Stroke Egines

7/24/2019 Stroke Egines

1/36

Thermal Engineering SystemsMEE 216

Lecture 02

Senthur Prabu S.

Asst. Professor(Sr.)

SMBS

Contact information:

Room no.: GDN G 09 E

Open hrs: Mon 05.00 pm- 06.00 pm

Thu 04.00 pm- 05.00 pm

Email: [email protected]


2/36

Review of construction and

working of engines


3/36

Definition of Engine

It is a device which transforms one form of energy into

another form.

It can convert thermal energy into mechanical energy

Definition of Heat Engine

It is a device which transforms the chemical energy of a

fuelinto thermal energy and utilizes this thermal energy to

perform useful work.


4/36


5/36

Heat Engines


6/36

Internal Combustion

Engines

(Combustion of fueltakes placewithin the

engine)

External Combustion

Engines

(Combustion of fuel

takes place outside theengine)


7/36

Classification of Heat Engines


8/36

Advantages of I.C. Engines

Overall efficiency is high (35%)

Mechanical Simplicity

Low weight to power ratio

Absence of heat exchangers

Maximum possible expansion ratio

Greatest possible working speed

Lower initial cost


9/36

Easy starting from cold conditions

Compact and require less space

Largest possible cylinder volume with minimum

boundary surface

Disadvantages of I.C. EnginesLow starting torque

Problem of vibration caused by reciprocation ofcomponents

Limited number of fuels


10/36

Components of Engine


11/36

Basic Nomenclature of Engines

Cylinder bore (d) :It is the nominal inner diameter of the working cylinder.

Piston Area (A):

It is the area of the circle of diameter equal to cylinder

bore.

Stroke (L):

It is the nominal distance through which a working piston

moves between two successive reversals of its direction ofmotion.


12/36

Displacement or Swept Volume (Vs):

The nominal volume swept by the piston when travelling

from one dead centre to the other.

Vs = (/4) d2L = A X L

Clearance Volume (Vc):

The nominal volume of the combustion chamber above the

piston when it is at its top dead centre.

Cubic Capacity or Engine Capacity:

The displacement volume of a cylinder multiplied by the

number of cylinders in an engine.

Example: If there are n cylinders in an engine, then

Cubic Capacity = n * Vs


13/36

Compression ratio (r):

The ratio of total cylinder volume when the piston is at the

bottom dead centre.

r = VT/VC= (VS+ VC)/VC= 1 + (VS/VC)


14/36

WORKING OF 4 STROKE SI ENGINE

(OTTO CYCLE)


15/36


16/36


17/36


18/36

P-V CURVE FOR OTTO CYCLE

IDEAL ACTUAL


19/36

WORKING OF 4 STROKE CI ENGINE

(DIESEL CYCLE)


20/36


21/36


22/36

P-V CURVE FOR DIESEL CYCLE

IDEAL ACTUAL


23/36

QUIZ TIME

Which cycle has higher efficiency?Otto Cycle

or

Diesel Cycle

The efficiency of diesel cycle differs from efficiency of Otto

cycle by the quantity in brackets. This quantity is always

greater than 1.

Therfore , Otto cycle has a higher efficiency.


24/36

VALVE TIMING DIAGRAMS FOR 4

STROKE ENGINE

IDEAL ACTUAL


25/36

TWO STROKE ENGINE


26/36

WORKING OF 2 STROKE SI ENGINE


27/36


28/36


29/36

PORT TIMING DIAGRAM FOR

TWO STROKE SI ENGINE


30/36

WORKING OF 2 STROKE CI ENGINE


31/36


32/36

ACTUAL PORT TIMING DIAGRAM

FOR TWO STROKE CI ENGINE


33/36

INDICATOR DIAGRAMS FOR TWO

STROKE ENGINES

IDEAL ACTUAL


34/36

COMPARISON OF SI AND CI ENGINES


35/36

COMPARISON OF 2 AND 4 STROKE ENGINES


36/36

THANK YOU

Stroke Egines

Documents

Transcript of Stroke Egines