1. Delhi Transport Corporation
Advantages of CNG over other
Fuels
Prepared by
Ravinder Minhas
Delhi Transport Corporation
(Govt. of NCT of Delhi)
New Delhi
for
EMBARQ’s Second Talking Transit workshop
held on August 30 – 31, 2012
at
Vishakapatnam – 530 020
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2. Delhi Transport Corporation
Introduction
• The use of CNG as an alternative fuel to diesel
and gasoline has offered numerous advantages,
which has increased the use of CNG
substantially in the last few years.
Some of these advantages of CNG are:
• CNG offers lower operating cost after initial
investment.
• CNG is cheaper than gasoline and diesel.
• CNG is cleaner and thus reduces pollution level
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3. Delhi Transport Corporation
Advantage
• CNG stands for Compressed Natural Gas. It
is one of the most viable alternatives to
traditional fuel energy resources for the
automotive industry. CNG is low in
pollutants, high in calorific value and heat
yield, economical and available in
abundance globally. Compressed Natural
Gas (CNG) is a substitute for gasoline
(petrol) or diesel fuel.
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4. Delhi Transport Corporation
• It is considered to be an environmentally
"clean" alternative to gasoline (petrol) or
diesel fuel. It is made by compressing
methane (CH4) extracted from natural gas.
It is stored and distributed in hard
containers, usually cylinders.
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5. Delhi Transport Corporation
Green fuel
• Commonly referred to as the green fuel
because of its lead and sulphur free
character, CNG reduces harmful emissions.
Being non-corrosive, it enhances the
longevity of spark plugs. Due to the absence
of any lead or benzene content in CNG, the
lead fouling of spark plugs and lead or
benzene pollution are eliminated.
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6. Delhi Transport Corporation
Increased life of oils and mixes
evenly in air
• Another practical advantage observed is the
increased life of lubricating oils, as CNG
does not contaminate and dilute the
crankcase oil.
• Being a gaseous fuel CNG mixes in the air
easily and evenly.
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7. Delhi Transport Corporation
Safety
• CNG is less likely to auto-ignite on hot
surfaces, since it has a high auto-ignition
temperature (540 degrees centigrade) and a
narrow range (5%-15%) of inflammability.
It means that if CNG concentration in the
air is below 5% or above 15%, it will not
burn. This high ignition temperature and
limited flammability range makes
accidental ignition or combustion very
unlikely.
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8. Delhi Transport Corporation
Low operational cost
• The operational cost of vehicles running on
CNG, as compared to those running on
other fuels, is significantly low. At the
prevailing price of fuel in Delhi, operational
cost of CNG vehicles is 68% lower than
petrol and 36% lower than diesel.
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9. Delhi Transport Corporation
Properties Unit Petrol Diesel LPG CNG
Relative density Water = 1 0.74 0.84 0.55 -
Relative density Air =1 - - 1.285 0.64
Auto-ignition
Temperature Degree C 360 280 374 540
% in Air 1-8 0.6-5.5 2.2-9.0 5-15
Flame Temperature Degree C 2,030 1,780 1,983 1,900
Octane Number - 87 - 93 127
Comparison of Properties of CNG
with other Fuels
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10. Delhi Transport Corporation
Why CNG is better than other
fuels?
• Compressed natural gas is the cleanest
burning fuel operating today. This means
less vehicle maintenance and longer engine
life.
• The cost of CNG is almost a third of the
cost of Petrol in terms of calorific value
resulting in substantial saving in fuel cost,
and investment on the CNG kit is paid back
in a short period.
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11. Delhi Transport Corporation
• The use of CNG as a fuel reduces vehicular
exhaust emissions significantly. Carbon
Monoxide emissions are reduced by 70 to
90% and Hydrocarbon emissions by 40 to
60% as compared to vehicles that use the
conventional fuel – Petrol or Diesel. Carbon
Dioxide emissions, a cause for global
warming, are also reduced significantly by
10%.
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12. Delhi Transport Corporation
• The basic engine characteristics of a vehicle
are retained while converting it to run on
CNG. The vehicle therefore is capable of
running either on Petrol or on CNG at the
flick of a switch on its dashboard.
• CNG vehicles produce the fewest emissions
of any motor fuel.
• CNG produces significantly less pollutants
than gasoline or Diesel.
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13. Delhi Transport Corporation
• Dedicated CNG engines are superior in
performance to gasoline engines
• Natural gas is cheaper per equivalent gallon
than gasoline (an average of 15% to 50%
less than gasoline).
• Converting a gasoline-powered vehicle to
CNG requires only minor engine
modifications.
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14. Delhi Transport Corporation
• Surveys indicate that NGVs are as safe or
safer than those powered by other fuels. A
1992 AGA (American Gas Association)
survey of more than 8,000 vehicles found
that with more than 278 million miles
traveled, NGV injury rates per vehicle mile
traveled were 34% lower than the rate for
gasoline vehicles. There were no fatalities
reported--even though these vehicles were
involved in over 1,800 collisions.
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15. Delhi Transport Corporation
• Saves 70% of fuel cost.
• CNG is cost effective as compared to
gasoline and diesel.
• CNG is a cleaner fuel and thus reduces
pollution level.
• CNG can be used with both the Otto Cycle
(spark ignition) and the modified Diesel
cycle.
• Flexibility of usage in conjunction with
other fuels such as gasoline or diesel.
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16. Delhi Transport Corporation
CNG is the best Auto Fuel as it is
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17. Delhi Transport Corporation
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18. Delhi Transport Corporation
What is CNG?
CNG stands for Compressed Natural
Gas. It is a gaseous fuel and is a
mixture of hydrocarbons, mainly
methane in the range of 95%. Due to
its low density, it is compressed to a
pressure of 200 bar to enhance the
vehicle on-board storage capacity.
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19. Delhi Transport Corporation
Is CNG safe?
Yes, it is safe. The properties of CNG
make it a safe fuel. It is lighter than
air, and hence in case of leakage it
disperses into the atmosphere rapidly.
Its high auto-ignition temperature of
540 degrees centigrade as against
petrol’s 360 degrees centigrade
makes it even more safe fuel. CNG
also has a narrow inflammability
range of 5% to 15%, making it much
safer than other fuels.
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20. Delhi Transport Corporation
Will my fuel expenses reduce
after conversion to CNG?
Yes, the fuel bill on the basis of average
running of vehicle reduces substantially
when compared to other conventional fuels.
Price of CNG is lesser than other fuels and
also it enhances the mileage of the vehicle,
making it the most economical fuel.
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21. Delhi Transport Corporation
Is CNG environmentally
friendlier than any other fuel?
Yes, it is. As CNG mainly consists of
methane which is the simplest hydrocarbon,
it is a much cleaner and efficient fuel. The
use of CNG significantly reduces harmful
exhaust gas emissions like carbon
monoxide, nitrogen dioxide and sulphur
dioxide which causes harmful diseases like
cancer, asthama etc. CNG also helps in
reducing the effects of global warming.
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22. Delhi Transport Corporation
Are cylinders used for filling
CNG safe?
Cylinders used for storing gas are designed with
very high safety factor in accordance with global
standards. These cylinders are tested and certified
for usage by statutory authorities and each cylinder
is defined with an expiry date of usage after which
they are to be tested again for safe use. These
cylinders have been designed to take impact of
collision in case of accidents.
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23. Delhi Transport Corporation
Which type of vehicles can be
converted into CNG?
All spark-ignited engines can be converted to
CNG, for which a specially designed conversion
kit is required for the conversion process. The kit
consists of a cylinder to be fixed in the boot of the
car and other equipments to allow gas flow into
the engine.
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24. Delhi Transport Corporation
What are the dimensions and
weight of a CNG cylinder?
CNG cylinders are manufactured from a special steel alloy
and are seamless in construction. Their compact size allows
them to easily fit into a small car. An empty CNG cylinder
with a 50 litre-water-carrying capacity weighs 48 kg
(approximately), and has a length of 835 mm and a
diameter of 316 mm. The 50 litre capacity cylinder is the
one most regularly used in CNG kits but cylinders with 45
litre, 55 litre, 60 litre and 65 litre capacity are used as well.
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25. Delhi Transport Corporation
What is the pressure of CNG in a cylinder? Is
refueling of a cylinder safe, given the pressure?
CNG cylinders are designed and built in such a way so as to
withstand high pressure. The maximum pressure in a CNG
cylinder is up to 200 bar. CNG cylinders are safe as they are
manufactured as per specific requirements and tested before
use, in accordance with international specifications and
standards, and are duly approved by the Chief Controller
of Explosives. Moreover, they are provided with a pressure
relief device (PRD) that consists of a fusible plug and a burst
disc that ruptures in case of extremely high pressure and
temperature
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26. Delhi Transport Corporation
Does CNG have any harmful
effect on the engine?
Owing to CNG's distinct features, it does not
contaminate or dilute crankcase oil, giving a new
lease of life to the engine. The absence of any lead
content in CNG helps avoid lead fouling of plugs,
thereby enhancing plug life. As CNG enters the
engine in the form of a gas (and not as a spray or
mist like other fuels),no carbon is generated
during the combustion of CNG reducing the
chances of wear and tear.
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27. Delhi Transport Corporation
rsminhas1961@gmail.com
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