2. Internal Combustion Engines – The Diesel

3. References Required Principles of Naval Engineering – (pP. 80-97) Optional Introduction to Naval Engineering – (Ch 11)

4. 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.

5. The Diesel is a Hacker

6. Engine Uses Harpers Ferry (LSD 49) LCU USS Oriole (MHC 55) Emergency Power Generators

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

8. 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

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

10. 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

11. Moving Components Crankshaft – Combines work done by each piston – Drives camshafts, generator, pumps, etc.

12. Moving Components Flywheel – Absorbs and releases kinetic energy of piston strokes -> smoothes rotation of crankshaft

13. 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

14. 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

15. 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

16. 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 http://www.myrctoys.com/engines/engine.swf

17. 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

18. 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

19. 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

20. 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

21. Gasoline vs. Diesel Engine

22. 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)

23. 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

24. 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

25. Questions?