Types of Engines and Their Working Mechanism

Engine Definition

• An engine is a machine that converts heat energy from fuel into mechanical energy through combustion, typically with a piston.

Types of Engines

• External Combustion Engines: Fuel burns outside the engine cylinder, for example, a steam engine.
• Internal Combustion Engines (I.C. Engines): Fuel burns inside the engine cylinder. These are further categorized as:
  • Spark Ignition Engines (S.I. Engines): A mixture of air and petrol is ignited by a spark plug.
    • Two-Stroke Engines: Complete cycle in two piston strokes.
    • Four-Stroke Engines: Complete cycle in four piston strokes.
  • Compression Ignition Engines (C.I. Engines): Compressed air ignites the fuel injected into the cylinder.
    • Two-Stroke Engines: Complete cycle in two piston strokes.
    • Four-Stroke Engines: Complete cycle in four piston strokes.

Four-Stroke S.I. Engine Working

• Suction Stroke: Piston moves from top dead centre (T.D.C.) to bottom dead centre (B.D.C.), creating a vacuum, drawing in the air-fuel mixture.
• Compression Stroke: Piston moves from B.D.C. to T.D.C., compressing the air-fuel mixture, increasing its temperature.
• Power Stroke: The compressed mixture is ignited by the spark plug, causing an expansion of gases that push the piston down.
• Exhaust Stroke: Piston moves from B.D.C. to T.D.C., pushing out the burnt gases.

Two-Stroke S.I. Engine Working

• Complete cycle occurs in two piston strokes, involving a transfer port for the mixture.

Four-Stroke C.I. Engine Working

• Suction Stroke: Piston moves from T.D.C. to B.D.C., drawing in air.
• Compression Stroke: Piston moves from B.D.C. to T.D.C., compressing the air, raising its temperature significantly (approx. 400°C - 600°C).
• Power Stroke: Diesel fuel is injected; the high temperature ignites the fuel directly. Pushing the piston generates power.
• Exhaust Stroke: Piston moves from B.D.C. to T.D.C., expelling the burnt gases.

Two-Stroke C.I. Engine Working

• Complete cycle occurs in two piston strokes, with fuel injection during the compression stroke. A transfer port transfers the compressed air/fuel mixture.

This quiz explores the definition and various types of engines, including external and internal combustion engines. Delve into the details of spark ignition and compression ignition engines, along with their distinctive two-stroke and four-stroke cycles. Test your knowledge on how these engines convert heat energy into mechanical energy.