Thermal efficiency. As may be expected, fuel economy is a factor in determining
the thermal efficiency of the auto engine. The engine’s efficiency increases with the
increase in compression ratio. However, with the increase in compression ratio,
there is an increasing need for fuels that do not knock. Since the 1980s, engine
manufacturers have been incorporating knock sensors to the engine electronic
management system to continuously adjust the ignition timing. This development
allows the timing of the spark to occur in advance of the piston reaching the top of
its travel. The maximum engine efficiency is produced with this timing control
measured and adjusted by the computer control of fuel-to-air ratio. Further development and testing of individual engine design sets optimum criteria for fuel octane
number of the fuel and air ratio for lean mixture combustion.
Volatility of the gasoline. Another important property of gasoline is its volatility.
The gasoline must be volatile enough to enable the engine to start at the lowest
temperature expected in its service. At too low a volatility, the engine would have
difficulty starting and would be prone to stalling in service. On the other hand, too
high a volatility would cause excessive vapor which in turn would cause vapor lock
in the fuel lines and fuel pump.
Engine deposits. Engine deposits affect fuel efficiency and emissions. Deposits
are of particular concern in the carburetor, fuel injectors, inlet valves, and combustion chamber. These deposits are essentially fine carbon granules which are formed
by high inlet valve temperatures, airflow inconsistencies, and minor oil
contamination.
Parameters Affecting Pollution by Emission
Air pollution is an important factor in motive fuel design and manufacture. There
are two main types of air pollutants that affect the manufacture of motive fuels.
These are:
• Hazardous air pollutants (HAPs)
• Criteria air pollutants
Hazardous Air Pollutants
These are air pollutants that have been shown statistically to cause major health
disorders such as cancer, neurological damage, respiratory irritation, and reproductive disorders. In general these pollutants are believed to have no threshold and are
harmful even in small doses or concentrations. The Environmental Protection
Agency (EPA) has been regulating these pollutants since the 1977 Clean Air Act.
There are more than 189 hazardous air pollutants including benzene, formaldehyde,
and 1,3-butadiene which are formed by combustion of motive fuels such as gasoline.
Criteria Air Pollutants
These are pollutants that can injure health, harm the environment, and cause property
damage. These pollutants do have a threshold level however, below which they
are relatively harmless. The EPA labels these pollutants as criteria air pollutants
Petroleum Products and a Refinery Configuration
71
the thermal efficiency of the auto engine. The engine’s efficiency increases with the
increase in compression ratio. However, with the increase in compression ratio,
there is an increasing need for fuels that do not knock. Since the 1980s, engine
manufacturers have been incorporating knock sensors to the engine electronic
management system to continuously adjust the ignition timing. This development
allows the timing of the spark to occur in advance of the piston reaching the top of
its travel. The maximum engine efficiency is produced with this timing control
measured and adjusted by the computer control of fuel-to-air ratio. Further development and testing of individual engine design sets optimum criteria for fuel octane
number of the fuel and air ratio for lean mixture combustion.
Volatility of the gasoline. Another important property of gasoline is its volatility.
The gasoline must be volatile enough to enable the engine to start at the lowest
temperature expected in its service. At too low a volatility, the engine would have
difficulty starting and would be prone to stalling in service. On the other hand, too
high a volatility would cause excessive vapor which in turn would cause vapor lock
in the fuel lines and fuel pump.
Engine deposits. Engine deposits affect fuel efficiency and emissions. Deposits
are of particular concern in the carburetor, fuel injectors, inlet valves, and combustion chamber. These deposits are essentially fine carbon granules which are formed
by high inlet valve temperatures, airflow inconsistencies, and minor oil
contamination.
Parameters Affecting Pollution by Emission
Air pollution is an important factor in motive fuel design and manufacture. There
are two main types of air pollutants that affect the manufacture of motive fuels.
These are:
• Hazardous air pollutants (HAPs)
• Criteria air pollutants
Hazardous Air Pollutants
These are air pollutants that have been shown statistically to cause major health
disorders such as cancer, neurological damage, respiratory irritation, and reproductive disorders. In general these pollutants are believed to have no threshold and are
harmful even in small doses or concentrations. The Environmental Protection
Agency (EPA) has been regulating these pollutants since the 1977 Clean Air Act.
There are more than 189 hazardous air pollutants including benzene, formaldehyde,
and 1,3-butadiene which are formed by combustion of motive fuels such as gasoline.
Criteria Air Pollutants
These are pollutants that can injure health, harm the environment, and cause property
damage. These pollutants do have a threshold level however, below which they
are relatively harmless. The EPA labels these pollutants as criteria air pollutants
Petroleum Products and a Refinery Configuration
71