Valves

VALVES IN IC ENGINES ACCORDING TO VTU SYLLABUS FOR ELECTIVE SUBJECT AUTOMOBILE ENGINEERING

1. AUTOMOTIVE ENGINEERING
SUBJECT CODE : 17ME655
BALLARI INSTITUTE OF TECHNOLOGY AND ENGINEERING
FACULTY : SHEKAR.K, ASSISTANT PROFESSOR, BITM

2. MODULE 1
Valves &
Valve actuating mechanisms

3. valves

4. Each engine cylinder will have two valves i.e inlet valve and
exhaust valve
The inlet and exhaust valves use different materials as they are
subjected to different operating conditions
The inlet valves are comparatively larger than the exhaust
valves as the air-fuel mixture enters the cylinder with lesser
speed than the velocity of the exhaust gases.

5. Classification of valves
The engine valves are classified into….
1. poppet valves
2. sleeve valves
3. rotary valves
Poppet valves are universally used for automobile vehicles, it is
also called as MUSHROOM valve because of its shape

7. Valve actuating
mechanisms
Valves located in the cylinder head are operated
by an eccentric projection called the cam which
is driven at half the crank shaft speed.
The different Valve actuating mechanisms are:
1. side valve mechanism
2. over head valve mechanism
3. overhead inlet and side exhaust valve
mechanism

8. Side valve mechanism
This is used for L-head engines, here the inlet and
exhaust valves are mounted in a single row and
operated from same crank shaft

9. Over-head valve
mechanism

10. This is suitable for I and F head engines.
Here the cam operates the valve lifter which in turn actuates
the push rod.
this action rotates the rocker arm to cause one end to push
down the valve stem to open the valve
Advantage of this mechanism is higher efficiency and higher
compression ratio

11. overhead inlet and side
exhaust valve mechanism

12. overhead inlet and side
exhaust valve mechanism
This is suitable for F-head engines. This is a
combination of the earlier two systems
Over head mechanism is used for inlet valve and
the side valve mechanism is used for the exhaust
valve

13. Valve and port timing
diagram
Valve timing diagram is one which represents the
position of the crank when the valves open and
close
there is a slight lead in opening and closing of the
valves practically than what is said theoretically
This lead time is necessary for the proper working of
the engine

14. Inlet valve
Inlet valve should open few degrees prior to the
arrival of the piston at TDC . This ensures full open
of the valve and entry of fresh charge
The valve is kept open for few degrees of rotation
of crank shaft after the suction stroke. This is done
inorder to get the charge completely in the
cylinder

15. Exhaust valve
It is necessary to open the exhaust valve before
the piston reaches end of expansion stroke, by this
the greater part of the burnt gases is removed
thereby reducing the amount of work to be done
by the piston in return stroke
It is seen that both the valves is open for 13
degrees of crank rotation. More overlapping is nor
advisable in case of petrol engine.

16. Valve timing diagram for
4s si engine

17. Valve timing diagram for
4s CI engine

18. Port diagram for 2s SI
engine

19. Port diagram for 2s CI
engine

20. COMBUSTION CHAMBER
DESIGN IN SI ENGINE

21. COMBUSTION CHAMBER
DESIGN IN CI ENGINE