ADDITIVES

What you mean by fuel Additive?

Any substance added in small amounts to something else to improve, strengthen, or otherwise alter it.

Fuel additive? Fuel additive is defined as they are

compounds formulated to enhance the quality and efficiency of the fuels used in motor vehicle

Requirements of additives? it must be effective in desired reaction it should be soluble in fuel under all

condition. it should be stable in storage and have no

adverse effect on fuel stability. it should be in the liquid phase at normal

temperature ,and volatile to give rapid vaporization in manifold

it must not produce any harmful deposits. its water solubility must be maintain to

minimize handling loses

Types of Additives

1.Tetra ethyl Lead (TEL)

significantly improve octane rating

poisonous, oily liquid, Pb(C2H5)4, was added to gasoline for internal-combustion engines as an antiknock agent.

It will delay auto ignition and allow it to occur at a high temperature .

How TEL works ?

Lead is heavy element and can exist in a number of different oxide forms

able to absorb the energy released within the end gas during chain branching reaction of fuel and oxygen prior to ignition

delay the process of spontaneous ignition,and permit the spark –ignited flame to travel normally

Disadvantage of Tel

Lead clogs catalytic converter

The  Earth  became covered in a thin layer of lead

increase the NOx levels in the exhaust

It also requires an increase in fuel consumption

2. Methyl Tertiary Butyl Ether (MTBE)

MTBE is the principal oxygenate and octane boosting additive

It is an oxygenate meaning that it adds oxygen to the reaction when it burns. Ideally, an oxygenate reduces the amount of unburned hydrocarbons and carbon monoxide in the exhaust.

It boosts  octane

Disadvantage of methyl Tertiary butyl ether

MTBE is that it is thought to be  carcinogenic

it mixes easily with water and low sorption onto soils

3. Antiknock additives

Knocking is due to chain branching reaction which produce highly energized particles or radicals.

result of breaking of chain reaction, thereby delaying the auto-ignition of the end mixture and permitting the normal flame to pass through it without combustion knock.

increase octane number

4. Carburetor Detergent Additives

The dust, soot, and smoke carried into the engine with the incoming air

tend to cause deposition in manifold and carburetor

prevent formation of these deposit and remove existing deposits.

5.Ethanol

extend the life of our oil reserves Ethanol is soluble in gasoline addition of ethanol helps the

combustion process Disadvantage ethanol makes the engine leaner production of pure anhydrous

ethanol is difficult and expensive  

Some of the additives and there function

Additive Antiknock

compounds

Scavengers

Combustion chamber

Function -Increases octane

number -Removes combustion

products of antiknock compounds

-Suppresses surface ignition and spark plug deposit modifiers fouling

Some of the additives and there function Antioxidants

Metal deactivators

Anti-rust agents

Anti-icing agents

Detergents

-Provides storage stability

-Supplements storage stability

-Prevents rusting in gasoline-handling systems

-Suppresses carburetor and fuel system freezing

-Controls carburetor and induction system cleanliness

Some of the additives and there function

Upper cylinder lubricants

Dyes

-Lubricates upper cylinder areas and controls intake system deposits

-Indicates presence of antiknock compounds and identifies makes and grades of gasoline

Commonly used fuel additives are

Ether  -extensively as starting fluid  for many difficult-to-start engines, especially diesel engines

Nitrous oxide- or simply nitrous, is an oxidizer used in auto racing

Nitromethane,- high-performance racing fuel

Acetone - a vaporization additive, mainly used with methanol racing fuel to improve vaporisation at start up

Butyl rubber-  (as polyisobutylen succinimi, detergent  to prevent fouling of diesel fue l injectors

Picrate- improves combustion, increases  fuel mileage

Silicone - an anti-foaming agent for diesel fuel, but may damage oxygen sensors  in gasoline engines

Tetranitromethane - can increase the  cetane number  of diesel fuel, improving its combustion properties

Benefits associated with the use of fuel additives

.Alter the engine performance - boost the octane level. Less Engine maintenance -preventing the buildup of

sludge and other deposits in different areas of the engine.

. Minimize corrosion -antiknock agents to ease the

stress on engine piston

HEALTH EFFECTS OF ADDITIVES _ Cardiovascular or Blood Toxicant _ Gastrointestinal or Liver Toxicant _ Neurotoxicant _ Respiratory Toxicant _ Skin or Sense Organ Toxicant