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This document provides an overview of internal combustion engines. It begins with definitions of heat engines and the two main types - external combustion engines and internal combustion engines. The key differences between spark ignition engines and compression ignition engines are outlined. Four-stroke and two-stroke engine cycles are described and compared. The main components of internal combustion engines are defined. The document also includes classifications of IC engines, histories of important developments, and diagrams illustrating valve and port timing. Thermal concepts like indicated power, brake power, and efficiency are defined.

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Thermal Engineering – I Mr. Pankaj Anadani, Lecturer Mechanical Engineering
CHAPTER-1- I.C ENGINE
INTRODUCTION Heat engine: A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this energy to produce mechanical work. It is classified into two types- (a) External combustion engine (b) Internal combustion engine Sub: THERMAL TOPIC:I.C ENGINE
4 • External combustion engine Fuel (chemical energy) burning-heat energy- outside of boiler-water-steam-force the piston to move (mechanical energy). • Internal combustion engine Fuel (chemical energy) burning-heat energy-inside of cylinder-expanding gases-force the piston to move (mechanical energy). Sub: THERMAL TOPIC:TYPES OF ENGINE
5 • Simple external and internal combustion engine Sub: THERMAL TOPIC:TYPES OF ENGINE
6 • I.C.E versus E.C.E (1) Similarity: ① both are heat engines. ② energy transforms in the same way -reciprocating motion to rotary motion (2) Differences: ①the fuel burns in different place ②the combustion rate Sub: THERMAL TOPIC:TYPES OF ENGINE
•INTRODUCTION I.C.ENGINE internal combustion engines are those engines in which combustion of fuel takes place inside the engine cylinder. These are petrol, diesel, gas engines. Combustion of fuel take place inside the engine cylinder by a spark and produces very high temp. Sub: THERMAL TOPIC:I.C ENGINE
8 • History of I c engine • In 1872, American George Brayton invented the first commercial liquid-fuelled i.c engine. • In 1876, Nicolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, patented the compressed charge, four-cycle engine. • In 1879, Karl Benz patented a reliable two- stroke gasoline engine. Later, in 1886, Benz began the first commercial production of motor vehicles with the internal combustion engine. • In 1892, Rudolf Diesel developed the first compressed charge, compression ignition engine. • In 1926, Robert Goddard launched the first liquid- fueled rocket. In 1939, the Heinkel He 178 became the world's first jet aircraft Sub: THERMAL TOPIC:TYPES OF ENGINE
•CLASSIFICATION OF I.C.ENGINE 1) According to the types of fuel used • Petrol engine • Diesel engine • Gas engine 2) According to the method of igniting the fuel • Spark ignition engine(SI) • Compression ignition engine(CI) Sub: THERMAL TOPIC:I.C ENGINE
3) According to the number of strokes per cycle • Four stoke cycle engine • Two stoke cycle engine 4) According to the speed of the engine • Slow speed • Medium speed • High speed 5) According to the cooling system • Air cooled • Water cooled • Evaporative cooling engine Sub: THERMAL TOPIC:I.C ENGINE
6) According to the method of fuel injection • Carburetor engines • Air injection engines • solid injection engines 7) According to the number of cylinders • Single cylinder engines • Multi cylinder engines 8) According to the method of governing • Quantity governed engines • Quality governed engines • Hit and Miss governed engines Sub: THERMAL TOPIC:I.C ENGINE
9) According to the Cylinder arrangement • Vertical • horizontal • Inline • V-type • Radial • opposed cylinder or piston engines. 10) According to the Application • Automotive engines for land transport, marine engines for propulsion of ships, aircraft engines for aircraft propulsion, industrial engines, prime movers for electrical generators. Sub: THERMAL TOPIC:I.C ENGINE
• Main Components Of I.C. Engines: Sub: THERMAL TOPIC:I.C ENGINE
• Main Components Of I.C. Engines: Sub: THERMAL TOPIC:I.C ENGINE
Sub: THERMAL TOPIC:I.C ENGINE
• Main Components Of I.C. Engines: 1. Cylinder: • It is one of the most important parts of the engine, in which the piston moves to and fro in order to develop power. Generally, the engine cylinder has to withstand a high pressure and temperature. Thus the material the engine cylinder should be such that it can retain sufficient strength at such a high pressure and temperature. 2. Cylinder head: • It is fitted on one end of the cylinder, and acts as a cover to close the cylinder bore. Generally, the cylinder head contains inlet and exit valves. Sub: THERMAL TOPIC:I.C ENGINE
• Main Components Of I.C. Engines: • In petrol engines, the cylinder head also contains a spark plug for igniting the fuel air mixture. But in diesel engines, the cylinder head contains nozzle for injecting into the cylinder. 3. Piston • It is consider as the heart of an I.C. engine, whose main function is to transmit the force exerted by the burning of charge to the connecting rod. The pistons are generally made of aluminum alloys which are light in weight. They have good heat conducting prosperity and also greater strength at higher temperatures. Sub: THERMAL TOPIC:I.C ENGINE
• Main Components Of I.C. Engines: 4. Piston ring • These are circular rings and made of special steel alloys which retain elastic properties even at high temperatures. The piston rings are housed in circumferential grooves provided on the outer surface of the piston. 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 providing effective seal to prevent the oil into the engine cylinder. Sub: THERMAL TOPIC:I.C ENGINE
• Main Components Of I.C. Engines: 5. Connecting rod: • It is link between the piston and crank shaft, whose main function it’s to transmit force from the piston to the crank shaft. Moreover it converts reciprocating motion of the piston into circular motion of the crank shaft. The upper end of the connecting rod is fitted to the piston and the lower end to the crank. 6. Crank shaft: • It is consider as the backbone of an I.C. engine. Whose function is to convert the reciprocating motion of the piston into the rotary motion with the help of connecting rod. Sub: THERMAL TOPIC:I.C ENGINE
• Main Components Of I.C. Engines: 7. Crank case: • It is a cast iron case, which holds the cylinder and crank shaft of an I.C. engine. It also serves as a sump for the lubricating oil. The lower portion of the crank case is known as bed plate, which is fixed with help of bolts. 8. Fly wheel: • It is a big wheel, mounted on the crank shaft, whose function is to maintain its speed constant. It is done by storing excess energy during the power stroke, which is returned during other strokes. Sub: THERMAL TOPIC:I.C ENGINE
•Differences of SI and CI engine: SI CI Working cycle is Otto cycle. Working cycle is diesel cycle. Petrol or gasoline or high octane fuel is used. Diesel or high cetane fuel is used Fuel and air introduced as a gaseous mixture in the suction stroke. Fuel is injected directly into the combustion chamber during compression stroke. Carburettor used to provide the mixture. Injector and high pressure pump used to supply of fuel. Compression ratio is 6 to 12. Compression ratio is 18 to 22 Power producing is more Produce less power. Speed Is higher. Lower in speed. Lighter in weight. Heavy in weight. Used in: Two wheelers, cars etc. Used in : cars, Buses,Trucks etc Sub: THERMAL TOPIC:I.C ENGINE
•Four stroke engine • Cycle of operation completed in four strokes of the piston or two revolution of the piston. Sub: THERMAL TOPIC:I.C ENGINE
Sub: THERMAL TOPIC:I.C ENGINE
Sub: THERMAL TOPIC:I.C ENGINE
Sub: THERMAL TOPIC:I.C ENGINE
Sub: THERMAL TOPIC:I.C ENGINE
Sub: THERMAL TOPIC:I.C ENGINE
Sub: THERMAL TOPIC:I.C ENGINE
•Two Stroke Engine Sub: THERMAL TOPIC:I.C ENGINE
•Two Stroke Engine Sub: THERMAL TOPIC:I.C ENGINE A two-stroke (or two-cycle) engine is a type of internal combustion engine which completes a power cycle with two strokes (up and down movements) of the piston during only one crankshaft revolution. This is in contrast to a "four-stroke engine", which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions.
• Comparison of Four-stroke and two-stroke engine: Sub: THERMAL TOPIC:I.C ENGINE Four-stroke engine Two-stroke engine •Four stroke of the piston and two revolution of crankshaft •Two stroke of the piston and one revolution of crankshaft •One power stroke in every two revolution of crankshaft •One power stroke in each revolution of crankshaft •Contains valve and valve mechanism •Contains ports arrangement •Heavier flywheel due to non-uniform turning movement •Lighter flywheel due to more uniform turning movement •Power produce is less •Power produce is more •Volumetric efficiency is more due to greater time of induction •Volumetric efficiency less due to lesser time of induction •Thermal efficiency is high and also part load efficiency better •Thermal efficiency is low, part load efficiency lesser •It is used where efficiency is important. •Ex-cars, buses, trucks, tractors, industrial engines, aero planes, power generation etc. •It is used where low cost, compactness and light weight are important. •Ex-lawn mowers, scooters, motor cycles, mopeds, propulsion ship etc.
Disadvantages of a two stroke • The engines do not last as long due to poor lubrication. • You have to mix two cycle engine oil with gasoline. • The engines do not use fuel efficiently. • These engines produce a lot of pollution. • Two stroke engines are great for the power to weight ratio and their simple design, however, due to there pollution concerns these engines will be harder to find. Sub: THERMAL TOPIC:I.C ENGINE
•Valve timing diagram • The exact moment at which the inlet and outlet valve opens and closes with reference to the position of the piston and crank shown diagrammatically is known as valve timing diagram. • It is expressed in terms of degree crank angle. The theoretical valve timing diagram is shown in Fig. Sub: THERMAL TOPIC:TYPES OF ENGINE
•Valve timing diagram • Four stroke Petrol engine Sub: THERMAL TOPIC:TYPES OF ENGINE
•Valve timing diagram • Four stroke Diesel engine Sub: THERMAL TOPIC:TYPES OF ENGINE
•Port timing diagram • Two stroke engine Sub: THERMAL TOPIC:TYPES OF ENGINE
•Scavenging of two stroke engine Sub: THERMAL TOPIC:TYPES OF ENGINE
•Supercharging Supercharging is the process of supplying the intake of an engine with air at a density greater than the density of surrounding atmosphere so that each intake cycle of engine gets more oxygen , which burns more fuel thus generating more power . Sub: THERMAL TOPIC:TYPES OF ENGINE
•Supercharging Supercharging is the process of supplying the intake of an engine with air at a density greater than the density of surrounding atmosphere so that each intake cycle of engine gets more oxygen , which burns more fuel thus generating more power . Sub: THERMAL TOPIC:TYPES OF ENGINE Method-1
•Supercharging Supercharging is the process of supplying the intake of an engine with air at a density greater than the density of surrounding atmosphere so that each intake cycle of engine gets more oxygen , which burns more fuel thus generating more power . Sub: THERMAL TOPIC:TYPES OF ENGINE Method-2
•PART -2 NUMERICALS Sub: THERMAL TOPIC:I.C ENGINE
•Terms Used in I C engine Sub: THERMAL TOPIC:I.C ENGINE
1. Cylinder bore (D): The nominal inner diameter of the working cylinder. 2. Piston area (A): The area of circle of diameter equal to the cylinder bore. 3. Stroke (L): The nominal distance through which a working piston moves between two successive reversals of its direction of motion. 4. Dead centre: The position of the working piston and the moving parts which are mechanically connected to it at the moment when the direction of the piston motion is reversed (at either end point of the stroke). (a) Bottom dead centre (BDC): Dead centre when the piston is nearest to the crankshaft. (b) Top dead centre (TDC): Dead centre when the position is farthest from the crankshaft. Sub: THERMAL TOPIC:I.C ENGINE
5. Displacement volume or swept volume (Vs): The nominal volume generated by the working piston when travelling from the one dead centre to next one and given as, Vs= A × L 6. Clearance volume (Vc): the nominal volume of the space on the combustion side of the piston at the top dead centre. 7. Cylinder volume (V): Total volume of the cylinder. V = Vs + Vc 8. Compression ratio (r): It is the ratio of total volume of cylinder to the clearance volume. r = Vs+Vc/ Vc 9. Piston speed: The distance moved by piston in one minute. Sub: THERMAL TOPIC:I.C ENGINE
Swept and Displaced Volumes • Swept Volume/cylinder: s A s d 4 = V p 2 B s     Vs = swept volume dB = bore diameter s = stroke s s x Ap Inlet Port Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
 Indicated Power (IP) The total power developed by combustion of fuel in the combustion chamber is called Indicated Power (IP). It can be calculated as: Where n = number of cylinders Pmi = Indicated mean effective pressure, (bars) L = Length of stroke, (m) A = Area of piston, (m2) K = 2 for 4 stroke engine = 1 for 2 stroke engine Indicated power is the total power of engine which is graphically represented by area of cycle on P-V chart. As the actual P-V diagram of an engine is drawn by an indicator mechanism, this power is called indicated power. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
Brake Power (BP) The power available at an engines output shaft is called its brake power. It is the power which can be positively used against resistive force or braking force of the application for which engine is being used. It can be calculated as: Where N = engine speed in rpm T = Torque at output shaft in N-m. B.P= (W-S)ΠDN KW 60*1000 Where Pmb = Brake mean effective pressure. All other notations are same as in the expression of I.P. given in equation Comparing equations BOTH , Torque T= Constant Pmb Thus the torque of an engine depends on its size (AL) and mean effective pressure. Torque of a given engine of constant size will be more when its mean effective pressure is more. Hence, mean effective pressure is a true parameter to compare power of engines. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
Frictional power It is the power required to overcome the internal friction of engine. It represents the total losses occurred from indicated power. It is the difference between Indicated power and Brake Power. F.P = I.P - B.P Mechanical efficiency It is the ratio of brake power to the indicated power of an IC Engine. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
Thermal efficiency It is the ratio of work done or power developed by an engine to the rate of chemical energy or heat supplied by burning of fuel in the engine. It can be based on indicated power or brake power and accordingly can be specified as Where, mf = Rate of fuel consumed (kg / sec) C = calorific value of fuel (kJ/ kg) I.P. = Indicated power (kW) B.P. = Brake power (kW) Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
Specific fuel consumption It is the mass of fuel consumed in kg/hour per kW of power developed by engine. It is a clear indicator of efficiency with which the engine burns fuel to produce power and is very important performance parameter. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
NUMERICAL PROBLEMS EXAMPLE-1- The following data is available for a two stroke cycle, single cylinder oil engine: Mean indicated effective pressure = 550 kPa. cylinder diameter = 21 cm, Piston stroke=28 cm Engine speed = 360 RPM. Brake torque = 628 N.m., Fuel on= 8.6 kg/hr. Calorific value of fuel= 42700 kJ/kg. Find (1) Mechanical efficiency (2) Indicated thermal efficiency (3) Brake thermal Sub: THERMAL TOPIC: I. C ENGINE
NUMERICAL PROBLEMS EXAMPLE-2- Following observations were recorded during a test on a single cylinder 4- stroke oil engine: Bore =300mm; Stroke = 450mm; Speed =300rpm; imep = 6bar; Net brake load = 1.5 kN; Brake drum diameter = 1.8m; Brake rope diameter = 2 cm. Calculate: (i) Indicated Power (ii) Brake Power (iii) Mechanical Efficiency Sub: THERMAL TOPIC: I. C ENGINE
NUMERICAL PROBLEMS EXAMPLE-3- The Following observations were recorded during a test on a single cylinder 4- stroke C.I engine: Cylindre diameter =0.1m; Stroke = 0.15m; Speed =450rpm; imep = 7.5bar; brake load =220N spring balance reading= 20N ; Brake wheel diameter = 0.6m; c.v = 43000 kj/kg mass of fuel = 3 kg/hr Calculate: (i) Indicated Power (ii) Brake Power (iii) Mechanical Efficiency (iv) Indicated thermal eff. (v) Brake thermal eff. Sub: THERMAL TOPIC: I. C ENGINE
NUMERICAL PROBLEMS EXAMPLE-4- The Following observations were recorded during a test on a single cylinder 4- stroke C.I engine: Bore diameter =24cm; Stroke = 40cm; Speed =250rpm; imep = 6.65bar; Net brake load =850N; Brake wheel radius = 75cm; C.V = 18690 kg/m^3 ; fuel used = 0.21 m^3/min Calculate: (i) Indicated Power (ii) Brake Power (iii) Mechanical Efficiency (iv) Indicated thermal eff. (v) Brake thermal eff. Sub: THERMAL TOPIC: I. C ENGINE
Sub: THERMAL TOPIC: I. C ENGINE VARIOUS SYSTEM OF I C ENGINE 1.Ignition system 2.Cooling system 3.Governing system 4.Fuel supply System 5.Lubrication system
1.Ignition system • 1.Battery coil ignition System The ignition system is divided into 2-circuits: • (i) Primary Circuit: -consists of 6 or 12 V battery, ammeter, ignition switch, primary winding -it has 200-300 turns of 20 SWG (Sharps Wire Gauge) gauge wire, contact breaker, capacitor. • (ii) Secondary Circuit: • -consists of secondary winding or coil which have 21000 turns of 40 (S WG) gauge wire. -bottom end of which is connected to bottom end of primary and top end of secondary winding or coil is connected to centre of distributor rotor. -distributor rotors rotate and make contacts with contact points and are connected to spark plugs which are fitted in cylinder heads.
1.Ignition system • 1.Battery coil ignition System
Ignition system 2.Magneto ignition system magneto will produce and supply the required current to the primary winding or coil - rotating magneto with fixed coil or rotating coil with fixed magneto for producing and supplying current to primary, remaining arrangement is same as that of a battery ignition system -no battery required - during starting the quality of spark is poor due to slow speed -very much compact
Ignition system
Cooling system • Due to the combustion of fuel inside the engine cylinder, intense heat is generated. It has been experimentally found that about 30% of the heat generated is converted into mechanical work. Out of the remaining 40% of heat is carried away by the exhaust gases. The remaining part of the heat, if left unattended will be absorbed by the engine cylinder, cylinder head, piston, and valves. The overheating of these parts causes thermal stresses in the engine parts, which may lead to their distortion, seizure of the piston, burning of the valves and valve seats and reduces the volumetric efficiency. In order to avoid the above said adverse effects, it is very essential to provide some cooling system for an IC engine. Two types of cooling methods will be used in IC engines, i.e. Air Cooling and Water Cooling
Cooling system • 1. Air cooling method
Cooling system 2. Water cooling method 1. Thermosyphon method
Cooling system 2. Water cooling method 2. Force cooling method
Cooling system 2. Water cooling method 3. Pressurized water cooling system
Lubrication system (a) Mist lubrication system (b)Wet sump lubrication system (c) Dry sump lubrication system Generally adopted in two stroke petrol engine line scooter and motor cycle. It is the simplest form of lubricating system. - It is the simplest form of lubricating system. It does not consist of any separate part like oil pump for the purpose of lubrication. - In this system the lubricating oil is mixed into the fuel (petrol) while filling in the petrol tank of the vehicle in a specified ratio (ratio of fuel and lubricating oil is from 12:1 to 50:10 as per manufacturers specifications or recommendations
Lubrication system (b)Wet sump lubrication • In this system of lubrication the lubricating oil is stored in an oil sump. A scoop or dipper is made in the lower part of the connecting rod. When the engine runs, the dipper dips in the oil once in every revolution of the crank shaft, the oil is splashed on the cylinder wall. Due to this action engine walls, piston ring, crank shaft bearings are lubricated.
Lubrication system (C)Dry sump lubrication • Supply of oil is carried in external tank. Oil pump draws oil from the supply tank and circulates it under pressure to various bearings of the engine
Governing system (a)Qauntitative Governing In this system of governing, the quality of charge (i.e. air-fuel ratio of the mixture) is kept constant. But the quantity of mixture supplied to the engine cylinder is varied by means of a throttle valve which is regulated by the centrifugal governor through rack and pinion arrangement.
Governing system (2)QaulityGoverning In this system of governing, a control valve is fitted in the fuel delivery pipe, which controls the quantity of fuel to be mixed in the charge. The movement of control valve is regulated by the centrifugal governor through rack and pinion arrangement.
Governing system (C)Hit and Miss Governing In this system of governing, whenever the engine starts running at higher speed (due to decreased load), some explosions are omitted or missed. This is done with the help of a centrifugal governor. This method of governing is widely used for I. C. engines of smaller capacity or gas engines
Fuel supply system Petrol Engine
Fuel supply system Diesel engine

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DME-THERMAL-5-I.C.ENGINE.ppt

  • 1. Thermal Engineering – I Mr. Pankaj Anadani, Lecturer Mechanical Engineering
  • 3. INTRODUCTION Heat engine: A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this energy to produce mechanical work. It is classified into two types- (a) External combustion engine (b) Internal combustion engine Sub: THERMAL TOPIC:I.C ENGINE
  • 4. 4 • External combustion engine Fuel (chemical energy) burning-heat energy- outside of boiler-water-steam-force the piston to move (mechanical energy). • Internal combustion engine Fuel (chemical energy) burning-heat energy-inside of cylinder-expanding gases-force the piston to move (mechanical energy). Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 5. 5 • Simple external and internal combustion engine Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 6. 6 • I.C.E versus E.C.E (1) Similarity: ① both are heat engines. ② energy transforms in the same way -reciprocating motion to rotary motion (2) Differences: ①the fuel burns in different place ②the combustion rate Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 7. •INTRODUCTION I.C.ENGINE internal combustion engines are those engines in which combustion of fuel takes place inside the engine cylinder. These are petrol, diesel, gas engines. Combustion of fuel take place inside the engine cylinder by a spark and produces very high temp. Sub: THERMAL TOPIC:I.C ENGINE
  • 8. 8 • History of I c engine • In 1872, American George Brayton invented the first commercial liquid-fuelled i.c engine. • In 1876, Nicolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, patented the compressed charge, four-cycle engine. • In 1879, Karl Benz patented a reliable two- stroke gasoline engine. Later, in 1886, Benz began the first commercial production of motor vehicles with the internal combustion engine. • In 1892, Rudolf Diesel developed the first compressed charge, compression ignition engine. • In 1926, Robert Goddard launched the first liquid- fueled rocket. In 1939, the Heinkel He 178 became the world's first jet aircraft Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 9. •CLASSIFICATION OF I.C.ENGINE 1) According to the types of fuel used • Petrol engine • Diesel engine • Gas engine 2) According to the method of igniting the fuel • Spark ignition engine(SI) • Compression ignition engine(CI) Sub: THERMAL TOPIC:I.C ENGINE
  • 10. 3) According to the number of strokes per cycle • Four stoke cycle engine • Two stoke cycle engine 4) According to the speed of the engine • Slow speed • Medium speed • High speed 5) According to the cooling system • Air cooled • Water cooled • Evaporative cooling engine Sub: THERMAL TOPIC:I.C ENGINE
  • 11. 6) According to the method of fuel injection • Carburetor engines • Air injection engines • solid injection engines 7) According to the number of cylinders • Single cylinder engines • Multi cylinder engines 8) According to the method of governing • Quantity governed engines • Quality governed engines • Hit and Miss governed engines Sub: THERMAL TOPIC:I.C ENGINE
  • 12. 9) According to the Cylinder arrangement • Vertical • horizontal • Inline • V-type • Radial • opposed cylinder or piston engines. 10) According to the Application • Automotive engines for land transport, marine engines for propulsion of ships, aircraft engines for aircraft propulsion, industrial engines, prime movers for electrical generators. Sub: THERMAL TOPIC:I.C ENGINE
  • 13. • Main Components Of I.C. Engines: Sub: THERMAL TOPIC:I.C ENGINE
  • 14. • Main Components Of I.C. Engines: Sub: THERMAL TOPIC:I.C ENGINE
  • 16. • Main Components Of I.C. Engines: 1. Cylinder: • It is one of the most important parts of the engine, in which the piston moves to and fro in order to develop power. Generally, the engine cylinder has to withstand a high pressure and temperature. Thus the material the engine cylinder should be such that it can retain sufficient strength at such a high pressure and temperature. 2. Cylinder head: • It is fitted on one end of the cylinder, and acts as a cover to close the cylinder bore. Generally, the cylinder head contains inlet and exit valves. Sub: THERMAL TOPIC:I.C ENGINE
  • 17. • Main Components Of I.C. Engines: • In petrol engines, the cylinder head also contains a spark plug for igniting the fuel air mixture. But in diesel engines, the cylinder head contains nozzle for injecting into the cylinder. 3. Piston • It is consider as the heart of an I.C. engine, whose main function is to transmit the force exerted by the burning of charge to the connecting rod. The pistons are generally made of aluminum alloys which are light in weight. They have good heat conducting prosperity and also greater strength at higher temperatures. Sub: THERMAL TOPIC:I.C ENGINE
  • 18. • Main Components Of I.C. Engines: 4. Piston ring • These are circular rings and made of special steel alloys which retain elastic properties even at high temperatures. The piston rings are housed in circumferential grooves provided on the outer surface of the piston. 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 providing effective seal to prevent the oil into the engine cylinder. Sub: THERMAL TOPIC:I.C ENGINE
  • 19. • Main Components Of I.C. Engines: 5. Connecting rod: • It is link between the piston and crank shaft, whose main function it’s to transmit force from the piston to the crank shaft. Moreover it converts reciprocating motion of the piston into circular motion of the crank shaft. The upper end of the connecting rod is fitted to the piston and the lower end to the crank. 6. Crank shaft: • It is consider as the backbone of an I.C. engine. Whose function is to convert the reciprocating motion of the piston into the rotary motion with the help of connecting rod. Sub: THERMAL TOPIC:I.C ENGINE
  • 20. • Main Components Of I.C. Engines: 7. Crank case: • It is a cast iron case, which holds the cylinder and crank shaft of an I.C. engine. It also serves as a sump for the lubricating oil. The lower portion of the crank case is known as bed plate, which is fixed with help of bolts. 8. Fly wheel: • It is a big wheel, mounted on the crank shaft, whose function is to maintain its speed constant. It is done by storing excess energy during the power stroke, which is returned during other strokes. Sub: THERMAL TOPIC:I.C ENGINE
  • 21. •Differences of SI and CI engine: SI CI Working cycle is Otto cycle. Working cycle is diesel cycle. Petrol or gasoline or high octane fuel is used. Diesel or high cetane fuel is used Fuel and air introduced as a gaseous mixture in the suction stroke. Fuel is injected directly into the combustion chamber during compression stroke. Carburettor used to provide the mixture. Injector and high pressure pump used to supply of fuel. Compression ratio is 6 to 12. Compression ratio is 18 to 22 Power producing is more Produce less power. Speed Is higher. Lower in speed. Lighter in weight. Heavy in weight. Used in: Two wheelers, cars etc. Used in : cars, Buses,Trucks etc Sub: THERMAL TOPIC:I.C ENGINE
  • 22. •Four stroke engine • Cycle of operation completed in four strokes of the piston or two revolution of the piston. Sub: THERMAL TOPIC:I.C ENGINE
  • 29. •Two Stroke Engine Sub: THERMAL TOPIC:I.C ENGINE
  • 30. •Two Stroke Engine Sub: THERMAL TOPIC:I.C ENGINE A two-stroke (or two-cycle) engine is a type of internal combustion engine which completes a power cycle with two strokes (up and down movements) of the piston during only one crankshaft revolution. This is in contrast to a "four-stroke engine", which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions.
  • 31. • Comparison of Four-stroke and two-stroke engine: Sub: THERMAL TOPIC:I.C ENGINE Four-stroke engine Two-stroke engine •Four stroke of the piston and two revolution of crankshaft •Two stroke of the piston and one revolution of crankshaft •One power stroke in every two revolution of crankshaft •One power stroke in each revolution of crankshaft •Contains valve and valve mechanism •Contains ports arrangement •Heavier flywheel due to non-uniform turning movement •Lighter flywheel due to more uniform turning movement •Power produce is less •Power produce is more •Volumetric efficiency is more due to greater time of induction •Volumetric efficiency less due to lesser time of induction •Thermal efficiency is high and also part load efficiency better •Thermal efficiency is low, part load efficiency lesser •It is used where efficiency is important. •Ex-cars, buses, trucks, tractors, industrial engines, aero planes, power generation etc. •It is used where low cost, compactness and light weight are important. •Ex-lawn mowers, scooters, motor cycles, mopeds, propulsion ship etc.
  • 32. Disadvantages of a two stroke • The engines do not last as long due to poor lubrication. • You have to mix two cycle engine oil with gasoline. • The engines do not use fuel efficiently. • These engines produce a lot of pollution. • Two stroke engines are great for the power to weight ratio and their simple design, however, due to there pollution concerns these engines will be harder to find. Sub: THERMAL TOPIC:I.C ENGINE
  • 33. •Valve timing diagram • The exact moment at which the inlet and outlet valve opens and closes with reference to the position of the piston and crank shown diagrammatically is known as valve timing diagram. • It is expressed in terms of degree crank angle. The theoretical valve timing diagram is shown in Fig. Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 34. •Valve timing diagram • Four stroke Petrol engine Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 35. •Valve timing diagram • Four stroke Diesel engine Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 36. •Port timing diagram • Two stroke engine Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 37. •Scavenging of two stroke engine Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 38. •Supercharging Supercharging is the process of supplying the intake of an engine with air at a density greater than the density of surrounding atmosphere so that each intake cycle of engine gets more oxygen , which burns more fuel thus generating more power . Sub: THERMAL TOPIC:TYPES OF ENGINE
  • 39. •Supercharging Supercharging is the process of supplying the intake of an engine with air at a density greater than the density of surrounding atmosphere so that each intake cycle of engine gets more oxygen , which burns more fuel thus generating more power . Sub: THERMAL TOPIC:TYPES OF ENGINE Method-1
  • 40. •Supercharging Supercharging is the process of supplying the intake of an engine with air at a density greater than the density of surrounding atmosphere so that each intake cycle of engine gets more oxygen , which burns more fuel thus generating more power . Sub: THERMAL TOPIC:TYPES OF ENGINE Method-2
  • 42. •Terms Used in I C engine Sub: THERMAL TOPIC:I.C ENGINE
  • 43. 1. Cylinder bore (D): The nominal inner diameter of the working cylinder. 2. Piston area (A): The area of circle of diameter equal to the cylinder bore. 3. Stroke (L): The nominal distance through which a working piston moves between two successive reversals of its direction of motion. 4. Dead centre: The position of the working piston and the moving parts which are mechanically connected to it at the moment when the direction of the piston motion is reversed (at either end point of the stroke). (a) Bottom dead centre (BDC): Dead centre when the piston is nearest to the crankshaft. (b) Top dead centre (TDC): Dead centre when the position is farthest from the crankshaft. Sub: THERMAL TOPIC:I.C ENGINE
  • 44. 5. Displacement volume or swept volume (Vs): The nominal volume generated by the working piston when travelling from the one dead centre to next one and given as, Vs= A × L 6. Clearance volume (Vc): the nominal volume of the space on the combustion side of the piston at the top dead centre. 7. Cylinder volume (V): Total volume of the cylinder. V = Vs + Vc 8. Compression ratio (r): It is the ratio of total volume of cylinder to the clearance volume. r = Vs+Vc/ Vc 9. Piston speed: The distance moved by piston in one minute. Sub: THERMAL TOPIC:I.C ENGINE
  • 45. Swept and Displaced Volumes • Swept Volume/cylinder: s A s d 4 = V p 2 B s     Vs = swept volume dB = bore diameter s = stroke s s x Ap Inlet Port Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
  • 46.  Indicated Power (IP) The total power developed by combustion of fuel in the combustion chamber is called Indicated Power (IP). It can be calculated as: Where n = number of cylinders Pmi = Indicated mean effective pressure, (bars) L = Length of stroke, (m) A = Area of piston, (m2) K = 2 for 4 stroke engine = 1 for 2 stroke engine Indicated power is the total power of engine which is graphically represented by area of cycle on P-V chart. As the actual P-V diagram of an engine is drawn by an indicator mechanism, this power is called indicated power. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
  • 47. Brake Power (BP) The power available at an engines output shaft is called its brake power. It is the power which can be positively used against resistive force or braking force of the application for which engine is being used. It can be calculated as: Where N = engine speed in rpm T = Torque at output shaft in N-m. B.P= (W-S)ΠDN KW 60*1000 Where Pmb = Brake mean effective pressure. All other notations are same as in the expression of I.P. given in equation Comparing equations BOTH , Torque T= Constant Pmb Thus the torque of an engine depends on its size (AL) and mean effective pressure. Torque of a given engine of constant size will be more when its mean effective pressure is more. Hence, mean effective pressure is a true parameter to compare power of engines. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
  • 48. Frictional power It is the power required to overcome the internal friction of engine. It represents the total losses occurred from indicated power. It is the difference between Indicated power and Brake Power. F.P = I.P - B.P Mechanical efficiency It is the ratio of brake power to the indicated power of an IC Engine. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
  • 49. Thermal efficiency It is the ratio of work done or power developed by an engine to the rate of chemical energy or heat supplied by burning of fuel in the engine. It can be based on indicated power or brake power and accordingly can be specified as Where, mf = Rate of fuel consumed (kg / sec) C = calorific value of fuel (kJ/ kg) I.P. = Indicated power (kW) B.P. = Brake power (kW) Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
  • 50. Specific fuel consumption It is the mass of fuel consumed in kg/hour per kW of power developed by engine. It is a clear indicator of efficiency with which the engine burns fuel to produce power and is very important performance parameter. Sub: THERMAL TOPIC:DIFF.BET TWO & FOUR STROKE ENGINE
  • 51. NUMERICAL PROBLEMS EXAMPLE-1- The following data is available for a two stroke cycle, single cylinder oil engine: Mean indicated effective pressure = 550 kPa. cylinder diameter = 21 cm, Piston stroke=28 cm Engine speed = 360 RPM. Brake torque = 628 N.m., Fuel on= 8.6 kg/hr. Calorific value of fuel= 42700 kJ/kg. Find (1) Mechanical efficiency (2) Indicated thermal efficiency (3) Brake thermal Sub: THERMAL TOPIC: I. C ENGINE
  • 52. NUMERICAL PROBLEMS EXAMPLE-2- Following observations were recorded during a test on a single cylinder 4- stroke oil engine: Bore =300mm; Stroke = 450mm; Speed =300rpm; imep = 6bar; Net brake load = 1.5 kN; Brake drum diameter = 1.8m; Brake rope diameter = 2 cm. Calculate: (i) Indicated Power (ii) Brake Power (iii) Mechanical Efficiency Sub: THERMAL TOPIC: I. C ENGINE
  • 53. NUMERICAL PROBLEMS EXAMPLE-3- The Following observations were recorded during a test on a single cylinder 4- stroke C.I engine: Cylindre diameter =0.1m; Stroke = 0.15m; Speed =450rpm; imep = 7.5bar; brake load =220N spring balance reading= 20N ; Brake wheel diameter = 0.6m; c.v = 43000 kj/kg mass of fuel = 3 kg/hr Calculate: (i) Indicated Power (ii) Brake Power (iii) Mechanical Efficiency (iv) Indicated thermal eff. (v) Brake thermal eff. Sub: THERMAL TOPIC: I. C ENGINE
  • 54. NUMERICAL PROBLEMS EXAMPLE-4- The Following observations were recorded during a test on a single cylinder 4- stroke C.I engine: Bore diameter =24cm; Stroke = 40cm; Speed =250rpm; imep = 6.65bar; Net brake load =850N; Brake wheel radius = 75cm; C.V = 18690 kg/m^3 ; fuel used = 0.21 m^3/min Calculate: (i) Indicated Power (ii) Brake Power (iii) Mechanical Efficiency (iv) Indicated thermal eff. (v) Brake thermal eff. Sub: THERMAL TOPIC: I. C ENGINE
  • 55. Sub: THERMAL TOPIC: I. C ENGINE VARIOUS SYSTEM OF I C ENGINE 1.Ignition system 2.Cooling system 3.Governing system 4.Fuel supply System 5.Lubrication system
  • 56. 1.Ignition system • 1.Battery coil ignition System The ignition system is divided into 2-circuits: • (i) Primary Circuit: -consists of 6 or 12 V battery, ammeter, ignition switch, primary winding -it has 200-300 turns of 20 SWG (Sharps Wire Gauge) gauge wire, contact breaker, capacitor. • (ii) Secondary Circuit: • -consists of secondary winding or coil which have 21000 turns of 40 (S WG) gauge wire. -bottom end of which is connected to bottom end of primary and top end of secondary winding or coil is connected to centre of distributor rotor. -distributor rotors rotate and make contacts with contact points and are connected to spark plugs which are fitted in cylinder heads.
  • 57. 1.Ignition system • 1.Battery coil ignition System
  • 58. Ignition system 2.Magneto ignition system magneto will produce and supply the required current to the primary winding or coil - rotating magneto with fixed coil or rotating coil with fixed magneto for producing and supplying current to primary, remaining arrangement is same as that of a battery ignition system -no battery required - during starting the quality of spark is poor due to slow speed -very much compact
  • 60. Cooling system • Due to the combustion of fuel inside the engine cylinder, intense heat is generated. It has been experimentally found that about 30% of the heat generated is converted into mechanical work. Out of the remaining 40% of heat is carried away by the exhaust gases. The remaining part of the heat, if left unattended will be absorbed by the engine cylinder, cylinder head, piston, and valves. The overheating of these parts causes thermal stresses in the engine parts, which may lead to their distortion, seizure of the piston, burning of the valves and valve seats and reduces the volumetric efficiency. In order to avoid the above said adverse effects, it is very essential to provide some cooling system for an IC engine. Two types of cooling methods will be used in IC engines, i.e. Air Cooling and Water Cooling
  • 61. Cooling system • 1. Air cooling method
  • 62. Cooling system 2. Water cooling method 1. Thermosyphon method
  • 63. Cooling system 2. Water cooling method 2. Force cooling method
  • 64. Cooling system 2. Water cooling method 3. Pressurized water cooling system
  • 65. Lubrication system (a) Mist lubrication system (b)Wet sump lubrication system (c) Dry sump lubrication system Generally adopted in two stroke petrol engine line scooter and motor cycle. It is the simplest form of lubricating system. - It is the simplest form of lubricating system. It does not consist of any separate part like oil pump for the purpose of lubrication. - In this system the lubricating oil is mixed into the fuel (petrol) while filling in the petrol tank of the vehicle in a specified ratio (ratio of fuel and lubricating oil is from 12:1 to 50:10 as per manufacturers specifications or recommendations
  • 66. Lubrication system (b)Wet sump lubrication • In this system of lubrication the lubricating oil is stored in an oil sump. A scoop or dipper is made in the lower part of the connecting rod. When the engine runs, the dipper dips in the oil once in every revolution of the crank shaft, the oil is splashed on the cylinder wall. Due to this action engine walls, piston ring, crank shaft bearings are lubricated.
  • 67. Lubrication system (C)Dry sump lubrication • Supply of oil is carried in external tank. Oil pump draws oil from the supply tank and circulates it under pressure to various bearings of the engine
  • 68. Governing system (a)Qauntitative Governing In this system of governing, the quality of charge (i.e. air-fuel ratio of the mixture) is kept constant. But the quantity of mixture supplied to the engine cylinder is varied by means of a throttle valve which is regulated by the centrifugal governor through rack and pinion arrangement.
  • 69. Governing system (2)QaulityGoverning In this system of governing, a control valve is fitted in the fuel delivery pipe, which controls the quantity of fuel to be mixed in the charge. The movement of control valve is regulated by the centrifugal governor through rack and pinion arrangement.
  • 70. Governing system (C)Hit and Miss Governing In this system of governing, whenever the engine starts running at higher speed (due to decreased load), some explosions are omitted or missed. This is done with the help of a centrifugal governor. This method of governing is widely used for I. C. engines of smaller capacity or gas engines