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| Mazda Premacy Hydrogen RE Hybrid |
Mazda will begin commercial leasing of the Premacy Hydrogen RE Hybrid (earlier post)
in 2008. The hybrid’s power will be increased by 40%, and it will offer
a hydrogen range of 200 km (124 miles), double the 100 km of the first
versions of the concept hybrid. Mazda will follow that with an improved
hydrogen hybrid system shortly after 2010.
Mazda started working with hydrogen-powered vehicles in 1991 and
announced last year that it was planning to begin leasing hydrogen
rotary engine vehicles starting with the RX-8 equipped with the
hydrogen RE engine (which will also be on display at the Tokyo show).
The hydrogen rotary engine and the hybrid unit are transversely
mounted at the front of the car, with the high-voltage battery located
beneath the second row seats and the high-pressure hydrogen tank beside
the third row seat.
The Premacy concept car has limited hydrogen range: some 100 km, or 62 miles.
Earlier prototypes of the Mazda mild hybrid system included
stop-start, power assistance when the engine is at low rpm, and
regenerative braking. An electric-motor-assist turbocharger system is
used at low rpm, beginning at approximately 1000 rpm. Here, an electric
motor assists the turbocharger to increase induction efficiency. At
high rpm, the turbocharger is driven in a traditional fashion, by the
flow of exhaust gas alone.
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| The dual-fuel hydrogen-gasoline hybrid |
More details will be available at the show, which opens 19 October.
Mazda will also introduce its new Tribute hybrid, based on Ford’s Excape hybrid technology, at the show. Ford owns 33.4% of the Japanese automaker. (Both companies are working on hydrogen-fueled combustion engines as well.)
Mazda will also display its “Smart Idling Stop System” and the
SENKU—a direct-injection rotary-engine hybrid based on the
next-generation 13B DI direct injection gasoline rotary engine.
Rotary combustion engines are less fuel-efficient than conventional
reciprocating engines, but they produce higher power output for a given
displacement volume. In other words, the same size (displacement)
engine produces more power but at the cost of worse fuel economy (and
higher emissions). These combustion characteristics, combined with the
nature of hydrogen, have also led many for some time have to consider
the rotary combustion engine as a good platform for a hydrogen
combustion engine (H2ICE).
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| RENESIS Hydrogen RE |
Because it offers separate chambers for intake and combustion, the
rotary engine is ideal for burning hydrogen without the backfiring that
can occur in a traditional piston engine. The separate induction
chamber also provides a safer temperature for fitting the dual hydrogen
injectors with their rubber seals, which are susceptible to the high
temperatures encountered in a conventional reciprocating piston engine.
Furthermore, the rotary works well with a lean fuel mixture.
The RENESIS Hydrogen RE incorporates an electronically controlled
hydrogen gas injector system. The system draws air from the side port
during the intake cycle and uses dual hydrogen injectors in each of the
engine’s twin rotor housings to directly inject hydrogen into the
intake chambers. (Diagram at right, click to enlarge.)
Also helping to maximize the benefits of the rotary engine in
hydrogen combustion mode, the RENESIS Hydrogen RE features adequate
space for the installation of two injectors per intake chamber. Because
hydrogen has an extremely low density, a much greater injection volume
is required compared with gasoline, thus demanding the use of more than
one injector.
Typically, this can be difficult to achieve with a conventional
reciprocating piston engine because of the structural constraints that
prevent mounting injectors in the combustion chamber. However, with its
twin hydrogen injectors, the RENESIS Hydrogen RE is both practical and
able to deliver sufficient volume.
Earlier Posts from Green Car Congress
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