BMW Writes Automotive History in Hydrogen Record Run
Munich / Miramas. Hydrogen does not only mean top performance in rockets
traveling to outer space: BMW has proven what the hydrogen car is capable
of, setting 9 records for cars powered by a hydrogen-fuelled internal
combustion engine. "Nine records marking the start into the hydrogen age.
BMW technology has already come a long way. Now, together with politicians
and the energy industry, we must turn our vision of sustained mobility into
reality", stated Professor Burkhard Göschel, Board Member of the BMW Group,
during the speed record trials in Miramas. Achieving this amazing success at
the high-speed Miramas Proving Grounds in France, the BMW Group has clearly
proven its conviction that hydrogen is able to replace conventional fuel
without requiring the driver to compromise dynamic performance.
The specifications of the H2R Record Car are a testament to this
possibility. The 6-liter V12 engine develops an output of more than 210 kW
or 285 bhp. This engine propels the BMW prototype to 100 km/h in
approximately 6 seconds and gives it a top speed of more than 302.4 km/h
(185.5 mph). Based on the gasoline power unit featured in the BMW 760i,
BMW's hydrogen combustion engine boasts the most advanced technologies such
as BMW's fully variable VALVETRONIC valve drive.
The main modifications to the engine involve the fuel injection system
adapted by BMW to the special attributes and requirements of hydrogen. The
H2R Record Car benefits from the results gained in series development of
BMW's future hydrogen engine for the world's first premium sedan built for
dual-mode operation.
BMW will launch a dual-mode version of the current 7 Series during the
production cycle of the present model, thus introducing the first car of its
kind able to run on both hydrogen and gasoline.
The H2R prototype set the following records shown here in terms of times
measured and speed achieved:
time in sec speed in mph
- Flying-start kilometer: 11.993 300.190
- Flying-start mile: 19.912 290.962
- Standing-start 1/8 mile: 9.921 72.997
- Standing-start ¼ mile: 14.933 96.994
- Standing-start ½ kilometer: 17.269 104.233
- Standing-start mile: 36.725 157.757
- Standing-start 10 miles: 221.052 262.094
- Standing-start kilometer: 26.557 135.557
- Standing-start 10 kilometers: 146.406 245.892
BMW works drivers Alfred Hilger, Jörg Weidinger and Günther Weber took turns
at the wheel of the Record Car during their record-breaking session.
BMW's motive in setting up these records was not only to prove the power and
performance of the hydrogen engine. In addition, the reliability and
durability of the technology used clearly demonstrates BMW?s leadership in
developing the hydrogen engine to production standard. In this process BMW
is concentrating on the combustion engine, simply because the combustion
power unit, given the sum total of all its features and characteristics,
still offers the largest number of advantages and benefits all in one.
The H2R Record Car: developed in just 10 months
The BMW H2R Record Car was conceived, designed and developed by BMW
Forschung und Technik GmbH, the legendary subsidiary of BMW AG. The
expressive, purposeful exterior design was created by DesignworksUSA, the
California-based strategic design consultancy owned by BMW Group. The name
?H2R? stands for ?Hydrogen Record Car?.
"We had just 10 months to develop the H2R prototype", states Jürgen Kübler,
the H2R Project Manager. But a short time span like this is quite normal for
the creative engineers that make this Company so very special.
In the process the engineers and development specialists were of course
supported by three factors: First, the components featured in BMW's hydrogen
production car of the future have now reached a high degree of maturity
allowing their straightforward adaptation for the record car. Second, the
development specialists were able, in the development process, to use proven
BMW chassis and suspension systems which matched the strict requirements.
And third, far-reaching use of CAD technology allowed for an effective and
efficient development process.
The engine: series production 12 cylinder specially adapted for hydrogen
The "heart" of the H2R Record Car is based by and large on BMW's
top-of-the-line power unit, the Company's 6.0-liter V12. It is able to run
on hydrogen fuel through the adjustment of engine management as well as the
fuel/air mixture formation components.
The most significant differences in terms of the engine's structural
components are the hydrogen injection valve and the choice of materials for
the combustion chambers: Contrary to the production engine with fuel
injected directly into the combustion chambers themselves, the injection
valves in the hydrogen engine are integrated into the intake manifolds. And
for the specific speed record requirements to be fulfilled in this case the
hydrogen combustion engine was designed and built for single-mode operation,
running exclusively on hydrogen.
This allowed the engineers to set up and tune the engine specifically for
hydrogen requirements, for example by using special valve seat rings made of
an appropriate material. The reason for this necessity is that hydrogen does
not have the lubricating effect of a conventional gasoline/air mixture. It
is worth noting in this context that this need to cope with a lower level of
lubrication has come up before. With the introduction of unleaded gasoline,
production engines have been built with even stronger and more resistant
materials.
Hydrogen providing enhanced efficiency
The combustion properties of hydrogen are quite different from those of
gasoline or diesel: While hydrogen burns faster than conventional fuels
under normal air pressure, the combustion temperature is slightly lower than
in the case of gasoline.
Inside the engine the high combustion speed of the hydrogen/air mixture
generates a higher temperature than in an engine running on gasoline. Engine
management of the BMW H2R Record Car has been modified accordingly. The
hydrogen/air mixture is not ignited until the piston reaches top dead
center, thus ensuring maximum output. With a gasoline/air mixture burning
relatively slowly, by comparison, the mixture must be ignited at an
increasingly early point as a function of engine speed, the pressure peak
thus being reached just as the piston starts to move down.
A significant advantage of the higher combustion pressure of the
hydrogen/air mixture is that the generation of more power from the same
amount of energy means a higher degree of efficiency.
As desirable as the high standard of ignitability of hydrogen within the
engine may be, it also requires a great deal of attention outside of the
combustion chamber. To avoid misfiring, for example, BMW's engineers have
developed a specific gas cycle and injection strategy, with BMW's VANOS
infinite camshaft adjustment masterminding the share of residual gas
according to specific, on-demand requirements:
Before the hydrogen/air mixture is able to flow into the cylinders, the
combustion chambers are cooled by air to ensure that the fuel/air mixture is
not able to ignite in an undesired, uncontrolled process.
VALVETRONIC providing optimum conditions for hydrogen drive
Exclusive to BMW, VALVETRONIC technology serving as a standard feature to
mastermind the valves on the 12 cylinder gives the Company's engine
development specialists an ideal tool for controlling this demanding gas
charge cycle. VALVETRONIC controls not only the duration of valve movement,
but also the actual valve lift. This effect is provided by an intermediate
lever between the camshaft and the two intake valves on each cylinder
infinitely modified in its position relative to the camshaft by an
additional eccentric shaft operated by an electric motor. Depending on the
position of this eccentric shaft, the lever transforms the "hump" on the
cams into a larger or smaller valve movement.
VALVETRONIC is based on BMW's infinite camshaft adjustment process. Already
well-known under its trade name VANOS, this system is an integral part of
the VALVETRONIC concept. Incorporating a hydraulically controlled adjuster
unit in the camshaft drive, VANOS modifies the beginning and end of the
valve opening period, fully variable valve management serving to adjust the
gas charge cycle in the 12 cylinder power unit perfectly to the requirements
and characteristics of hydrogen drive.
Special injection valves for hydrogen power
With hydrogen being injected into the intake manifold as late as possible,
the injection valves have to meet very demanding requirements. Hence, the
valves are a trendsetting new development for BMW. And since gaseous
hydrogen takes up a larger volume per unit of energy than liquid gasoline,
the hydrogen injection valves are larger than conventional injection valve
units.
In addition, the valves have to cover a far wider range of different
requirements, operating under all kinds of system pressure levels and with
injection periods ranging from very short to relatively long. One of the
main objectives in developing the valves was to inject exactly the right
amount of hydrogen required into the intake manifold within a very short
time-frame at very high engine speeds and under full load.
A clean mixture formation process: less fuel consumption under part load,
extra power under full load
Under full load the 12 cylinder power unit runs on a fuel/air mixture of
lambda = 1. This is exactly the same mixture we find on a state-of-the-art
gasoline engine and one which, in principle, offers the highest and most
efficient power output in a combustion engine. Under part load - again a
significant benefit offered by hydrogen - the engine runs efficiently in the
lean burn mode with surplus air.
Under specific conditions, that is with a specific fuel/air mixture, the
combustion of hydrogen leads to the generation of nitric oxides. This
mixture "slot" starts slightly above lambda = 1 and extends to the range of
lambda > 2.
The simple solution to this problem is to leave out this mixture "window"
altogether, since it is not required for running the engine. Hence, the fast
management system controlling the BMW hydrogen engine skips this operating
range completely, thus avoiding NOx emissions in the process. As a result,
the H2R Record Car?s emissions are limited, for all practical purposes, to
nothing but steam.
Safety technology
The fuel system featured in the BMW H2R Record Car is based on a proven
series development concept. Fuel is filled into the tank of the H2R
prototype at a mobile hydrogen filling station through a manual tank
coupling. The vacuum-insulated, double-walled tank has a capacity of more
than 11 kilos of liquid hydrogen and is fitted next to the driver's seat. A
total of three valves ensure optimum safety, the operating valve on the tank
opening at a pressure of 4.5 bar.
Two additional safety valves rule out any dangerous consequences of possible
leaks in the jacket around the tank serving to keep the hydrogen at the low
temperature required, opening up as soon as pressure within the tank exceeds
the limit of 5 bar. This double-redundant safety system guarantees optimum
safety at all times, ensuring that the hydrogen tank will not burst as a
result of excess pressure.
Heat exchanger instead of a gasoline pump
Gas pressure builds up in the fuel supply system simply because of the
rising temperature of the cryogenic, liquid hydrogen in the tank and is kept
at an operating pressure of approximately 3 bar by a tank pressure
controller. Then the coolant running within the 12 cylinder power unit warms
up the hydrogen gas in a heat exchanger to ambient temperature.
Valve technology
Additional valves monitor the pressure of gas in the fuel pipes leading to
the engine: Cold low-temperature valves inside the tank control the removal
of hydrogen from the tank itself. Should any of the pre-flow pipes develop a
leak, with supply pressure dropping below 0.4 bar, the fuel supply valves
close automatically, disconnecting and sealing the tank off from its
surroundings. The supply pipe can also be interrupted manually by an
interruptor tap.
To maintain optimum supply pressure on the injection valves at all times ?
especially as this pressure may vary as a function of driving conditions ?
engine management reduces pressure in the supply pipe to approximately 1.2
bar by means of a control valve fitted specifically for this purpose.
This comprehensive safety system featured in the H2R Record Car is
supervised additionally by a telemetric system of the same type as in
Formula 1. Four hydrogen sensors fitted at neuralgic points - for example in
the tank itself and around the tank coupling - recognize any leakage
immediately and inform the driver accordingly.
Chassis and suspension
Focusing on the structure and chassis of the BMW H2R Record Car, the
engineers and development specialists at BMW Forschung und Technik GmbH used
series components carried over from a sophisticated, thoroughbred BMW sports
car: the monocoque aluminum spaceframe as well as the entire chassis and
suspension system. High-strength aluminum structure panels using the
advantages of aluminum as a particularly light material resistant to
corrosion fill in the open spaces between the extra-large extrusion-pressed
profiles giving the car its stable "skeleton".
The result for the driver is a very stable driving experience without the
slightest vibration or body "tremble".
The front suspension is based on a double-wishbone spring strut front axle
together with rack-and-pinion steering, aluminum track control arms, a
tiebar, and an anti-roll bar. The front axle subframe is formed by a welded
aluminum structure made up of extrusion-pressed profile bars and plates
holding all front axle components and bolted to the body at six points. The
track control arm made of forged aluminum comes complete with two ball
joints in the interest of precise wheel guidance and directional stability.
Wheel guidance and stability at the rear is provided by an integral
four-link axle, a multi-arm principle patented by BMW and rounded off in
this case by an anti-roll bar. Optimum road contact and safety, finally, is
ensured by tires measuring 245/40 x 19.
The bodyshell: outer skin made of carbon fiber
The designers have also given the H2R Record Car a truly unique body: ?We
wanted to embrace the aerodynamic requirements we defined in the wind tunnel
with a form language that was appropriate to the purpose of the car; the
results are a true expression of the car's functional requirements and
objectives to be clean, fast, and uniquely BMW," said Michael Scully, Senior
Designer of DesignworksUSA , who combines his intense involvement in
motorsports with the intellectual and aesthetic challenges of
multidisciplinary design.
Measuring 5.40 meters in length and 2 meters in width, the body of the car
is designed through and through for optimum streamlining. And to reach
record speeds, the frontal area measures just 1.85 square meters and the
drag coefficient is a mere 0.21. At the rear a 20-centimeter-long diffuser
prevents air swirl behind the car, which might potentially slow it down.
The side profile and sheer length of the H2R prototype also serve to ensure
stable driving characteristics at very high speeds. Like on a Formula 1
racing car, the outer skin is made of carbon-fiber reinforced plastic
offering the optimum combination of superior stiffness and low weight:
Overall weight of the H2R with a full tank and the driver at the wheel is
1560 kg or 3440 lb.
-BMW
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