How does an IC engine differ from an external combustion engine?

Short Answer:

An internal combustion (IC) engine and an external combustion (EC) engine differ mainly in the place where fuel is burned. In an IC engine, fuel combustion occurs inside the engine cylinder, and the generated gases directly act on the piston to produce power. In contrast, in an EC engine, fuel is burned outside the cylinder, and the heat produced is used to generate steam or gas, which then drives the piston or turbine.

The IC engine is compact, lightweight, and provides high efficiency, while the EC engine, such as a steam engine, is larger and heavier but can use different types of fuels. IC engines are mainly used in vehicles, whereas EC engines are used in power plants and industrial applications.

Detailed Explanation :

Difference between IC Engine and External Combustion Engine

An internal combustion (IC) engine and an external combustion (EC) engine are both types of heat engines that convert thermal energy into mechanical energy. However, the main difference lies in the location of fuel combustion. In an IC engine, the combustion of the air-fuel mixture takes place inside the engine cylinder itself, while in an EC engine, fuel is burned outside the engine, and the heat is transferred to another working fluid like steam, which drives the piston or turbine.

This fundamental difference affects their design, working, efficiency, maintenance, and applications. Both types of engines are important in mechanical engineering, but IC engines are more widely used in vehicles due to their compactness and quick response.

Working Principle of IC Engine

In an IC engine, the combustion process occurs directly inside the combustion chamber of the cylinder. The fuel (petrol or diesel) is mixed with air and ignited either by a spark (in petrol engines) or by compression (in diesel engines). The rapid combustion produces high-pressure gases that push the piston downward, creating useful mechanical work.

The motion of the piston is then converted into rotary motion by the crankshaft. The engine operates in a continuous cycle of intake, compression, power, and exhaust strokes, making it efficient and suitable for mobile applications like cars, bikes, and generators.

Working Principle of External Combustion Engine

In an external combustion engine, the fuel burns in a separate chamber outside the engine cylinder. The heat generated from combustion is used to heat a working fluid, such as water, which turns into steam. This steam expands and moves the piston or turbine blades to produce mechanical work.

A steam engine and steam turbine are the most common examples of external combustion engines. Since the combustion process is separated from the working cylinder, EC engines can use a wide range of fuels such as coal, wood, or oil. However, their operation is slower and less efficient compared to IC engines.

Main Differences Between IC Engine and External Combustion Engine

  1. Location of Combustion:
    • IC Engine: Combustion takes place inside the engine cylinder.
    • EC Engine: Combustion takes place outside the cylinder.
  2. Working Fluid:
    • IC Engine: The working fluid (air-fuel mixture and burnt gases) directly acts on the piston.
    • EC Engine: The working fluid (steam or gas) is heated externally and then used to drive the piston.
  3. Fuel Type:
    • IC Engine: Uses liquid or gaseous fuels like petrol, diesel, or gas.
    • EC Engine: Can use solid, liquid, or gaseous fuels like coal, oil, or wood.
  4. Thermal Efficiency:
    • IC Engine: Has higher thermal efficiency because of direct combustion.
    • EC Engine: Has lower efficiency due to heat transfer losses.
  5. Size and Weight:
    • IC Engine: Compact, lightweight, and portable.
    • EC Engine: Bulky, heavy, and less portable.
  6. Starting Time:
    • IC Engine: Starts quickly and reaches working condition in a short time.
    • EC Engine: Takes more time to start because the boiler needs to generate steam.
  7. Maintenance:
    • IC Engine: Requires frequent maintenance due to high working temperatures and pressures.
    • EC Engine: Easier to maintain but less efficient for mobile use.
  8. Applications:
    • IC Engine: Used in automobiles, motorcycles, and small power generators.
    • EC Engine: Used in power plants, ships, and industrial applications.

Advantages of IC Engine over EC Engine

  • Higher efficiency and better fuel economy.
  • Compact design suitable for vehicles.
  • Faster start and stop operation.
  • Cleaner combustion when modern fuels are used.
  • Requires less space and infrastructure.

Advantages of EC Engine over IC Engine

  • Can use low-grade fuels, making operation cost-effective.
  • Less vibration and noise compared to IC engines.
  • Suitable for large-scale, steady power generation.
  • Produces less direct exhaust emission near the working area.
Conclusion:

The main difference between an IC engine and an external combustion engine lies in the location where the fuel burns. The IC engine burns fuel inside the cylinder, making it compact, efficient, and ideal for vehicles and mobile machinery. On the other hand, the EC engine burns fuel outside the cylinder and transfers heat to another fluid, making it suitable for large stationary applications like power plants. Both engines are vital for different engineering purposes, but the IC engine dominates modern transportation due to its simplicity and performance.