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Chapter 1
INTRODUCTION
A hydrogen vehicle is an alternative fuel vehicle that uses hydrogen as its onboard fuel for motive
power. The term may refer to a personal transportation vehicle, such as an automobile, or any other
vehicle that uses hydrogen in a similar fashion, such as an aircraft. The power plants of such
vehicles convert the chemical energy of hydrogen to mechanical energy either by burning
hydrogen in an internal combustion engine, or by reacting hydrogen with oxygen in a fuel cell to
run electric motors. Widespread use of key hydrogen for fueling transportation is element of a
proposed hydrogen economy.
Hydrogen fuel does not occur naturally on Earth and thus is not an energy source, but is an energy
carrier. Currently it is most frequently made from methane or other fossil fuels. However, it can be
produced from a wide range of sources (such as wind, solar, or nuclear) that are intermittent, too
diffuse or too cumbersome to directly propel vehicles. Integrated wind-to-hydrogen plants, using
electrolysis of water, are exploring technologies to deliver costs low enough, and quantities great
enough, to compete with traditional energy sources.
Many companies are working to develop technologies that might efficiently exploit the potential of
hydrogen energy for mobile uses. The attraction of using hydrogen as an energy currency is that, if
hydrogen is prepared without using fossil fuel inputs, vehicle propulsion would not contribute to
carbon dioxide emissions. The drawbacks of hydrogen use are low energy content per unit volume,
high tank age weights, the storage, transportation and filling of gaseous or liquid hydrogen in
vehicles, the large investment in infrastructure that would be required to fuel vehicles, and the
inefficiency of production processes.
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Chapter 2
BACKGROUNDHydrogen is widely regarded as a promising transportation fuel because it is clean, abundant, and
renewable. In a gaseous state, it is colorless, odorless, and non-toxic. When hydrogen is combusted
with oxygen, it forms water as the by-product. Due to hydrogens high flammability range, it can
be completely combusted over a wide range of air/fuel ratios. Unlike gasoline, which if combusted
outside its optimal air/fuel ratio will produce excess carbon monoxide (CO) and hydrocarbons
(HC), hydrogen does not have a carbon element and therefore will not produce those toxic gases?
Like gasoline however, when hydrogen is combusted in air (mixture of oxygen and nitrogen) thetemperature of combustion can cause the formation of the nitric oxidizes (NOx). Hydrogen
however has an advantage over gasoline in this area because it can be combusted using very high
air/fuel ratios. Using a high air/fuel ratio (i.e. combusting hydrogen with more air than is
theoretically required) causes the combustion temperature to drop dramatically and thus causes a
reduction in the formation of NOx. Unfortunately, the use of excess air also lowers the power
output of the engine.
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Chapter 3
PROPERTIES OF HYDROGEN AS A FUEL
Hydrogen is eco-friendly and a clean fuel with products of combustion causing no severe
environmental degradation. Hydrogen, which is nature's best example of an ideal gas, is very
difficult to compress. It has high specific energy per unit weight. Its heat of combustion per unit
weight is about 2.5 times higher than ethanol. Hydrogen also posses higher thermodynamic
conversion efficiency (30-35 percent) as compared to petrol (20-25 percent). The lower limit of the
hydrogen air flammability range is higher than that of petrol and LPG. The lower limit of
detonability of hydrogen is higher than that of methane or petrol. Hydrogen combustion is free
from harmful emissions that invariably accompany fossil fuels combustion. Hydrogen rapidly
disperses in air which prevents its concentration from reaching lower limits of flammability and
detonability in air.
During combustion process in the heat of hydrogen reaction, part of the atmospheric nitrogen
combines with oxygen to form oxides of nitrogen. The problem of oxide formation can be
minimized to some extent by injecting water which vaporizes in the cylinder as the hydrogen
burns, and lowers temperature to a level which stops oxide formation. Apart from preventing oxide
formation, water vapor provides weight to the expanding gases in the cylinder and up to a limit
even improves power output. In earlier prototype designs, water tank was provided where as in
subsequent designs water is recovered from the water vapours present in the exhaust through a
suitable arrangement.
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Chapter 4
4.1 PRODUCTION OF HYDROGEN
Hydrogen is available in surpluses a byproduct in several industrial processes in petroleum
refineries or alkali industries. Hydrogen can also be produced using offpeak electricity mainly by
improving the plant load factor of the power stations in the country. Hydrogen can also be
produced by biophotolysis which utilizes leaving systems to split water into hydrogen and oxygen
Hydrogen in small quantities can be produced by partial oxidation of hydrocarbons and electrolysis
of water. Electrolysis is a very clean and reliable process to produce high purity hydrogen.
The efficiency of electrolysis (E) is defined by the following equation
E= Hydrogen produced ( meter cube ) F x100
Power input by cells (kWhr.)
Based on experimental studies, value of F can be chosen as 3.3 kWhr. / meter cube.
Hydrogen can be efficiently produced with photo electrolysis. Hydrogen can also be produced by
photosynthesis and biochemical reactions activated by sunlight. Hydrogen can be produced with
the help of photochemical cells which require a liquid electrolyte sandwiched between cathode and
anode.
4.2HYDROGEN STORAGE
Hydrogen can be stored in a tank. The tank uses a plastic bladder wrapped with high strength
composite graphite. The tank has a water volume of 87 liters and is rated up to 3,600 psi. At 3,600
psi, the tank holds 590 SCF of hydrogen, which is equivalent to 1.4 gallons of gasoline. At 200 HP,
this tank is emptied in about 5 minutes.
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Liquid hydrogen containers are available in all sizes ranging from small 100 liters containers to
large volume containers of 5000 meter cube. Metal hydride storage systems are specially
appropriate where storage space is limited and pressurized gas storage is very expensive. Metalhydride systems are ideal for mobile storage applications. On account of high operating costs for
long distances, metal hydride tanks are more appropriate for short-range vehicles. Both metal
hydride and liquid storage tanks have been demonstrated to be practical for mobile applications.
For longer distances, say beyond 200 km liquid storage tanks are more appropriate than metal
hydride systems. Metal hydride tanks are much lighter in weight (8.5 to 11 kg) as compared to
liquid storage tanks (50 to 150 kg). Quantity of hydrogen stored through metal hydrides is roughly
3 times more than that stored in liquid or gaseous form for the same weight of the tank.
The iron and titanium hydride system offers several significant advantages over compressed
hydrogen gas storage systems, but can not compete with gasoline on an equal energy content basis.
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Chapter 5
HYDROGEN FUEL INJECTION SYSTEM
One of the primary problems encountered in the development of operational hydrogen engines is pr
mature ignition (pre-ignition). Pre -ignition occurs when the cylinder charge becomes ignited
before the ignition by the spark plug. If this condition occurs when the intake valve is open, the
flame can travel back into the induction system. Various fuel injection methods have been
experimented with over the years. These methods have included carbureted systems, which mix the
air and fuel at a central point upstream of the intake valves; port injection systems that inject the
fuel into the air stream near the intake valve; and direct injection systems that inject the fuel
directly into the combustion chamber.
For carburetor-type systems, which can have a substantial amount of air and fuel in the manifold,
pre-ignition can have a devastating effect. Port injection systems, which tend to have less fuel in
the manifold at any one time, can minimize this effect. Running lean (excess air) and precisely
timing the injector opening and closing times (tuning the system), can virtually eliminate pre-
ignition from occurring. Direct injection system can eliminate pre-ignition in the intake manifold;
however it does not necessarily eliminate it in the combustion chamber. Direct injection systems
also require higher fuel pressure and tend to be a little more complicated than the other two
methods. The method that was chosen for this project was the port injection system. The fuel
injectors used to meter the fuel are solenoid operated pulse-width modulated, sonic flow injectors
especially designed for gaseous fuels.
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Figure-1 Cross section of injector
Each injector body was designed to incorporate a inch tube that transported the hydrogen from
the injector outlet to within an inch of the intake valve. This was to minimize the amount of
hydrogen that would be in contact with the air in the runner. That way if pre-ignition was to occur
damage to the intake system would negligible.
This new manifold provided short, single runners for each cylinder. For each runner, a 1 inch
tall injector body was designed and fabricated to house the injectors.
A distinct advantage of using hydrogen as a fuel, with its wide range of flammability, is the fuel-to-
air ratio or the quality of the charge mixture can easily be varied to meet different driving
conditions or loads. This is similar to the strategy used by diesel engines. In contrast, for a gasoline
engine, the fuel-to-air ratio must be kept more or less constant throughout the driving range. In
other words, the quantity of the charge is controlled. Using a quality controlled strategy
enables the engine to operate at a constant wide-open-throttle (WOT) position throughout the
power band (just add more fuel for more torque).To facilitate the starting of the engine, a choke
(butterfly valve) was designed and fabricated for each injector body.
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All eight chokes are linked together and centrally controlled by a hand-operated cable located in
the cockpit of the vehicle. Once the engine started, the chokes are pulled to the wide-open positionand the quality controlled fuel metering strategy is implemented.
Since the design of this system allows the flow of hydrogen and air to each cylinder to be
independent of each other, any occurrence of pre-ignition in one cylinder would not influence
(ignite) the air/fuel mixture of another. Whereas with systems that manifold all the intake runners
together, a pre-ignition in one cylinder can light the whole intake manifold on fire. To maximize
the airflow to engine, each manifold runner, intake port, and injector body and throttle body werematch-ported.
To supply fuel to each injector, a single fuel rail was designed and fabricated. This fuel rail
contains a port for each of the fuel injectors.
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Chapter 6
HYDROGEN ANCILLIARY SYSTEM
The hydrogen ancillary system consists of a high flow capacity pressure regulator, a manual shut-
off valve, a solenoid operated on/off valve, three pressure gauges and a fuel line. The pressure
regulator, provided by Control Seal Controls, is used to reduce the pressure of the fuel in the
storage tank (3600 psi) to a useable fuel rail pressure of 100 psi. Upstream of this valve is a
manually operated ball valve and pressure gauge. A quarter-turn of this valve will shut off the
hydrogen in the event of a leak or fire. The pressure gauge reads the pressure of the fuel in the
storage tank. Downstream of the pressure regulator is a solenoid-operated valve and a secondpressure gauge. The solenoid valve is controlled via a switch mounted in the cockpit of the vehicle.
This valve is a normally closed valve, meaning in the event of a power failure this valve will
automatically close. This pressure gauge reads the pressure at the outlet of the pressure regulator.
The third pressure gauge is located at the engine fuel rail and reads fuel pressure at the engine
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Chapter 7
VALVE TIMING
The camshaft that comes with the gasoline engine was designed to produce its maximum power at
high engine speeds. It was ground to have 48 degrees of valve overlap and 268 degrees of
duration with a 0.74-inch valve lift at .050-inch tappet lift. This type of grind will typically
produce excellent airflow (high volumetric efficiency) at high engine speeds, at the expense poor
air dynamics at the lower engine speeds. For gasoline fueled engines, this typically means low
efficiencies, poor idle and high emissions. For racing purposes, this compromise for high enginespeeds is worth it.
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Chapter 8
DRIVE TRAIN
If 5-speed manual transmission was installed, this transmission has the following gear ratios:
1st gear: 3.27:1
2nd gear: 1.98:1
3rd gear: 1.34:1
4th gear: 1:1
5th gear: 6.8:1
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Chapter 9
IGNITION SYSTEM
The engine comes with a Magnetic Breaker less distributor that uses mechanical weights for timing
advance (maximum of 32 degrees). This system is mechanically linked to the engine through a
gear on the camshaft. Each time the camshaft completes one revolution the rotor of the distributor
also makes one revolution. On the same shaft as the rotor are 8 vanes, one for each cylinder.
Figure-2 View distributor vanes
Each time one of these vanes pass by the magnetic pick up sensor on the distributor, the coil
(single) discharges, sending a high voltage signal through the coil wire to the distributor. This
signal would then be distributed to the proper cylinder via the rotor, rotor cap and spark plug wire.
This type of ignition system works well for engines that do not have an Engine Control Computer
(ECC).
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Chapter 10
ENGINE PERFORMANCE
The theoretical maximum power output from a hydrogen engine depends on the fuel injection
method used. This is because hydrogen will displace a large portion of the incoming air, and thus
limiting the amount of air that will enter the combustion chamber. For example, the stoichiometric
air/fuel ratio for hydrogen 34:1. For this mixture, hydrogen will displace 29% of the combustion
chamber, leaving only 71% for the air. As a result, the energy content of this mixture will be 15%
less than it would be if the fuel were gasoline (since gasoline is a liquid, it only occupies a very
small volume of the combustion chamber, and thus allows more air to enter). Since both thecarbureted and port injection methods mix the fuel and air prior to it entering the combustion
chamber, these systems limits the maximum power obtainable to 85% of that of gasoline engines
(rough order of magnitude). For direct injection systems, which mix the fuel with the air after the
intake valve has closed (and thus the combustion chamber has 100% air), the maximum output of
the engine can be 15% higher than that for gasoline engines (again, rough order of magnitude).
Therefore, depending on how the fuel is metered, the maximum output for a hydrogen engine can
be either 15% higher or 15% less than that of gasoline if a stoichiometric air/fuel ratio is used.
However, at a stoichiometric air/fuel ratio, the combustion temperature is very high and as a result
it will form a large amount of nitric oxides (NOx), which is a criteria pollutant. Since one of the
reasons for using hydrogen is low exhaust emissions, hydrogen engines are not normally designed
to run at a stoichiometric air/fuel ratio.
Shown in Figure 12 is a plot of NOx formation versus equivalence ratio phi (equivalence ratio is
the actual air/fuel ratio divided by the stoichiometric air/fuel ratio. If the value for phi is less than
one, the mixture has excess air and therefore is lean. If the value for phi is greater than one, the
mixture has excess fuel and therefore rich).
From this plot is can be seen that in order to keep the NOx formation low, a phi of 0.45 (A/F of80:1) or less is required (above a phi of .45, NOx emissions increase very quickly as the phi
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increases). Also shown on this graph is a relationship of power (based on an engine speed of 6,100
rpm) and torque as phi changes. At a phi equal to 1 (stoichiometric), this engine would
theoretically produce a maximum power and torque of 510 HP and 440 ft- respectively. However
at this lb,
Power output, the engine would be producing a large amount of NOx emissions. From Figure 8 it
can be seen that the maximum clean power (at 6,100 rpm) and torque (i.e. near zero pollution
without any exhaust gas after-treatment or pollution control devices) would be about 270 HP and
230 ft -lb, respectively. This would occur at a .45 phi.
Figure-3 Compression Vs Air/Fuel mixtures
Running at a phi of 0.45 also has other benefits besides reducing NOx emissions. The first is its
effective octane rating is increased (i.e. its ability to operate at higher compression ratio
increases). As it can be seen in Figure 9, hydrogen can tolerate compressions of 15:1 at a 60% lean
mixture (.4 phis). Whereas, at a stoichometric or a chemically correct mixture (CCM), it can only
tolerate compression ratios slightly above 8:1. Limiting the maximum fueling rate to a phi of .45
(based on low emissions), the engine will have a power vs. engine speed curve similar to the one
shown in Figure 13.
Hydrogens simple atomic structure along with its ability to burn under ultra-lean conditions also
contributes to a ratio of specific heat closer to 1.4.
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(Ideal gas) . Both the compression ratio and the ratio of specific heat are the two variables in the
calculation of thermodynamic efficiency (see equation 1).
Where rv = the compression ratio and ,
k= the ratio of specific heats
The higher these values, the higher the thermodynamic efficiency of the engine. The lean air/fuel
mixtures also lower the chances of pre-ignition occurring.
Another factor having a significant impact on hydrogen fuel storage is the increase in thermal
efficiency observed when an engine is converted for operation on hydrogen. This is especially true
under part-load or stop-start driving conditions.
The impact of the increase in engine operating efficiency becomes significant when evaluatinghydrogen's potential as a vehicular fuel. The efficiency boost
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Figure-4
Increases the vehicle's range, relieving the needed BTU (J) capacity of fuel storage. The end result
is a reduction in the storage container's weight and size, and a significant improvement in the cost
per mile (kilometer) of the fuel.
Chapter 11
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AIR POLLUTION
Advancements in engine technology have resulted in the virtual elimination of pollution from
hydrogen-powered automobiles. Since no carbon is present in a hydrogen fuel system, hydrocarbon
and carbon monoxide pollution do not exist. However, when the air, consisting of nitrogen and
oxygen, is heated inside the engine, nitric oxide pollution is formed.
Using water induction technique, peak combustion temperatures inside the hydrogen engine can be
maintained at levels below the threshold for nitric oxide formation. This results in a substantial
decrease in nitric oxide formation, as shown in Figure 16.
Figure-5
Chapter 12
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ECONOMICS
The recent observation of improved engine operating efficiencies, the development of successful
methods for virtually eliminating nitric oxide formation, and development and refinement of metal
hydride storage systems, have all enhanced hydrogen's potential as an alternate fuel for vehicular
transportation.
ALL THE TABLES GIVEN ARE ONLY FOR COMPARISON PURPOSES.
Table 1
(In dollars)
Fuel
Cost at pump 100,000
Penalties Total$/106 BTU mile cost
*Coal gasoline 3.35 2,150 350 2,500
*Shale gasoline 2.65 1,750 300 2,050
*Methanol 3.45 2,450 250 2,700
*Water hydrogen (liquid) 10.2 7,200 1000 8,200
Coal hydrogen (liquid) 9.9 6,988 1000 7,988
*Ammonia 7.65 5,100 1050 6,150
*Hydrazine 10+ 14,000 850 14,850
Metal hydride with efficiency correction
Coal hydrogen (liquid) 5.88 4,150 5001 4,650
Coal hydrogen (metal hydride) 2.79 21,452 5001 26,453
1. Penalty is reduced to 1/2 since 1/2 the hydrogen is stored.
2. A double efficiency penalty is included to compensate for extra weight of hydride storage.
3. When the advantages of less engine wear and maintenance are factored in hydrogen competes
better with the other candidates.
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Table 2Variations in hydrogen production costs
$/106BTU $/106BTU
Coal
gasification8 1.35
Nuclear
electrolysis8 5
Coal
gasification10 1.5
Nuclear
decomposition8 2
Coal
gasification13 2.6
Solar
decomposition8 5
Coal
gasification14 1.3 Electrolysis9 2.95
Coal
gasification15 2.5 Electrolysis10 3.5Coal
gasification16
(liquid) 5.44
Nuclear
electrolysis12 4.95
Wind
electrolysis8 3.75
Nuclear
decomposition1
2 1.9
Natural gas8 1
Nuclear
electrolysis13 4.6CTR11
2.45Electrolysis14
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Table-3
Comparison of ideal thermodynamic cycle analysis for
Hydrogen- and gasoline-fueled engines.
Cycle
Hydrogen Gasoline
Engine1 Engine2
Intake pressure, psi.
14 14
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Compression pressure, (psi) 190 231
Combustion pressure, (psi) 884 1149
Blow down pressure, (psi) 60 79
Intake temperature, (K) 540 600
Compression temperature, (K) 796 1166
Combustion temperature, (K) 4120 5791
Blow down temperature, (K) 2360 3388
Thermal efficiency
0.456 0.421
Work/inlet mixture volume (BTU/ft3) 240.9 340.3
Work per lb. of air, (BTU) 488 481
The following can be noted from Table 3:
1. Peak cycle pressures and temperatures are lower in the hydrogen engine.2. The ideal thermal efficiency of the hydrogen engine is slightly higher than that of the gasoline
engine.
3. The work output per unit of air intake is about the same in either case.
4. The work output per unit volume of inlet mixture is 27 percent lower for the hydrogen engine.
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Table 4Vehicular Storage Requirements of Fuels Based on 20 gallons of gasoline
(2.27 x 106 BTU)
FUEL & CONTAINER
POUNDS CUBIC FEET
*Gasoline 134 2.76
*Methanol 285 5.7
*Ethanol 214 4.78
*Methane (g)1 500 27.6*Methane (l)2 240 16.1
*Hydrogen (g)3 2250 66
*Hydrogen (l)4 353 10.2
*Hydrogen (MgH2)5 692 10.8
Corrected for 80% efficiency increase.
Hydrogen(g)3 -1250 -37
Hydrogen (l)4 -198 -5.7
Hydrogen (MgH2)5 -388 -6.1
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Table 5
Exhaust emissions -Total oxides of nitrogen
(Otto spark ignition engine)
*Fed. Req. 3.0 gms/mi.
345
gms/106
BTU
*Fed. Req.(a) 0.4 gms/mi.
46
gms/106
BTU
2.3 gms/mi.
265
gms/106
BTU
*Methanol 0.37 gms/mi.
43
gms/106
BTU
*Hydrogen 2.04 gms/mi.
235
gms/106
BTU
Hydrogen(d) 0.2 gms/mi.
23
gms/106
BTU
Hydrogen(e) 0.02 gms/mi.
2 gms/106
BTU
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Chapter 13
OPERATIONAL PROBLEMS AND SOLUTIONS
1. Preignition
Preignition is caused by catalytic reactions at the cylinder surface which can be minimised
by keeping cylinder and piston surface clean.
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2. Backfiring
Backfiring can be minimized by avoiding hydrogen and air mixing priors to their entry to
mixing chamber.
Figure-6
3. Engine Knock
Knock in hydrogen engines is caused by the same phenomenon as in case of petroleum fuels It is
generally seen that knock occurs when hydrogen engine is operated close to the rated capacity.
Problems of preignition, backfiring and knock can also be overcome by suitable engine
modifications.
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4. Water Formation And Engine Corrosion
Hydrogen engines also cause problems of water formation which apart from engine corrosion alsoform oil-water emulsion which lowers oils ability to lubricate. For overcoming this problem
special lubricating oils and additives are being developed to check emulsification. A B Welch and J
S Wallace demonstrated that a hydrogen fueled compression ignition engines can deliver higher
power outputs than a diesel engine. Further improvements in efficiency can result from some
modifications in injector geometry and combustion chamber design.
Chapter 14
ADVANTAGES OF HYDROGEN FUELED IC ENGINE
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Eco-friendly and a clean fuel with products of combustion causing no severe
environmental degradation.
High specific energy of hydrogen per unit weight.
In several respects superior to other fuels.
Easy ignability of hydrogen.
Wider flammability range.
It is less hazardous than other fuels.
Engine can be run on leaner mixtures.
In certain respects hydrogen is safer than other fuels.
Many heavy and bulky items.
Chapter 15
DISADVANTAGES
Easy diffusability and lack of visibility make detectivity of leaking gas difficult.
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The equipment for storage is costly.
Production may be polluting and costly.
Preignition, backfiring and knock may occur.
Chapter 16
FUTURE DEVELOPMENTS
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There have been noted efforts in India in developing hydrogen as an alternative fuel The US
National Hydrogen Association is planning transition role of hydrogen as an interim measure
before it could be finally accepted. The transition strategy is concerned with economics of
hydrogen production, storage and transport, development of alternative captive fuel market, andselection of eco-friendly production systems and safety guidelines for the use of hydrogen as a
fuel. California state authorities are reportedly trying to make hydrogen cars environmentally
acceptable under a very stringent new exhaust emissions legislation which the state proposes to
enforce strictly from 1997 onwards. It may still take several years of R&D efforts to make
hydrogen vehicles competitive in performance and cost.
CONCLUSION
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Hydrogen is a very clean fuel which hardly leaves any deposits on engine parts. Emissions from
hydrogen engine are practically non-existent although some problems of nitrous oxide formation
are encountered. Hydrogen is an ideal fuel for certain types of mobile applications. Hydrogen as a
vehicular fuel may help to reduce independence on fossil fuels in future.
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Dept. of Mechanical Engg. Page 30
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Buchman, Isidor.Batteries in a Portable World A Handbook on Rechargeable Batteries for Non-
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