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13-10-2010, 12:12 PM
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22-10-2010, 11:14 AM
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 aninternal combustion engine, or by reacting hydrogen with oxygen in a fuel cell to run electric motors. Widespread use of hydrogen for fueling transportation is a key 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, usingelectrolysis 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 tankage 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.
Buses, trains, PHB bicycles, canal boats, cargo bikes, golf carts, motorcycles, wheelchairs, ships, airplanes, submarines, and rockets can already run on hydrogen, in various forms. NASA uses hydrogen to launch Space Shuttles into space. There is even a working toy model car that runs on solar power, using a regenerative fuel cell to store energy in the form of hydrogen and oxygen gas. It can then convert the fuel back into water to release the solar energy.
The current land speed record for a hydrogen-powered vehicle is 286.476 mph (461.038 km/h) set by Ohio State University's Buckeye Bullet 2, which achieved a "flying-mile" speed of 280.007 mph (450.628 km/h) at the Bonneville Salt Flats in August 2008. For production-style vehicles, the current record for a hydrogen-powered vehicle is 333.38 km/h (207.2 mph) set by a prototype Ford Fusion Hydrogen 999 Fuel Cell Race Car at Bonneville Salt Flats in Wendover, Utah in August 2007. It was accompanied by a large compressed oxygen tank to increase power. Honda has also created a concept called the FC Sport, which may be able to beat that record if put into production.
Many companies are currently researching the feasibility of building hydrogen cars, and some automobile manufacturers have begun developing hydrogen cars (see list of fuel cell vehicles). Funding has come from both private and government sources. However, the Ford Motor Company has dropped its plans to develop hydrogen cars, stating that "The next major step in Ford’s plan is to increase over time the volume of electrified vehicles".Similarly, French Renault-Nissan announced in 2009 that it is cancelling its hydrogen car R&D efforts. As of October 2009, General Motors CEO Fritz Henderson noted that GM had reduced its hydrogen program because the cost of building hydrogen cars was too high. "It's still a ways away from commercialization", he said. The "Volt will likely cost around $40,000 while a hydrogen vehicle would cost around $400,000. Most hydrogen cars are currently only available in demonstration models or in a lease construction in limited numbers and are not yet ready for general public use. The estimated number of hydrogen-powered cars in the United States was 200 as of October 2009, mostly in California.
Honda introduced its fuel cell vehicle in 1999 called the FCX and have since then introduced the second generation FCX Clarity. In 2007 at the Greater Los Angeles Auto Show, Honda unveiled the first production model of the FCX Clarity. Limited marketing of the FCX Clarity began in June 2008 in the United States, and it was introduced in Japan in November 2008. The FCX Clarity is available in the U.S. only in Los Angeles Area, where 16 hydrogen filling stations are available, and as of July 2009, 10 drivers had leased the Clarity for US$600 a month. Honda stated that it could start mass producing vehicles based on the FCX concept by the year 2020. Honda reaffirmed, in 2009, that it continues to put resources into hydrogen fuel cell development, which it sees as "a better long term bet than batteries and plug-in vehicles".
In 2008, Hyundai announced its intention to produce 500 FC vehicles by 2010 and to start mass production of its FC vehicles in 2012. In early 2009, Daimlerannounced plans to begin its FC vehicle production in 2009 with the aim of 100,000 vehicles in 2012-2013. In 2009, Nissan started testing a new FC vehicle in Japan
In September 2009, Daimler, Ford, General Motors, Honda, Hyundai, Kia, Renault, Nissan and Toyota issued a joint statement about their undertaking to further develop and launch fuel-cell electric vehicles as early as 2015.
In February 2010 Lotus Cars announced that it was developing a fleet of hydrogen taxis in London, with the hope of them being ready to trial by the 2012 Olympic Games. London's deputy mayor, Kit Malthouse, said he hoped six filling stations would be available and that around 20-50 taxis would be in operation by then, as well as 150 hydrogen-powered buses.
In March 2010, General Motors said it had not abandoned the fuel-cell technology and still targeted to introduce hydrogen vehicles to retail customers by 2015. Charles Freese, GM’s executive director of global powertrain engineering, stated that the company believes that both fuel-cell vehicles and battery electric vehicles are needed for reduction of greenhouse gases and reliance on oil, and the U.S. should follow Germany and Japan in adopting a more uniform strategy on advanced technology options. Both have announced plans to open 1,000 hydrogen fuel stations.
Fuel cell buses (as opposed to hydrogen fueled buses) are being trialed by several manufacturers in different locations. The Fuel Cell Bus Club is a global fuel cell bus testing collaboration.
Hydrogen was first stored in roof mounted tanks, although models are now incorporating inboard tanks. Some double deck models uses between floor tanks.
Pearl Hydrogen Power Sources of Shanghai, China, unveiled a hydrogen bicycle at the 9th China International Exhibition on Gas Technology, Equipment and Applications in 2007.
Motorcycles and scooters
ENV is developing electric motorcycles powered by a hydrogen fuel cell, including the Crosscage and Biplane. Other manufacturers as Vectrix are working on hydrogen scooters. Finally, hydrogen fuel cell-electric hybrid scooters are being made such as the Suzuki Burgman Fuel cell scooter and the FHybrid
Autostudi S.r.l's H-Due is a hydrogen-powered quad, capable of transporting 1-3 passengers.
A concept for a hydrogen powered tractor has been proposed.
Companies such as Boeing, Lange Aviation, and the German Aerospace Center are pursuing hydrogen as fuel for manned and unmanned airplanes. In February 2008 Boeing tested a manned flight of a small aircraft powered by a hydrogen fuel cell. Unmanned hydrogen planes have also been tested. For large passenger airplanes however, The Times reported that "Boeing said that hydrogen fuel cells were unlikely to power the engines of large passenger jet airplanes but could be used as backup or auxiliary power units onboard."
In July 2010 Boeing unveiled its hydrogen powered Phantom Eye UAV, powered by two Ford internal combustion engines that have been converted to run on hydrogen.
In Europe, the Reaction Engines A2 has been proposed to use the thermodynamic properties of liquid hydrogen to achieve very high speed, long distance (antipodal) flight by burning it in a precooled jet engine.
A HICE forklift or HICE lift truck is a hydrogen fueled, internal combustion engine powered industrial forklift truck used to lift and transport materials. The first production HICE forklift truck based on the Linde X39 Diesel was presented at an exposition in Hannover on May 27, 2008. It used a 2.0 liter, 43 kW diesel internal combustion engine converted to use hydrogen as a fuel with the use of a compressor and direct injection. The hydrogen tank is filled with 26 liters of hydrogen at 350 bar pressure.
Rockets employ hydrogen because hydrogen gives the highest effective exhaust velocity as well as giving a lower net weight of propellant than other fuels. It performs particularly well on upper stages, although it has been used on lower stages as well, usually in conjunction with a dense fuel
The main disadvantage of hydrogen in this application is the low density and deeply cryogenic nature, requiring insulation- this makes the hydrogen tanks relatively heavy, which greatly offsets much of the otherwise overwhelming advantages for this application.
The main advantage of hydrogen is that although the velocity change of a stage employing it is little different to a stage using denser fuel, the lift-off weight of the stage is less. Particularly when used for upper stages this permits a lighter rocket for any given payload
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22-01-2011, 03:12 PM
_HYDROGEN_FUEL_VEHICAL.DOC (Size: 2.02 MB / Downloads: 219)
Interest in the use of hydrogen as a vehicular fuel has been revived in recent times by the desire to control urban pollution resulting from the ever-increasing number of internal combustion engines in our major cities, and by concern over our dwindling petroleum reserves. In fact, serious penalties associated with the storage and use of hydrogen rendered it virtually unusable as recently as one year ago.
Hydrogen 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 hydrogen’s 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) the temperature 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.
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 therodynamic conversion efficiency ( 30-35 per cent ) as compared to petrol ( 20-25 per cent ). 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 vapourises in the cylinder as the hydrogen burns, and lowers temperature to a level which stops oxide formation. Apart from preventing oxide formation, water vapour 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.
PRODUCTION OF HYDROGEN
Hydrogen is available in surplus as a by- product in several industrial processes in petroleum refineries or chlor 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 photoelectrolysis. 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 sandwitched between cathode and anode.
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.
Liquid hydrogen containers are available in all sizes ranging from small 100 litre 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. Metal hydride 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 mobilr 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. ( see figure 3 )
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 and implimentation 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.
Each injector body was designed to incorporate a ¼ 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 ½ 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.
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 position and 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, injector body and throttle body were match-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.
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 second pressure 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
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 engine speeds is worth it.
The engine comes with a Magnetic Breakerless 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.
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).
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 the carbureted and port injection methods mix the fuel and air prior to it entering the combustion chamber, these systems limit 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 of 80:1) or less is required (above a phi of .45, NOx emissions increase very quickly as the phi 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.
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,
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.
Hydrogen is a very clean fuel which hardly leaves any deposits on engine parts. Emmisions 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 tp reduce independence on fossil fuels in future.