Presentation on theme: "Chapter 10 Motive Power Types– Spark-Ignition (SI) Engines"— Presentation transcript:
1 Chapter 10 Motive Power Types– Spark-Ignition (SI) Engines
2 Introduction Internal combustion engine is irreplaceable. Hauls food and water, delivers passengers, saves lives
3 Principles of Thermodynamic Internal Combustion Engines (1 of 3) Science branch dealing with heat and energyUsed in internal combustion engineMoves vehicle down road and provides powerOnce powered all equipmentSteam engines
4 Principles of Thermodynamic Internal Combustion Engines (2 of 3) Steam engine.Stirling engine.
5 Principles of Thermodynamic Internal Combustion Engines (3 of 3) <insert fig 44- 2>Stirling engineInternal replaced external combustion.Gas and diesel enginesICE classified in two waysPiston engines are SI or CI engines.
6 Principles of Engine Operation (1 of 9) Operate on physics and thermodynamicsUnderstanding will help diagnose.Tightly packed molecules increase expansion pressure.Burning black powder = fire.
7 Principles of Engine Operation (2 of 9) Pressure and temperatureDirectly relatedCylinder with moveable plungerDiesel engines use same principle.Heating increases molecule movement.
8 Principles of Engine Operation (3 of 9) Pressure changes temperature.Temperature changes pressure.
9 Principles of Engine Operation (4 of 9) <insert fig 44- 6>Temperature and energyMeasures energyLatent heat in various fuelsExpressed in Btu
10 Principles of Engine Operation (5 of 9) Pressure and volumeInversely related
11 Principles of Engine Operation (6 of 9) Force, work, and powerForce: effort to push or pullCompressed spring/cable moves to create work.Power: rate or speed at which work is performed
12 Principles of Engine Operation (7 of 9) Power and torqueTorque: twisting forceUnit of measurement: ft-lb or newton metersAmount of torque at crankshaft and speed of turning1 hp = 33,000 ft-lb/min
13 Principles of Engine Operation (8 of 9) Power and torque (cont'd)Calculate twisting by adding distance moved and time.Converting torque to work requires movement.
14 Principles of Engine Operation (9 of 9) Torque vs. horsepowerTorque: twisting or turning force and horsepowerNaturally aspirated enginesEngine rpm rises faster as torque falls.
15 Four-Stroke Spark-Ignition Engines (1 of 5) SI engines operate on four-stroke principle.Takes four strokes to complete one cycleCan be simple or complicated
16 Four-Stroke Spark-Ignition Engines (2 of 5) Basic four-stroke operationOne stroke out of the four delivers energy.Compression strokeIgnition occurs as piston reaches TDC.Exhaust stroke: end of power stroke
17 Four-Stroke Spark-Ignition Engines (3 of 5) Engine measurement—sizeICEs designated by volume pistons displaceCylinder borePiston strokePiston displacementEngine displacementCompression ratio
18 Four-Stroke Spark-Ignition Engines (4 of 5) Atkinson and Miller cycle enginesVariations on four-stroke engineUse larger throttle opening for powerAtkinson efficient within specific rangeLower max operating rpmCrankshaft mounted slightly off center
19 Four-Stroke Spark-Ignition Engines (5 of 5) ScavengingUses column of moving airEngine displacement.
20 Components of Spark-Ignition Engines (1 of 9) Widely used to power passenger vehiclesMain power plantGains in manufactureDivided into two assembliesThe compression ratio of an engine is found by taking the volume of the cylinder at BDC and comparing it to the volume at TDC. In this example, a 9:1 compression ratio is found.
21 Components of Spark-Ignition Engines (2 of 9) Short block and long blockSubassembly may be used.The engine contains many parts that work together to power the vehicle.
22 Components of Spark-Ignition Engines (3 of 9) Cylinder block, crankshaft, flywheelBlock is largest part of engine.Oil pan completes crankcase.Crankshaft is composed of cast iron or steel.Crankshaft has main journals.
23 Components of Spark-Ignition Engines (4 of 9) Connecting rod and pistonConnecting rod is made of cast iron, steel, aluminum, or titanium.Rod causes piston movement.Piston is composed of aluminum or synthetic materials.Head is exposed to heat and pressure.
24 Components of Spark-Ignition Engines (5 of 9) Ring landsAreas between the ring grooves that support the rings as the piston moves
25 Components of Spark-Ignition Engines (6 of 9) The oil panSeals and holds oilHouses oil pump
26 Components of Spark-Ignition Engines (7 of 9) The cylinder headMade of cast iron or aluminum
27 Components of Spark-Ignition Engines (8 of 9) Engine cam and camshaftICE uses poppet valves.Flathead engines had valves in block.Camshaft is mounted on top of cylinder head.Lobes open to hold and close valve.
28 Components of Spark-Ignition Engines (9 of 9) Camshaft specificationsBase is rounded bottom part.Duration is used when designing lobe.High-performance engines have overlap.Two listings for cam specs
29 Valves (1 of 8) Open or close cylinder heads Intake controls flow of air/fuel in combustion chamber.Valve head is disc shaped.
30 Valves (2 of 8)Intake and exhaust valvesControl ICE
31 Valves (3 of 8) Mechanical and hydraulic valve train Combo of parts open and close engine valves.Adjustments are made by lifter.
32 Valves (4 of 8) Valve clearance Amount of slack between rocker arm and valve stem
33 Valves (5 of 8) Valve train drives Driven by camshaft Chains louder than beltsFreewheeling engineTiming chain differs between cam-in-block and OHC.
34 Valves (6 of 8) Valve train drives (cont'd) OHC requires longer timing chains.Belts use toothed or cogged belt.
35 Valves (7 of 8) Intake manifold Part of air intake/induction Many changes
36 Valves (8 of 8) Exhaust manifold Output side of engine breathing apparatus
37 Two-Stroke Spark-Ignition Engines (1 of 2) Produce large power to weight ratioEvery other stroke is power.
38 Two-Stroke Spark-Ignition Engines (2 of 2) Basic two-stroke cycle engine principlesDiffers from four-stroke SI engineOne revolution for every cycle in two-strokePiston movement creates suction.Piston moves up to TDC.Piston moves up, compression in cylinder
39 Rotary Combustion Spark-Ignition Engines (1 of 2) Fewer parts usedIncreased power and smaller engineRotary combustion in many applications
40 Rotary Combustion Spark-Ignition Engines (2 of 2) Basic principlesNot as commonNo reciprocating pistonSmooth and vibration freeBasic principles as rotary engineIntake cycle
41 Summary (1 of 9) Internal combustion engines are common. Combustion engines are piston or rotary.Piston engines are spark or compression ignition.Pressure and temperature are directly related.Internal combustion engines heat a gas.Pressure and volume are inversely related.
42 Summary (2 of 9) Force causes movement. Work = distance moved × force applied.Power = distance × force/time in minutes.Engine power is measured in torque.Torque is called engine output.Horsepower is the speed of torque.
43 Summary (3 of 9)Load factor = time a vehicle can operate at max speed and powe.Piston stroke = distance traveled from TDC to BDCInternal engines are two- or four-stroke.Five events must occur in a four-stroke engine.Compression ratio is based on cylinder volume.
44 Summary (4 of 9)Piston displacement: bore squared × 3.14 × stroke ÷ 4.Engine displacement: piston displacement × number of engine cylinders.Miller and Atkinson are variations of the four-stroke engine.Miller has engine-driven compressor.Atkinson has lower power output and torque.
45 Summary (5 of 9)Valve overlap: time intake and exhaust valves are openThere are 11 major components of an internal combustion engine.Cylinder block includes additional parts.Crankshaft: converts piston's reciprocating motion into rotary motionFlywheel stores energy from piston.
46 Summary (6 of 9) Connecting rod connects piston to crankshaft. There are seven components of the piston.Gases can leak past piston rings.Intake manifolds deliver air to cylinder head.Oil is stored in the oil pan.Camshaft opens valves.
47 Summary (7 of 9) There are four parts to a camshaft. Engineers must consider several issues when designing camshaft lobes.There are four parts of an intake valve.Intake valve is large and runs cool.Exhaust valves are small and run hot.
48 Summary (8 of 9) Valve clearance must be accurate. ECM controls variable cam timing.Engines are freewheeling or interference.Two-stroke engines use piston to open and close exhaust ports.
49 Summary (9 of 9)Internal combustion engine events are controlled by a piston.Rotary and Wankel engines use a rotor in place of a piston.Rotary engines have two spark plugs.Rotary engines have four phases.Faces of the rotor have a combustion chamber.
50 CreditsUnless otherwise indicated, all photographs and illustrations are under copyright of Jones & Bartlett Learning.