Internal Combustion Engine

An Internal Combustion Engine is what unleashes and provides us with the power that drives our cars and that fuels our world ! In order to understand how Internal Combustion Engines work, we will start by understanding the Otto Cycle. This cycle demonstrates how an IC engine generates power.
The Intake Stroke: The piston will move down the cylinder from the Top Dead Center (TDC) to the Bottom Dead C enter (BDC) while the intake valve is open. The downward movement of the piston generates a difference in pressure which results in the air-fuel mixture being drawn into the combustion chamber.

 

The Compression Stroke: The piston will move upwards from the BDC to the TDC, compressing this air-fuel mixture and thus raising the pressure and temperature of this mixture. In this stroke both the intake and exhaust valves remain closed.

 

The Power Stroke: The spark plug will now ignite this air-fuel mixture which results in combustion and therefore generating energy. The thrust produced as a result of the combustion of the air-fuel mixture will push the piston downwards from the TDC to the BDC. This downward motion grants and caters driving energy to the flywheel. The flywheel is a mechanical device located on one of the ends of the crankshaft, that stores energy in the form of rotational momentum. We will be diving into these engine components shortly, so don’t worry if you don’t understand the full picture yet.

The Exhaust Stroke: The combustion of this air-fuel mixture generates some residue gases (exhaust gases) that comprise of unburnt fuel particles and harmful pollutants. Now the piston will move back up and due to the pressure differential, the exhaust valves will open, and the exhaust gases will be routed to the exhaust system.

Make sure to check out this video as it is a 3-D animation illustrating the four strokes of the Otto Cycle. If the cycle is not clear to you yet, rest assured that this video will clear things up! smile

The Main Components of an Internal Combustion Engine

  • Cylinder: This is where the piston will move in a reciprocating motion.
        • Cylinder Liner: The liner’s main function is to provide a smooth sliding surface for the reciprocating motion of the piston; thus, aiding in the reducing of wear and resistance due to friction.
  • Connecting Rod: Its function is transferring the reciprocating motion of the piston into rotational (circular) motion in the crankshaft.
                • Wrist pin (Gudgeon pin): This wrist pin connects the smaller end of the connecting rod to the piston.
                • Crank pin: This crank pin connects the bigger end of the connecting rod to the crankshaft.
  • Flywheel (Driver Plate): The flywheel is positioned at the rear end of the crankshaft and its main function is storing energy in the form of rotational momentum.
  • Crankshaft: The crankshaft drives the flywheel and the camshaft. The crankshaft to camshaft ratio is (2:1) in a four-stroke engine, that is it takes two crankshaft revolutions to complete one camshaft revolution.
              • Main bearing caps: These bearing caps are positioned on the lower portion of the main bearings, and they are fastened to the engine block by means of bolts. This results in better strength; thus, the engine will be able to withstand higher RPM.
              • Thrust bearings: Their function is to control any axial/thrust loading and control the axial movement of the crankshaft.
              • Crank webs: This is what connects the main bearings to the crankshaft.
              • Crankshaft balance masses (Counterweights): Their function is to balance the crankshaft.
  • Cam Shaft: The function of this camshaft is controlling and operating the intake and exhaust valves.
  • Spark plug: It is an electrical device responsible for igniting the air-fuel mixture in the combustion chamber by providing a spark.

DONE!

Well done on navigating through the intricacies of internal combustion engines! You’ve uncovered the mechanics behind automotive power, from combustion to performance. With each concept grasped, you’re propelling yourself closer to becoming an expert in automotive engineering. Keep your curiosity ignited as you journey through the dynamic realm of internal combustion engines!

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