APPLIED THERMAL ENGINEERING Prof. kiran gore

Contents 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

Classification of boiler According to relative position of boiler Fire Tube Boiler Water Tube Boiler

Classification of boiler B) According to water circulation arrangement Natural circulation Forced circulation C) According to use Stationary boilers Mobile boilers

Classification of boiler D) According to position of furnace Internally fired 2)Externally fired E) According to position of boiler Horizontal boiler Vertical boiler Inclined boiler

Classification of boiler F) According to pressure of steam generation Low pressure boiler (15-20 bar) Medium pressure boiler (20-80bar) High pressure boiler ( more than 80 bar) Super critical boiler (more than 150 bar)

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 Boiler Hot combustion gases flow through tube which surrounded by water

Examples of Fire Tube Boiler Cochron Lancashire Locomotive & package boiler

CRITERIA FOR SELECTION OF BOILER : Floor area available Rate of steam generation Working pressure required Quality of steam required Fuel & water available Repair , operating & maintains cost

Internal combustion engine

Classification of I.C. engine According to number of stroke Two stroke engine Four stroke engine b) According to cycle of combustion Otto cycle engine Diesel cycle engine Dual cycle engine

Classification of I.C. engine c) According to fuel used Petrol engine Gas engine Diesel engine d) According to method of ignition S.I. engine C.I. engine

Classification of I.C. engine e) According cooling system Air cooled engine 2.Water cooled engine

Classification of I.C. engine f) According to speed of engine Low speed engine Medium speed engine High speed engine

Classification of I.C. engine g) According to arrangement of cylinder Horizontal engine 2. Vertical engine 4. Radial engine 3. V-type engine

Classification of I.C. engine h) According to number of cylinder Single cylinder engine 2. Multicylinder engine

Classification of I.C. engine I) According to their used Stationary engine Marine engine Automobile engine Aero 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.

Parts of I.C. engine Cylinder Piston

Cylinder 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. Piston 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.

Parts of I.C. engine Piston Ring Piston

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 Fuel Injector Cylinder Head

Cylinder head 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

Connecting Rod Gudgeon Pin Connecting Rod 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 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 Cam-Shafts Valve Spring

Valves Inlet valve Exhaust valve

Valves Inlet valve Exhaust valve Exhaust Cam & Valve Inlet Cam & Valve Spring Inlet Passage Exhaust Passage

Valves – 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.

Flywheel Crank-Shaft

Flywheel 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.

Parts for Petrol engines only carburetor

Carburetor – Main function of carburetor is to supply limited quantity of fuel to engine

Parts for Petrol engines only Spark plug

Spark plug It is provided on petrol engine. Main function is ignite air fuel mixture by producing spark at the end of compression stroke

Parts for diesel engines only Fuel Injector 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

Parts for diesel engines only 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.

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 Stroke First Stroke The piston moves down the cylinder from 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 ratio of 14.7 : 1 (air : fuel) is drawn into the cylinder. Intake valve stays open and the Exhaust valve stays closed during this stroke.

Compression stroke Second stroke The piston moves from BDC to TDC Intake and exhaust valves stay closed Air and fuel mixture is compressed 8:1 to 12:1 The pressure in the cylinder is raised

Power stroke Third stroke At the end of compression stroke the sparkplug fires, igniting the air/fuel mixture. Both the valves stay closed in this stroke. The expanding gases from the combustion in the cylinder (with no escape) push the piston down. The piston travels from TDC to BDC.

Exhaust stroke Fourth 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 the exhaust system. Intake valve remains closed.

Four strokes All four strokes Suction Compression Power Exhaust

Four Stroke Diesel Engine (C.I. Engine) The only difference between diesel engine and a four-stroke gasoline engine is: No sparkplug on Diesel engine. Has a higher compression ratio(14:1 to 25:1) Better fuel mileage.

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 Engine Compression 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 Engine Power 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 Engine Exhaust Stroke Piston moves from BDC to TDC Exhaust valve opens and the exhaust gases escape Intake valve remains closed

Diesel Engine Operation Stroke 3 (power) diesel is injected, high air temperature ignites diesel. Stroke 1 (intake) only air enters cylinder. Stroke 2 (compression) air is compressed to high extent, raising its temperature. Stroke 4 (exhaust) burnt gases are expelled from the engine.

Diesel Engine Four Strokes of Diesel Engine

Operation of two-stroke engine The two stroke engine employs the crankcase as well as the cylinder to achieve all the elements of the cycle in only two strokes of the piston. 360 degrees rotation of crankshaft completes the cycle.

Intake & Compression stroke 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).  

Power & Exhaust/Transfer 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 to escape 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. 

Operation of Two-stroke engine

Operation of Two-stroke engine

PETROL ENGINE (S.I. ENGINE) DIESEL ENGINE (C.I. 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.

PETROL ENGINE (S.I. ENGINE) DIESEL ENGINE (C.I. ENGINE) 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.

One power stroke is obtained in each revolution of crank shaft. 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.

Construction is simple. Construction is complicated. 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.

Two Stroke Advantages 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.

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.

Oil Requirements 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.

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: 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. 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. Two-stroke engines do not use fuel efficiently, so you would get fewer miles per gallon. 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.