Internal Combustion Internal Combustion Engines –Engines –The DieselThe Diesel

ObjectivesObjectives

• Uses for internal combustion engines

• Thermodynamic principles involved• Components and purposes of each• Operation of systems

• Two stroke engines• Four stroke engines

The Diesel is a HackerThe Diesel is a Hacker

Engine UsesEngine Uses

• Emergency Diesel Generators (EDG)• Propulsion

• Certain amphibious landing ships• Mine warfare ships• Patrol craft• Tug boats• Small boats• Outboard motors

Thermodynamic Thermodynamic PrinciplesPrinciples

• All internal combustion• Open cycle, heated engine

• Gasoline (Otto) engine• Spark ignition• Compresses air-fuel

mixture• Diesel engine

• Compressed ignition• Compresses air only

Structural ComponentsStructural Components

• Cylinder Block• Part of engine

frame that contains cylinders in which piston moves

• Supports liners & head

Structural ComponentsStructural Components

• Cylinder Head/Assembly• Serves to admit, confine, and release

fuel/air• Cover to cylinder block• Supports valve train

• Crankcase• Engine frame section that houses the

crankshaft• Oil sump

• Reservoir for collecting and holding lube oil

Moving ComponentsMoving Components

• Three Groups – according to motion• Reciprocating only (pistons and

valves)• Reciprocation & rotary (connecting

rods)• Rotary only (crankshafts and

camshafts)

Moving ComponentsMoving Components• Piston

• Acted on by combustion gases• Lightweight but strong/durable

• Piston Rings• Transfer heat from piston to

cylinder• Seal cylinder & distribute lube

oil• Piston Pin

• Pivot point connecting piston to connecting rod

• Connecting Rod• Connects piston & crankshaft• reciprocating rotating

motion

Moving ComponentsMoving Components• Crankshaft

• Combines work done by each piston• Drives camshafts, generator, pumps, etc.

• Flywheel• Absorbs and releases kinetic energy of

piston strokes -> smoothes rotation of crankshaft

Moving ComponentsMoving Components

• Valves• Intake: open to admit air

to cylinder (with fuel in Otto cycle)

• Exhaust: open to allow gases to be rejected

• Camshaft & Cams• Used to time the addition

of intake and exhaust valves

• Operates valves via pushrods & rocker arms

OperationOperation

• Increased pressure of combustion gases acts on piston -> converted to rotary motion

• Can be 2 or 4 stroke engines• 2-stroke: 1 power stroke per 1

crankshaft rev• 4-stroke: 1 power stroke per 2

crankshaft rev

OperationOperation• Engine stroke

• A stroke is a single traverse of the cylinder by the piston (from TDC to BDC)

• 1 revolution of crankshaft = 2 strokes of piston

Four-Stroke Diesel Four-Stroke Diesel EngineEngine

• Intake stroke• Intake valve open, exhaust valve shut• Piston travels from TDC to BDC• Air drawn in

• Compression stroke• Intake and exhaust valves shut• Piston travels from BDC to TDC• Temperature and pressure of air

increase

Four-Stroke Diesel Four-Stroke Diesel EngineEngine

• Power stroke• Intake and exhaust valves shut• Fuel injected into cylinder and ignites• Piston forced from TDC to BDC

• Exhaust stroke• Intake valve shut, exhaust valve open• Piston moves from BDC to TDC• Combustion gases expelled

Four-Stroke Diesel Four-Stroke Diesel EngineEngine

• Strokes• Intake• Compressi

on

• Power• Exhaust

Two-Stroke Diesel Two-Stroke Diesel EngineEngine

• 1 power stroke every crankshaft revolution (vice every two w/ 4-stroke)

• Uses pressurized air to simultaneously supply new air and expel combustion gases

• Scavenging• Exhaust valve open, inlet port exposed• Pressurized air enters, expels combustion

gases• Piston near BDC

Two-Stroke Diesel Two-Stroke Diesel EngineEngine

• Compression• Intake and exhaust valves shut• Piston travels from BDC to TDC• Temperature and pressure of air

increase• Power stroke

• Intake and exhaust valves shut• Fuel injected into cylinder and ignites• Piston forced from TDC to BDC

Two-Stroke Diesel Two-Stroke Diesel EngineEngine

• Strokes• Compression

• Power• (Intake/Exhaust)

Two vs. Four-Stroke Two vs. Four-Stroke EnginesEngines

• Two-stroke advantages• Higher power to weight ratio• Less complicated valve train

• Four-stroke advantages• More efficient burning process• As size increases, power-to-weight

ratio improves

Gasoline vs. Diesel Gasoline vs. Diesel EngineEngine

Supporting SystemsSupporting Systems

• Air system• Supplies & removes air/gases• Air supplied at constant pressure by

blower/compressor• Fuel System

• Carburetor: mixes air & fuel in proper proportion (NOT on diesels)

• Fuel injector: sprays fuel in (more efficient)

Supporting SystemsSupporting Systems

• Ignition system• Diesel has compression ignition• Gasoline has spark plugs

• Cooling system• Uses fresh water and/or salt water to

cool• Lubrication system

• Provide lubrication and cooling• Drive Train – Direct or Indirect

Safety PrecautionsSafety Precautions

• Noise• Fuel Flammability• Maintenance• Water Issues

QuestionQuestions?s?