DEPARTMENT OF MECHANICAL ENGINEERING
BASIC CIVIL & MECHANICAL ENGINEERING TWO MARKS QUESTION AND ANSWERS
UNIT-III
POWER PLANTS, PUMPS AND TURBINES
1. What are the classifications of power plants based on non-renewable source of energy?
o Steam power plant.
o Nuclear power plant.
o Diesel power plant.
o Gas turbine power plant.
2. What are the classifications of power plants based on renewable source of energy?
o Hydro-electric power plant.
o Solar power plant.
o Wind power plant.
o Tidal power plant.
3. Write the steam power plant circuits.
o Coal and ash
o Air and flue gas
o Feed water and steam.
o Cooling water circuit.
4. What is the function of economiser?
The economiser is used to pre-heat the feed water.
5. What is the function of super heater?
The function of super heater is used to super heat the saturated steam and to supply the steam to turbine.
6. What are the advantages of thermal power plants?
o Power can be generated continuously.
o Power plant can withstand the varying load.
o Initial cost low
o The construction period for the power plant is minimum.
7. What are the dis-advantages of thermal power plants?
o Power generation cost is high.
o Handling of coal is a major problem.
o Handling of coal is a major problem.
o Life of the plant is low.
o Plant efficiency is less.
8. What is the function of penstock?
Penstock is the pipe made up of steel or concrete used to carry water from the dam to power house.
9. What is meant by trash rack?
Trash rack is provided to prevent the debris from getting entry to power house. This consists of number of steel bars and it is placed across the intake to prevent debris.
10. What is meant by draft tube?
Draft tube is an integral part of reaction turbine. Draft tube connects the runner exit to tail race. The area of the draft tube is same as that of the runner to avoid shock and is circular cross section. The water after doing work on the turbine runner passes through the draft tube.
11. Write the advantages of hydro electric power plant. o This plant uses water for power generation.
o Water is easily available.
o Beside power generation, this also provides benefits like irrigation, flood control, affore
station-culture.
o Fuel cost is eliminated.
o Plants are automated and hence operating labor cost is low.
12. Write the dis-advantages of hydro electric power plant.
o The plant disrupts the surrounding aquatic ecosystems.
o Initial cost of plant is very high.
o Failure of dams is potentially serious.
o Large investments, long gestation periods are major issues.
13. Draw the layout of diesel power plant.
Fuel storage Oil cooler
I/P air
Feed pump
Diesel engine
Generator
Air compressor
Water pump
Layout of diesel power plant
14. What are the advantages of diesel power plants?
o Power plant can be easily installed.
o The plant is smaller in size and fuel handling and storage is easier.
o Quick starting and easy pickup is possible.
o No ash disposal problem.
15. What are the dis-advantages of diesel power plants?
o Fuel is more expensive.
o Repair and maintenance cost is high.
o Capacity of diesel engine is low.
o Lives of plants are low.
16. What is the function of re-generator?
The heat obtained in the
exhaust gases
of
LPT
is
utilized
in
the re-generator
for transferring heat to the cold air coming out of HPC.
17. What is the function of intercooler?
This reduces the work of compressor; hence the power spent by compressor is less when
the air is cooled.
18. Write the advantages of gas turbine power plants.
o The capital cost of plant is low.
o This can be quickly commissioned.
o It requires less space.
o Capacity to use wide variety of fuels.
19. Write the advantages of gas turbine power plants
o About two third of the power developed by the turbine is used to drive the compressor.
Hence net output of plant is low.
o Low effiency.
o Needs special cooling arrangements.
o Operating temperature is high of the order of 20000C.
20. Define nuclear fission.
Nuclear fission is
defined as the splitting up
the nucleus of an
atom into parts where enormous amount of energy is released and this energy is used to generate power.
21. Write the function of moderator
In the chain reaction, the neutrons produced are fast moving neutrons.
They are less effective in causing fission of U235 and try to escape from the reactor. To improve the utilization of these fast neutrons, their speed is reduced in this moderator.
22. What is the function of control rods?
The energy produced in the reactor during chain reaction is enormous.
If this is not controlled properly entire core and
structure may melt and radioactive rays may come out of the reactor. The control rods do this control.
23. Explain about Biological shielding of nuclear reactor.
During fission reaction alpha particles, beta particles, gamma rays and
neutrons are produced. These radioactive rays are harmful to operating men. To protect from such harmful effects, thick concrete shielding is provided all round the reactor.
24. What are the advantages of nuclear power plant?
o Requires less space compared to steam power plant.
o Fuel required is negligible compared to coal requirement in steam power plant.
o Fuel transport cost is less.
o Cost of Erection is less.
o Water required is very less.
25. What are the dis-advantages of nuclear power plant?
o Initial cost is higher.
o Not suitable for varying load condition.
o Maintenance cost is higher.
o Trained workers / Engineers are required to handle the operation.
26. What is pump?
Pump is a mechanical
device which is used for moving liquids or gases from lower
pressure to higher pressure. In a pump mechanical forces are used to move the fluids.
27. Write the classification of pump with examples.
o Rotodynamic eg; Centrifugal pump.
o Positive displacement pump eg: Reciprocating pump
28. What is meant by centrifugal pump?
Centrifugal pump is rotodynamic pump which uses the mechanical energy of the rotating
impeller to increase the velocity of a fluid by the application
of centrifugal
force. The fluid enters the pump impeller along the rotating axis and gets accerelated.flows radially outwards into a casing and exits
through the piping
system.
It
is generally used for
large discharge through smaller heads.
29. What is meant by reciprocating pump?
A reciprocating pump is a positive displacement pump
in which liquid is sucked and then it is pushed or displaced due to the thrust exerted on it by a moving member which results in lifting height. The pump has one or more chamber which are alternately fitted with liquid to be pumped and then emptied again. Thus reciprocating action is being continued
within the pump and hence, the pump is called reciprocating pump.
30. What are the types of reciprocating pump?
o Single acting reciprocating pump
o Double acting reciprocating pump
31. What is priming?
Priming is
the operation of filling up of water in the suction pipe, casing and a portion of delivery valve to remove the air present inside. If any air is present, the pressure developed
across the impeller will not be sufficient to suck the water from the sump. The delivery valve is kept closed during priming.
32. What are the types of casing?
o Volute casing.
o Vortex casing.
o Diffuser casing.
33. Defined turbine.
A turbine is defined as a hydraulic machine which converts hydraulic energy into mechanical energy and this mechanical
energy is used to use to run an electrical generator which is
directly coupled to the shaft of the turbine. Thus, mechanical energy is converted into electrical energy. A
simple turbine will have one moving part and a rotor assembly. The rotating
system is called a runner in a turbine.
34. What is meant by impulse turbine with example?
In this energy is available is only kinetic energy, then the turbine is known as impulse turbine. Eg: Pelton wheel turbine.
35. What is meant by reaction turbine with example?
In this the energy available is kinetic energy and pressure energy, then the turbine is known as reaction turbine. When the fluid through the
runner, it is under pressure and the pressure energy goes on changing into kinetic energy. Eg: Francis turbine
36. Write the function of casing.
o To prevent splashing of water.
o To lead the water to the tail race.
o To act as a safeguard against any accidents.
UNIT-IV
INTERNAL COMBUSTION ENGINES
1. What is meant by I.C. engine?
In this type of engine, combustion of
fuel takes place within the cylinder. This type of
engine includes
gas engine, petrol engines and
diesel engines.
These
are
generally used
for road vehicles, locomotives, and aircraft and for other industrial applications.
2. Write the classification of I.C. engines.
Based on ignition:
o Spark ignition
o Compression ignition.
Based on fuel:
o Petrol engine
o Diesel engine.
Based on cooling system:
o Air cooled
o Water cooled.
3. What are the basic components of I.C. engines?
o Cylinder block. o Cylinder head. o Cylinder liners. o Crankcase.
o Piston.
4. What is meant by Top dead centre?
This refers to the position of the crankshaft when the piston is in its top most position i.e., the position closest to the cylinder head.
5. What is meant by Bottom dead centre?
This refers to the position of the crankshaft when the piston is in its lowest position i.e., the position closest to the cylinder head.
6. Define stroke.
Stroke is defined as the distance traveled by the piston while moving from T.D.C to the
B.D.C.
7. What is meant by clearance volume?
The volume of cylinder above the piston when it is in the T.D.C. position is referred to as Clearance volume (Vc).
8. What is compression ratio?
This indicates the extent to
which the charge in the engine is compressed. This is calculated as the ratio of the volume above the piston at B.D.C to
the
volume above the piston at T.D.C. If V is the compression ratio
VS + VC
V = ---------------------
VC
9. What is mean effective pressure?
This Is
the average pressure throughout the whole power stroke. The cylinder pressure
varies considerably during power stroke. Thus it is more helpful to refer to
the mean pressure
instead.
10. Define Engine torque.
It is defined as the force of rotation acting about the crankshaft axis at given instant of
time.
T = Fr
11. Define Scavenging.
It is defined as a process of forcing out the exhaust gases from the cylinder by admitting the fresh charge into the cylinder. This action takes place in two-stroke cycle engines.
12. Write any two differences between two stroke and four stroke engines.
|
S.No
|
Two stroke
|
Four stroke engines
|
|
1
|
For each
revolution of
crank shaft
one power stroke is produced.
|
For two revolution of crank shaft
one power stroke is produced
|
|
2
|
Uniform torque is obtained. Hence a
lighter flywheel can be used
|
Non-uniform torque
is obtained.
Hence a heavier flywheel can be used
|
13. Write any two differences between petrol and diesel engines.
|
S.No
|
Petrol engines
|
diesel engines
|
|
1
|
Operating speed is more. Speed
range is 3000 to 6000 rpm.
|
Operating
speed
is more.
Speed
range is 400 to 3500 rpm.
|
|
2
|
Produce less noise.
|
Produce less noise.
|
|
3
|
Specific fuel consumption is more.
|
Specific fuel consumption is
more.
|
14. Write the basic components in the Fuel Feed System
o Tank
o Feed pump
o Filter
o Injection pump
o Injector
o Leak off pipe
15. Define Carburettor.
The carburetor is a device for atomizing and vaporizing the fuel and mixing it with the air in varying proportions to
suit
the changing conditions of spark ignition engines. The air fuel mixture so obtained from the carburetor is called the combustible mixture.
16. What are the main functions of a carburetor?
o It preserves fuel at a constant head.
o It vaporizes and atomizes the fuel and mixes it with the air. Vaporization means the
change of fuel from a liquid to a vapour where as ‘atomization’ is the breaking up of fuel
by mechanical system, so that every small particle of the fuel is surrounded by air.
o It provides and controls the amount and strength of air-fuel mixture under varying conditions of load and speed of the engine.
o It provides easy starting with the engine in cold
o It ensures the engine to run slowly without missing and without undue wastage of fuel,
o It provides maximum acceleration without hesitation to pick up speed when the throttle
is suddenly or slowly opened.
17. Write the basic components in the carburetor.
o Venturi
o Throttle valve
o Choke valve
o Fuel jet.
18. What are the functions of Fuel injection pump?
In diesel engine, the fuel consists of a cylindrical barrel having two ports called supply port and spill port. A spring loaded delivery valve is provided at the top
of the barrel for fuel delivery.
19. What are the functions of Fuel injector?
The purposes of the fuel injector is to injector a small volume of fuel in a fine spray and, to assists in bringing
each droplet into contact
with
a sufficient
oxygen
to give quick
and complete combustion.
20. Write the types of Ignition system.
|
o Magneto ignition system.
21. Draw the layout of coil Ignition system.
Coil Ignition system
22. Draw the layout Magneto Ignition system.
Magneto Ignition system
23. Define spark plug.
Spark plug is defined as a device which is used to ignite the compressed air-fuel mixture
by producing an electric spark. It is usually mounted on the cylinder head.
24. Write the basic components of spark plug.
o Insulator.
o Central electrode.
o Earth electrode.
o Metallic shell.
o Gasket.
25. What are the purposes of cooling system?
o To maintain smooth running of engine. o To avoid the distortion of engine parts. o To avoid pre-ignition of charge.
o To maintain the temperature of engine within the limit.
o To maintain the strength of the cylinder and piston
26. What are the types of cooling system? o Direct cooling or Air cooling.
o Water cooling.
27. What are the advantages of air cooling system?
o The design is simple and occupies less space.
o Low cost.
o Less weight.
o Warming the engine is easier.
28. What are the types of water cooling system?
o Thermo-siphon or Natural circulation system.
o Forced circulation system.
29. Write about lubrication system.
Lubrication is the process of applying the lubricant between the surfaces of contact of two moving parts.
30. What are the purposes of lubrication system.
o To reduce the friction between moving parts.
o To minimize the vibration.
o To reduce the wear and tear.
o To reduce the corrosion and carbon deposits.
o To reduce the heat of moving parts.
31. What are the types of lubrication system?
o Petroil or Mist lubrication.
o Wet sump lubrication.
32. What is meant by Boiler?
A boiler is a closed
vessel
in which
water
or
other fluid is
heated. The
heated or vaporized fluid exits the boiler for use in various processes or heating applications.
33. What is the function of Boiler?
The function of the boiler is to evaporate water into steam at
a pressure higher than the atmospheric pressure. Water free from impurities such as
dissolved salts, gases and non soluble solids should be supplied to boilers. This is
done by suitable water treatment. Steam is useful for running steam turbines in electrical power stations.
34. Write the classification of boilers.
o Fire tube boilers.
o Water tube boilers.
35. Write the two differences between Fire tube and water tube boiler.
|
S.No
|
Fire tube boiler
|
water tube boiler
|
|
1
|
Hot gasses pass through the tubes,
water surrounds
them
|
Water pass through the tubes, hot
gases surrounds
them
|
|
2
|
Used for low pressure steam(say
10bar)
|
Used for medium to high pressure
steam
|
|
3
|
Thermal efficiency low
|
Thermal efficiency high
|
36. What are the advantages of steam boiler?
o Cost of production is cheap when compared with other boilers.
o Less space is required.
o Fuel used is cheaper.
o Steam engines can work under overload of 25percent continuously.
37. What are the dis-advantages of steam boiler?
o Water requirement is more.
o Required more time for installation.
o Maintenance and operating costs are high.
o Coal handling is difficult.
UNIT-V
REFRIGERATION AND AIR CONDITIONING SYSTEM
1. What is Refrigeration?
Refrigeration is
the process of
removing
heat from an
enclosed
space or from a substance, under controlled conditions and moving the heat to an unobjectional place.
2. What is meant by refrigerator?
A refrigerator
is a machine
that removes heat from a low temperature region. Since energy cannot be destroyed, the heat taken in at
a low
temperature must be dissipated to the surroundings.
3. State the second law of Thermodynamics.
Second law of Thermodynamics states that heat will not pass from cold region to a warm one without the aid of an external agent. Therefore, a refrigerator will require this external agent or energy input, for its operation.
4. What is meant by refrigerant? Give some examples.
The
substance which
absorbs heat the materials
placed in refrigerator is called refrigerant.
E.g.: Freon-12, Freon-22, and Ammonia.
5. Define Ton of refrigeration.
The capacity if air conditioner and ice plant is represented in Tons.
1ton = 3024 kilo calories/hr
6. What is meant by sensible heat/
The amount of heat removed from the body or given to the body to decrease or increase its temperature is called sensible heat.
7. Write the different kinds of heat transfer modes with examples.
o Conduction E.g.: Metal and other solids
o Convection E.g.: Heat through fluid
o Radiation E.g.: Sun light
8. Define Co-efficient of performance.
The purpose of the refrigerator is to remove heat from the cold region while requiring as little external work as possible.
COP = Heat exerted / Work supplied
9. What are the applications of refrigeration?
o Preserving foodstuffs in homes, restaurants and in large warehouses. o Used to liquefy gases like oxygen, Nitrogen, Propane and Methane. o Preserving dairy products, fruits and vegetables.
o Preserving Meats, poultry and fish.
10. What are the types of refrigeration system?
o Vapour compression refrigeration system
o Vapour absorption refrigeration system
11. Write the difference between Vapour compression and Vapour absorption refrigeration system.
|
S.No
|
Vapour compression system
|
Vapour absorption system
|
|
1
|
The capacity of the system is above
1000 tons
|
Maximum capacity is limited to
1000 tons
|
|
2
|
The operation is quit
|
The operation is noisy
|
|
3
|
Maintenance cost is low
|
Maintenance cost is high
|
12. Write the classification of refrigerants with examples.
o Primary refrigerants E.g. R12, Ammonia, Freon.
o Secondary refrigerants E.g. Co2, CaCl2, NaCl
13. What is meant by Air conditioning?
Air conditioning is the process of controlling the temperature and humidity of air by heating or cooling, humidifying or dehumidifying, and filtering the atmospheric air, and thus creating a healthy and comfortable condition for human beings.
14. What are the applications of Air conditioning?
o Providing relatively constant indoor environment for a building as per human comfort.
o For taller buildings where natural ventilation is not possible due to high
o In hospital operation theatres, to reduce infection risk.
15. Define Psychometry
It is the science which deals with the study of the behavior of air and water vapour mixture.
16. Define dry bulb temperature.
It is the temperature of air measured by an ordinary thermometer.
17. Define Wet bulb temperature.
It is the temperature of air
measured by thermometer when its bulb is
covered with a wet cloth and is exposed to atmospheric air.
18. Define dew point temperature.
It is the temperature
at which
the moisture present in the air begins
to condense. It corresponds to the saturation temperature of water vapour in the mixture of air and water vapour.
19. Write the types of Air conditioner?
o Window air conditioner
o Package air conditioner
o Centralised air conditioner
o Split type air conditioner
20. Define relative humidity
It is defined as the ratio of water vapour present in the given amount of air to the mass of water vapour present in the same volume under same temperature conditions.
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