Overview of Internal Combustion Engines

Aug 26, 2024

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.