Internal Combustion Engines The Diesel Objectives Uses for

Internal Combustion Engines – The Diesel

Objectives • • 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 Hacker

Engine Uses • • Emergency Diesel Generators (EDG) Propulsion • • • Certain amphibious landing ships Mine warfare ships Patrol craft Tug boats Small boats Outboard motors

Thermodynamic Principles • All internal combustion • • Gasoline (Otto) engine • • • Open cycle, heated engine Spark ignition Compresses air-fuel mixture Diesel engine • • Compressed ignition Compresses air only

Structural Components • Cylinder Block • • Part of engine frame that contains cylinders in which piston moves Supports liners & head

Structural Components • Cylinder Head/Assembly • • Crankcase • • Serves to admit, confine, and release fuel/air Cover to cylinder block Supports valve train Engine frame section that houses the crankshaft Oil sump • Reservoir for collecting and holding lube oil

Moving Components • Three Groups – according to motion • • • Reciprocating only (pistons and valves) Reciprocation & rotary (connecting rods) Rotary only (crankshafts and camshafts)

Moving Components • Piston • • • Piston Rings • • • Transfer heat from piston to cylinder Seal cylinder & distribute lube oil Piston Pin • • Acted on by combustion gases Lightweight but strong/durable Pivot point connecting piston to connecting rod Connecting Rod • • Connects piston & crankshaft reciprocating rotating motion

Moving 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 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

Operation • • 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

Operation • 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 Engine • 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 Engine • 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 Engine • Strokes • • Intake Compression Power Exhaust

Two-Stroke Diesel Engine • • • 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 Engine • 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 Engine • Strokes • • • Compression Power (Intake/Exhaust)

Two vs. Four-Stroke Engines • 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 Engine

Supporting 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 Systems • Ignition system • • • Cooling system • • Uses fresh water and/or salt water to cool Lubrication system • • Diesel has compression ignition Gasoline has spark plugs Provide lubrication and cooling Drive Train – Direct or Indirect

Safety Precautions • • Noise Fuel Flammability Maintenance Water Issues

Questions?