Internal Combustion Engines (IC Engines)

[Buela_Vigneswaran]

Internal Combustion Engines (IC Engines)


Internal Combustion Engines (IC Engines) are the heart of most traditional vehicles, converting chemical energy from fuel into mechanical energy to power the vehicle. They are classified into different types based on design, operation, and fuel type.

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1. Basic Principle

• Combustion Process: Fuel is burned inside a combustion chamber, generating high-temperature and high-pressure gases that expand to produce mechanical work.
• Energy Conversion:
  • Chemical energy (fuel) → Thermal energy (combustion) → Mechanical energy (piston motion).

2. Types of IC Engines

1. Spark Ignition (SI) Engines:

• Uses petrol or gasoline.
• Air-fuel mixture is ignited by a spark plug.
• Example: Engines in most cars and motorcycles.

2. Compression Ignition (CI) Engines:

• Uses diesel fuel.
• Air is compressed to high pressure and temperature, igniting the diesel fuel injected into the chamber.
• Example: Heavy vehicles like trucks and buses.

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3. Two-Stroke and Four-Stroke Engines:

• Two-Stroke Engine:
  • Combustion cycle is completed in two strokes of the piston (one revolution of the crankshaft).
  • Lightweight, compact, but less efficient and more polluting.
• Four-Stroke Engine:
  • Combustion cycle is completed in four strokes of the piston (two revolutions of the crankshaft).
  • More efficient, cleaner, and widely used in modern vehicles.

3. Components of an IC Engine

• Cylinder: Combustion chamber where the fuel burns.
• Piston: Moves up and down, converting gas expansion into mechanical motion.
• Crankshaft: Converts the reciprocating motion of the piston into rotational motion.
• Connecting Rod: Links the piston to the crankshaft.
• Valves: Regulate the flow of air-fuel mixture and exhaust gases.
• Spark Plug: (For SI engines) Ignites the air-fuel mixture.
• Fuel Injector: (For CI engines) Delivers diesel fuel into the cylinder.

4. Working of a Four-Stroke Engine

1. Intake Stroke:

• Air-fuel mixture enters the cylinder as the piston moves down.

2. Compression Stroke:

• The piston moves up, compressing the mixture.

3. Power Stroke:

• The spark plug ignites the mixture (in SI engines) or the diesel self-ignites (in CI engines), producing expansion and driving the piston down.

4. Exhaust Stroke:

• The piston moves up, expelling exhaust gases.

5. Efficiency and Performance

• Thermal Efficiency: Ratio of work output to heat input. Diesel engines are typically more efficient than petrol engines.
• Power Output: Depends on engine displacement, air-fuel ratio, and design.
• Turbocharging: Increases air intake, improving power and efficiency.

6. Emissions and Environmental Impact

• Major Pollutants:
  • Carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM).
• Emission Control Technologies:
  • Catalytic converters, diesel particulate filters (DPFs), and exhaust gas recirculation (EGR).

7. Challenges and Limitations

• Fuel Dependency: Relies on non-renewable fossil fuels.
• Environmental Concerns: Significant source of greenhouse gas emissions.
• Efficiency Limitations: Limited by thermodynamic laws and energy losses (e.g., friction, heat).

8. Future of IC Engines

• Hybridization: Integration with electric motors to improve efficiency and reduce emissions.
• Alternative Fuels: Use of biofuels, hydrogen, and synthetic fuels to minimize environmental impact.
• Advanced Technologies:
  • Variable valve timing (VVT).
  • Direct fuel injection for better combustion control.
  • Downsizing with turbocharging to improve efficiency.

Applications

• Passenger Vehicles: Cars, motorcycles, and scooters.
• Commercial Vehicles: Trucks, buses, and construction machinery.
• Stationary Applications: Power generation and industrial machinery.