The decreasing of the fossil fuels and the
deteriorating of environment has pushed forward study on the utilization of
hydrogen as the alternative fuel. Although the first attempt was reported by Reverend W. Cecil
as early as 1817, the development of the hydrogen engine began in the 1930s,
and was built to a crescendo in 1970s. In the 1930s there were 1000 vehicles
which run with the hydrogen in America and German, and the hydrogen engine was
used by the former Soviet Union during the Great Patriotic War. It has been
proven that the regular vehicle body structure is suitable for hydrogen power
system while the standard gasoline engines can be easily converted to hydrogen ICE.
It was not until the 1990s that the researches
in the hydrogen engine were again rekindled. Mazda, who has made
irreplaceable contributions in the hydrogen rotary engine field, introduced
their first prototype, Mazda HR-X, which was using a hydrogen Wankel engine in
the year 1991. The Mazda5, which is the second generation of the Mazda Premacy,
was offered by Mazda in 2005. In the same year, BMW was focusing their
attention on the research of the BMW Hydrogen 7 and BMW H2R, both of which were
using a liquid hydrogen internal combustion engine while a Tri-Flex engine
pickup, F-250 Super Chief was introduced by Ford.
The prosperity of hydrogen engine cannot go
without the hydrogen production and storage. Gas, coal and biomass energy are
the main source of hydrogen. Hydrogen can also be recycled during the process
of chlor-alkali industry, metallurgical industry, etc. Currently, more
economical methods to obtain hydrogen (e.g. Steam Reforming of Methane,
exhaust-gas purification, SPEWE) have been developed and optimized the hydrogen production. However, the
hydrogen storage is more urgent to be solved compared with the hydrogen
production. For automotive applications, the methods will be discussed in this
paper.
Advantages
of H2 as a fuel
Hydrogen has superior properties which gives significant advantages
compared with other types of fuel.
l Wide range of
flammability
l High flame speed
l Small quenching
distance
l High auto ignition
temperature and low ignition energy
l High diffusivity
Hydrogen engine has
a better performance at high speed operation compared to gasoline engine. Besides,
the emission of CO and HC, which is determined by the air-fuel ratio, is less
than gasoline operation. Due to the combustion properties of hydrogen, shorter
time for combustion produces lower end gas temperature, thus increases the
operating range of the utilisation of hydrogen.
However the emission
of NOx is, in some cases, even more than gasoline operation. NOx is the general
term of NO, NO2, N2O3, N2O4 and N2O5. The main part of NOx, which is NO, can be
oxidized to NO2, a toxic gas with an
offensive smell, by the Ozone in the atmosphere.
BMW Hydrogen 7
A New Method of Driving Clean---BMW Hydrogen 7