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IC vs EC Engine

Engine is a device which converts chemical energy into thermal energy or heat energy and then uses this energy to perform some mechanical work. As mentioned there are two main types of heat engines viz. IC engine and EC engine. The full forms of IC and EC engine are Internal Combustion engine and External Combustion engine respectively. Both IC and EC engines follow the fundamental principles of heat engines, which are described by the laws of thermodynamics. They serve as essential devices for various applications such as transportation, power generation and industrial machinery. The IC and EC Engines differ in several key ways including their combustion processes, working principles, efficiency and applications.

IC (Internal Combustion) Engine working principle

The IC engine type operates based on the principle of converting chemical energy stored in a fuel into mechanical work. In a typical four-stroke IC engine such as a gasoline or diesel engine, the working cycle consists of four phases viz. intake, compression, power and exhaust. The figure-1 depicts typical IC engine. In this type of engine, burning of fuel occurs in confined space known as combustion chamber.

IC Engine

➨During the intake stroke, air (in the case of SI engines) or a mixture of air and fuel (in CI engines) is drawn into the engine's combustion chamber as the piston moves downward.
➨In the compression stroke, the piston moves upward, compressing the air or air-fuel mixture to a high pressure.
➨The power stroke begins when a spark (in SI engines) or the high compression (in CI engines) ignites the fuel, causing a rapid expansion of gases. This expansion forces the piston downward, creating mechanical work.
➨Finally, in the exhaust stroke, the spent gases are expelled from the cylinder as the piston moves upward once again.
This continuous cycle of intake, compression, power and exhaust strokes produces the engine's rotational motion, which is used to drive vehicles or power machinery.

Types and examples of IC engine

Following are the types and examples of internal Combustion engines.
• Spark Ignition Engines : The characteristics include ignition by spark plug, low compression ratio, smooth operation, used with gasoline or natural gas. Example : Gasoline engines used in most passenger cars.
• Compression Ignition (CI) Engines : The characteristics include ignition by compression, high compression ratio, more fuel efficient, run on diesel fuel. Example : Diesel engines found in trucks, buses and some passenger vehicles
• Rotary Engines : Uses rotary design with no pistons, compact and light in weight, smooth high speed operation; Example : Wankel engine, used in Mazda sports cars
• 2-stroke engine : Characteristics include simple design, few moving parts, less fuel efficient, more polluting compared to 4-stroke engine; Example : Older small engines such as used in mopeds and chainsaws

EC (External Combustion) engine working principle

EC engine operates by using an external heat source to generate steam or heat a working fluid. This will then expands and performs mechanical work.
For example, in a steam engine, water is heated externally to produce steam, which is directed into a piston or turbine. The steam's expansion against the piston or blades drives them, creating mechanical motion.

EC Engine

The figure-2 depicts typical EC engine. It uses working fluid either liquid or gas or both. In this type of engine, working fluid is heated by a fuel burned outside of the engine.

Types and examples of EC engine

Following are the types and examples of External Combustion engines.
• Steam engines
• Stirling engines
• Gas turbines or Brayton Cycle Engines
• External Combustion Rocket Engines
• External Combustion Stirling Engines (Thermal engines)

Difference between IC Engine and EC Engine

Let us compare IC vs EC engine with respect to various comparison parameters and derive differences between them in tabular form.

Specifications IC Engine EC Engine
Full form Internal combustion engine External combustion engine
Combustion location Occurs internally in combustion chamber of the engine Occurs externally and heat is transferred to working fluid
Types SI (Spark Ignition) and CI (Compression Ignition) engines Steam engines, stirling engines, some Brayton engines
Heat source Fuel air mixture combustion External heat source (e.g. furnace) is required to heat a working fluid (e.g. steam, water)
Fuel Type Typically uses gasoline, diesel, natural gas or other liquid/gaseous fuels Can use wide range of heat sources including solid fuels, gas and concentrated solar energy
Ignition SI engines use spark plugs for ignition, CI engines rely on compression for spontaneous ignition Combustion is initiated externally, and no spark plugs or compression ignition are needed within the engine
Efficiency Generally higher thermal efficiency Often lower thermal efficiency compared to modern IC engines
Environmental Impact Produces tailpipe emissions (CO2, NOx etc.) and may contribute to air pollution More environmental friendly due to reduced emissions depending on the heat source
Noise level Can be noisy Generally quieter operation
Size Small Large
Advantages Simple in design, less in weight, high overall efficiency, portable, lower cost High starting torque, cheap fuels including solid fuels
Disadvantages Vibration issue, inability to use wide variety of fuels. Less suitable for transport vehicles due to heavy weight , high initial cost, difficult to transport working fluid
Examples Diesel engine, Petrol engine, Gas engine Steam Engine, Steam turbine
Applications Widely used in automobiles, motorcycles and small engines Less common in modern applications; used in steam locomotives, ships and some power plants

Conclusion : The primary difference between IC Engine and EC Engine lies in their combustion processes and where they generate mechanical work. IC Engines combust fuel and air internally, within the engine's combustion chamber. EC Engines generate heat externally and transfer it to a working fluid like water or steam. IC Engines are versatile and commonly used in vehicles and machinery where as EC engines are less common in modern applications as they have lower thermal efficiency.

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