RFIC vs EC Engine: Key Differences Explained
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An engine is a device that converts chemical energy into thermal energy (heat) and then uses this energy to perform mechanical work. There are two main types of heat engines: IC (Internal Combustion) engines and EC (External Combustion) engines.
Both IC and EC engines follow the fundamental principles of heat engines, which are described by the laws of thermodynamics. They are essential devices for various applications, including transportation, power generation, and industrial machinery.
IC and EC engines differ significantly in their combustion processes, working principles, efficiency, and applications.
IC (Internal Combustion) Engine Working Principle
The IC engine operates by converting the chemical energy stored in a fuel into mechanical work. A typical four-stroke IC engine (gasoline or diesel) consists of four phases: intake, compression, power, and exhaust.
Figure 1 depicts a typical IC engine. In this type of engine, fuel combustion occurs in a confined space known as the combustion chamber.
IC Engine
- Intake Stroke: Air (in 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.
- Compression Stroke: The piston moves upward, compressing the air or air-fuel mixture to a high pressure.
- Power Stroke: A spark (in SI engines) or high compression (in CI engines) ignites the fuel, causing a rapid expansion of gases. This expansion forces the piston downward, creating mechanical work.
- Exhaust Stroke: The spent gases are expelled from the cylinder as the piston moves upward 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 Engines
Following are the types and examples of internal Combustion engines:
- Spark Ignition (SI) Engines:
- Characteristics: 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:
- Characteristics: 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:
- Characteristics: Uses rotary design with no pistons, compact and lightweight, smooth high-speed operation.
- Example: Wankel engine, used in Mazda sports cars.
- 2-Stroke Engine:
- Characteristics: Simple design, few moving parts, less fuel-efficient, more polluting compared to 4-stroke engines.
- Example: Older small engines used in mopeds and chainsaws.
EC (External Combustion) Engine Working Principle
An EC engine operates by using an external heat source to generate steam or heat a working fluid. This fluid 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
Figure 2 depicts a typical EC engine. It uses a working fluid (liquid, gas, or both). In this type of engine, the working fluid is heated by fuel burned outside of the engine.
Types and Examples of EC Engines
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’s compare IC vs. EC engines with respect to various parameters and highlight the differences between them in a tabular form.
| Specifications | IC Engine | EC Engine |
|---|---|---|
| Full form | Internal combustion engine | External combustion engine |
| Combustion location | Occurs internally in the combustion chamber of the engine | Occurs externally, and heat is transferred to the 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 a wide range of heat sources, including solid fuels, gas, and concentrated solar energy |
| Ignition | SI engines use spark plugs; CI engines rely on compression for spontaneous ignition | Combustion is initiated externally; no spark plugs or compression ignition 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 environmentally 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 a wide variety of fuels | Less suitable for transport vehicles due to heavy weight, high initial cost, and difficulty transporting 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 and EC engines 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, whereas EC engines are less common in modern applications as they have lower thermal efficiency.
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