Fuel in a Diesel Engine Mat.

1. In this presentation you will:
Fuel in a Diesel Engine
 explore the primary features of the fuel that is used in a diesel engine
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Moosealope

2. Introduction
Diesel fuel is
produced by distilling
crude oil in a refinery.
The product contains
a number of different
hydrocarbons, such
as paraffins and
naphthalenes.
Diesel is extracted
at a specific point in
the process, giving it
certain characteristics.
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Libelul
20 ºC Refinery gas
70 ºC Petrol
120 ºC Naphtha
170 ºC Kerosene
270 ºC Diesel
300 ºC Lubricating oil
370 ºC Fuel oil
+370 ºC Bitumen
Heater
Crude Oil
Fractioning
tower
Cetane is a hydrocarbon commonly found in diesel fuel

3. Key Properties
The following properties
of diesel fuel must meet
certain criteria to ensure
adequate performance:
 Ignition quality
 Cold behavior
These are determined
by the constituents that
make up the diesel fuel,
plus any additives.
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4. Ignition Quality
Combustion in
a diesel engine is not
initiated by a spark.
Ignition quality is
measured using a
cetane number (CN).
The diesel fuel must
ignite readily when
mixed with hot
compressed air.
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Injector
Intake valve Exhaust valve
Air in Air out

5. Cetane Number
The Cetane number
is a measure of a
fuel’s ignition delay.
The higher the CN,
the more easily a fuel
will combust under
compression.
This is the time between
fuel injection and the
start of combustion.
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Typical diesel fuels
range in value from
CN 50 to CN 55.
Start of Injection
100 90 80 70
Slow
burning
Petrol
30 40 50 60
Fast
burning
Diesel
CN 50 – CN 55
Rate-controlled
combustion
Late
combustion
Ignition
delay
Rate
of
heat
release
Pre-mixed
combustion
Sequence of the processes that occur during
diesel combustion
Typical CN values

6. Cold Behavior
At temperatures below freezing, paraffin wax may precipitate out of diesel
fuel to form large crystals which can clog fuel filters.
The temperature at which this starts to occur is known as the ‘cloud point’.
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Untreated diesel fuel
Treated diesel fuel
0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
Cloud point
Diesel fuel can be treated by adding cold flow improvers, to combat the
problem of paraffin wax precipitation.
32
23
14
5
-4
-13
-22
-31
-40
-49
-58
-67
°C
°F

7. Cold Behavior
The CFPP depends
on the design of the
fuel system as well
as the fuel itself.
The ‘Cold Filter Plugging
Point’ (CFPP) is the
temperature when fuel
no longer flows freely
through a fuel filter.
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Cold flow improvers
can be added to lower
the CFPP, giving
better performance in
low temperatures.
Fuel filters
Fuel filters that have been clogged by paraffin wax

8. Additional Properties of Diesel
A high-quality diesel fuel
may be characterised by
other properties:
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 Low upper boiling limit
 Narrow density and
viscosity spread
 Low sulfur content
(<10 ppm)
 Good lubricant qualities
 Absence of free water
 Low foreign particle
content
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9. Question 1
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“Diesel fuel contains no hydrocarbons.”
Is this statement true or false?

10. Question 1
False
A diesel fuel contains a number of different hydrocarbons, such as
paraffins and naphthalenes.
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“Diesel fuel contains no hydrocarbons.”
Is this statement true or false?

11. A) A high octane number
B) A low boiling point
C) A low cloud point
D) A high cetane number
Question 2
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For a diesel fuel to ignite easily, what property should it have?

12. A) A high octane number
B) A low boiling point
C) A low cloud point
D) A high cetane number
Question 2
Cetane number is a measure of how easily a fuel will combust. The
higher the CN, the easier it will ignite.
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For a diesel fuel to ignite easily, what property should it have?

13. Question 3
Which environmental condition might require the addition of fuel flow
improvers to ensure satisfactory performance?
A) B)
C) D)
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14. Question 3
Which environmental condition might require the addition of fuel flow
improvers to ensure satisfactory performance?
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Freezing conditions might require the addition of fuel flow improvers
to lower the CFPP.
A) B)
C) D)

15. Summary
 the primary features of the fuel that is used in a diesel engine
In this presentation you have seen:
End