 |
Latest Specs |
 |
|
|
|
|
Popular |
|
|
|
|
|
|
Page 4 of 5
Hydrogen tank: compact instead of all-round insulation.
The dual-mode drive concept of BMW Hydrogen 7 requires not only
a suitable engine management and fuel supply, but also proper integration of two separate fuel tanks: To offer the longest conceivable cruising range,
the BMW Hydrogen 7 comes with both a conventional 74-litre (16.3 Imp gal) gasoline tank and an additional fuel tank taking up approximately 8 kilos
or 17.6 lb of liquid hydrogen.
This hydrogen tank is a key component of the hydrogen car, with the
BMW Group being supported in the implementation of hydrogen technology in the automobile by Magna Steyr as an important partner in development.
The hydrogen tank is made up of a double-wall tank structure consisting of two-millimetre-thick stainless steel plates and featuring a 30-millimetre-thick vacuum super-insulation layer between the inner and outer tank.
This configuration reduces heat transfer to a minimum, the interim layer offering the same insulating effect as approximately 17 metres or 56 feet of styropor. The connection pieces between the inner and outer tanks are made of carbon-fibre bands minimizing the conduction of heat.
The insulation technology developed for the hydrogen tank in the BMW Hydrogen 7 ensures a standard of temperature consistency never seen before in practice. Following a simple analogy to explain the concept – if a tank of this kind were filled, say, with boiling coffee, the coffee would remain hot for more than 80 days before cooling down to a temperature suitable for drinking.
A consistently cold temperature is maintained in exactly the same way
with the same supreme effect: Highly effective insulation serves to keep liquid hydrogen at a pressure of 3–5 bar and at a consistent temperature of approximately – 250 °C over a long period. The infusion of heat causing hydrogen to evaporate is very small indeed, and any loss of hydrogen resulting from the increase in pressure caused by higher temperatures is controlled
with maximum efficiency by boil-off management limiting the inner pressure within the tank and ensuring controlled purge of hydrogen already evaporated.
Gaseous hydrogen able to escape in this way is diluted in a venturi pipe and oxidated in a catalyst to form vapour. The period in which a half-full hydrogen tank will be emptied completely in a controlled process is about 9 days,
and even then the car is still able to cover approximately 20 kilometres or
12 miles in the hydrogen mode with the fuel remaining in the tank.
Defined conversion of liquid into gaseous hydrogen forms a permanent, ongoing process whilst driving: hydrogen is removed from the tank in gaseous condition and fed to the fuel mixing and supply system. For this reason liquid hydrogen is evaporated in a specific, controlled process within the tank, building up a gas “cushion” under defined pressure.
Gaseous hydrogen extracted from the tank uses heat from the engine’s coolant circuit to be warmed up for the subsequent fuel mixing process. This heat is generated by a system of two interacting heat exchangers. The heat exchanger in the so-called secondary system capsule (SSC) receives its heat from the engine’s cooling circuit and delivers this heat, first, via the second heat exchanger to the hydrogen tank and, second, to the hydrogen itself warmed up for the subsequent fuel mixing process.
Filling the tank in a process standardized worldwide.
After manually connecting the tank pump coupling, the hydrogen tank is filled up automatically without any intervention on the part of the driver. So all the driver has to do is open the tank filler flap by pressing a button in the cockpit. Then he connects the tank filling coupling to the fuel tank cap simply by interlinking the two components with one another, the subsequent process of filling up the tank being completed automatically in about eight minutes.
BMW’s engineers have developed a standardized tank coupling for all liquid hydrogen filling stations worldwide. This tank filler has been engineered
in close cooperation between car makers, fuel supply companies,
and the German company Linde with the technical know-how required for the generation, distribution and use of hydrogen.
The European automotive industry was represented in this joint development by the BMW Group, ensuring a worldwide technical standard for liquid hydrogen filling systems.
The driver can check the fuel level and the remaining range on both fuel systems simply by pressing a button in the direction indicator lever, the levels measured then being shown in the cockpit display beneath the speedometer.
The driver is able to switch from hydrogen to gasoline manually by way of a separate button in the multifunction steering wheel – and with both engine power and torque remaining exactly the same regardless of the mode
of operation. Switching over from one mode to another has no effect on the driving behaviour and performance of the BMW Hydrogen 7.
While driving in the hydrogen mode, the display presents not the outside temperature and the time of day, but rather the chemical symbol for molecular hydrogen: H2, thus showing the driver quite clearly that the car is currently running on hydrogen fuel.
The operation control system in the BMW Hydrogen 7 gives priority to the use of hydrogen, with the engine always starting in the hydrogen mode in order to minimise CO and HC emissions during the warm-up phase until the catalyst has reached its normal operating temperature.
This configuration serves to further improve exhaust emissions to an even higher standard. And should one of the two types of fuel be fully consumed, the system will automatically switch over to the other type of fuel in the interest of securing an ongoing supply.
Modified where necessary: chassis, suspension, and body.
The BMW Hydrogen 7 comes as standard on 8J x 18 light-alloy wheels
and is available as an option with 19-inch light-alloy wheels including
a BMW Mobility Set.
All 18-inch tires, whether summer or winter, are run-flat tires enabeling the driver to continue operating the car even under complete loss of tire pressure, until reaching the nearest repair shop without any hassle.
Another feature is that a new generation of the TPC Tire Pressure Control system permanently monitors the car’s wheels. Integrated in the valves of
all four wheels, the TPC sensors register even minor deviations from the ideal tire pressure, thus recognising the risk of a flat in good time even with only
a gradual loss of pressure.
Accommodation of additional components in the rear end of the car called for re-alignment of the suspension and damping systems in the BMW Hydrogen 7. So despite the higher load on the rear axle, both driving stability and motoring comfort remain at an optimum standard. And yet a further feature is BMW’s electronic AdaptiveDrive anti-roll stability system with continuously adjustable dampers featured as standard in the BMW Hydrogen 7 and specially tailored to the car.
The bodyshell of the BMW Hydrogen 7 has been modified exactly
where required in order to set off the increase in weight resulting from this new
drive technology and at the same time fulfil all demands in terms of passive safety. Use of carbon-fibre-reinforced plastic (CFP), for example, ensures an even higher level of crash strength and safety with only a minimum increase
in weight.
Focusing especially on BMW Hydrogen 7, BMW’s engineers have furthermore developed an innovative combined CFP/steel body structure, with the side frames right and left being reinforced all round by CFP in order to give the body shell additional strength and stiffness.
One of the car’s most eye-catching features is the engine compartment lid characterized in its contours by a distinctive powerdome. This change in design is indeed essential due to the greater height of the engine compared with a conventional twelve-cylinder – and at the same time it is a clear indication of the unique power unit beneath the engine lid.
|
|
|
|
|
Login |
|
|
|
|
|
Poll |
|
|
|
|
|
Latest Pictures |
|
|
files: 4982
albums: 256 (latest)
categories: 68
5 latest additions:
|
|
BMW contract hire
