Internal combustion engine fuel properties

IC ENGINE FUEL PROPRTIES

I wrote this article to understand internal combustion engine fuel properties. These properties are common to petrol, diesel, lubrication oil and coolant oil. I hope students will enjoy with this post. Leave your comment.

The followings are the internal combustion engine fuels (Both petrol and diesel) properties

• Calorific value
• Volatility
• Flash point
• Fire point
• Viscosity
• Octane number
• Cetane number

Calorific value

• The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.
• The calorific value of a fuel is expressed in a unit called kilojoule per kg (kJ/kg).
• Water vapour is generated in the combustion process and the heat should be recovered by using certain techniques.
• If the heat contained in the water vapour could be recovered then it has high calorific value.
• If heat contained in the water vapor could not be recovered when it has low calorific value.

Volatility

• Volatility refers to how easily a fuel vaporizes. 
• It affects how easily you can start your car, warm it up, and how well it runs. 
• Diesel fuel comes in two basic grades, each with a different volatility.

Flash point

• The flash point of a fuel is the temperature at which it will ignite when exposed to a flame or spark

Fire point

• The fire point of a fuel is the higher temperature at which it vapors will continue to burn when ignited.

Viscosity

• Viscosity is the measure of a fluid's resistance to flow. 
• When temperature of liquid increase viscosity will be decreased.

Octane number

• Octane number, also called Antiknock Rating, measure of the ability of a fuel to resist knocking when ignited in a mixture with air in the cylinder of an internal combustion engine
• The octane rating indicates the quality of the petrol to resist detonation.
• e.g., with a mixture containing 65% of iso – octane and 35% of normal heptane, the octane value of the fuel will be 65. Higher this value, higher the anti – knock property of the fuel.

Cetane number

• It is defined as the percentage volume of normal cetane in a mixture of normal cetane and alpha methyl naphthalene which gas the same tendency to knock as the fuel under examination.
• Normal cetane has a good ignition quality and a short ignition lag but methyl naphthalene possesses poor ignition quality and longitudinal lag. 
• The cetane value can be improved by the addition of dops like ethyl nitrate but because of their high cost these are not used. 
• The cetane levels for high speed engines are about 45 – 50.