4 Internal Combustion Engine Operation It is important to know and understand that there are several types of internal combustion engines but they all operate on the same basic principle or concept.Types of Internal Combustion EnginesTwo Stroke (Lawn Equipment, R.C. Hobby, Dirt Bikes, and Small Boats)Four Stroke (Cars, Trucks, SUV, Generators)Rotary (Wankle Design Mazda RX 8, Helicopters)Turbine (Jets)Rockets (Space Flight)
5 Internal Combustion Engine Operation Two Stroke, Four Stroke, Rotary, Turbine, & RocketsWhat do these Internal Combustion Engines Have in Common?While the overall design of these internal combustion engines is vastly different they all operate or function by converting an fuel/air mixture into heat inside a combustion chamber.The purpose of the internal combustion engine is to convert stored chemical energy into kinetic energy or the energy of motion.In this unit we will focus our attention on the four stroke internal combustion engine because most highway automobiles operate on the 4 stroke cycle.
7 Fuel & The four stroke engine There are 3 common fuels used in four stroke enginesDiesel FuelEthanolGasoline
8 Fuel & The four stroke engine Diesel FuelNamed after Rudolf Diesel the inventor of the four stroke diesel engine in 1894, Diesel fuel is a type oil that has a relatively low flash point of about 205ºF. Diesel oil will ignite within the combustion chamber as a result of the extreme heat generated on the compression stroke of the four stroke cycle. Because of diesel fuels low flash point and the diesel engines high compression ratio diesel engines do not require ignition systems for combustion to take place. Instead they use glow plugs to raise the temperature inside the combustion chamber on the first cycle of the four stroke process. Diesel Fuel is the leading fuel for heavy equipment like trains, heavy trucks, ocean vessels, power generators, and tractors.
9 Fuel & The four stroke engine EthanolEthanol is another name for denatured alcohol or pure grain alcohol. Ethanol was one of the first alternatives to diesel fuel. One of the earliest mass produced vehicles to operate on Ethanol was Henry Fords Model T. Prohibition in the 1920’s included alcohol produced for fuel so after 7 years of production Henry Ford switched to gasoline to power his engine. After this ethanol was not used as a common fuel until the late 1990’s when it was used as a 10% additive to gasolineAfter the turn of the century fuel manufacturers began to market E85 a mixture of 85% ethanol to 15% gasoline.While ethanol will work in modern gasoline engines it will corrode the fuel delivery components. Ethanol has once again claimed it status as an alternative fuel in passenger vehicles.
10 Fuel & The four stroke engine GasolineGasoline is the result of distilling crude oil. This process breaks crude oil down into several components including tar, grease, refined oil, kerosene, diesel oil, gasoline, natural gas, and other light gasses. Gasoline is most commonly used in light trucks and passenger vehicles. Gasoline has a much higher flash point of approximately 495ºF. Gasoline engines require an ignition system to ignite the air fuel mixture. Ignition systems include spark plugs, ignition wires, distributor, and an ignition coils. Even though gasoline is not the most efficient type of engine they lead the industry because they are versatile, quite, and their tailpipe emissions or exhaust are cleaner than most.
11 Fuel & The four stroke engine Comparing the Power Stroke of Diesel Vs. GasolineFuel InjectorSpark PlugDIESEL ENGINEGASOLINE ENGINEA fuel injector introduces fuel into the combustion chamber at the start of the power stroke.The heat from generated from the previous stroke ignites the fuel forcing the piston downward.The compressed fuel air mixture is ignited by a spark from the spark plug at the start of the power stroke forcing the piston downward.
13 The four stroke CycleCYCLE: A term that refers to the repetitive function of a mechanical system. The cycle is a function the is performed repeatedly.Stroke: One linear motion of a piston from TDC to BDC or from BDC to TDC. There are 4 strokes for every cycle in an internal combustion engine.TDC: Top Dead Center when the piston is at its absolute highest point of a given stroke.BDC: Bottom Dead Center when the piston is at its absolute lowest point of a given stroke.
14 What Are The Four Strokes The four stroke CycleWhat Are The Four StrokesINTAKESTROKECOMPRESSION STROKEPOWER STROKEEXHAUST STROKE1STSTROKE2NDSTROKE3RDSTROKE4THSTROKE
15 Air Fuel Mixture Is Drawn Into The four stroke CycleIntake StrokeFirst stroke of cyclePiston moves from TDC to BDCIntake valve openExhaust valve closedOn the intake stroke a precision mixture of fuel & air are drawn into the combustion chamber through the open intake valve. The Intake stroke may also be called the induction stroke.Exhaust Valve ClosedIntake Valve OpenAir Fuel Mixture Is Drawn IntoCombustion ChamberCrankshaftRotates180ºPistonMoves Downward
16 The four stroke Cycle Compression Stroke Second stroke of cycle Piston moves from BDC to TDCIntake & exhaust valves closedOn the compression stroke both valves remain closed while the piston is forced upward, as a result the air fuel mixture is squeezed or compressed preparing the mixture for ignition.Exhaust Valve ClosedIntake Valve ClosedAir Fuel Mixture is CompressedPiston Is Forced UpwardActing on the Air Fuel MixtureCrankshaftRotates180º
17 Combustion Gases Expand Spark Plug Fires Igniting The four stroke CyclePower StrokeThird stroke of cyclePiston moves from TDC to BDCIntake & exhaust valves closedSpark plug firesThe power stroke is the result of a process called ignition. When the spark plug fires the compressed fuel air mixture ignites. As the fuel air mixture ignites the gases begin to expand rapidly. Because the valves remain closed the gases push against the piston forcing it down.Exhaust Valve ClosedIntake Valve ClosedCombustion Gases ExpandSpark Plug Fires IgnitingAir Fuel MixtureCrankshaftRotates180ºPistonIs Forced DownwardWhen TheExpanding CombustionGasesAct On It
18 pushing against exhaust gasses The four stroke CycleExhaust StrokeFourth and final stroke of cyclePiston moves from BDC to TDCIntake valve closedExhaust Valve OpenDuring the exhaust stroke the piston travels upward forcing the spent exhaust gasses out of the combustion chamber through the open exhaust valve.Exhaust Valve OpenIntake Valve ClosedExhaust GassesForced outPiston forced upwardpushing against exhaust gassesCrankshaftRotates180º
19 The Four Stroke Process Animated The four stroke CycleThe Four Stroke Process Animated
21 Engine Components & Sub-Assemblies pushing against exhaust gasses Engine BlockThe Heart Of The Engine AssemblyCylinder BoresCoolant PassagesOil PassagesThe Engine Block is called the heart of the engine because all other components bolt to it. The block is the foundation for the entire engine assembly “The Engine Block contains the bearings that support the crankshaft and the cylinder…” bores where the pistons reciprocate. Some engine blocks house the camshaft. These are called pushrod type enginesIntake Valve ClosedPiston forced upwardpushing against exhaust gasses
22 Engine Components & Sub-Assemblies pushing against exhaust gasses CrankshaftMain bearing journals are supported by the engine block.Connecting rod bearing journals support connecting rod . Connecting rod journals are offset from main journalsCounter weights use gravitational forces keep the crankshaft rotating on 1st, 2nd, & 4th strokesThe purpose of the crankshaft is to convert the reciprocating (Up & Down) motion of the piston and rod assembly into rotary (Circular) motion. Rotary motion is needed to drive the camshaft and the output shaft.Intake Valve ClosedPiston forced upwardpushing against exhaust gasses
23 Engine Components & Sub-Assemblies pushing against exhaust gasses Piston AssemblyPistonWristpin or Piston PinConnecting RodConnecting Rod BearingsConnecting Rod Bearing End CapsThe Piston Assembly transfers the force of combustion from the piston through the connection rod to the crankshaft assembly.Intake Valve ClosedPiston forced upwardpushing against exhaust gasses
24 Engine Components & Sub-Assemblies pushing against exhaust gasses Camshaft AssemblyTiming Chain & SprocketCam BearingsCam Bearing JournalsCam LobesDistributor/Oil Pump GearThe crankshaft drives the camshaft at ½ the speed of itself. This is because of the 2:1 cam to crank gear ratio. Force can be transferred to the camshaft via belt & pulley, chain & sprocket, or gear to gear. As the camshaft rotates it transmits valve signals through the valve train assembly to the intake & Exhaust valves to command them open upon the appropriate stroke.Intake Valve ClosedPiston forced upwardpushing against exhaust gasses
25 Engine Components & Sub-Assemblies Cylinder Head AssemblyCast iron or cast aluminumCylinder heads contain spark plugs in gasoline engines and glow plugs in diesel enginesIn Most engines the cylinder head contains most of the valve train assembly.Cylinder heads are located at the top of the cylinder block and seal the combustion chamber on the 2nd and 3rd stroke. In many cases the cylinder may contain the camshaft these engines are called overhead Cam Design.Intake Valve ClosedPiston forced upwardpushing against exhaust gasses
26 Engine Components & Sub-Assemblies pushing against exhaust gasses Valve Train AssemblyValve lifters or tappetsPushrodRocker armValve springIntake & Exhaust ValvesThe Valve Train Assembly receives signals from the camshaft lobes to command open intake and exhaust valves on the appropriate strokes. Valves close when the valve springs return to their relaxed state.Intake Valve ClosedPiston forced upwardpushing against exhaust gasses
27 Engine Components & Sub-Assemblies Chevy 350 Small Block Exploded DiagramIntake Valve ClosedPiston forced upwardpushing against exhaust gasses
28 Engine Components & Sub-Assemblies Building A Complete Engine Assembly AnimationIntake Valve ClosedPiston forced upwardpushing against exhaust gasses