Detail presentation on "piston of IC engines"

1. SEMINAR ON
PISTON OF I.C. ENIGNE
Presented By
Tejinderpal Singh
1508478
D4ME/B2
Department of Mechanical Engineering,
Guru Nanak Dev Engineering College, Ludhiana

2. CONTENTS
 Introduction
• Piston
• Parts of piston
• Piston Functions
• Desirable characteristics of piston
• Piston head shape
• Piston types
 Piston failures
 Piston Materials
 Future piston Shape
 References

3. INTRODUCTION
A Solid cylinder or disk that fits snugly into a hollow cylinder and moves back
and forth under the pressure of a fluid{typically a hot gas formed by combustion,
as in many engines}, or moves or compresses a fluid, as in a pump or compressor.

4. PARTS OF PISTON
• The Crown is the top surface of the
piston which is subjected to tremendous
forces and heat during all engine
operation.
• The Ring Lands are the distance
between the piston crown and the ring
groove.
• Ring Groove is a recessed area located
around the perimeter of the piston that is
used to retain the piston ring.
• Skirt of a piston is the portion which is
closest to the crank shaft that helps align
the piston as it moves in the cylinder
bore.
• Wrist Pin Boss is a bore that connects
the small end of the connecting rod and
the piston by a wrist pin.

5. PISTON FUNCTIONS
• To transmit the force of explosion to the crankshaft.
• To form a seal so that the high pressure gases in the combustion chamber do
not escape into the crankcase.
• To serve as a guide and a bearing for small end of the connecting rod.
Piston Skirt Functions
• Its function is to form a guide suitable for absorbing the side thrust produced on
account of the inclination of the connecting rod.
• It must be of sufficient length to resist tilting of the piston under load.
• The combustion pressure from the piston crown is transmitted to the
connecting rod through the ‘webs’ inside the piston.
• The webs also form heat path from the piston crown to the gudgeon pin bosses
and the skirt. The ‘Bosses’ form a bearing surface for the rocking motion of the
connecting rod.

6. DESIRABLE CHARACTERISTICS OF A
PISTON
• It should be silent in operation.
• The design should be such that seizure does not occur.
• It should offer sufficient resistance to corrosion.
• It should have the shortest possible length.
• It should be lighter in weight.
• Its material should have a high thermal conductivity.
• It must have a long life.

7. PISTON HEAD SHAPE
Flat head piston Recessed head pistonDomed head piston
Top of the piston is called head or crown.
• Some pistons head is provided valve relief.
• Pistons used in some high powered engines may have raised domes,
which increases compression ratio as well as controls the Combustion.
• In some engines pistons may be specially dished to form the desired
shape of the combustion chamber.

8. PISTON TYPES

9. Piston with horizontal slot Piston with Vertical slot
Piston with T - slot Piston with Inclined Slot

10. OFFSET PIN TYPE PISTON
 Piston Description:
• The piston pin is offset
towards the major thrust
side of the piston to reduce
piston wear, and piston
noise.
• The major thrust side is the
side that is loaded during
the power event.
• The minor thrust side is the
side loaded during the
compression event.

11. CAM GROUND PISTON
 Piston Description:
• Most pistons are cam ground, this means they are not perfectly round.
• The diameter is larger on the non-thrust sides, because they tend to expand
more as the temperature of the piston increases.

12. OIL COOLED PISTON
 Piston Description:
• A cavity is provided
underneath the piston crown.
• To reduce the piston
temperatures at the top ring
to prevent carbon formation
in the groove and to achieve
sufficient oil film thickness
on the ring periphery.
• This type of piston is
provided in the medium and
heavy speed diesel engines.

13. Taper Piston (a) cold ; (b) hot
TAPER PISTON
 Piston Description:
• The crown side being smaller in diameter than the skirt end.
• As higher temperature occurs towards the crown, that side expands
more than the skirt, due to which the piston diameter becomes
uniform under running conditions.

14. Steel wire wound piston
Aconoguide Piston
 Piston Description:
• A Band of steel wire under
initial tension is put
between the piston pin
and the oil ring, thus
restricting the expansion of
skirt which is of spilt type
or cam ground type.
 Piston Description:
• This type of piston consists
of raised pads which are
specially shaped to assist
the creation of
hydrodynamic lubrication.
• By this method up to 75%
skirt contact area is
reduced.

15. Piston with Heat Dam
 Piston Description:
• A groove cut near the top of the
piston.
• This reduces the path of heat
travel from the piston crown to
the skirt.
• The skirt, therefore, runs cooler
and does not expand much.
Autothermic Piston
 Piston Description:
• Piston contains low expan- sion
steel inserts at piston pin boses.
• At higher temperatures, this
arrangement causing the piston
to expand along the piston pin.
• In the direction perpendicular to
piston pin there is corresponding
contraction of the piston due to
metallic action.

16. BI-METAL PISTON
 Piston Description:
• Made from both steel and
aluminium.
• Skirt is formed by the steel and the
aluminium alloy cast inside it forms
piston head and piston pin bosses.
• As the coefficient of thermal
expansion for steel is quite small,
the piston will not expand much and
hence smaller cold clearances can
be maintained.

17. PISTON FAILURE

18. Piston Scuffing
Burnt Piston
 Damage Description:
• Due to excessive heat, the piston
expands and becomes tight in the
cylinder.
• As, a result the lubricant is squeezed
out from the cylinder walls causing
metal to metal contact.
 Damage Description:
• This may be chiefly on account of
detonation or preignition.
• The burning due to detonation is
generally at a farthest from the spark
plug where the hot end gases rapidly
releases their energy.
• In case of preignition, however, the
burning is usually near the center of the
piston head.

19. PISTON DRY RUNNING
 Damage Description:
• Unburned fuel has condensed
at the cylinder running surface
and diluted or washed off the
load-bearing oil film.
• As a result, the interacting
sliding parts (piston and
cylinder bore) run dry against
each other, which results in
long, narrow friction marks.
• The piston ring zone usually
remains undamaged.

20. PISTON PIN BOSS DAMAGE
 Damage Description:
• Boss fatigue fractures arise as
a consequence of mechanical
overstressing.
• If there is no sufficient oil
supply: an incipient crack in
the piston pin boss will then
spread even under normal
loads, and will cause the
piston to split.

21. PISTON MATERIAL MELT OUT
 Damage Description:
• It occurs due to glow ignition on
pistons.
• Glow ignition is triggered by
glowing parts in the combustion
chamber that are hotter than the
self-ignition temperature of the
air-gas mixture.
• These are essentially the spark
plug, the exhaust valves and any
oil carbon deposits on the
combustion chamber walls.
• In the quenching area, the piston
head is heated up significantly due
to the glow ignition.

22. PISTON FAILURE DUE TO CIRCLIP
DAMAGE
 Damage Description:
• End of the piston pin bore on both sides of
the piston suffered serious damage.
• Circlip jumped out of the retaining groove
and broke into fragments.
• Second circlip damaged.
• Due to the lack of retention.
• Front face of the piston pin worn to a
convex shape.
• Asymmetrical running pattern of the
piston.
• Asymmetrical piston wear pattern
• Piston pin boss and piston pin broken
• Pin bore hammered out in the area of the
circlips.

23. PISTON MATERIALS
 Cast iron pistons
• High strength.
• Good wearing characteristics.
• Low thermal expensions.
• Heavier then aluminium pistons.
• Low thermal conductivity.
 Aluminium - cast pistons
• Si-9to12%, Ni-1%. Cu-1%,Mg-1%etc.
• Light weight.
• Economical.
• General usage.
• Brittle.

24. PISTON MATERIAL
 Hypereutectic
• Si-18to24%, Ni-1%. Cu-1%,Mg-1%etc.
• Cast Aluminium with a high Silicon Content.
• 25%,Lighter weight then normal cast aluminium piston.
• High performance.
• Less Brittle.
• More Scuffing resistance.
• Expensive then cast pistons.
 Aluminium –Forged piston:
• Si-9to12%, Ni-1%. Cu-1%,Mg-1%etc.
• Lighter in weight than normal cast piton.
• Stronger then normal cast piston.
• Due to less porosity they can conduct heat more rapidly.
• Approximately runs 20% cooler then cast piston.

25. FUTURE PISTON SHAPE
Piston with reduced skirt length
 Piston Description:
• Reduced Skirt length.
• Reduction in Friction.
• Reduction in Weight.
• Effective Lubrication.
• Less Heat transfer from crown to the skirt.

26. REFERENCES
a. A text book of Automobile Engineering, Vol. 2, Dr. Kirpal Singh, Standard
Publishers Distributers, Delhi, 2011.
b. Piston Damage – recognizing and rectifying, Motor Service,
Kolbenschmidt.
c. Presentation on Piston and Piston rings, Slideshare.com
d. Piston Evolution, Engine Technology International.com, March 2015.
e. Pdf file of The aluminium automotive manual.