the effort has been made to explain how engine power and torque can be enhanced by improving the volumetric efficiency

1. NATIONAL INSTITUTE OFNATIONAL INSTITUTE OF
TECHNICAL TEACHERSTECHNICAL TEACHERS
TRAINING AND RESEARCHTRAINING AND RESEARCH
CHANDIGARHCHANDIGARH
103/22/15

2. Vehicle ownership is still growing worldwide
By 2020
– 15% vehicle ownership
– 1.1 billion vehicles
– Circle the earth 125 times

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CONVENTIONALCONVENTIONAL
AUTOMOBILEAUTOMOBILE

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MODERNMODERN
AUTOMOBILEAUTOMOBILE

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SIMPLIFIEDSIMPLIFIED
TEACHINGTEACHING
CONCEPT OF DIESEL AND PETROL ENGINE

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SIMPLIFIEDSIMPLIFIED
TEACHINGTEACHING

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SIMPLIFIEDSIMPLIFIED
TEACHINGTEACHING
LOADING ON ENGINE

8. Purpose of an engine
Converts the heat of burning fuel into
useful energy

9. Internal Combustion
Engines

10. The basic requirements of an engine
are to provide:
• High power output
• High thermal efficiency and low
specific fuel consumption
• Smooth engine operation
• Reduced exhaust pollutants.
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11. 11

12. 12
• Volumetric efficiency (ηv) = (mass of air actually drawn into
cylinder) / (mass of air that ideally could be drawn into cylinder)
where ρair is at ambient = Pambient/RTambient and R - 287 J/kgK for air
• Volumetric efficiency indicates how well the engine “breathes” -
what lowers ηv below 100%?
– Pressure drops in intake system (e.g. throttling) & intake
valves
– Temperature rise due to heating of air
– Volume occupied by fuel
– Non-ideal valve timing
– “Choking” (air flow reaching speed of sound) in part of intake
system having smallest area
Volumetric Efficiency
nNVdair
v
/
(measured)mair
ρ
η

≡

13. • The final parameter to be defined is the
volumetric efficiency of the engine; the
ratio of actual air flow to that of a perfect
engine is
• In general, it is quite easy to provide an
engine with extra fuel; therefore, the
power output of an engine will be limited
by the amount of air that is admitted to an
engine.

15. 15

16. 16
Indicated Mean Effective Pressure (Pim):
p-V diagram for an ideal four-stroke cycle
engine

18. Turbochargers &
Superchargers
• Superchargers:
mechanically driven from
engine crankshaft
• Turbochargers:
driven by waste exhaust
gases increased air mass
improves the engine's
thermal efficiency (fuel
economy) and emissions
performance,

20. 2 NITTTR Chandigarh

21. 21
• Engine performance is specified in both in
terms of power and engine torque - which is
more important?
–Wheel torque = engine torque x gear ratio
tells you whether you can climb the hill
Power and Torque

22. Engine Torque and Power
Torque is measured using a dynamometer.
Load cell
Force FStator
Rotor
b
N
The torque exerted by the engine is: T = F b with units: J
The power Wdot delivered by the engine turning at a speed N and
absorbed by the dynamometer is:
Wdot = ω T = (2π N) T w/units: (rad/rev)(rev/s)(J) = Watt
Note: ω is the shaft angular velocity with units: rad/s

23. 23
–Power tells you how fast you can climb the hill
–Torque can be increased by transmission (e.g.
2:1 gear ratio ideally multiplies torque by 2)
Power can’t be increased by transmission; in
fact because of friction and other losses, power
will decrease in transmission
–Power tells how fast you can accelerate or how
fast you can climb a hill, but power to torque
ratio ~ N tells you what gear ratios you’ll need
to do the job

24. 24

25. 25
Mathematically different from
the British unit
1 Power PS = 0.986 Bhp
Pferde Stärke = Horse
Strength (German)
Power
(PS@rpm)
67@5500 65@6200
Torque
(Nm@rpm)
99@2800 84@3500

26. 26
S No. duo Engine
RPM
Number of
Cycles
/Minute
Unit Air
Charge
gm/cycle
Total Air
Sucked/
Minute in
gms
1 500 250 2 500
2 1000 500 3 1500
3 1500 750 4 3000
4 2000 1000 5 5000
5 2500 1250 6 7500
6 3000 1500 5.5 8250
7 3500 1750 5 8750
8 4000 2000 4.5 9000
9 4500 2250 4 9000
10 5000 2500 3 7500
11 6000 3000 2 6000

27. 27

28. 28
Engine
Engine Type/Model 1.4L SOHC Petrol
Displacement cc 1405
Power (PS@rpm) 60PS @4500rpm
Torque (Nm@rpm) 105Nm @2500rpm
Valve Mechanism SOHC
Bore (mm) 75
Stroke (mm) 95
Compression Ratio 9:1
No of Cylinders (cylinder) 4
Cylinder Configuration Inline
Valves per Cylinder (valve) 2
Fuel Type Petrol
Fuel System Carburettor mechanical fuel pump

30. 30

31. 31
• Engine performance is specified in both in
terms of power and engine torque - which is
more important?
–Wheel torque = engine torque x gear ratio
tells you whether you can climb the hill
Power and Torque

32. 32
–Power tells you how fast you can climb the hill
–Torque can be increased by transmission (e.g.
2:1 gear ratio ideally multiplies torque by 2)
Power can’t be increased by transmission; in
fact because of friction and other losses, power
will decrease in transmission
–Power tells how fast you can accelerate or how
fast you can climb a hill, but power to torque
ratio ~ N tells you what gear ratios you’ll need
to do the job

33. There is a maximum in the brake power
versus engine speed called the rated
brake power.
At higher speeds brake power decreases as
friction power becomes significant compared
to the indicated power
There is a maximum in the torque versus
speed called maximum brake torque (MBT).
Brake torque drops off:
• at lower speeds do to heat losses
• at higher speeds it becomes more difficult to
ingest a full charge of air.
Max brake torque
1 kW = 1.341 hp
Rated brake power
Power and Torque versus
Engine Speed

34. 2 NITTTR Chandigarh

35. 2 NITTTR Chandigarh

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