler’s tube arrange in Lamont boiler?
a) parallel in Vertical
b) Inclined vertically
c) parallel in horizontal
d) Horizontally inclined

View Answer

Answer: c [Reason:] The boiler heating surface includes a number of tubes arranged in a parallel form and the inlet ends are welded to the distributors or the headers. A circulation pressure is to be provided during the installation of the pump as per the boiler design and it should be sufficient to overcome the resistance offered by the tubes.

5. Through which does the even circulation of feed water is possible in Lamont boiler?
a) Nozzles
b) Water trough
c) Feed pump
d) Hose

View Answer

Answer: a [Reason:] An even circulation of feed water in Lamont boiler takes place with the help of nozzles provided at the inlet of the tubes which create the differential pressure adequate to cover the variations occurring at fluctuating loads or uneven firing conditions.

6. What is the pressure range between which Lamont boilers operates?
a) 80-120bar
b) 120-160bar
c) 180-360bar
d) 450-560bar

View Answer

Answer: b [Reason:] The Lamont boiler operates between the pressure range of 120-160bar, due to this natural circulation is limited because of density difference between the liquid and vapor. Hence the external centrifugal pump is used to assist the circulation.

7. In which year was Lamont boiler invented?
a) 1905
b) 1910
c) 1920
d) 1925

View Answer

Answer: d [Reason:] The Lamont boiler was invented by Walter Douglas Lamont in year 1925; He bought the idea from papers to existence. He also introduced the concept of forced circulation boiler. The initial design of Lamont for this boiler confirmed lighter, safer and higher rates of heat transfer.

8. What type of steam is generated by evaporator tube of Lamont boiler?
a) Saturated steam
b) Unsaturated steam
c) Superheated steam
d) Flash steam

View Answer

Answer: a [Reason:] The steam generated by the evaporator tube of the Lamont boiler is saturated steam. If it is directly used in steam turbine, it can cause the corrosion. So the saturated steam sends to the super heater where it increases the temperature of steam.

9. Where is water steam separator drum located in Lamont boiler?
a) Inside of the boiler
b) Right above the furnace
c) Before the feed water pump
d) Outside of boiler

View Answer

Answer: d [Reason:] The steam separator is situated outside of the boiler. In this the mixture of water and steam from the evaporator tube is sent, where it separates the steam and sends it to the super heater. The remaining water is again sent to the economizer.

10. What is the main disadvantage of Lamont boiler?
a) Less flexible in design
b) Low heat transfer rate
c) Formation of bubbles
d) Low steam generation capacity

View Answer

Answer: c [Reason:] The main disadvantage of Lamont boiler is the formation of bubbles. These bubbles come in contact with the inner surface of the heating tubes and subsequently are attached to it. The bubbles attached to the tube surface have higher thermal resistance and consequently reduce the heat flow and steam generation.

11. In which year was Benson boiler was invented?
a) 1918
b) 1920
c) 1921
d) 1922

View Answer

Answer: d [Reason:] Benson boiler is high pressure, drum less, water tube boiler with forced circulation. This was invented by Mark Benson in year 1922. It was Mark Benson who first proposed the idea to compress the water eat supercritical pressure before heating in boiler.

12. What type of boiler is a Benson boiler?
a) Super critical boiler
b) Fire tube boiler
c) Natural circulation boiler
d) Over-through boiler

View Answer

Answer: a [Reason:] Benson boiler is a super critical boiler with pressure range of 225bar to 500bar in which the feed water is compressed to a supercritical pressure and this eliminates the formation of bubbles completely, bubbles do not form because at supercritical pressure the density of water and steam becomes same.

13. What is the capacity of Benson boiler?
a) 180 tonnes/hr & above
b) 150 tonnes/hr & above
c) 250 tonnes/hr & above
d) 300 tonnes/hr & above

View Answer

Answer: b [Reason:] Feed water from the hot-well is forced through the economizer tubes. The hot water enters the radiant section of the evaporator tubs and then passes through convective section of the evaporator tubes. Since the boiler has no drum, thee steam generated in the evaporator enters the super heater tube where it is heated above the critical pressure. So the Steam rising capacity of the boiler is 150tonnes/hr & above.

14. What is the major disadvantage of the Benson boilers?
a) Boiler is big in size
b) Has large storage capacity
c) Deposition of salts
d) Bubble formation

View Answer

Answer: c [Reason:] The major disadvantage of the Benson boiler is that when water transforms into steam in the convective section of the evaporator, salts are deposited in the transformation zone. Hence periodic flashing of evaporator tubes in the convective section is necessary.

15. Why starting valve is closed and valve 2 is opened while taking boiler on range in Benson boiler?
a) Avoid excessive heating of tube
b) To maintain the constant flow of water
c) To avoid pressure built up in tubes
d) To avoid pipe leakages at joints

View Answer

Answer: a [Reason:] The boiler is started from cold by circulating the feed water from the hot well by operating the starting valve. While taking the boiler on range, starting valve is closed and valve 2 is opened. This method avoids excessive heating of tubes.

Set 3

1. PWR stands for ________
a) Power
b) Partially weathered rock
c) Pressurized water Reactor
d) Packaging waste regulations

View Answer

Answer: c [Reason:] PWR stands for pressurized water reactor. A PWR power plant consists of two loops in series. One is the coolant loop called primary loop and other is the water steam or working fluid loop. Pressurized water reactor falls under the category of light water reactor.

2. What does the top of the pressurizer in pressurized water reactor consists of at primary system pressure?
a) Steam
b) Air
c) Water
d) Fluids

View Answer

Answer: a [Reason:] The pressurizer is a pressure vessel with a heater at the bottom and water spray at the top. The top of the pressurizer is filled with steam at primary system pressure. If the primary loop pressure drops, the heater is energized to increase the steam content in the pressurizer and thus increases the pressure of primary cooling system.

3. Select the incorrect statement which supports PWR.
a) Water is used as coolant
b) PWR is stable in operation
c) Uses natural fuel
d) PWR has positive power demand coefficient

View Answer

Answer: c [Reason:] PWR uses enriched fuel making the reactor more compact in size. And due to high negative temperature coefficient, a PWR is stable. Water is used as the coolant. It does have positive power demand coefficient and responds greatly to more power demand.

4. Select the incorrect statement about PWR.
a) High primary circuit pressure requires a strong pressure vessel
b) Corrosion is less in PWR
c) During fuel charging in PWR, the reactor has to be shut down at least for a month
d) PWR results in uneven heating

View Answer

Answer: b [Reason:] Presence of high temperature and high pressure water, the corrosion is severe. This means use of stainless steel adds to further costing. When γ- radiations pass through the pressure vessel it results in uneven heating which induces thermal stresses on vessels.

5. LWR stands for _________
a) Lower water reactor
b) Line water reactor
c) Liquefied water reactor
d) Light water reactor

View Answer

Answer: d [Reason:] The light water reactor is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator – furthermore a solid fissile element is used as fuel. These are most common type of Thermal-neutron reactors.

6. In which reactor is the coolant in direct contact with the heat producing nuclear fuel?
a) Fast breeder reactor
b) Pressurized water reactor
c) Boiling water reactor
d) Heavy water reactor

View Answer

Answer: c [Reason:] In boiling water reactor, the coolant is in direct contact with the heat producing nuclear fuel and boils in the same compartment in which the fuel is located. The reactor pressure is maintained at 70bar. The coolant thus serves the triple function of coolant, moderato and working fluid.

7. How many types of Boiling water reactor cycles are there?
a) 2
b) 3
c) 4
d) 5

View Answer

Answer: b [Reason:] There are three different types of BWR cycles commonly used: Single cycle internal circulation: This system uses internal recirculation system to generate power ranging from 50- 100 MW. Single cycle forced circulation: This type uses a forced circulation system using a circulation system using a circulating pump. The heat in the reactor is used to generate steam. Dual cycle forced circulation: this arrangement has two cycles, steam cycle and gas cycle.

8.Which country invented CANDU heavy water reactor?
a) Canada
b) Germany
c) Russia
d) Bolivia

View Answer

Answer: a [Reason:] The CANDU is a Canadian pressurized heavy water reactor design used to generate electric power. Heavy water nuclear reactors and light water nuclear reactors differ in how they create and manage the complex physics of nuclear fission or atom-splitting which produces the energy and heat to create steam to drive generators.

9. In which of the Following reactor is heavy hydrogen isotope H-2 is used as moderator?
a) Boiling water reactor
b) Pressurized water reactor
c) Candu reactor
d) Thermal reactor

View Answer

Answer: c [Reason:] Heavy water composed of heavy hydrogen isotope H-2 is used as a moderator and coolant in some power and research reactors. These reactors use heavy water as a moderator and primary coolant and light water as secondary coolant.

10. CANDU stands for ____________
a) Canadian Natural Darmstadtium Uranium
b) Canadian Natural Deuterium Uranium
c) Canadian Natural Dubnium Uranium
d) Canadian Natural Dysprosium Uranium

View Answer

Answer: b [Reason:] The CANDU, for Canada Deuterium Uranium, is a Canadian pressurized heavy water reactor design used to generate electricity. The acronym refers to its deuterium oxide (heavy water) moderator and its use of (originally natural) Uranium fuel.

11. Which reactor consists of both fertile and fissile material?
a) Fast breeder reactor
b) Pressurize water reactor
c) Boiling Water reactor
d) Converter reactor

View Answer

Answer: a [Reason:] If the reactor produces more fissionable material than it consumes, it is fast breeder reactor. The breeder fuel consists of both fertile and fissile material. The number of neutrons released is sufficient to propagate the fission reaction and to produce more fissionable material by conversion of fertile isotopes to fissile isotopes.

12. What is acronym of LMFBR?
a) Liquid molecular fast boiling reactor
b) Liquid metal fast breeder reactor
c) Liquefied metal fast boiling reactor
d) Liquid metal fast boiling reactor

View Answer

Answer: b [Reason:] LMFBR stands for Liquid metal fast breeder reactor. The fuel consists of 80% by weight of UO2 by weight of PuO2 in small diameter stainless steel clad tubes operating at temperature of 670oC – 700oC.

13. GCFBR stands for ____________
a) Gas conditioned fast breeder reactor
b) Gas cooled fast breeder reactor
c) Gas conditioned fast boiling reactor
d) Gas cooled fast breeder reactor

View Answer

Answer: b [Reason:] The GCFBR stands for Gas cooled fast breeder reactor; it is cooled by helium gas at 85bar. Also helium doesn’t become radioactive under neutron bombardment AND hence secondary coolant is not needed.

14. Using Helium gas in GCFBR has many advantages?
a) True
b) False

View Answer

Answer: a [Reason:] Using helium as coolant posses less severe metallurgical and safety problems. Heat transfer coefficient of helium is much superior than sodium with artificial roughening of fuel rod surfaces. Low doubling time as compared to sodium cooled reactors.

15. Which reactor uses orthometaerhenyl and paratherphenyl as coolant and moderator?
a) Liquid metal fast breeder reactor
b) Gas cooled fast breeder reactor
c) Organic substance cooled reactor
d) CANDU Heavy water reactor

View Answer

Answer: c [Reason:] Organic substance cooled reactor uses enriched uranium as fuel and a mixture of orthometaterhenyl and paratherphenyl as coolant and moderator, and boron control rods, generating 11.4 MW capacities with an overall efficiency of 25%.

16. Nuclear plant is located near the area where cooling water is available.
a) True
b) False

View Answer

Answer: a [Reason:] Some of the major factors to locate a nuclear station considered are, Availability of cooling water, transportation facilities, Distance from load centre, safety, radioactive waste, disposal facility and foundation requirement.

Set 4

1. Select the formula for total power pt?
energy-engineering-questions-answers-velocity-power-wind-q1

View Answer

Answer: a [Reason:] energy-engineering-questions-answers-velocity-power-wind-q1-exp

2. Why blade velocity of wind turbine varies?
a) Due to varying wind speeds
b) Long length of blades
c) Due to the height of mount
d) Because of hotness of Sun

View Answer

Answer: b [Reason:] Wind turbine experiences change in velocity dependent upon the blade inlet angle and the blade velocity. Since the blades are long, the blade velocity varies with the radius to a greater degree than steam or gas-turbine blades and the blades are therefore twisted.

3. When was the Halladay wind mill introduced?
a) 1920
b) 1923
c) 1854
d) 1864

View Answer

Answer: c [Reason:] Invented by Daniel Halladay in 1854, the Halladay Standard was the first commercially successful self-governing windmill in 1854 was the firms of Halladay, McCray & Co., Ellington, Conn. Partners in the company were inventor Daniel Halladay, John Burnham and Henry McCray.

4. How much ideal efficiency should practical turbine have?
a) 10 – 12%
b) 18 – 25%
c) 80 – 90%
d) 50 – 70%

View Answer

Answer: d [Reason:] As wind turbine wheel cannot be completely closed, and because of spillage and other effects, practical turbines have 50 to 70% of the ideal efficiency. The real efficiency η is the product of this and ηmax and is the ratio of an actual to total power. P = ηPtot.

5. How many types are acting on propeller type wind mill?
a) 2
b) 3
c) 4
d) 5

View Answer

Answer: a [Reason:] There are two types of forces operating on the blades of a propeller type wind turbine. They are the circumferential forces in the direction of wheel rotation that provide the torque and the axial forces in the direction of the wind stream that provide an axial thrust that must be counteracted by proper mechanical design.

6. Calculate the air density, when 10m/s wind is at 1std atmospheric pressure and 15oC?
a) 1.226 kg/m3
b) 1.033 kg/m3
c) 2.108 kg/m3
d) 0.922 kg/m3

View Answer

Answer: a [Reason:] For air, gas constant R = 287 J/kgK, 1atm = 1.01325 X 105 Pa Air density, ρ = P/RT = (1.01325 ×10⁵)/(287(15+273.15)) = 1.226 kg/m3.

7. Calculate the air density when 18m/s wind is at 1std atmospheric pressure and 34oC?
a) 1.149 kg/m3
b) 1.9 kg/m3
c) 2.88 kg/m3
d) 5.89 kg/m3

View Answer

Answer: a [Reason:] For air, gas constant R = 287 J/kgK, 1atm = 1.01325 X 105 Pa Air density, ρ = P/RT = (1.01325 ×10⁵)/(287(34+273.15)) = 1.149 kg/m3

8. What is the total power produced if the turbine diameter is 120m?
a) 0.277 KW
b) 1.224 KW
c) 4.28 KW
d) 0.89 KW

View Answer

Answer: a [Reason:] Total power P, P = 0.245 X (πD2/4) = 0.245 X (π (120)3/4) = 0.277 KW.

9. What is the total power produced if the turbine diameter is 90m?
a) 0.155KW
b) 0.982 KW
c) 1.452 KW
d) 3.12 KW

View Answer

Answer: a [Reason:] Total power P, P = 0.245 X (πD3/4) = 0.245 X (π (90)3/4) = 0.155KW.

Set 5

1. In which wind measuring device a tubular piece of thin flexible fabric hanged vertically to determine direction?
a) Wind socks
b) Weather vane
c) Pin wheels
d) Anemometers

View Answer

Answer: a [Reason:] Wind sock is a very basic device that measure wind direction and provide a rough idea of the wind’s intensity. A wind sock is a tubular piece of fabric or thin, flexible fabric attached to a pole. When there is no wind, the fabric hangs vertically from the attached pole.

2. A device which is used as device for showing direction wind as well used as a decorative purpose?
a) Wind socks
b) Weather vane
c) Pin wheels
d) Anemometers

View Answer

Answer: b [Reason:] A weather vane works similarly to wind sock. Instead of a tubular sock, the weather vane is made by placing a horizontal pole at the top of vertical pole. The poles are joined together so that the horizontal pole has a flattened, vertical end that reacts to wind.

3. Which is the wind direction showing device that spins perpendicularly?
a) Wind socks
b) Weather vane
c) Pin wheels
d) Anemometers

View Answer

Answer: c [Reason:] A pinwheel is a windmill-style turbine that spins perpendicularly to the wind affecting it. Like wind socks and weather vanes, a pinwheel can be attached to a rotating base. This allows the pinwheel to change direction with the wind, and it will spin facing into the oncoming wind.

4. Which is the device that measures wind direction and its intensity?
a) Wind socks
b) Weather vane
c) Pin wheels
d) Anemometers

View Answer

Answer: d [Reason:] An anemometer is any device that measures wind direction and intensity. It may be simple, such as the devices described above, or it may be a complex, computer-aided machine that measures and records wind patterns over time. More advanced anemometer machines are used to aid in professional weather reporting and air traffic control.

5. What units does the anemometer measure in?
a) Feet per minute
b) Liters per minute
c) Centimeters per minute
d) Meter per seconds

View Answer

Answer: a [Reason:] The anemometer measures in feet per minute, or FPM. The rotation is sensed by a magnetic or optical sensor that converts the signal to FPM measurement. An arrow on the vane head identifies the direction the airflow must travel through the vane to obtain proper measurements.

6. Which of the following type of turbine or the rotor requires relatively low velocity winds for operation?
a) Cup anemometer
b) Savonius rotor
c) Darrieus type rotor
d) Magnus effect rotor

View Answer

Answer: b [Reason:] Savonius rotor is a simple WEC system which woks like a cup anemometer. This type was invented by S.J. Savonius in the year 1920. It requires relatively low velocity winds for operation. It consists of two half cylinders facing opposite directions forming as S-shaped cross section.

7. Which type of axis does a Savonius Rotor has?
a) Horizontal axis
b) Mediolateral axis
c) Vertical axis
d) Lateral Axis

View Answer

Answer: c [Reason:] A Savonius wind energy conversion system has a vertical axis and hence eliminates the expensive power transmission system from the rotor to the axis. Since it is a vertical axis machine it does not matter much about the wind direction.

8. Why is Savonius rotor not suitable for installation?
a) Because of long drive shaft
b) Because of its low capacity motor
c) Because of its typical blade design
d) Due to the light material it is made of

View Answer

Answer: a [Reason:] Savonius rotor is not useful for very high installation because of long drive shaft problems. Bracing of the topmost bearing above the rotor of a very tall vertical axis machine is difficult requiring very long guy wires.

9. When was the Darrieus type machine invented?
a) 1925
b) 1932
c) 1929
d) 1948

View Answer

Answer: a [Reason:] Darrieus type machine was invented originally and patented in 1925 by G.J.M> Darrieus, a French engineer. The Darrieus wind mill is a vertical axis machine that has the same advantage of a modern rapidly rotating propeller type windmill, by use of an efficient airfoil, effectively intercepts large area of wind with a small blade area.

10. What form of force acts on the blades of Darrieus machine?
a) Pure tension
b) Compression
c) Shear force
d) Air resistance force

View Answer

Answer: a [Reason:] Darrieus wind mill has two or three thin, curved blades with airfoil cross section and constant chord length. Both ends of blades are attached to a vertical shaft. Thus the force in the blade due to rotation is pure tension.

11. Which type of vertical wind machine has relatively low solidity and low starting torques?
a) Cup anemometer
b) Savonius rotor
c) Darrieus type rotor
d) Magnus effect rotor

View Answer

Answer: c [Reason:] Darrieus type rotors are lift devices characterized by curved blades with air foil cross sections. They have relatively low solidity and low starting torques, but high tip to wind speeds and therefore relatively high power outputs per given rotor weight and cost.

12. Which type of vertical wind machine consists of spinning cylinders?
a) Cup anemometer
b) Savonius rotor
c) Darrieus type rotor
d) Magnus effect rotor

View Answer

Answer: d [Reason:] Magnus effect rotor concept was first demonstrated by Magnus in 1912. It consists of spinning cylinders. When cylinders spun in wind stream, translational forces are produced perpendicular to the wind stream by the Magnus effect. Such a device can be used to propel ships or land vehicles.

13. Aero turbine is the fraction of power in the wind through the swept area which is converted into useful mechanical shaft power is called _____________
a) Coefficient of performance
b) Coefficient of variation
c) Coefficient of lift
d) Coefficient of spin

View Answer

Answer: a [Reason:] The coefficient of performance of an aero turbine is the fraction of power in the wind through the swept area which is converted into useful mechanical shaft power. Cp for horizontal axis wind machine has theoretical maximum value = 0.593.