1. Reciprocating :- (a) Single Cylinder
(b) Multi-cylinder (I)
2. Rotary :-
(a) Single Rotor
(For Conventional SI Engine)
(For Complete Expansion SI Engine)
(For Early or Late Inlet Valve Closing type SI
(For the Ideal Diesel Engine)
(For the Actual Diesel Engine)
Four Stroke Cycle:- (a) Naturally Aspirated
Two Stroke Cycle:- (a) Crankcase Scavenged
(b) Uniflow Scavenged
(i) Inlet valve/Exhaust Port
(ii) Inlet Port/Exhaust Valve
(iii) Inlet and Exhaust Valve
May be Naturally Aspirated
Piston Controlled Porting
Based on the Valve Location
I-head (i) Over head Valve (OHV)
(ii) Over head Cam (OHC)
1.Conventional: (a) Crude oil derived: (i) Petrol
(b) Other sources:
(ii) Wood (includes bio-mass)
2. Alternate: (a) Petroleum derived (i) CNG
(b) Bio-mass Derived (i) Alcohols (methyl and ethyl)
(ii) Vegetable oils
(iii) Producer gas and biogas
4. Dual fueling
2. Fuel Injection
1. Homogeneous Charge:
(Also Pre-mixed charge)
Admission of air-fuel mixture at near
2. Stratified Charge: (i) With carburetion
(ii) With fuel injection
Admission of mixture at pressure above
Open Chamber: (i)
Divided Chamber: (For CI): (i) Swirl chamber
(For SI): (i) CVCC
(ii) Other designs
(To keep mixture strength constant)
Also called Charge Control
Used in the Carbureted S.I. Engine
2. Fuel Control:
(To vary the mixture strength according to
Used in the C.I. Engine
Used in the Fuel-injected S.I. Engine.
Cylinder Bore (d)
Piston area (A)
Stroke to Bore ratio (L/d)
Top Dead Centre(TDC)
Bottom Dead Centre(BDC)
Displacement of Swept
Cubic Capacity or Engine
Clearance Volume (Vc)
Compression Ratio (r)
Top Dead Center (TDC):
Position of the piston when it stops at the furthest
point away from the crankshaft.
Top because this position is at the top of the engines
(not always), and dead because the piston stops as
this point. Because in some engines TDC is not at the
top of the engines(e.g: horizontally opposed
engines, radial engines,etc,.) Some sources call this
position Head End Dead Center (HEDC).
Some source call this point TOP Center (TC).
When the piston is at TDC, the volume in the cylinder
is a minimum called the clearance volume.
Bottom Dead Center (BDC):
Position of the piston when it stops at the point closest to
Some sources call this Crank End Dead Center (CEDC)
because it is not always at the bottom of the engine.Some
source call this point Bottom Center (BC).
Distance traveled by the piston from one extreme position
to the other : TDC to BDC or BDC to TDC.
It is defined as cylinder diameter or piston face diameter;
piston face diameter is same as cylinder diameter( minus
Swept volume/Displacement volume :
Volume displaced by the piston as it travels through one
Swept volume is defined as stroke times bore.
Displacement can be given for one cylinder or entire
engine (one cylinder times number of cylinders).
The area of a circle of diameter equal to the
cylinder bore is called the piston area.
Stroke to bore ratio:
Ratio of stroke to cylinder bore is important
parameter in classifying the size of the
If d<L, it is called under-square engine.
If d=L, it is called square engine.
If d>L, it is called over-square engine(It can
operate at higher speeds).
Clearance volume :
It is the minimum volume of the cylinder available for
the charge (air or air fuel mixture) when the piston
reaches at its outermost point (top dead center or
outer dead center) during compression stroke of the
Minimum volume of combustion chamber with piston
Compression ratio :
The ratio of total volume to clearance volume of the
cylinder is the compression ratio of the engine.
Typically compression ratio for SI engines varies form
8 to 12 and for CI engines it varies from 12 to 24
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