PEPM AEL2501
Automotive Engines
Lecture delivered by: Prof. Ashok C.Meti MSRSASMSRSAS--BangaloreBangalore
1 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501 Session Objectives • To understand the classification of automotive engines. • Study the constructional features and arrangement of various parts of IC engines. • Discus the new developments to improve the low-end performance of an engine • Understand the lubrication system and cooling system of an IC engine
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1 PEPM AEL2501 Topics • Introduction to automotive engines • 4S, Petrol and Diesel engines • Main engine components • Cooling system • Lubrication system
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PEPM AEL2501 Introduction to Automotive Engines • An automotive engine is acomplex piece of precisionprecision--builtbuilt machinery. • It provides power to drive the vehicle’s wheels. • In addition, it is also a source of power to other sub-systems like- – charging, – a/c unit, – hydraulic system for power steering, suspension, etc. • The engines used in automobiles are also
known as internal combustion engines as Ex: The mHawk Engine the burning of air and fuel mixture takes place inside the cylinder.
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2 PEPM Engine classification AEL2501 Some engine classifications include: • Cylinder arrangement • Type of aspiration – In-line*, V engine, opposed – Naturally aspirated engine piston / flat engine – Turbo* / super charged engine •Type of fuel burned • Number of valve / cylinder – Diesel* – 2 valves per cylinder* –Petrol – Multi valve engines – CNG / LPG • Valve location – Dual fuel engine • Type of ignition – L – head engine – Compression ignition* – I – head engine ( OHV)* – Spark ignition • Camshaft location • Number of strokes / cycle – Overhead cam engine – 4 – stroke cycle* – Cam in the block engine* – 2 – stroke cycle • Combustion chamber design • Cooling system type – Shapes: Pancake, wedge, – Water cooled engine* hemispherical, pent roof, pre- combustion chamber – Air cooled engine 5 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501
In-line Engines
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3 PEPM AEL2501 V- Engines
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PEPM AEL2501 Horizontally Opposed
PORSCHE 911 Carrera –flat 6, 3.8 Lt. 283 kW (380bhp), DFI 120bar multiple injection (at high load and speed<3500rpm), CR 12.5:1, 7 speed DCT,2W/4W, 0-100kmph in 4.3s, VarioCam+ Valve system, 8 M.S Ramaiah School of Advanced Studies - Bangalore
4 PEPM AEL2501 Four Stroke Petrol Engine Operation
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PEPM AEL2501 Four-stroke cycle: Diesel Engine
The four strokes of the engine operation requires 2 rotations of the crankshaft. 1Id1. Induc tion StkStroke • Starting from TDC, the piston moves downwards. • The inlet valve also opens at the same time and air is drawn into cylinder with out restriction by a throttle valve . • When the piston reaches the BDC, the cylinder capacity is the largest.
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5 PEPM AEL2501 2. Compression stroke • The inlet and exhaust valves are closed. • The piston’s upward movement compresses the air to the degree didbhdetermined by the compression ratio (16:1 to 24:1). • The air, in this process, heats up to 9000C. • Near the completion of the compression stroke, the fuel- injection system injects the fuel at high pressure (as much as 2000 bar in modern engines) in to hot compressed air in the CC. • When the cylinder reaches the TDC, the cylinder capacity is at its minimum. 11 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501 3. Ignition stroke • After the ignition lag (a few degrees of C/s rotation) the ignition stroke begins. • The finely atomized and easily combiblbustible diesel f uel spontaneously ignites and burns. • As a result, the cylinder charge heats up even more and pressure in the cylinder rises. • The mass of the fuel injected (quality based control) determines the amount of energy released. • The pressure forces the piston downwards. The C/s drive translates the KE of the piston into torque. 12 M.S Ramaiah School of Advanced Studies - Bangalore
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4. Exhaust stroke • Just before the piston reaches the BDC, the exhaust valve opens. • The hot pressurized gases flow out of the cylinder. • The upwards movement of the piston forces the remaining exhaust gas out of the cylinder .
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PEPM AEL2501
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7 PEPM Piston Assembly AEL2501 • The piston converts the potential energy of the combustion gases, into the kinetic energy that turns the crankshaft. • The piston is a cylindrical shaped Diesel Engine Piston hollow part that moves up and down inside the engine's cylinder. • It has grooves around its perimeter near the top where rings are placed. • The wrist pin connects the piston to the connecting rod. The connecting rod comes up through the bottom of the piston. • The wrist pin is inserted into a hole (b(about h hlfalf way up) )h that goes th rough the side of the piston, where it is attached to the connecting rod. • Pistons are usually made of aluminum alloy, because it is light and a good heat conductor. Petrol Engine Piston 15 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501
• Pistons perform several functions. – Transmit the driving force of combustion to the crankshaft. This causes the crankshaft to rotate. – Also acts as a moveable gas-tight plug that keeps the combustion in the cylinder. – Acts as a bearing for the small end of the connecting-rod. • The piston head or "crowncrown" is the top surface against which the explosive force is exerted. It may be flat, concave, convex or any one of a great variety of shapes to promote turbulence or help control combustion.
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8 PEPM Crank Shaft AEL2501
• The crankshaft converts the reciprocating motion of the pistons into a turning (rotary) motion. • The crankshaft is usually either alloy steel or cast iron. • The crankshaft is connected to the pistons by the connecting-rods. • Some parts of the shaft do not move up and down; they rotate in the stationary main bearings. These parts are known as journals. • There are usually five journals in a four cylinder engine
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PEPM AEL2501 Engine Block
Typical Cummins Engine Block
• A metal casting containing the cylinders and cooling ducts of an engine. • All other sub-systems are bolted to the block. • Cast Iron or Aluminum alloys are used to build the blocks.
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Cylinder sleeves or liners • They are inserts that fit into the cylinder block •Thlidllhey act as cylinder walls for the piston to reciprocate • Many vehicles use aluminum or CI cylinder blocks with cast iron, wet sleeves
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PEPM AEL2501 Engine Head • The cylinder head is the metal part of the engine that encloses and covers the cylinders. • Bolted on to the top of the block, the cylinder head contains combustion chambers (petrol engine), water jackets and valves (in overhead-valve engines). • The head gasket seals the passages within the head-block connection, and seals the Typical Diesel Engine Heads cylinders as well.
20 M.S RamaiahTypical SchoolPetrol Engineof Advanced Head Studies - Bangalore
10 PEPM AEL2501 Diesel combustion chambers
Indirect Injection: • In indirect injection, the fuel is injected into a separate chamber that is connected to the main chamber above the piston by a narrow passage-way. • When the piston rises toward top-dead-center, the air is forced through the connecting passage athiht high vel lititthocity into the small llh chamb er, call llded a swi ilhrl chamb er. • The high velocity air rotates at high velocity in the chamber as fuel is injected. • A glow plug inserted into the chamber helps during cold starting. • This type of system relies on the high velocity air swirl to mix the air so the fuel injection system can operate at lower pressures and be less expensive. • After the fuel ignites, the combusting mixture pushes back out through the passage-way where the rise in pressure does work on the piston. 21 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501
Direct Injection: • In the direct injection diesel engine, the fuel is sprayed into the combustion chamber directly above the piston. • The ppyiston usually has a recess or bowl that is designed to confine the air into a region that matches the fuel spray trajectory. • This type of system relies primarily on the momentum of the fuel spray to mix the fuel and air. • The indirect injection (IDI) engine is less efficient than the direct injection (DI) engine. • This is because the high velocity air motion in the combustion chamber causes high heat transfer rates resulting in greater loss of fuel energy.
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11 PEPM AEL2501 Valve Train • The valve train consists of the valves and a mechanism that opens and closes them. • The opening and closing system is made up of a camshaft and rocker arms. • The camshaft has lobes on it that move the valves up and down. Diesel Engine Cam shaft
Poppet valves
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PEPM AEL2501 Common valve mechanisms
Overhead cam engine with OHV
Valve in block or L-head Cam-in-block / I –head (pushrod valve M/sm 24 M.S Ramaiah School of Advanced Studies - Bangalore
12 PEPM AEL2501 Valve Timing Diagram – Petrol Engine
(Advanced inlet gives more top end power at the expense of low end power, and vice-versa) 25 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501 Valve Timing Diagram – Diesel Engine
SOC- start of combustion IO- Inlet open IC- Inlet close IP- Injection point EO-Exhaust open EC-Exhaust close
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13 PEPM AEL2501 Flywheels • A flywheel is bolted to the crankshaft flange • The flywheel is also fitted wwggeowceith a ring gear to which the starter pinion meshes while cranking the engine using starter. • The clutch cover with the clutch disc are bolted to the flywheel. • In certain diesel engines used on light vehicle, the flywheel will be replaced with a DMF for smoother, vibration free operation. 27 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501
Engine Cooling System
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14 PEPM AEL2501 Cooling System: Introduction • In a typical gasoline engine, about 33% of the total heat input is lost to the coolant. • The cooling system is responsible for dissipating this heat to the atmosphere • The cooling system used in engines can be – – Liquid cooled system –used in engines used in cars and trucks Heat loss in an engine – Air cooled system –used in smaller engines like two- wheelers
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PEPM AEL2501 Functions of cooling system • Cooling system has several functions: – Removing excess heat from engine • The combustion of the fuel produces tremendous amount of heat • Combustion flame temperatures can reach approx 2500 degree Centigrade- enough to melt the metal parts • Part of this is removed by the cooling system fluid to protect the metal parts from damage – Maintaining a constant operating temperature • Engine operating temperature is the temperature the engine coolant reaches under normal running conditions • Typically, an engine’s operating temperature is in the range of 80 – 100 degree Centigrade • This temperature ensures that all part clearances are correct after expansions. • Also ensures proper combustion, emission output levels and engine performance – Increase the temperature of a cold engine quickly •An enggppypp,p,,ine must warm up rapidly to prevent poor combustion, part wear, oil contamination, reduced fuel economy, increased emissions and other problems. • Too much of clearances • Oil in a cold engine can be thick- increased wear • Improper vaporization of fuel – improper combustion – Provide a means for warming the passenger compartment • A cooling system commonly circulates coolant to the vehicle’s heater. • The engine coolant is warm, its heat can be used to warm the passenger compartment. 30 M.S Ramaiah School of Advanced Studies - Bangalore
15 PEPM AEL2501 Liquid cooling system • Circulates coolant (a solution of water and cooling fluid) through water jackets. • The coolant then collects excess heat and carries it out of the engine • Liquid cooling: – more precise control of the engine temperature – Less temperature variations in side the engine – Better temperature control leading to reduced ehaust emissions – Improved heater operation for Engine water jackets warming the passenger space
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PEPM AEL2501 Coolants • Ethylene glycol based engine coolant concentrate • 40 to 70 percent concentration in water • Effective during both winter and summer in automotive vehi cl e cooli ng systems to provid e protection against freezing, boiling and corrosion. • A typical coolant fluid used in cooling system consists essentially of: – ethylene glycol – corrosion inhibitors, –a foam suppressor, – sufficient water to dissolve the additives • Can be poured at temperatures as low as zero degrees -17.8 degrees C.
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16 PEPM AEL2501 Cooling system components
Conventional coolant flow type
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PEPM AEL2501
• Water pump: – A centrifugal pump forces coolant through the engine block, cylinder head, intake manifold, hoses and radiator – It is often driven by engine crankshaft through belt • Radiator – Transfers coolant heat to the outside air – Normally mounted in the front of the engine Scorpio water pump – Consists: • Radiator core • Radiator tanks • Radiator filler neck • Transmission oil cooler • Radiator drain cock
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17 PEPM AEL2501 Radiator Types
• Availability of space generally dictates the choice of the radiator. • Both cross flow and down flow radiators are used
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PEPM AEL2501 Radiator Pressure Cap
Closed system
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18 PEPM AEL2501 Thermostat • Senses engine temperature and controls the coolant flow through the radiator.
• It reduces the coolant flow when WllttthtttiWax pellet type thermostat operation engine is cold and increases as the engines gets warmer • Wax pellet type is commonly used. • When heated, the pellet expands and pushes the valve open. • As the pellet and the thermostat cool, the spring tension overcomes pellet expansidthllion and the valve closes • The rating of the thermostat is its operating temperature which is normally 82 – 91 degree Centigrade
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PEPM AEL2501
Engine Lubrication System
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19 PEPM AEL2501 Lubrication system functions • Important functions of lubricating systems. The system: – Reduces friction and wear and tear between moving parts – Helps transfer heat away from engine parts – Cleans the inside of the engine by removing contaminants (metal, dirt, plastic, rubber and other particles) – Cuts power loss and increases fuel economy – Absorbs shocks between moving parts to quiet engine operation and increase engine life
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PEPM AEL2501 Engine Oil Classifications: American Petroleum Institute (API) • API established a classification system for the designation of gasoline and diesel engine oils, which reflects the quality, performance, and suitability of the oils for various engines. • These classifications arearrangedintotwo different groups, – For automotivegasoline engine service – For commercial diesel engine service. • The former is listed in "S" or "Service" categories (*presently SA through SM) • The later is listed in "C" or "Commercial"
categories (*presently CA through CI-4 PLUS). # Energy conserving – reduce friction, Friction modifiers and other additives. 1.5% / 2.7% 40 M.S Ramaiah School of Advanced Studies - Bangalore
20 PEPM AEL2501 SAE Classification • A higher viscosity oil is very thick and resists flow and vise versa • SAE has established anoil viscosity classification system. • It is a numeric rating in which higher the number, higher the viscosity. • Single-viscosity oil: – Rated and designated for a limited range of operating temperatures. Its viscosity is not stable as multiviscosity oil • Multiviscosity oil: – Will exhibit operating characteristics of a thin oil light oil when cold and a thicker, heavier oil when hot. • Although singlesingle--viscosityviscosity oils are available, most engine oils aremultiviscosity oils .Ex: SAE 10W-30 • To specify engine oil, both the API service designation and the SAE viscosity grade are required. 41 M.S Ramaiah School of Advanced Studies - Bangalore
PEPM AEL2501 Components of Lubricating Systems • Main components of a typical lubricating systems: – Oil pump – Oil pump pi ck -up – Oil pan or sump – Pressure relief valve – Oil filter – Engine oil passage or galleries – Oil pressure indicator – Dipstick – Oil cooler
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21 PEPM AEL2501 Typical heavy duty diesel engine lubrication circuit
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PEPM AEL2501
• Oil pump: – Most commonly used oil pumps: • Rotor type • Gear type – Both are positive displacement type pumps. – The output volume is proportional to the speed of the pump. – Pump is directly or indirectly driven by the cam shaft or a gear at the front of the crankshaft.
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22 PEPM AEL2501 • Engine oil galleries: – The oil galleries consist of interconnecting passages that have been drilled completely through the engine block during manufacturing. – The oil is routed through these passages to various parts of the engine. – The crankshaft also contains oil passages to route the oil from the main bearing to the connecting rod bearing surfaces.
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PEPM AEL2501 • Oil filters – All the oil that leaves the pump is directed to the oil filter (Full-flow filter). – This is to ensure that very small particles of dirt and metal carried by the oil will not reach the close-fitting engine parts. – From filter, oil flows into engine’s main oil gallery.
Full-flow filtration system
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23 PEPM Example: Commercial vehicle engine AEL2501
Specifications 6.12TCA 6.12TCE Euro III, capability for Euro III, capability for Emissions Euro IV Euro IV Configuration 6, Inline 6, Inline Valves / Cylinder 44 Displacement – Lts 7.2 7.2 Bore x Stroke – mm 105 x 137 105 x 137 Combustion system Direct Injection Direct Injection Injection system Mechanical Common Rail • The combustion technology with 4 valve per 180 - 210 (132.5 - 260 - 315 (190 - 232) Power Output hp (kW) @ rpm cylinder and optimised fuel injection system 154.5) @ 2200 @ 2200 helps in achieving the stringent BS III 97.8 - 112 (960 - emissions without any after treatment and Peak Torque kgf-m (Nm) @ rpm 89.7 (880) @ 1400 not even EGR system. 1100) @ 1250 - 1500 • The superior combustion technology Weight (Dry) – kg 540 570 enables to meet the futuristic emission norms of BSIV also without any after‐ Dimensions – mm treatment like SCR or Catalytic convertors. Length 1100 1100 Width 734 734 Height 985 985
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PEPM AEL2501 Summary • The classification of IC engines based on various parameters, and engine applications have been explained. • The constructional details of the main parts of an engine like – piston assembly, block, head and valve mechanisms including the recent developments have been discussed. • The lubrication system and cooling systems of an IC engine has been explained
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