Internal Combustion Engine (IC Engine) Overview

• Definition: An IC engine is an internal combustion engine where ignition and combustion of fuel occur inside the engine.
• Principle: Charge is ignited inside a combustion chamber under high pressure.

Historical Background

• First Commercially Successful IC Engine: Created by ATN Lenore around 1860.
• First Modern IC Engine: Known as the Auto Engine, created in 1876 by Nikolaus Otto.

Types of IC Engines

• Common Types:
  • Two-stroke piston engines
  • Four-stroke piston engines
  • Six-stroke piston engines
  • Wankel rotary engines

Components of IC Engine

Main Parts

• Cylinder Block: Structure containing cylinders and other components.
• Cylinder: Chamber where fuel is combusted and power is generated.
• Cylinder Head: Sits above the cylinders and forms the roof of the combustion chamber.
• Piston: Movable part that converts energy from combustion into mechanical work.
• Piston Rings: Metallic rings sealing the combustion chamber, minimizing gas loss to the crankcase.
• Connecting Rod: Connects the piston to the crankshaft; converts reciprocating motion into rotary motion.
  • Small End: End that connects to the piston.
  • Big End: Connects to the crankshaft.
• Crankshaft: Converts reciprocating motion into rotational motion.
• Crankcase: Main housing providing support for the cylinder and crankshaft bearings.
• Valves: Control air intake and exhaust from the cylinder.
• Crank Pin: Connects the crankshaft to the connecting rod.
• Intake and Exhaust Ports: Passages between the manifold and the valves.
• Spark Plug: Used in petrol engines to ignite the air-fuel mixture.
• Injector: Used in diesel engines to spray fuel into the combustion chamber.

Working Principles of Different Engine Types

Four-Stroke Petrol Engine

• Cycle: Autocycle (constant volume cycle)
• Four Strokes: Intake, Compression, Power, Exhaust (completed in two revolutions of the crankshaft).
  • Intake Stroke: Inlet valve opens, and air-fuel mixture enters the cylinder.
  • Compression Stroke: Piston moves upward, compressing the mixture.
  • Power Stroke: Spark ignites the mixture, pushing the piston down.
  • Exhaust Stroke: Exhaust valve opens, burnt gases exit.

Four-Stroke Diesel Engine

• Cycle: Diesel cycle (constant pressure cycle)
• Similar to Petrol Engine but uses an injector instead of a spark plug.
  • Intake Stroke: Air enters the cylinder.
  • Compression Stroke: Air is compressed; diesel fuel is injected.
  • Power Stroke: Combustion pushes the piston down.
  • Exhaust Stroke: Exhaust gases are expelled.

Two-Stroke Petrol Engine

• Cycle: Completes in one revolution of the crankshaft.
• Two Strokes: Combines intake, compression, power, and exhaust.
  • First Stroke: Piston moves up, compressing the mixture and drawing in fresh charge.
  • Second Stroke: Combustion occurs, pushing the piston down and expelling exhaust.

Two-Stroke Diesel Engine

• Similar Operation to the two-stroke petrol engine but uses diesel fuel.

Advantages and Disadvantages

Four-Stroke vs. Two-Stroke Engines

Advantages of Two-Stroke Engines:

• Higher power output (1.7 times that of four-stroke).
• More uniform turning effort on the crankshaft.
• Lighter and smaller.
• Simpler gear arrangement for reversing.

Disadvantages of Two-Stroke Engines:

• Higher cylinder temperature increases fire risk.
• More lubricant consumption.
• Lower thermal efficiency due to fuel losses during scavenging.
• Higher wear and tear due to faster valve gear operation.

Conclusion

• Understanding IC engines is crucial for various applications in automotive and mechanical engineering.
• Further learning resources available.