236
Alternative Fuels for Transportation
TABLe 8.2
Ranking Order of Hazards for Fuels
Property
Ranking Order of Hazard
Lower flammability
Diesel > Petrol > Natural gas
Autoignition temperature
Diesel > Natural gas
Energy content by volume
Diesel > Petrol > Natural gas
Ignition energy
Almost equal
Heat release rate
Diesel > Petrol > Natural gas
the interior of the car could result in an explosion being ignited by the remote
central locking system being operated when the car is to be used, or by the
switch for the interior light being operated when the door is opened. CNG
powered vehicles stored in domestic garages present a risk of explosion.
Small leaks of CNG will tend to rise toward the roof-space of a garage, as the
density of CNG is only 60% of that of air. Thus a small leak will accumulate
by the fluorescence light fitting, and this may present a source of ignition.
For domestic CNG powered vehicles, it would be prudent either to park the
vehicle outside at all times, or to make sure that the garage is ventilated at
both low and high levels to ensure adequate natural ventilation.
Inspection and maintenance of the cylinders would be difficult, particularly if cylinders were exchanged at different sites or were owned by different companies. Leakage due to poor sealing of the connection is high, as it
is probable that minor leakage would not be noticed or would be ignored by
the average nontechnical user of the system (Astbury 2008).
8.6 Engine Tests
Natural gas is not pure methane or a homogeneous mixture, but varies in
composition by location, season, and through transmission network. It does
not have a narrow range of specification like gasoline or diesel. The fuel
composition affects the vehicular emissions. Concentration of methane and
Webbe number describes the characteristics of NG.
CNG can be used in engines as sole fuel or bi-fuel operation. Bi-fuel engines
are Otto cycle (spark ignited) that run on either NG or gasoline. The gasoline
vehicles can be converted for CNG/gasoline operation; that is, the engine
uses either CNG or gasoline for its operation. Dedicated NG engines are Otto
cycle (spark ignited); that is, operated only on NG. They tend to be optimized;
that is, they have a compression ratio designed to take advantage of the 130
octane of NG, and have been designed to take into consideration the combustion characteristics of the fuel so that the engine is very low polluting.
Alternative Fuels for Transportation
TABLe 8.2
Ranking Order of Hazards for Fuels
Property
Ranking Order of Hazard
Lower flammability
Diesel > Petrol > Natural gas
Autoignition temperature
Diesel > Natural gas
Energy content by volume
Diesel > Petrol > Natural gas
Ignition energy
Almost equal
Heat release rate
Diesel > Petrol > Natural gas
the interior of the car could result in an explosion being ignited by the remote
central locking system being operated when the car is to be used, or by the
switch for the interior light being operated when the door is opened. CNG
powered vehicles stored in domestic garages present a risk of explosion.
Small leaks of CNG will tend to rise toward the roof-space of a garage, as the
density of CNG is only 60% of that of air. Thus a small leak will accumulate
by the fluorescence light fitting, and this may present a source of ignition.
For domestic CNG powered vehicles, it would be prudent either to park the
vehicle outside at all times, or to make sure that the garage is ventilated at
both low and high levels to ensure adequate natural ventilation.
Inspection and maintenance of the cylinders would be difficult, particularly if cylinders were exchanged at different sites or were owned by different companies. Leakage due to poor sealing of the connection is high, as it
is probable that minor leakage would not be noticed or would be ignored by
the average nontechnical user of the system (Astbury 2008).
8.6 Engine Tests
Natural gas is not pure methane or a homogeneous mixture, but varies in
composition by location, season, and through transmission network. It does
not have a narrow range of specification like gasoline or diesel. The fuel
composition affects the vehicular emissions. Concentration of methane and
Webbe number describes the characteristics of NG.
CNG can be used in engines as sole fuel or bi-fuel operation. Bi-fuel engines
are Otto cycle (spark ignited) that run on either NG or gasoline. The gasoline
vehicles can be converted for CNG/gasoline operation; that is, the engine
uses either CNG or gasoline for its operation. Dedicated NG engines are Otto
cycle (spark ignited); that is, operated only on NG. They tend to be optimized;
that is, they have a compression ratio designed to take advantage of the 130
octane of NG, and have been designed to take into consideration the combustion characteristics of the fuel so that the engine is very low polluting.