New Polytechnic, Kolhapur

Transcription

1 01. Fundamentals of I.C. Engine 01. Fundamentals of I.C. Engine 16 marks Content 1.1 Introduction 4 Marks Definition of I C engine. Engine nomenclature. 1.2 The working principle of Engine 6 Marks Four-Stroke Spark Ignition Engine. Four-Stroke Compression Ignition Engine. Comparison of Four-Stroke SI and CI Engine. Two-Stroke Engines Scavenging. Comparison of Four-Stroke and Two-Stroke Engine. 1.3 Classification, Specifications and applications 6 Marks Classification of engine on the basis of: Cycle of operation, Fuel, Method of Charging, Ignition, Cooling, Cylinder arrangement, camshaft layout. Merits and Demerits of Vertical and horizontal engines. Engine Specifications - Two Wheelers, Light Motor Vehicle, Medium Motor Vehicle and Heavy Motor Vehicle. Applications of I C Engines Introduction: Definition of I C engine. The internal combustion engine is an engine in which the combustion of a fuel (normally a fossil fuel) occurs with an oxidizer (usually air) in a combustion chamber. It is an engine in which combustion of fuel and air takes place in closed chamber Basic Engine nomenclature:(basic Engine Components) Spark Plug Inlet Valve Outlet (Exhaust) Valve Combustion Chamber Gudgeon Pin Piston Rings Piston Cylinder Crank Pin Connecting Rod Crank arm Crank Case Crank Shaft Figure shows single cylinder spark ignition internal combustion engine 1

2 1. In cylinder a piston travels in reciprocating motion. The space between upper part of cylinder and top of piston is called combustion chamber. 2. Piston has circumferential grooves for piston rings, which prevents leakage of charge from combustion chamber. 3. In the cylinder head there are 2 valves, Inlet valve for talking charge inside cylinder & Exhaust valve for discharging the products of combustion. 4. A spark plug at top of cylinder initiates the combustion. The energy of expanding gas is transmitted by the piston through gudgeon pin to connecting rod. 5. The connecting rod and the crank arm of crankshaft translate the reciprocating motion of piston in to rotational motion of crankshaft. 6. Crankshaft is supported in bearing attached to the crankcase. 7. Crankcase is the main body of the engine to which the cylinder block is attached. Terminologies used in internal combustion Engine: 1. Cylinder bore (D): The nominal inner diameter of the engine cylinder. 2. Piston area (A): The area of a circle whose diameter is equal to the cylinder bore. 3. Stroke (L): The distance travelled by the piston in moving from T.D.C to B.D.C. 4. Dead centre: The position of the working piston and the moving parts which are 2

3 mechanically connected to it at the moment when direction of the piston s motion is reversed. a) Bottom Dead centre (BDC): This refers to the position of the crankshaft when piston is in its lowest position i.e. when piston is nearest to the crankshaft. b) Top Dead centre (TDC): This refers to the position of the crankshaft when the piston is in its topmost position i.e. when the piston is farthest from the crankshaft. 5. Displacement volume or Piston swept volume (Vs): The nominal volume generated by the piston when travelled from 1 dead centre to the other. It is calculated as product of piston area and stroke. Swept Volume (Vs) = A x L (W-12) 6. Clearance Volume (Vc): The volume of the space on the combustion side of the piston at TDC. Clearance Volume (Vc) = V - Vs 7. Cylinder Volume(V): The sum of piston swept volume and clearance volume. Cylinder volume (V) = Vs + Vc. 8. Compression ratio (r): The ratio of cylinder volume divided by the clearance volume. Compression ratio (r) = V/ Vc Above given are some important terminologies used in internal combustion engine. 3

4 1.2 The working principle of Engine A. Four Stroke Spark ignition engine (SI): Stroke Suction Compression Power Exhaust Crank Rotation Inlet Valve Open Close Close Close Exhaust valve Close Close Close Open 1) Exhaust Valve, 2) Spark Plug, 3) Inlet Valve,4)Piston Pin, 5)Piston,6)Cylinder, 7)Connecting rod, 8) Crank, 9)Crank shaft, 10)Crank Pin. Working: In this working cycle is completed in 4 strokes of piston or 2 complete revolutions of crankshaft. In this engine, valve s are used and complete compression of the charge takes place. 1. Suction stroke : In the stroke inlet valve is opened and exhaust valve is closed. When piston goes down from TDC to BDC, the Vacuum is created inside the cylinder and charge (proportionate mixture of air and fuel) is drawn inside the cylinder. This will continue till piston reaches BDC (i.e.: crank rotates through 180 ). 2. Compression stroke: The Inlet and exhaust valve are closed. The charge is compressed as piston moves from BDC to TDC. The crank completes 1 complete revolution (i.e.: 360 ). 3. Power stroke or Working stroke: The Inlet and exhaust valves are closed. The charge is ignited by means of Spark plug and results in high temperature, high pressure gases push the piston from TDC to BDC. This stroke is known as Power stroke. The crank completes one and half rotation (i.e.: 540 ). 4. Exhaust stroke: 4

5 The Inlet valve is closed and exhaust valve is opened. The piston begins to move from BDC to TDC, exhaust valve is open through which the piston forces the burnt gases into the atmosphere. So working cycle is completed in 2 full rotation of crankshaft (i.e: 720 ).Above given is working principle of four stroke SI (PETROL) engine. B. Four Stroke Compression engine (CI): The working of four stroke CI engine is similar to 4 stroke S.I engine but it operates at much higher compression ratio. The compression ratio of SI engine is 6 10 while that of CI engine is In CI engine during suction stroke, only air is sucked instead the cylinder instead of air-fuel mixture as in SI engine. Due to high compression ratio the temperature generated in compression stroke is sufficient to self ignite the fuel which is injected into the combustion chamber at the end of compression stroke. In CI engine, a fuel pump and injector are provided to inject fuel into combustion chamber. Carburetor and sparkplug is not necessary in CI engine. Stroke Suction Compression Power Exhaust Crank Rotation Inlet Valve Open Close Close Close Exhaust valve Close Close Close Open 1) Exhaust Valve, 2) Injector, 3) Inlet Valve,4)Piston Pin, 5)Piston,6)Cylinder, 7)Connecting rod, 8) Crank, 9)Crank shaft, 10)Crank Pin. Working: The working of 4 stroke CI engine is as given below: 1. Suction stroke: During this stroke inlet valve is open and exhaust valve is closed. Only air is sucked into cylinder during this stroke. The piston moves from TDC to BDC and crank shaft rotates through Compression Stroke: The air inducted in the cylinder is compressed to the clearance volume. Both the valves are closed during this stroke. 5

6 The piston moves from BDC to TDC and crank shaft rotates through Power stroke or Working stroke: At the end of the compression stroke the fuel (diesel) is injected into the hot compressed air. The rate of injection is such a that pressure remains constant instead of change in piston position. Thus this stroke is called constant pressure stroke. After injection of the fuel is complete the hot gases expand. The piston moves from TDC to BDC position and crank shaft rotates through Exhaust Stroke: The inlet valve remains closed and the exhaust valve opens. The piston move from BDC to TDC position which pushes the burnt gases outside the combustion chamber. Crankshaft rotates by two complete revolutions through 720.Above given is working principle of four stroke CI (DIESEL) engine. Differentiate between SI and CI engine: (S12/W11/W12) 6

7 Two Stroke Cycle Engine: A. Two stroke Spark Ignition (Petrol) engine: (S12/W12) Working Principle of 2 stroke (SI) engine In 2 stroke SI engine working cycle is completed in 2 strokes of the piston or in 1 revolution of the crankshaft. It is a crankcase compression in which charge (proportionate mixture of air and fuel) before being supplied to engine cylinder is compressed by the pump action of underside of piston. It is used in small engines. In these engines ports are used instead of valves in the cylinder wall. Below given are 3 ports; 1. Transfer Port: The charge from crankcase is supplied to cylinder by means of transfer port. 7

8 2. Inlet Port: Charge is taken to crank case through inlet port. 3. Exhaust Port: It is used to discharge the burnt gases. Working: 01. Fundamentals of I.C. Engine The working principal of 2 stroke (CI) engine is as given below: FIG A: FIG B: The piston is at TDC and charge is being fired due to combustion of fuel, heat energy is produced. At the same time, the edge of piston uncovers the inlet port. Fresh charge enters in the crankcase. Due to the combustion piston goes down & the inlet port is covered then charge is compressed in crankcase. After completion of 4/5 th of the power stroke the exhaust port is uncovered and some of the burnt gases escape to the atmosphere. Later the piston uncovers the transfer port and allows fresh charge to enter into the combustion chamber through transfer port. Due to the deflector on the piston crown, fresh charge will move up to the top of the cylinder and forces out the remaining burnt gases through exhaust port. During scavenging process a apart of the fresh charge leaves the cylinder along with burnt gases. FIG C: After the piston reaches BDC it moves up and closes the transfer port first and then the exhaust port closes. The compression begins until piston reaches TDC, when piston is at TDC, the inlet port is again uncovered and the fresh charge is taken inside the crank case due to the partial vacuum created in crank case and at the same time charge is compressed in the combustion chamber due to ascending piston. Now piston is at TDC and the charge at high temperature and high pressure is burnt due to spark generated by spark plug and the cycle goes on repeating itself. (S12) Scavenging: Scavenging is process of forcing the burnt gases by deflecting the fresh charge across the cylinder. At the end of the expansion stroke, combustion chamber of the 2 stroke engine is left full of product of combustion. This is because there is no separate exhaust stroke to clear burnt gases. The process of clearing the cylinder after expansion stroke is called scavenging. B. Two stroke Compression ignition (Diesel) engine: (W11) In 2 stroke cycle compression ignition engine only air is compressed inside the cylinder and the fuel (diesel) is injected by an injector fitted in the head of the cylinder. There is no spark plug in this engine. The remaining operation of the 2 stroke cycle, compression ignition engine is exactly the same as those of spark ignition engine. 8

9 Comparison of 4 stroke and 2 stroke engine. Reason for using single cylinder 2 stroke & 4 stroke cycle engine (W11) a) 2 stroke engine find their application in scooters, small generating sets, pumping sets because of their simplicity and low cost. b) 2 stroke diesel engines are generally high powered engines because every revolution of the crankshaft we get 1 power stroke thus they are used in ships. c) 4 stroke single cylinder engine s find application in bikes, scooters, Mobile electricity generating sets because of high fuel efficiency as compared to 2 stroke engine, compactness, smooth working ability & less pollution as compared to 2 stroke engine. 9

10 1.3 Classification, Specifications and applications 01. Fundamentals of I.C. Engine Classification of Automobile engines: (W11/S12/W12) The automobile engines are classified on following basis: Engine classified on the basis of the types of cycle: A) Otto Cycle or Constant Volume cycle: (S12) The engine operating on this cycle are known as Otto cycle engine. The petrol engine operates on this cycle. 10

11 1 2 Adiabatic Compression. 2 3 Heat addition at constant volume. 3 4 Adiabatic Expansion. 4 5 Heat rejected at constant volume. At Point 1: The air in the cylinder is initially corresponding to p1, v1, T1 (pressure, volume & absolute temperature). The piston compresses the air adiabatically during compression stroke. Point 2: The condition of air is p2, v2, T2. The air now compresses to clearance volume of cylinder. A hot body is then brought into contact with cylinder end such a that heat is supplied at constant volume. This increases pressure and temperature of air, corresponding to p3, v3, T3. Point 3: The hot body is removed and the air is expanding adiabatically during the expansion stroke, up to point 4 corresponding to p4, v4, T4. Point 4: A cold body is then brought in contact with the cylinder end such a that the pressure drops at constant volume, corresponding condition p1, v1, T1. Thus the air finally returns to its original condition and the cycle is completed. B) Diesel Cycle or Constant Pressure Cycle: Diesel cycle was introduced by Dr. Rudolf Diesel. The engine operating on this cycle is known as Diesel engine. 1 2 Adiabatic Compression. 2 3 Heat addition at constant pressure. 3 4 Adiabatic Expansion. 4 5 Heat rejection at constant Volume. The diesel cycle differs from the Otto cycle in one respect. In Diesel cycle, the heat is added at constant pressure instead of at constant volume. From point 1 to 2: The air is compressed in the cylinder during the compression stroke. From point 2 to 3: Heat is added at constant pressure. From point 3 to 4: The air expands adiabatically. From point 4 to 1: finally the heat is rejected at constant volume. The air returns to its original condition and the cycle is completed. 11

12 1.2. Merit n Demerit of vertical and horizontal engine (W-12) Horizontal and vertical engine are identified by the line of stroke. If the line of an engine piston is vertical, its vertical engine. The line of stroke is horizontal it horizontal engine. Merits of vertical engine: (W 11/S12) Demerits of Vertical engine: (S12) Merits of Horizontal engine: Demerits of horizontal engine: Use of Engine (Application): (S12) I.C. engines are used in following application. 1. Road vehicles: 2 wheelers, Passenger cars, Light & heavy commercial vehicles. 2. Small aircrafts, Helicopters & Railway locomotives. 3. Marine applications, Ships. 4. Industrial electric power generation. 12

13 01. Fundamentals of I.C. Engine Motorcycle Specifications - Definitions of Terms The following provides definitions of terms to engine specifications as usually listed in the automobile magazines and on Internet Web sites. These definitions of terms should be easier to understand by user who would rather ride than learn the technical complexities of their machines. Bear in mind that whole books could be written about each term. We are only touching the basics. Engine Specifications Terms: No. of Strokes: Two Stroke or Four Stroke. No. of Cylinder: One Cylinder or Two Cylinder. Cooling: An engine can be liquid-cooled, air-cooled or oil-cooled Valves: There may be one or more valves used for intake and exhaust. The specs may indicate how many valves are used per cylinder or for the whole engine. Terms such as SOHC (Single OverHead Cam) and DOHC (Double OverHead Cam), etc. are used to indicate how the valves are opened and closed. There are other methods to operate the valves as well. Number of Cylinders: Engines can have one to six cylinders. A single-cylinder engine, sometimes called a thumper, is used in small bikes. Most power bikes have engines with two-cylinders arranged in many configurations including: V-twin, Parallel and Flat-twins. Engines may have more than two cylinders such as: Triples where three cylinders are lined up next to each other in a vertical position; In-line fours similar to a triple except with another cylinder added; V-4 engines such as used in Honda ST1300; V-6 engines such as used in Boss Hoss; Flat-six engines such as used in Honda Gold Wing 1500/1800s. There are other engines not described. Displacement: Displacement is the volume displaced in the cylinders of an engine as the pistons move from their bottom position to their highest position in the cylinders. Displacement is measured in either cubic centimeters (CC) or cubic inches (CI). Bore and Stroke: Bore is the diameter of the cylinder in the engine in which a piston moves up and down. Stroke is the distance that the piston moves up and down inside the cylinder. Fuel System: Either carburetor(s) or fuel injection is used. Specs usually identify the carburetor name. Fuel injection comes with different names such as Fuel Injection (FI), Digital Fuel Injection (DFI), Electronic Sequential Port Fuel Injection (ESPFI), Programmed Fuel Injection (PGM-FI),CRDI and TDI etc. Compression Ratio: When the piston is at the bottom of the cylinder, say you could pour 100cc of water into the sparkplug hole (both valves closed) and it would be full. When the piston is at the top of its stroke, you can only pour 10cc of water into the hole to fill it. The compression ratio would be 100 to 10 or 10 to 1. That's about as easy to understand as I can make it. Oops, forgot to say -- Higher compression ratios (in general) will let the engine make more power, require higher octane gas and be harder for the starter to turn over." Maximum Torque: Torque is described as twisting force. This is the maximum amount of twisting force the engine can put out and at what value of engine Revolutions Per Minute (RPM). Put simply, torque is the "grunt, stretch your arms, push your eyeballs into their sockets" quality when you aggressively use the throttle 13

14 and accelerate hard. The higher the number, the more forceful that feeling is. Maximum Horsepower: This is the maximum amount of horsepower delivered by the engine. It occurs at a particular engine speed. Horsepower (HP) and torque are interrelated with RPM by the formula HP = TORQUE X RPM / Other Various Dimensional Specifications: Various Dimensions: Seat Height: Seat height may be given as measured with a rider aboard (laden) or it may be given unladen. Riders may be interested in the seat height to tell them how easy it will be for them to get their feet flat on the pavement when stopped. Rake and Trail: Rake is the angle of the fork away from vertical toward the rider. Trail is the distance on the ground between a vertical line dropped straight down from the center of the wheel and a projection of the fork extended until it touches the ground. As the rake increases, the trail increases. The more rake, the more stable the handling at speed. As rake decreases, handling becomes easier at low speeds. Wheelbase: This is the number of inches measured from front axle to rear axle. Weight: Weight may be given as wet weight with all lubricants, liquids and gasoline added or it may be dry weight with nothing added. Fuel Tank Capacity: Capacity is usually given including reserve tank. Some Engine Specification: Royal Enfield Bullet 500 Bike Technical Specifications: 499cc, Single Cylinder, 4 Stroke Engine Maximum Power: rpm Maximum Torque: rpm Bore x Stroke: 84mm x 90mm Compression Ratio: 8.5:1 Lubrication: Wet Sump Clutch Type: Wet, Multiple Plate Ignition System: Digital Electronic Ignition Transmission Type: 5-Speed Constant Mesh Chasis: Single Downtube, Using Engine As Stressed Member Suspension: Front- Telescopic, 35mm Forks, 130mm Travel, Rear- Twin Gas Charged Shock Absorbers With 5-Step Adjustable Preload, 80mm Travel Brakes: Front- 280mm Disc, 2-Piston Caliper, Rear- 153mm Drum, Single Lead Internal Expanding Front Tyre: 3.25 x 19 Rear Tyre: 3.50 x 19 Battery: 12V, 14 Ah Head Lamp: 60W/55W, Halogen Tail Lamp: 21W/5W Fuel Tank Capacity: 14.5 Ltr Ground Clearance: 135 mm Wheelbase: 1370 mm Dimensions: 2200 x 1120 x 800 mm Kerb Weight: 187 kg Royal Enfield Bullet 500 Price in India: Approx. Rs. 1,24,000 /- INR. 14

15 Honda Activa-i 2-wheeler Technical Specifications: 109cc, 4-Stroke, Single Cylinder, Air Cooled OHC Engine Maximum Power: 7,500rpm Maximum Torque: 5,500rpm Air Filter: Viscous Paper Filter Transmission Type: V-Matic Chasis Type: High Rigidity Underbone Type Suspension: Front- Bottom Link With Spring Loaded Hydraulic Damper, Rear- Unit Swing With Spring Loaded Hydraulic Damper Brakes: Drum, 130mm dia With CBS Tyre: Tubeless Battery: 12V-5 Ah Head Lamp: 35/35W, Helogen Fuel Tank Capacity: 5.3 Ltr Under Seat Storage: 18 Ltr Ground Clearance: 165 mm Weight: 103 kg Maruti Swift VDi Technical Specs Dimensions & Weight Length Width Height Capacity Seating Capacity Doors 3850 mm 1695 mm 1530 mm 5 Person 5 Doors No of Seating Rows 2 Rows Engine & Transmission Engine Type DDis Diesel,CRDI Displacement 1248 cc Fuel Type Diesel Wheelbase 2430 mm Ground Clearance 170 mm Kerb Weight Bootspace 1060 kg 205 litres Fuel Tank Capacity 42 litres Alternate Fuel Bore x Stroke Not Applicable 69.9 mm x 82 mm Compression Ratio 17.6:1 Max Power RPM Valve/Cylinder (Configuration) 4, DOHC Max Torque Mileage (ARAI) RPM 22.9 kmpl Cylinders Fuel System Transmission Type 4, Inline CRDI Manual 15

16 No of gears 5 Gears 01. Fundamentals of I.C. Engine Sport Mode 0 Dual Clutch 0 Suspensions, Brakes, Steering & Tyres Drivetrain FWD Suspension Front Suspension Rear Front Brake Type Rear Brake Type Steering Type MacPherson Strut Torsion Beam Disc Drum Power Steering with Tilt ASHOK LEYLAND 2516 SPECIFICATION Engine : 6 Cylinder Turbocharged Intercooled Max. Power : rpm Max. Torque: rpm Clutch :Hydraulic Single Plate Ceramic clutch Gearbox :6 speed Syncromesh Rear Axle :Fully floating single speed hypoid gear Front Axle :Forged Section I reverse elliot type Suspension:Semi Elliptic laminated multi leaf Steering :Power Assisted steering RH / LH Brakes :Full air pressure diaphragm, dual line circuit Minimum Turning Radius Front Tyres Rear Tyres 4.8 metres 165 / 80 R / 80 R14 Tyres: 10 x 20-16PR Max speed : 74.5 kmph Max Gradeability:18% GVW : kg Wheelbase : 810 / 4572 / 5029 mm Overall length:7153 / 8580 / 9335 mm Overall Width: 2432 mm Turning circle Diameter :18.5 / 19.7 / 21 m Options :Day / Sleeper Cabin Payload :10T Tanker : Water/Fuel - 15KL, Fuel - 18KL Tipper:14 cu.m. Goods carrier: 21ft / 23.5ft RMC : 6 cu.m. 16