Internal Combustion (IC) engines are heat engines in which fuel combustion occurs within the engine itself. They are mainly classified into Petrol (Gasoline) Engines and Diesel Engines based on the type of fuel used and their working principles.
In this article:
- 1. What is Internal Combustion Engine?
- 2. Classification of IC Engines:
- 3. The Working of IC Engines:
- 4. Key Components of IC Engines:
- 5. Important Technical Terms in IC Engines:
- 6. Thermodynamic Cycles Behind the Scenes:
- 7. Losses in IC Engines:
- 8. Environmental Concerns:
- 9. Applications of IC Engines:
- 10. Future Trends in IC Engines:
- IC Engine CAD Modelling :
- Video Tutorial :
- 20 FAQ On Internal Combustion Engine:
- Other courses:
1. What is Internal Combustion Engine?
An Internal Combustion Engine (IC Engine) is a mechanical device where fuel is combusted inside the engine cylinder, producing high-pressure gas that moves a piston, which in turn rotates a crankshaft, converting chemical energy into mechanical work.
🔁 Unlike external combustion engines (e.g., steam engines), IC engines burn the fuel inside the engine.
Also Read : Difference between IC Engine and EC Engine.
2. Classification of IC Engines:
📌 Based on Fuel Type:
- Petrol (Gasoline) Engine
- Diesel Engine
- Gas Engines (CNG, LPG)
- Biofuel Engines (Ethanol, Biodiesel, etc.)
📌 Based on Ignition Method:
- Spark Ignition (SI): Uses spark plug (petrol).
- Compression Ignition (CI): Fuel self-ignites under pressure (diesel).
📌 Based on Number of Strokes:
- Four-Stroke Engine
- Two-Stroke Engine
📌 Based on Cooling System:
- Air-Cooled Engine
- Water-Cooled Engine
3. The Working of IC Engines:
✅ Four-Stroke Cycle (Most Common in Cars)
- Intake Stroke
- Piston moves down.
- Intake valve opens.
- Air-fuel mixture (or air alone) enters.
- Compression Stroke
- Both valves close.
- Piston moves up, compressing the mixture.
- Power Stroke
- In SI: Spark plug fires.
- In CI: Fuel is injected into compressed air.
- Mixture explodes, pushing piston down.
- Exhaust Stroke
- Exhaust valve opens.
- Burnt gases expelled as piston moves up.
🔁 One power stroke every two crankshaft revolutions.
✅ Two-Stroke Cycle (Used in Scooters, Chainsaws, etc.)
- Combines intake and compression in one stroke.
- Combines power and exhaust in the other.
🔁 One power stroke every revolution, more power but less efficient and dirtier.
4. Key Components of IC Engines:
| Component | Function |
|---|---|
| Cylinder | Chamber where combustion occurs |
| Piston | Reciprocates to transmit force |
| Connecting Rod | Connects piston to crankshaft |
| Crankshaft | Converts piston motion to rotary motion |
| Camshaft | Opens/closes valves at correct timing |
| Valves | Control intake of air/fuel and exhaust gases |
| Spark Plug | Ignites air-fuel mixture (SI engines) |
| Fuel Injector | Injects fuel (CI engines) |
| Flywheel | Smooths engine rotation |
| Gudgeon Pin | Connects piston and connecting rod |
| Lubrication System | Reduces friction, prevents wear |
| Cooling System | Prevents overheating (radiator, water pump, etc.) |
5. Important Technical Terms in IC Engines:
| Term | Description |
|---|---|
| Bore | Diameter of the cylinder |
| Stroke | Distance piston travels |
| Displacement | Volume swept by all pistons |
| Compression Ratio | Ratio of cylinder volume at BDC to TDC |
| Top Dead Center (TDC) | Highest point piston reaches |
| Bottom Dead Center (BDC) | Lowest point piston reaches |
| Mean Effective Pressure (MEP) | Average pressure inside cylinder |
| Brake Horse Power (BHP) | Usable power output |
| Thermal Efficiency | Ratio of power output to heat input |
6. Thermodynamic Cycles Behind the Scenes:
- Otto Cycle: Used in petrol engines.
- Processes: Adiabatic compression, constant volume heat addition, adiabatic expansion, constant volume heat rejection.
- Diesel Cycle: Used in diesel engines.
- Similar to Otto, but heat addition occurs at constant pressure.
- Dual Cycle: Hybrid of Otto and Diesel.
7. Losses in IC Engines:
- Heat Loss: To cooling system and exhaust.
- Friction Loss: Due to moving parts.
- Pump Losses: Intake and exhaust pumping.
- Unburnt Fuel Loss: Due to incomplete combustion.
8. Environmental Concerns:
- Pollutants:
- CO₂ → Greenhouse gas
- CO → Toxic gas
- NOx → Acid rain, smog
- PM (Particulate Matter) → Lung diseases
- Control Methods:
- Catalytic converters
- Exhaust Gas Recirculation (EGR)
- Direct fuel injection
- Cleaner fuels and biofuels
9. Applications of IC Engines:
- Automobiles (cars, bikes, buses)
- Generators
- Construction machinery
- Aircraft (older models, UAVs)
- Agricultural equipment
- Boats and ships
10. Future Trends in IC Engines:
- Turbocharging for higher power output
- Hybridization with electric motors
- Variable Valve Timing (VVT) for efficiency
- Downsizing with higher efficiency engines
- Alternative Fuels like hydrogen, ethanol, CNG
IC Engine CAD Modelling :
Interested to design and model your own Engine in CAD Software, then check out below links:
Also Read : Engine Design in Solidworks.
To model Engine in PTC Creo, follow the link below;
Also Read : Engine design in Creo.
Video Tutorial :
20 FAQ On Internal Combustion Engine:
What is an internal combustion engine?
An engine where fuel combustion occurs inside the engine cylinder, producing power directly.
What are the main types of IC engines?
Spark ignition (SI) engines and compression ignition (CI) engines.
What fuels are commonly used in IC engines?
Petrol (gasoline), diesel, natural gas, and ethanol blends.
How does a four-stroke engine work?
It operates in four steps: intake, compression, power, and exhaust.
What is the difference between a two-stroke and a four-stroke engine?
A two-stroke engine completes a power cycle in two strokes of the piston, while a four-stroke does it in four.
What is the role of a spark plug in an SI engine?
It ignites the air-fuel mixture using an electric spark.
How is fuel injected in CI engines?
Diesel is injected directly into the combustion chamber at high pressure.
What is engine knocking?
Premature combustion of the air-fuel mixture, causing a knocking sound and potential damage.
What is compression ratio?
The ratio of the maximum to the minimum volume in the cylinder.
Why are diesel engines more fuel-efficient than petrol engines?
Higher compression ratios and energy density of diesel fuel.
What is meant by engine displacement?
The total volume swept by all the pistons in an engine.
What is torque in an engine?
The rotational force produced by the engine’s crankshaft.
What is horsepower?
A measure of the engine’s power output over time.
Why is cooling important in IC engines?
To prevent overheating and maintain efficient operation.
What are the main cooling methods?
Air cooling and liquid (usually water) cooling.
What causes black smoke from an engine?
Incomplete combustion due to excess fuel or poor air-fuel mixture.
What is the purpose of the carburetor?
It mixes air and fuel in correct proportions (mainly in older engines).
What is the function of the crankshaft?
Converts linear piston motion into rotational motion.
What is the role of the camshaft?
Controls the opening and closing of intake and exhaust valves.
What are the common emissions from IC engines?
Carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter.
Other courses:
