Cooling a n d Lubrication in IC Engine

Necessity of Cooling System

Cooling System A system, w h i c h controls the engine temperature,is
k n o w n as a cooling system.

Necessity of Cooling System

The t e m p e r a t u r e of t h e b u r n i n g gases in t h e e n g i n e cylinder reaches
u p t o 1500 t o 2000°C, which is above the melting point of the
material of the cylinder body and head of the engine. Therefore, if
the heat is not dissipated, it would result in the failure of the
cylinder material.

D u e t o overheating, large temperature differences may lead to a

distortion of the engine components due to the thermal stresses set
up. This m a k e s it necessary for, t h e t e m p e r a t u r e variation t o b e kept
to a minimum.
Higher t e m p e r a t u r e s also lower the volumetric efftciency of t h e
engine.
R e q u i r e m e n t s of Efficient Cooling System
It m u s t b e c a p a b l e of removing only a b o u t 30% of t h e h e a t g e n e r a t e d
in t h e c o m b u st i o n c h a m b e r . Too m u c h removal of h e a t lowers t h e
t h e r m a l efficiency of t h e engine.

It is also t o b e n o t e d t h a t
(a) About 20-25% of total h e a t g e n e r a t e d is u s e d for p r o d u c i n g
brake p o w e r (useful work).
(b) Cooling system is designed t o remove 30-35% of total heat.
(c) Remaining h e a t is lost in friction a n d carried away by
exhaust gases.

It s h o u l d remove h e a t a t a fast rate w h e n t h e e n g i n e is hot. During t h e

starting of t h e engine, t h e cooling sh o u l d b e very slow so t h a t t h e
different working p a r t s r e a c h their operating t e m p e r a t u r e s in a s h o r t
time.

Types of Cooling System

Air cooling (or direct cooling) system a n d
Air Cooling System
I n this type of cooling system, t h e heat, w h i c h is c o n d u c t e d t o t h e o u t e r
p a r t s of t h e engine, is radiated a n d c o n d u c t e d away by t h e s t r e a m of air,
w h i c h is o b t a i n e d f r o m t h e a t m o sp h e r e . In order to have efftcient cooling
by means of air, providing fins around the cylinder and cylinder h e a d
increases t h e c o n t a c t area. The fins are metallic ridges, w h i c h are f o r m e d
d u r i n g t h e casting of t h e cylinder a n d cylinder h e a d .

The a m o u n t of h e a t carried off by t h e air-cooling d e p e n d s u p o n t h e

following factors
(i) The total a r e a of t h e fin surfaces,
(ii) The velocity a n d a m o u n t of t h e cooling air a n d
(iii) The t e m p e r a t u r e of t h e fins a n d of t h e cooling air.

Air-cooling is mostly of less horsepower, motorcycles, scooters, small cars

a n d small aircraft engines w h e r e t h e forward m o t i o n of t h e m a c h i n e gives
g o o d velocity t o cool t h e engine. Air-cooling is also provided in s o m e
small industrial engines. I n this system, individual cylinders are generally
e m p l o y e d t o provide a m p l e cooling a r e a by providing fins. A blower is
u s e d t o provide air.
Cooling Fins in Air Cooled System
Water Cooling System

It serves t w o p u r p o s e s in t h e working of a n e n g i n e
a) It takes away t h e excessive h e a t g e n e r a t e d in t h e e n g i n e
a n d saves it f r o m over heating.
b) It keeps t h e e n g i n e a t working t e m p e r a t u r e for efficient a n d
e c o n o m i c a l working.

This cooling syst em h a s four types of systems

(i) Direct or n o n - r e t u r n system,
( i i ) T h e r m o - S y p h o n e system,
( i i i ) H o p p e r system a n d
( i v ) P u m p / f o r c e d circulation system.
Types of Water Cooling System

Direct or N o n - r e t u r n Water Cooling System This is suitable for large

installations and where plenty of water is available. The
water f r o m a storage t a n k is directly supplied t o t h e e n g i n e
cylinder. The hot water is not cooled for reuse b u t simply
discharges. The low H.P. engine, c o u p l e d with t h e
irrigation pump is an example.
Types of Water Cooling System
T h e r m o - S y p h o n e Water Cooling System This system works o n t h e
principle t h a t h o t water being lighter rises u p a n d t h e cold
water being heavier goes d o w n . In this system t h e radiator
is p l a c e d a t a higher level t h a n t h e e n g i n e for t h e easy flow
of water towards t h e engine. H e a t is c o n d u c t e d t o t h e water
jackets f r o m w h e r e it is t a k e n away d u e t o convection by
t h e circulating water. As t h e water jacket b e c o m e s hot, it
rises t o t h e t o p of t h e radiator. Cold water f r o m t h e r adi at or
takes t h e place of t h e rising h o t wat er a n d in this way a
circulation of water is set u p m t h e system. This helps in
keeping t h e e n g i n e a t working t e m p e r a t u r e .

Disadvantages of T h e r m o - S y p h o n e System
Rate of circulation is t o o slow.
Circulation c o m m e n c e s only w h e n t h e r e is a m a r k e d difference in
t e m p e r a t u re .
Circulation st ops as t h e level of water falls below t h e t o p of t h e
delivery p i p e of t h e radiator. For t h e se r ea so ns this syste m h as
Types of Water Cooling System

H o p p e r Water Cooling System This also works o n t h e s a m e principle as

t h e t h e r m o - s y p h o n e system. I n this t h e r e is a h o p p e r o n a
jacket containing water, w h i c h su r r o u n d s t h e e n g i n e
cylinder. I n this system, as s o o n as water starts boiling, it is
replaced by cold water. An e n g i n e fitted with this system
cannot run for several hours without it being refilled with
water.
Force Circulation Water Cooling System The use of a centrifugal pump to
circulate the water throughout t h e water jackets a n d
radiator The water flows f r o m t h e lower p o r t i o n of t h e
radiator t o t h e wat er jacket of t h e e n g i n e t h r o u g h t h e
centrifugal p u m p . After t h e circulation water c o m e s b a c k
t o t h e radiator, it loses its h e a t by t h e process of radiation.
This system is e m p l o y e d in cars, trucks, tractors, etc
Force Circulation Water Cooling System
Parts of Liquid Cooling System

Water cooling system mainly consists of :

(a) Radiator,
( b ) T h e r m o s t a t valve,
(c) Water p u m p ,
(d) Fan,
(e) Water Jackets, a n d
(f) Antifreeze mixtures.
Advantages a n d Disadvantages of Air Cooled Engines

Advantages of Air Cooled System

( a ) R a d i a t o r / p u m p is a b s e n t h e n c e t h e system is light.
(b) I n case of water cooling system t h e r e are leakages, b u t in
this case t h e r e are n o leakages.
(c) Coolant a n d antifreeze solutions are n o t required.
(d) This system c a n b e u s e d in cold climates, w h e r e if water is
u s e d it m a y freeze.

Disadvantages of Air Cooled System

(a) Comparatively it is less efficient.
(b) It is u se d in a e r o p l a n e s a n d motorcycle engines w h e r e t h e
engines are exposed t o air directly.
Advantages a n d Disadvantages of Water Cooling System
Advantages
(a) Uniform cooling of cylinder, cylinder h e a d a n d valves.
(b) Specific fuel c o n s u m p t i o n of e n g i n e improves by using
water cooling system.
(c) If w e employ water cooling system, t h e n e n g i n e n e e d n o t
b e provided a t t h e front e n d of moving vehicle.
(d) Engine is less noisy as c o m p a r e d with air cooled engines,
as it h a s water for d a m p i n g noise.

Disadvantages
(a) It d e p e n d s u p o n t h e supply of water.
(b) The water p u m p w h i c h circulates wat er a b s o r b s
considerable power.
(c) If t h e water cooling system fails t h e n it will result in severe
d a m a g e of engine.
(d) The water cooling s ystem is costlier a s it h a s m o r e n u m b e r
of parts. Also it r equi r es m o r e m a i n t e n a n c e a n d c are for its
parts.
Lubrication System

I.C. e n g i n e is m a d e of m a n y moving parts. D u e t o c o n t i n u o u s m o v e m e n t

of t w o metallic surfaces over e a c h other, t h e r e is wearing moving parts,
generation of h e a t a n d loss of p o w e r in t h e e n g i n e lubrication of moving
p a r t s is essential t o prevent all t h e s e h a r m f u l effects.

P u r p o s e of Lubrication
(a) Reducing friction effect
(b) Cooling effect
(c) Sealing effect a n d
(d) Cleaning effect.