An Engine is a Device which transforms one form of energy into another form of Energy. In the previous article, we have discussed the classification of the Heat Engines, and the list of the basic engine components. Now we are going to discuss the nomenclature used in the Internal combustion engines.
IC engine Nomenclature
The following terms/Nomenclature associated with an engine are explained for the better understanding of the working principle of the Internal Combustion engines.
- Piston Area
- Top Dead Center
- Bottom Dead Center
- Clearance Volume
- Swept Volume
- Compression Ratio
- Mean Effective Pressure
The nominal inside diameter of the engine cylinder is called Cylinder bore. Designate by the Letter D and expressed in millimetres (mm)
Piston Area (A)
The area of the circle of diameter equal to the cylinder bore is called the Piston Area. Designate by the Letter A and expressed in square centimetres (cm²)
A = πd²/4
Top Dead Center (TDC)
The extreme position of the piston at the top of the cylinder of the vertical engine is called the top dead centre (TDC).
Bottom Dead Center (BDC)
The extreme position of the piston at the bottom of the cylinder of the vertical engine called bottom dead centre (BDC).
The maximum distance travelled by the piston in the cylinder in one direction is known as stroke. In other words, The distance travelled by the piston from TDC to BDC is called the stroke.
Designate by the Letter L and expressed in in millimetres (mm)
Clearance Volume (Vc)
The volume contained in the cylinder above the top of the piston, when the piston is at the top dead centre is called the clearance volume.
Designate by the Letter Vc and expressed in in cubic centimetres (cc)
Swept Volume (Vs)
Swept volume is the volume covered by the piston while moving from TDC to BDC. In other words, The volume swept by the piston during one stroke is called the swept volume or piston displacement.
Swept Volume (Vs) = Vs = AxL
Compression ratio is a ratio of the volume when the piston is at the bottom dead centre to the volume when the piston is at top dead centre.
Compression ratio = Maximum Cylinder Volume/ Minimum Cylinder Volume
Compression ratio = (Swept Volume + Clearance Volume)/ Minimum Cylinder Volume
usually the compression ratio will vary from 5: 1 to 10: 1 for petrol engines and from 12:1 to 22: 1 for diesel engines.
Mean Effective Pressure
This is the Average pressure acting on the piston during the thermodynamic processes.
Mean Effective Pressure = Torque × Number of revolution for the power stroke × 2π / Displacement
The Bore, Piston Area, Stroke, Top Dead Center, Bottom Dead Center, Clearance Volume, Swept Volume, Compression Ratio, Mean Effective Pressure is described with the units used for them. Please leave your thought in the comment section below.