Brief discussion on IC engine. Including testing and performance measure

1. Testing and Performance of
Diesel and Petrol Engine
Group Members:
1. Muhammad Fahad
2. Adeel Ashraf
3. Muhammad Irfan
4. Huma
5. Mustafa Naqvi

2. Diesel Engine
• an internal-combustion engine in which heat
produced by the compression of air in the
cylinder is used to ignite the fuel.

3. Petrol Engine:
• A petrol engine (known
as a gasoline engine in
American English) is an
internal
combustion engine with
spark-ignition, designed
to run
on petrol (gasoline) and
similar volatile fuels.

4. Diesel Engine Under variable Load

7. Characteristics of IC Engines
1. Brake Thermal Efficiency
2. Indicated Thermal Efficiency
3. Specific Fuel Consumption
4. Mechanical Efficiency
5. Volumetric Efficiency
6. Air Fuel Ratio
7. Mean Effective Pressure

8. Brake thermal efficiency
Brake thermal
efficiency is defined as break power of a heat
engine as a function of the thermal input from
the fuel. It is used to evaluate how well an
engine converts the heat from a fuel to
mechanical energy

9. Indicated thermal efficiency
The thermal efficiency is a dimensionless
performance measure of a device that
uses thermal energy, for example engine, a
steam turbine, a steam engine, a boiler, a
furnace, etc, . Thermal efficiency indicates the
extent to which the energy added by work is
converted to net heat output.

10. Mechanical efficiency
Mechanical efficiency is the measure of
effectiveness of a machine's energy and
power that is input into the device into an
output that makes force and
movement. Mechanical advantage by
comparing the input and output force you can
find the advantage of a machine

11. Specific fuel consumption
Thrust specific fuel consumption (TSFC) or
sometimes simply specific fuel consumption,
SFC, is an engineering term that is used to
describe the fuel efficiency of an engine
design with respect to thrust output.

12. Volumetic Efficiency
• Volumetric efficiency in internal combustion
engineengineering is defined as the ratio of
the mass density of the air-fuel mixture drawn
into the cylinder at atmospheric pressure
(during the intake stroke) to the mass density
of the same volume of air in the intake
manifold.

13. Air Fuel Ratio
• Air–fuel ratio (AFR) is the
mass ratio of air to fuel present in a
combustion process such as in an internal
combustion engine

14. Mean Effective Pressure
• Mean effective pressure is a quantity relating
to the operation of a reciprocating engine and
is a valuable measure of an engine's capacity
to do work that is independent
of engine displacement.

15. Performance characteristic at variable
Speed
• Load and Speed One common way to present
the operating characteristics of an internal
combustion engine over its full load and speed
range is to plot brake specific fuel
consumption contours on a graph of brake
mean effective pressure versus engine speed.

17. • Operation of the engine coupled to a
dynamometer on a test stand, over its load and
speed range, generates the torque and fuel flow-
rate data from which such a performance map is
derived. The upper envelope of the map is the
wide-open-throttle performance curve. Points
below this curve define the part-load operating
characteristics, While details differ from one
engine to another, the overall shapes of these
maps for spark-ignition engines are remarkably
similar.

19. • When mean piston speed Sp is used instead of
crankshaft speed for the abscissa, the
quantitative similarity of such maps over a wide
range of engine sizes is more apparent. Maximum
bmep occurs in the mid-speed range; the
minimum bsfc island is located at a slightly lower
speed and at part load. These map characteristics
can be understood in terms of variations in
volumetric efficiency, gross indicated fuel
conversion efficiency and mechanical efficiency.

21. Torque and Power under variable
speed

22. Performance characteristic at variable
load
• Increasing load at constant speed from the
minimum bsfc point increases bsfc due to the
mixture enrichment required to increase
torque as the engine becomes increasingly air-
flow limited, Decreasing load at constant
speed increases bsfc due to the increased
magnitude of friction (due to increased
pumping work), the increased relative
importance of friction, and increasing
importance of heat transfer.

23. • The effect of speed and load variation on NO
and HC emission are can be elaborated as
follows. NO concentration increase
moderately with increasing speed at constant
load. At lower loads, the proportional increase
in NO is greater than at higher loads. The
residual gas fraction decreases as speed
increases, this effect being greater at lower
inlet manifold pressures (lighter loads).

24. • Also, the relative importance of heat transfer
per cycle is less as speed increases , which
would also be expected to increase NO
concentration. With increasing load (at
constant speed), NO concentrations also
increase. Again, as inlet manifold pressure and
load increase, the residual gas fraction
decreases also, the relative importance of
heat transfer per cycle decreases with
increasing load.

27. The performance of an engine is
evaluated on the basis of the
following;
• (a) Specific Fuel Consumption.
• (b) Measurement of brake Power
• (c) Specific Power Output.

28. Fuel consumption measurement
• Fuel consumption is measured in two ways:
• The fuel consumption of an engine is measured
by determining the volume flow in a given time
interval and multiplying it by the specific gravity
of the fuel which should be measured
occasionally to get an accurate value.
• Another method is to measure the time required
for consumption of a given mass of fuel

29. Measurement of brake power
• The brake power measurement involves the
determination of the torque and the angular
speed of the engine output shaft. The torque
measuring device is called a dynamometer.
• Dynamometers can be broadly classified into
two main types, power absorption
dynamometers and transmission
dynamometer.

30. Types Of Dynamometers
• Absorption Dynamometers
• These dynamometers measure and absorb the
power output of the engine to which they are
coupled. The power absorbed is usually
dissipated as heat by some means. Example of
such dynamometers is prony brake, rope
brake, hydraulic dynamometer, etc.

31. • Transmission Dynamometers: In transmission
dynamometers, the power is transmitted to
the load coupled to the engine after it is
indicated on some type of scale. These are
also called torque-meters.

32. Measurement of friction power
• The difference between indicated power and the brake
power output of an engine is the friction power.
• Almost invariably, the difference between a good
engine and a bad engine is due to difference between
their frictional losses.
• The frictional losses are ultimately dissipated to the
cooling system (and exhaust) as they appear in the
form of frictional heat and this influences the cooling
capacity required. Moreover, lower friction means
availability of more brake power; hence brake specific
fuel consumption is lower.

33. THANK YOU