Engine Basics

Internal Combustion Engine

3/2/2009 AST335_2000 1Source: John Deere FOS Series

Engine Components• Cylinder Block

• Main housing of Engine

• Cylinder Head• Valves, Intake & Exhaust Passages, Injectors (Spark Plugs)

• Valve Train• Camshaft, Opens and closes the valves• Rocker Arm

• Piston, Connecting Rod• Piston• Connecting Rod

• Crankshaft, Flywheels, Balancers• Flywheel, maintains momentum

B l D F• Balancers, Dampen Forces

• Bearings• Main Bearing

B i I t

3/2/2009 AST335_2000 2

• Bearing Inserts

Engine Cylinder• Types Cylinders• Types Cylinders

• EnBloc• Dry Liner

W Li• Wet Liner

• Wear• Taper

– Larger Dia at Top• Out-of-roundness

– Perpendicular to Crankshaft– Major Thrust Face– Minor Thrust Face

• Replace 0.005” (0.13mm)

• Honing of Cylinders• Cross-Hatch Pattern

– Rings catching

3/2/2009 AST335_2000 3

– Provide Lubrication





Cylinder HeadC li d H d• Cylinder Head– Iron and Copper, Aluminium– Oil Ports, Valves, Intake & Exhaust Ports, ,– Cylinder Head Gasket

C li d H d W i• Cylinder Head Warping– Tightening sequence

• Order of tighteningSource: John Deere FOS Series

• Multiple stage process» Torque 1, Torque 2» Additional 1/x turns

• Leaks and Cracks– Water & Air Method

3/2/2009 AST335_2000 8

– Magnetic Crack Detector




Four Stroke Engine• Intake Stroke

• Piston TDC Piston BDC» Intake Valve Open (10o before TDC)» Intake Valve Closes (50o after BDC)

• Compression Stroke• Piston BDC Piston TDC

All V l Cl d» All Valves Closed

• Power Stroke (Ignition/Injection at TDC)• Piston TDC Piston BDC

E h S k• Exhaust Stroke• Piston BDC Piston TDC

» Exhaust Valve Open (50o before BDC)» Exhaust Valve Closes (10o after TDC)» Exhaust Valve Closes (10 after TDC)

Source: John Deere FOS Series

Two Stroke Engine (Roots Blower)


Two Stroke Engine (Crankcase Scavenging)



Characteristics of Four Stroke Compression Ignition & Spark Ignition EnginesCompression Ignition & Spark Ignition Engines

Characteristics Compression-Ignition Engine Spark- Ignition Engine

Compression Ratio 14-22 : 1 5-8 : 1Ignition Compression Electric SparkThermal Efficiency 30-60% 25-30%Fuel induction Injector Carburettor (Fuel Injection)Fuel System Fuel Oil / Diesel Gasoline (LP gas)Fi H d L G tFire Hazard Less GreaterPower Variation Increase in Fuel Increase in Air/Fuel MixtureAir Induction Constant VariableAir-Fuel Ratio 15-100 : 1 10-20 : 1Relative Fuel Consumption Lower HigherRelative Fuel Consumption Lower HigherEnergy per litre of fuel Higher LowerManifold Throttle Absent PresentExhaust Gas Temperature 482o C / 900 F 704o C / 1300 FStarting Harder EasierLubricants Heavy duty oils Regular and Premium OilsSpeed Range Limited (600-3200 rpm) Wide range (400-6000 rpm)Engine Mass per Horsepower 8 kg (17.5 lb) Average 4 kg (9 lb)Initial Cost High Much LowerLugging ability (Torque) Excellent LessLugging ability (Torque) Excellent LessTime Before Maintenance Good FairContinuous Duty Good Fair

The Valve Train• Valve Actuation

• Valve Timing – Camshaft• Camshaft Profile

– Base Circle, Flank, Nose, Valve Lift

– Cam Follower (Tappet)• Hydraulic Lifter

• Valve Timing• Valve Sealing

• Hydraulic Lifter– Push Rod

• No used in overhead cam– Rocker Arm

• Valve Clearance (Adjustment Screw)Valve Clearance (Adjustment Screw)– Hot Clearance, Cold Clearance

• Valve Seating– Valve Face, Valve Seat

• Tight Sealing of air (narrow contact area)g g ( )• Heat Transfer (wider contact area

– Valve Inserts• Valve Stem Clearance

– Valve guidesValve guides• Cooling, Oil consumption

• Valve Rotators– Release, Positive Rotators

• Crush Deposits

3/2/2009 AST335_2000 18

• Crush Deposits• Even Temperature


Valve Timing and Cam Profile

• Valve Overlap


• Valve OverlapIntake & Exhaust valve open

• Valve Profile• Base Circle• Flank• Nose

3/2/2009 AST335_2000 20

• Valve Lift

Valve Actuation• Valve Lift• Valve Lift

• Distance the valve lifts off the valve seat

• Valve (Tappet) Clearance• The gap betweem the top of the valve

stem and rocker arm when the valve follower is on the camshaft base

i l l ( / ld )• Typical Clearance (Hot/Cold ?)» Intake 0.25-0.50mm (0.010-0.020”)» Exhaust 0.3-0.75mm (0.12-0.030”)

• Clearance too smallClearance too small» Valve opens early, closes late» Valve may not close

• Clearance too large» Valve open late, closes early» Valve may remain closed

3/2/2009 AST335_2000 21


Valve Seating and Cooling• Valve Seating

• Valve Face, Valve Seat• Valve Inserts• Seating WidthSeating Width

– Wide Seating Width (3/32”), Better Cooling– Narrow Seating Width (1/64”), crushing of deposits– Interference Seating, good crushing but hotter valve

• Intake / Exhaust Valvesta e / aust Va ves• Exhaust Valves

– Smaller, less heat Transfer• Intake Valves

– Reduce pressure losses causing “vacuum”p g

• Heat Loss• Valve Seat / Valve Guides

– Heat Transfer to head

• Incorrect Seating / Valve Clearance• Incorrect Seating / Valve Clearance– Hot gas blow-bay, Greater Heating– Burnt Valves

3/2/2009 AST335_2000 23

V l R t tValve Rotators

• Wiping Action• Heat Distribution


Major Cause of Valve Failures• Distortion of Valve Seat

C li O t f R d & l t W d H d/Bl k I t i di• Cooling, Out of Round & loose seats, Warped Head/Block, Incorrect grinding

• Deposits on Valve• Blow-by, weak springs, tappet clearance, sticking valves, wide valve seats, lack valve

rotation

• Burnt Valves• Cooling system, Tappet clearance, • Pre-ignition

– Timing, Chamber deposits (Long Idling, Rich mixtures, Oil Burning, High Heat plugs, g, p ( g g, , g, g p g ,Compression ration, fuel

• Valve Erosion• Incorrect fuel, Incomplete burning, Lean Air/Fuel Ratios

• Cracked Valves• Cracked Valves• Thermal Fatigue

– Temperature & Pressure• Impact Damage

W id l l– Worn guides, valve clearance

• Warn Guides• Consequences

– Bad Seating, Impact at angle, oil burning, carbon deposits

3/2/2009 AST335_2000 25

• Causes– Worn rockers, poor lubrication, carbon deposits, cocked springs






Piston and Connecting Rod• Piston

• Eye, Shank, Head, Cap, Bearing Inserts, Piston Pin

j h ( f f i )• Major Thrust Face (Left of Piston)» Greater side thrust» Connecting Pin slightly Offset

• Minor Thrust Face

• Major Diameter (Perpendicular to Piston Pin• Minor Diameter (Parallel to Piston Pin)

Uneven expansion of piston as it heats up– Uneven expansion of piston as it heats up– Round when hot

• Top Piston slightly smaller than bottom skirt– Uneven expansion

3/2/2009 AST335_2000 31





Piston DesignDirect Combustion

– Low Surface area per unit vol– Higher Premix Combustion– Swirl

Swirl Ratio = Swirl Speed (rpm) / Engine Speed (rpm)

Indirect Combustion• Precombustion Chambers

– 20% to 30% clearance volume – High Temp (600 to 750°C).

• Swirl Chambers or Turbulence Chamber– 50% to 90% clearance volume – clean burning low levels of smoke, NOx, and HC

• Air Cell or Energy Cells – 5% to 15% clearance volume– Ignition occurs in the main chamber – 60% of the unburned fuel into the auxiliary chamber. – Lower peak pressures Low indicated thermal efficiency

Piston Rings• Compression Rings, Oil Ring

• Rectangularg• Inexpensive

• Taper Ring• Good Wiping of oil on down stroke, Seats quickly, only fair control blowbyp g q y y y

• Barrel Ring• Small contact area (low friction), Greater sealing pressure, lower blowby

• Inside Barrel• Twists in groove to form tighter seal during combustion

• Keystone Ring• Resist sticking of ring in carbon depositsg g p

• Ring require both side clearance and end clearance

3/2/2009 AST335_2000 37


Oil Consumtion and Blow-By

• Causes– Pumping by worn rings

• See figure• See figure– Rings incorrectly installed– Stuck Rings, plugged oil ring

• Deposits freeze rings– Heat, Unburnt fuel, oil breakdown

(sludge), PreIgnition, Broken Rings, worn groovesg

– Wear Piston, rings, cylinder• Abrasive wear• Scuffing & scouringScuffing & scouring• Corrosive wear

– Physical Damage

3/2/2009 AST335_2000 39

Major Cause of Piston Failures• Stuck Broken Rings

S ffi d i f Pi• Scuffing and scouring of Piston• Local Hot spot

• Corrosive wear• Physical Damage• Physical Damage

• Piston Pin locking• Pre-Ignition

– Lean Mixture, Low Octane, Advanced Timing, Over-fuelling, High Torque, Over-heating

Major Cause of Bearing Failures• Dirt (85%)• Dirt, (85%)• Lubrication (15%)• Assembly (14%)• Misalignment (10%)• Misalignment (10%)• Overload (8%)• Corrossion (5%)

3/2/2009 AST335_2000 40








Firing Interval & Order• Average Firing Interval

– Av. Interval = (B * 180o) / (# cylinders) – b=4 Four stroke, b=2 Two Stroke

• Firing Order (4 stroke)• 2 Cylinder

1 2– 1,2• 3 cylinder

– 1,2,3• 4 cylinder

– 1,2,4,3 or 1,3,4,2• 6 cylinder

– 1,5,3,6,2,4



Crank Dynamics

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Crank Dynamics

0 50 100 150 200 250 300 350 400

Position

Velocity

Accel_1

Crank Dynamics

0 50 100 150 200 250 300 350 400

Accel_1

Accel_2

Accel_3

Accel_4

Accel_

Types of Engines• Fuel Type

• Spark Ignition (Gasoline, LP-gas)• Compression Ignition (Diesel)

• Cylinder Arrangement• In-Line• V-Type• Opposed• Opposed

• Valve Arrangement• I-Head• H-HeadH Head• L-Head• T-Head


Intake and Exhaust Systems

• Intake• Air Filters• Blower/Supercharger Intercooler• Blower/Supercharger, Intercooler• Intake Manifold• Intake Valves

E h t• Exhaust• Exhaust valves• Exhaust Manifold• Turbocharger Turbine• Muffler


Cooling System

• Regulate Engine Temperature• Prevent overheating

• Air Cooling• Small engines aircraft Deutz• Small engines, aircraft, Deutz

• Liquid Cooling• Water (anti-freeze)• Radiator• Pump


Lubrication

• Reduce Friction• Dissipated Heat• Seal Piston Rings and Walls• Clean and Flush Parts

R d N i• Reduce Noise









Engine Basics

Documents

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