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Exp. # 5 Diesel Index and Cetane Number: Sherwan M.Simo 1

The document discusses methods for determining the diesel index and cetane number of fuels. The diesel index indicates ignition quality and is calculated from aniline point and specific gravity. It correlates to cetane number, which measures combustion quality and is defined as the percentage of normal cetane that matches a fuel's ignition delay. Higher cetane numbers are associated with improved combustion and emissions. The cetane rating indicates cold starting ability, with higher ratings meaning easier ignition.

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Nabee Doski
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99 views10 pages

Exp. # 5 Diesel Index and Cetane Number: Sherwan M.Simo 1

The document discusses methods for determining the diesel index and cetane number of fuels. The diesel index indicates ignition quality and is calculated from aniline point and specific gravity. It correlates to cetane number, which measures combustion quality and is defined as the percentage of normal cetane that matches a fuel's ignition delay. Higher cetane numbers are associated with improved combustion and emissions. The cetane rating indicates cold starting ability, with higher ratings meaning easier ignition.

Uploaded by

Nabee Doski
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Exp.

# 5
Diesel Index and Cetane
Number

Sherwan M.Simo 1
Objective
• To determine the diesel index of liquid petroleum product and
hydrocarbons.

Sherwan M.Simo 2
Introduction
• The diesel index is indication of ignition quality of diesel fuel.

• The diesel index is useful for controlling ignition temp.

• It is found to correlate, approximately, to the cetane number of commercial fuels.

• Diesel Index and cetane number are usually about 30-65. Lower values will result
in smoky exhaust.

• It is calculated from aniline point of the diesel oil and specific gravity of diesel fuel
at 60OF.
Sherwan M.Simo 3
141.5
• 𝐴𝑃𝐼 = − 131.5
𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑔𝑟𝑎𝑣𝑖𝑡𝑦

𝐷𝑒𝑔𝑟𝑒𝑒 𝑜𝑓 𝐴𝑃𝐼 ∗𝐴𝑛𝑖𝑙𝑖𝑛𝑒 𝑝𝑜𝑖𝑛𝑡 (℉)


• 𝐷𝑖𝑒𝑠𝑒𝑙 𝐼𝑛𝑑𝑒𝑥 =
100

• high-quality fuel has a high index number.

Sherwan M.Simo 4
Cetane number
• Cetane number is a significant expression of diesel fuel quality; it is a
measure of the combustion quality of diesel fuel.

• Cetane number of a fuel is defined as the percentage by volume of normal


cetane (n-C16H34, CN=100) in a mixture of normal cetane and alpha-methyl
naphthalene (CN=0) which has the same ignition characteristics (ignition
delay) as the test fuel when combustion is carried out in a standard engine.

• Cetane of injector and start of combustion (ignition) of the fuel. In a


particular diesel engine, higher cetane fuels will have shorter ignition delay
periods than lower cetane fuels.

Sherwan M.Simo 5
Fuel Ignition Quality

The ignition characteristics of the fuel affect the ignition delay.

The ignition quality of a fuel is defined by its cetane number.

1) For low cetane fuels


2)For high cetane fuels
Sherwan M.Simo 6
Cetane Numbers (CN)

• Higher cetane related with:

1. improved combustion

2. improved cold starting

3. reduced noise, white smoke, CO and particulate emissions.

Sherwan M.Simo 7
Cetane Rating
• This is the time period between the start of injection and start of
combustion (ignition) of the fuel.

• Indicates the cold starting ability of diesel fuel

• High cetane rating means the fuel will ignite easily from heat and
pressure and burn quickly

Sherwan M.Simo 8
Cetane Rating

Sherwan M.Simo 9
Calculation:
• DI = AP (℉) x API/100

• CN = (DI x 0.72) + 10

• Where:
AP = Aniline Point (℉)
DI = Diesel Index
CN = Cetane Number

Sherwan M.Simo 10

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