Internal Combustion Engines – The Diesel References Required Principles of Naval Engineering –...
-
Upload
maximillian-chandler -
Category
Documents
-
view
217 -
download
0
Transcript of Internal Combustion Engines – The Diesel References Required Principles of Naval Engineering –...
Internal Combustion Engines –The Diesel
References
Required•Principles of Naval Engineering–(pP. 80-97)
Optional•Introduction to Naval Engineering–(Ch 11)
Objectives
A. Know the advantages, disadvantages, and capabilities of diesel engines in propulsion plants.
B. Comprehend the basic operation, key components, and safety considerations of diesel engines and propulsion plants.
C. Know the features of the diesel fuel systems and how it functions with respect to the safe operation of the engine.
The Diesel is a Hacker
Engine Uses
Harpers Ferry (LSD 49)
LCU
USS Oriole (MHC 55)
Emergency Power Generators
Structural Components
• Cylinder Block– Part of engine frame
that contains cylinders in which piston moves
– Supports liners & head
Structural 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 Components
• Three Groups – according to motion– Reciprocating only (pistons and valves)– Reciprocation & rotary (connecting rods)– Rotary only (crankshafts and camshafts)
Moving 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 Components• Crankshaft– Combines
work done by each piston
– Drives camshafts, generator, pumps, etc.
Moving Components• 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 increasehttp://www.myrctoys.com/engines/engine.swf
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
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 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– 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
Take Aways
• Draw a P-V diagram for a gas engine and diesel engine and explain the Otto cycle. Label the thermodynamic processes.
• Describe the major differences between a two stroke and four stroke engine. Give advantages and disadvantages of each.
• Describe a 4 stroke engine operation through one complete revolution of the crank shaft
• Discuss the necessity for starting air in a diesel engine
Questions?