This thesis describes an investigation into the use of hydrogen
as a fuel for automotive use. Due to problems of backflash into the
engine intake when hydrogen is used as the sole fuel, a dual-fuel
system using petrol and hydrogen together was studied. Using this
system, a spark-ignited engine has been run at all speeds with a wideopen
throttle, and the specific fuel consumption and BTE figures
indicate a greater part load efficiency than those from a throttled
engine. The performance and emissions curves of the engine are presented,
both at the standard compression ratio of 8.9:1 and at a
higher compression ratio of 11.7:1. Emissions data indicate reduced
levels of CO, and NOx at part load due to the very lean mixtures used.
No problem of backfiring was experienced since the concentration of
hydrogen was very low.
A vehicle was modified to run on such a dual-fuel system, and
details of this modification are also presented.
A major problem with using hydrogen as an automotive fuel is its
on-board storage. This is discussed in some detail, with particular
reference to the use of metal hydrides as storage media. Metal hydride
tanks are now commercially available, and a detailed mathematical model
of such a tank has been developed to describe its behaviour under both hydriding and dehydriding conditions. In contrast to other hydride
models previously reported in the literature, this model simulates an
actual, commercially available containment vessel, rather than that of
an abstract ideal situation. Thus the model provides a convenient means
of predicting the time taken to release or absorb given amounts of
hydrogen. These are calculated from the heat transfer characteristics
and diffusion properties of particular metal alloys. Comparisons are
given between the actual operating characteristics and those simulated
by the model.
A brief discussion of the reaction kinetics of hydriding certain
metal alloys is also included.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.