Nomenclature of I.C. Engine

What is an internal combustion engine?

 The heat engine in which the combustion takes place inside the cylinder or the product of combustion directly goes to the cylinder and the heat energy of the flue gas is converted to mechanical energy, is known as Internal Combustion Engine or I.C engine in short.

In an internal combustion engine, the products of combustion are directly the motive fluid. Petrol, gas and diesel engines, Wankel engine and open-cycle gas turbines are examples of I.C engines. Jet engines and rockets are also internal combustion engines.

What is the terminology used in I.C engine?

        

Nomenclature of I.C. Engine

• CYLINDER BORE (d) (mm)

    The nominal inner diameter of a cylinder is called cylinder bore which is designed by an English letter ‘d’ and expressed in millimeter (mm).

• PISTON AREA (A) (cm2) or (mm2)

    The area of the inner diameter of a cylinder is known as piston area. It is measured in terms of a square centimeter or square millimeter.

Note: For an engine in which a piston rod passes through the combustion space, as in a double-acting engine, this area must be reduced by the area of the cross-section of the piston rod.

• STROKE (L) (mm)

    The nominal distance through which a working piston moves between two successive reversal of its direction of motion is known as a stroke and measured in millimeter.

• DEAD CENTERS

    The position of the working piston and the moving parts which are mechanically connected to it at the moment when the direction of the piston motion is reversed (at either endpoint of the stroke) are known as dead centers.

    (A) Bottom Dead Centre (BDC)

        The dead center when the piston is nearest to the crankshaft is known as BDC. In horizontal engines, it is also called Outer Dead Center (ODC).

    (B) Top Dead center (TDC)

        The dead center when the piston is farthest from the crankshaft is known as TDC. In horizontal engines, it is also called Inner Dead Center (IDC).

• DISPLACEMENT/STROKE/SWEPT VOLUME (Vs) (cc)

    The nominal volume swept by the working piston when traveling from one dead center to another is known as stroke volume and expressed in a cubic centimetre (cc).

Vs =A×L =(π/4)d2 L

• CLEARANCE VOLUME (Vc) (cc)

    The nominal volume of the space on the combustion side of the piston at TDC ( i.e the volume between the cylinder head and the piston top when the piston is at top dead center) is known as clearance volume.

    It can also be defined as the volume of a cylinder that is not swept by the piston and expressed in a cubic centimetre (cc).

• CYLINDER VOLUME (V)

    This is the sum of displacement volume and clearance volume.

V= Vs + Vc

• COMPRESSION RATIO (rk)

    It is the ratio between total cylinder volume (maximum volume of the cylinder) to the clearance volume (minimum volume of the cylinder).

rk = V/Vc = (Vc+Vs)/Vc = 1 + (Vs/Vc)

• PISTON SPEED 

    The average distance traveled by the piston per minute in an engine is know as piston speed.

         

            * It is linear speed of piston.

            * It is measured in m/min.

                    Piston speed = 2LN m/min

Where,

           L = Length of stroke in 'm' 

           N = Speed of crank shaft in r.p.m.

Below Video for clearing your concept.