treated by air blowing to achieve the required hardness and ductility of the
product. Asphalt becomes an important product because of its wide use in road
and other building industries.
A Discussion on the Motive Fuels of Gasoline and Diesel
Of all the petroleum products that are marketable, motive fuels are the ones that are
most common to the general public. Because of this, they are continually in the
public focus with respect to their performance, their availability and cost, and their
effect on the environment. This section of the current chapter continues with a
closer look at the makeup, manufacture, and the environmental impact of these two
motive fuels. It begins with the gasolines.
The Parameters of Gasoline
Parameters Affecting Engine Performance
The following parameters are the major criteria in the production of finished
gasoline with respect to its performance: These are:
• Octane number
• Thermal efficiency
• Volatility of the gasoline
• Engine deposits
Octane number. Among the most important parameters in the manufacture of
gasoline is its resistance to “knocking.” This resistance is expressed as an “octane
number.” A definition of octane number and its measurement has already been
given in the introductory chapter of this book.
Knocking limits the power that can be developed by the engine/fuel combination. Detonation is the spontaneous explosion of the residual fuel (after almost
complete combustion) and the air in the combustion chamber as the normal
mechanism of combustion nears its end. It’s a very fast oxidation reaction which
sets up its own flame front. The knocking occurs when this front and that of the
normal combustion collide, creating a pressure wave.
Another, and perhaps, more destructive form of engine knock is “preignition”.
This is the spontaneous ignition of the fuel/air mixture before the ignition spark.
This in turn is caused when the unburned gases are compressed in the cylinder and
the resulting temperature reaches the auto ignition point before the ignition spark
occurs. This preignition usually causes major engine damage in just a few seconds
or minutes.
Increasing humidity, cooler ambient air temperatures, and altitude reduce
requirements for antiknock.
70
D.S.J. Jones and S.A. Treese
product. Asphalt becomes an important product because of its wide use in road
and other building industries.
A Discussion on the Motive Fuels of Gasoline and Diesel
Of all the petroleum products that are marketable, motive fuels are the ones that are
most common to the general public. Because of this, they are continually in the
public focus with respect to their performance, their availability and cost, and their
effect on the environment. This section of the current chapter continues with a
closer look at the makeup, manufacture, and the environmental impact of these two
motive fuels. It begins with the gasolines.
The Parameters of Gasoline
Parameters Affecting Engine Performance
The following parameters are the major criteria in the production of finished
gasoline with respect to its performance: These are:
• Octane number
• Thermal efficiency
• Volatility of the gasoline
• Engine deposits
Octane number. Among the most important parameters in the manufacture of
gasoline is its resistance to “knocking.” This resistance is expressed as an “octane
number.” A definition of octane number and its measurement has already been
given in the introductory chapter of this book.
Knocking limits the power that can be developed by the engine/fuel combination. Detonation is the spontaneous explosion of the residual fuel (after almost
complete combustion) and the air in the combustion chamber as the normal
mechanism of combustion nears its end. It’s a very fast oxidation reaction which
sets up its own flame front. The knocking occurs when this front and that of the
normal combustion collide, creating a pressure wave.
Another, and perhaps, more destructive form of engine knock is “preignition”.
This is the spontaneous ignition of the fuel/air mixture before the ignition spark.
This in turn is caused when the unburned gases are compressed in the cylinder and
the resulting temperature reaches the auto ignition point before the ignition spark
occurs. This preignition usually causes major engine damage in just a few seconds
or minutes.
Increasing humidity, cooler ambient air temperatures, and altitude reduce
requirements for antiknock.
70
D.S.J. Jones and S.A. Treese