Compression Ignition Engine: Definition, Components, Working & Applications [PDF]

In this article, we shall cover the Compression Ignition Engine. Its definition, components, working, and applications. A PDF is also shared at the end.

What are Compression Ignition Engine

Compression ignition engines, like diesel engines, compress intake air at extremely high pressure, often combined with recirculating exhaust gas. This compression creates the high heat necessary to ignite diesel fuel, which has a higher density than gasoline. The engine ignites fuel without relying on spark plugs.

What are Compression Ignition Engine
What are CI Engine

Instead, it injects fuel into the compressed and heated air in the cylinders, promoting movement in the rotating assembly and allowing the engine to generate torque. The fuel-air mixture spontaneously ignites in the combustion chambers. Fueling plays a crucial role in diesel engine performance, with a richer fuel supply resulting in greater torque. While turbocharging and improved airflow contribute to efficiency, notable performance gains can be achieved through fueling enhancements alone.

Components of Compression Ignition Engine

The components of the Compression Ignition Engine are as follows

  • Injector: Injects fuel into the cylinder while compressing air.
  • Inlet Valve: Draws air into the cylinder during the suction stroke.
  • Exhaust Valve: Expels burnt or exhaust gases from the cylinder.
  • Combustion Chamber: Serves as the location for fuel combustion.
Components of Compression Ignition Engine
Parts of Compression Ignition Engine
Parts of CI Engine
Parts of CI Engine
  • Piston: Undergoes reciprocating motion within the cylinder, transmitting the thrust force generated during the power stroke to the crankshaft through the connecting rod.
  • Connecting Rod: Connects the piston to the crankshaft.
  • Crankshaft: Converts the piston’s reciprocating motion into rotary motion.

Working of Compression Ignition Engine

The working of the compression ignition engine is as follows

  • Suction Stroke: Air is drawn into the cylinder.
  • Compression Stroke: Air is compressed.
  • Power Stroke: Fuel undergoes ignition and combustion.
  • Exhaust Stroke: Burnt or exhaust gases escape.

1. Suction Stroke

The piston moves downward (from TDC to BDC), drawing air into the cylinder through the inlet valve.

2. Compression Stroke

During this stroke, the engine compresses the air taken in during the suction stroke, raising its temperature to facilitate diesel combustion.

Working of Compression Ignition Engine
Working of CI Engine
CI Engine Working

3. Power Stroke

Just before the compression stroke concludes, the injector introduces fuel into the cylinder. The ignited fuel undergoes combustion, generating hot exhaust gases that exert a powerful thrust on the piston, prompting its downward movement. This motion, assisted by the connecting rod, rotates the crankshaft. This stage is named the power stroke because it is where power is generated.

4. Exhaust Stroke

The piston moves upward (from BDC to TDC) during this stroke, expelling burnt gases from the engine cylinder through the exhaust valve.

Repetition of Strokes

After the exhaust stroke, the entire cycle repeats. In a two-stroke engine, there is one power stroke in every single rotation of the crankshaft. Conversely, in a four-stroke engine, one power stroke occurs every two rotations of the crankshaft.

Sr NoStrokeInlet ValveExhaust ValveOperations
1Suction StrokeOpenClosedAir is drawn into the cylinder.
2Compression StrokeClosedClosedAir is compressed.
3Power StrokeClosedClosedFuel undergoes ignition and combustion.
4Exhaust StrokeClosedOpenBurnt or exhaust gases escape.

Applications of Compression Ignition Engine

  • Automotive Transportation: Commonly employed in cars, trucks, buses, and commercial vehicles for their high torque and fuel efficiency.
  • Industrial Machinery: Powering construction equipment, generators, pumps, and compressors due to their capacity for heavy-duty tasks.
  • Marine Applications: Found in ships, boats, and auxiliary power units, diesel engines excel in providing reliable, efficient power for marine travel.
  • Agriculture: Widely used in tractors, farm equipment, and irrigation pumps, offering the needed torque for agricultural tasks.
  • Military Applications: Deployed in tanks, military vehicles, and power generators, diesel engines demonstrate durability and versatility in various conditions.
  • Rail Transportation: Diesel locomotives leverage these engines for hauling heavy loads efficiently over long distances.
  • Mining and Construction: Integral to mining equipment and power generators in remote sites, diesel engines provide robust performance for demanding operations.
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