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APPLIED THERMAL ENGINEERING
Prof. kiran gore
Contents a) Power producing devices Boiler Internal combustion engine Turbines
b) Power absorbing devices Pump Compressor Refrigeration Window air conditioner
Contents
c) Power plant engineering Conventional & non-conventional
energy resources Thermal power plant Hydro-electric power plant Nuclear power plant Wind power plant Solar power plant
Power producing devices
Boiler Internal combustion engine Turbines
Boiler or steam generator
*FUNCTION – It converts the water in to steam by application of heat energy.
*The heat energy required for generation of steam is produced by burning of fuel in closed furnace.
STEAM POWER PLANT
a) According to relative position of boiler
1. Fire Tube Boiler
2. Water Tube Boiler
Classification of boiler
Classification of boiler
B) According to water circulation arrangement 1)Natural circulation2)Forced circulation
C) According to use1)Stationary boilers2)Mobile boilers
Classification of boiler D) According to position of furnace
1)Internally fired 2)Externally fired
E) According to position of boiler
1)Horizontal boiler2)Vertical boiler3)Inclined boiler
F) According to pressure of steam generation
1) Low pressure boiler (15-20 bar)2) Medium pressure boiler (20-80bar)3) High pressure boiler ( more than 80
bar)4) Super critical boiler (more than 150
bar)
Classification of boiler
Water Tube Boiler Water is flowing through the tube which
surrounded by hot combustion gases
Examples of Water Tube Boiler
Babcock-wilcox Stirling & package boilers
Fire Tube BoilerHot combustion gases flow through tube
which surrounded by water
Examples of Fire Tube Boiler
Cochron Lancashire Locomotive & package
boiler
CRITERIA FOR SELECTION OF BOILER
:
1. Floor area available2. Rate of steam generation 3. Working pressure required4. Quality of steam required5. Fuel & water available6. Repair , operating & maintains
cost
Internal combustion
engine
Classification of I.C. engine
a) According to number of stroke
1. Two stroke engine
2. Four stroke engine
b) According to cycle of combustion
3. Otto cycle engine
4. Diesel cycle engine
5. Dual cycle engine
c) According to fuel used
1. Petrol engine
2. Gas engine
3. Diesel engine
d) According to method of ignition
4. S.I. engine
5. C.I. engine
Classification of I.C. engine
e) According cooling system
1. Air cooled engine
2.Water cooled engine
Classification of I.C. engine
f) According to speed of engine
1. Low speed engine
2. Medium speed engine
3. High speed engine
Classification of I.C. engine
g) According to arrangement of cylinder Classification of I.C. engine
1. Horizontal engine 2. Vertical engine
3. V-type engine
4. Radial engine
h) According to number of cylinder
1. Single cylinder engine
Classification of I.C. engine
2. Multicylinder engine
I) According to their used
1. Stationary engine
2. Marine engine
3. Automobile engine
4. Aero engine
Classification of I.C. engine
construction of I.C. engine A. Parts common to both Petrol and Diesel engine:
1.Cylinder, 2.Cylinder head,
3. Piston, 4.Piston rings, 5.Gudgeon pin, 6.Connecting rod,
7.Crankshaft, 8.Crank, 9.Engine bearing, 10.Crank case.
11.Flywheel, 12.Governor, 13. Valves and valve operating mechanism.
B. Parts for Petrol engines only: 1.Spark plug,
2. Carburetor,
C. Parts for Diesel engine only : 1. Fuel pump,
2. Injector.
Cylinder
Piston
Parts of I.C. engine
It is heart of the engine, in which the piston reciprocates (moves to and fro) in order to develop power. It is made of C.I.
Cylinder
It is reciprocating member of an I.C. engine. Main function is to transmit the force exerted by the burning of charge to the connecting rod. The piston are generally made of aluminum alloys which are light in weight.
Piston
Parts of I.C. engine
Piston
Piston Ring
Piston Ring Generally, there are two sets of rings
mounted for the piston. The function of the upper rings is to
provide air tight seal to prevent leakage of the burnt gases into the lower portion.
Similarly, the function of the lower rings is to provide effective seal to prevent leakage of the oil into the engine cylinder
Cylinder head
Cylinder Head
Fuel Injector
It is fitted on one end of the cylinder, while other end is open to crank case.
The cylinder head contains inlet and exit valves for admitting fresh charge and exhausting the burnt gases
Cylinder head
Connecting Rod
Connecting Rod
Gudgeon Pin
Crank-Shaft
Connecting Rod It is a link between the
piston and crankshaft. whose main function is
to transmit force from the piston to the crankshaft.
Moreover, it converts reciprocating motion of the piston into circular motion of the crankshaft.
Gudgeon Pin
Gudgeon Pin
Gudgeon pin is used to connect piston and connecting rod
Crank & crank shaft
Crank-Shaft
Crank shaft It is considered as the backbone of an I.C.
engine. The power developed by the engine is
transmitted outside by this shaft.
Valves Inlet valve Exhaust valve
Spring
Inlet Passage
Exhaust Passage
Inlet Cam & Valve
Exhaust Cam & Valve
Valves Inlet valve Exhaust valve
– Two types of valves are used in I.C engine
1) Inlet valve :- This valve is used to admit charge into cylinders.
2) Outlet valve :- This valve is used to remove exhaust gases from the cylinder.
Valves
Flywheel
Crank-Shaft
It is a big wheel, mounted on the crankshaft.
It is done by storing excess energy during power stroke, which is returned during other stroke.
Flywheel
Parts for Petrol engines only
carburetor
Carburetor– Main function of carburetor is to supply
limited quantity of fuel to engine
Spark plugParts for Petrol engines only
It is provided on petrol engine.
Main function is ignite air fuel mixture by producing spark at the end of compression stroke
Spark plug
Fuel InjectorParts for diesel engines only
Nozzle tip with several small holes for fuel spray
Fuel Injector It is provided on Diesel
Engine. Its function is to inject
diesel at the end of compression stroke at very high pressure
Fuel pump
It is used in diesel engine It forces the fuel at high pressure
through fuel injector in to the cylinder at the end of compression stroke.
Parts for diesel engines only
i.C engine terminology
1.Bore The inside diameter of the cylinder is called
bore.
2. Top dead centre (TDC)The top most position of piston towards the
cylinder head is called “top dead centre”.
3. Bottom dead centre (BDC)The Lowest position of piston towards the
crank case is called “bottom dead centre”.
4.Stroke The maximum distance travel by the piston
during its motion from TDC to BDC is called stroke.
5. Clearance volume The volume contained in the cylinder above
the top of the piston, when the piston is at top dead centre, is called the clearance volume.
Four Stroke petrol Engine (S.I. Engine)
The four strokes of a internal combustion engine are:
• Intake• Compression • Power• Exhaust
Each stroke = 180˚ of crankshaft revolution.
Each cycle requires two revolutions
of the crankshaft (720˚ rotation), and one revolution of the camshaft to
complete (360˚ rotation).
Intake StrokeFirst StrokeThe piston moves down the cylinderfrom TDC (Top Dead Center) to BDC (Bottom Dead Center).
This movement of piston causes low air pressure in the cylinder (vacuum)
Mixture of Air and Fuel in the ratioof 14.7 : 1 (air : fuel) is drawn intothe cylinder.
Intake valve stays open and theExhaust valve stays closed duringthis stroke.
Compression stroke
Second stroke
The piston moves from BDC to TDC
Intake and exhaust valves stay closed
Air and fuel mixture is compressed8:1 to 12:1
The pressure in the cylinder is raised
Power strokeThird stroke
Both the valves stay closed in this stroke.
The expanding gases from the combustion in the cylinder(with no escape) push the pistondown.
The piston travels from TDC to BDC.
At the end of compression strokethe sparkplug fires, igniting the air/fuel mixture.
Exhaust strokeFourth and last stroke
The momentum created by the Counter-weights on the crankshaft,move the piston from BDC to TDC.
The exhaust valve opens and the burned gases escape into theexhaust system.
Intake valve remains closed.
Four strokes
All four strokes
1. Suction 2. Compression 3. Power 4. Exhaust
• No sparkplug on Diesel engine.
• Has a higher compression ratio(14:1 to 25:1)
• Better fuel mileage.
Four Stroke Diesel Engine (C.I. Engine)
The only difference between diesel engine and a four-stroke gasoline engine is:
Diesel Engine
Intake Stroke:
• Piston moves from TDC to BDC creating vacuum in the cylinder
• Intake valve opens allowing only air to enter the cylinder and exhaust valve remains closed
Diesel EngineCompression Stroke
• Both valves stay closed
• Piston moves from BDC to TDC, compressing air to 22:1
• Compressing the air to this extent increases the temperature inside the cylinder to above 1000 degree F.
Diesel EnginePower Stroke
• Both valves stay closed
• When the piston is at the end of compression stroke(TDC) the injector sprays a mist of diesel fuel into the cylinder.
• When hot air mixes with diesel fuel an explosion takes place in the cylinder.
• Expanding gases push the piston from TDC to BDC
Diesel EngineExhaust Stroke
• Piston moves from BDC to TDC
• Exhaust valve opens and the exhaust gases escape
• Intake valve remains closed
Stroke 1 (intake) only
air enters cylinder.
Diesel Engine Operation
Stroke 2 (compression) air is compressed to high extent, raising its
temperature.
Stroke 3 (power) diesel is injected, high air
temperature ignites diesel.
Stroke 4 (exhaust) burnt
gases are expelled from the
engine.
Diesel EngineFour Strokes of Diesel Engine
Operation of two-stroke engineThe two stroke engine employs the crankcase aswell as the cylinder to achieve all the elements ofthe cycle in only two strokes of the piston.
360 degrees rotation of crankshaft completes the cycle.
Intake. The fuel/air mixture is first drawn into the crankcase by the vacuum created during the upward stroke of the piston through the reed valve.
Compression. The piston then rises, driven by flywheel momentum, and compresses the fuel mixture. (At the same time, another intake stroke is happening beneath the piston).
Intake & Compression stroke
Power. At the top of the stroke the spark plug ignites the fuel mixture. The burning fuel expands, driving the piston downward.
Exhaust/Transfer : Toward the end of the stroke,the piston exposes the intake port, allowing the compressed fuel/air mixture in the crankcase toescape around the piston into the main cylinder. This expels the exhaust gasses out the exhaust port, usually located on the opposite side of the cylinder.
Power & Exhaust/Transfer Stroke
Operation of Two-stroke engine
Operation of Two-stroke engine
Sr. no.
PETROL ENGINE (S.I. ENGINE)
DIESEL ENGINE (C.I. ENGINE)
01 Based on Otto cycle Based on diesel cycle
02 Petrol used as fuel. Diesel used as fuel .
03 For ignition Spark plug is required.
Spark plug is not required.
04 In these engine, air – fuel mixture is sucked during suction stroke.
In these engine, only air is sucked during suction stroke.
Sr. no.
PETROL ENGINE (S.I. ENGINE)
DIESEL ENGINE (C.I. ENGINE)
05 Compression ratio is low (about 6 to 12)
Compression ratio is high (about 14 to 22)
06 Light in weight. Heavier in weight.
07 Due to light in weight threes engines can rotate at high speed.
Due to heavy in weight threes engines can not rotate at high speed
08 The operation of these engine is silent
The operation of these engine is noisy.
09 Initial cost is low. Initial cost is high.
10 These engines are used in light duty vehicle like motor cycle, scooters, cars etc.
These engines are used heavy duty vehicle like buses, trucks etc.
SR. NO. TWO STRKE ENGINE FOUR STROKE ENGINE
1 The cycle is completed in two stroke of piston or one revolution of crank shaft.
The cycle is completed in four stroke of piston or two revolution of crank shaft.
02 One power stroke is obtained in each revolution of crank shaft.
One power stroke is obtained in every two revolution of crank shaft
03 2- stroke engine have port mechanism.
4- stroke engine have valve mechanism.
04 The piston head has crown shape.
The piston head is flat.
SR. NO. TWO STRKE ENGINE FOUR STROKE ENGINE
05 Engine is lighter. Engine is heavier.
06 Construction is simple.
Construction is complicated.
07 Initial cost is less. Initial cost is high.
08 Efficiency is low Efficiency is high.
Two-stroke engines have three important advantages over four-stroke engines:
Two-stroke engines do not have valves, which simplifies their construction and lowers their weight.
Two-stroke engines fire once every revolution, while four-stroke engines fire once every other revolution. This gives two-stroke engines a significant power boost.
Two-stroke engines can work in any orientation, which can be important in something like a chainsaw. A standard four-stroke engine may have problems with oil flow unless it is upright, and solving this problem can add complexity to the engine.
These advantages make two-stroke engines lighter, simpler and less expensive to manufacture.
Two-stroke engines also have the potential to pack about twice the power into the same space because there are twice as many power strokes per revolution.
The combination of light weight and twice the power gives two-stroke engines a great power-to-weight ratio compared to many four-stroke engine designs.
You don't normally see two-stroke engines in cars, however. That's because two-stroke engines have a couple of significant disadvantages that will make more sense once we look at how it operates.
Two Stroke Advantages
You can see that the piston is really doing
three different things in a two-stroke engine: On one side of the piston is the combustion
chamber, where the piston is compressing the air/fuel mixture and capturing the energy released by the ignition of the fuel.
On the other side of the piston is the crankcase, where the piston is creating a vacuum to suck in air/fuel from the carburetor through the reed valve and then pressurizing the crankcase so that air/fuel is forced into the combustion chamber.
Meanwhile, the sides of the piston are acting like valves, covering and uncovering the intake and exhaust ports drilled into the side of the cylinder wall.
It's really pretty neat to see the piston doing so many different things! That's what makes two-stroke engines so simple and lightweight.
If you have ever used a two-stroke engine, you know that you have to mix special two-stroke oil in with the gasoline.
Oil Requirements
Now that you understand the two-stroke cycle you can see why.
In a four-stroke engine, the crankcase is completely separate from the combustion chamber, so you can fill the crankcase with heavy oil to lubricate the crankshaft bearings, the bearings on either end of the piston's connecting rod and the cylinder wall.
In a two-stroke engine, on the other hand, the crankcase is serving as a pressurization chamber to force air/fuel into the cylinder, so it can't hold a thick oil. Instead, you mix oil in with the gas to lubricate the crankshaft, connecting rod and cylinder walls.
If you forget to mix in the oil, the engine isn't going to last very long!
Two-Strokes Usage
You can now see that two-stroke engines have two important advantages over four-stroke engines: They are simpler and lighter, and they produce about twice as much power. So why do cars and trucks use four-stroke engines?
There are four main reasons:
1. Two-stroke engines don't last nearly as long as four-stroke engines. The lack of a dedicated lubrication system means that the parts of a two-stroke engine wear a lot faster.
2. Two-stroke oil is expensive, and you need about 4 ounces of it per gallon of gas. You would burn about a gallon of oil every 1,000 miles if you used a two-stroke engine in a car.
3. Two-stroke engines do not use fuel efficiently, so you would get fewer miles per gallon.
4. Two-stroke engines produce a lot of pollution -- so much, in fact, that it is likely that you won't see them around too much longer. The pollution comes from two sources. The first is the combustion of the oil. The oil makes all two-stroke engines smoky to some extent, and a badly worn two-stroke engine can emit huge clouds of oily smoke.
