Marine Engine Principles Chapter 2

1
Marine Engine Principles(Chapter 2)
2
Overview

• How Engine Work
• Engine Energy Conversion
• Horsepower and Torque
• Displacement and Compression Ratio
• Internal Combustion
• Spark-Ignition, 4-Stroke
• Compression-Ignition, 4-Stroke
• Compression-Ignition, 2-Stroke
• Spark-Ignition, 2-Stroke

3
How Engines Work

• Internal Combustion within closed volume
• Require
• Fuel
• Air (oxygen)
• Source of Ignition
• The fuel burns inside the engine, where the
  rapidly expanding hot gases of the burning fuel
  act directly on the engines internal components.

4
Engine Energy Conversion

• Basic Support Systems
• Fuel
• Induction
• Ignition
• Cooling
• Lubrication
• Exhaust
• Gas engines are spark-ignition
• Diesel engines are compression-ignition

5
Horsepower and Torque

• Horsepower
• Amount of Work the engine is
  doing
• Measured in brake horsepower or kilowatts
• Torque
• Rotational Force of the
  engine
• Measured in pound-feet

6
Displacement

• Total Volume of the engines cylinders measured
  between Bottom Dead Center to Top Dead Center

7
Compression Ratio

• Combustion Chamber Volume at Bottom Dead Center
  divided by volume at Top Dead Center
• Gas engines 81 to 111
• Diesel engines 161 to 251

8
Internal Combustion Engines

• Steps
• Intake (power consumed)
• Compression (power consumed)
• Power (power delivered)
• Exhaust (power consumed)
• Power strokes of multiple-cylinder engines occur
  at equally-spaced intervals
• Flywheel used to store energy

9
Spark-Ignition, 4-Stroke
1 - Intake
2 - Compression
3 - Power
4 - Exhaust
One cycle every two crankcase revolutions
10
Spark-Ignition, 4-Stroke

• One cycle consists of four piston strokes
• Down, up, down and up
• Power delivered only during Power Stroke
• Ignition from Spark Plug
• Fuel and air in cylinder during compression cycle
• 81 to 111 compression ratio
• One Power Stroke for two complete revolutions of
  the crank shaft
• Intake (air and fuel) and Exhaust valves

11
Compression-Ignition, 4-Stroke
1 - Intake
2 - Compression
3 - Power
4 - Exhaust
One cycle every two crankcase revolutions
12
Compression-Ignition, 4-Stroke

• One cycle consists of four piston strokes
• Power delivered only during Power Stroke
• Ignition from compression heat
• Fuel injected at end of compression cycle
• 161 to 251 compression ratio
• One Power Stroke for two complete revolutions of
  the crank shaft
• Intake (air only) and Exhaust valves
• Diesel engines are heaver than gas

13
Compression-Ignition, 2-Stroke
1 - Intake
2 - Compression
3 - Power
4 - Exhaust
One cycle every crankcase revolution
14
Compression-Ignition, 2-Stroke

• One cycle consists of two piston strokes
• Power delivered only during Power Stroke
• Ignition from compression heat
• Fuel injected at end of compression cycle
• 161 to 251 compression ratio
• One Power Stroke per complete revolutions of the
  crank shaft
• Intake port for compressed air
• Exhaust valve

15
Spark-Ignition, 2-Stroke
1 - Intake
2 - Compression
3 - Power
4 - Exhaust
One cycle every crankcase revolution
16
Spark-Ignition, 2-Stroke

• One cycle consists of two piston strokes
• Power delivered only during Power Stroke
• Ignition from spark plug
• Fuel and air in cylinder during compression cycle
• 81 to 111 compression ratio
• One Power Stroke per complete revolutions of the
  crank shaft
• No cam driven valves
• Lubrication Oil mixed with fuel
• Few moving parts

17
Summary

• Internal combustion engine requires
• Fuel, Air (oxygen) and Source of Ignition
• Basic support systems
• Fuel, Induction, Ignition, Cooling, Lubrication
  and Exhaust
• Horsepower is work in bhp or kW
• Torque is rotation force in lb-ft
• Displacement is volume between BDC to TDC
• Compression Ratio is V at BDC / v at TDC

18
Summary -2

• Spark-Ignition (Gas)
• Low compression ratio of 81 to 111
• Spark plug used to ignite fuel and air
• Compression-Ignition (Diesel)
• High compression ratio of 161 to 251
• Fuel injected into hot (compressed) air

19
Summary - 3

• 4-Stroke
• Two revolutions of crankcase per Power Stroke
• Separate piston stroke for Intake, Compression,
  Power and Exhaust
• Uses Valves
• 2-Stroke
• One revolution of crankcase per Power Stroke
• Intake and Compression in one piston stroke
• Power and Exhaust in one piston stroke