Challenges for cryogenic injection are related to the
low boiling temperature of liquid hydrogen ð253 CÞ and
the resulting extremely low temperatures of even thegaseous phase fuel. Care must thus be taken to avoid the
occurrence of injector icing. Research has been performed
in an attempt to take advantage of the related cooling
effects. As outlined in Fig. 2, injection of cryogenic,
gaseous hydrogen into the intake manifold significantly
lowers the temperature, thus increasing the density of the
air/fuel mixture and therefore results in higher power
output. Calculations based on a verified model suggest that
the trapped air mass per cycle can be increased by up to
16% with cryogenic hydrogen port injection (injection
temperature around 90 K) compared to ambient hydrogen
injection [30]. Besides an increase in attainable power
output, cryogenic injection also leads to a higher efficiency
in the medium and upper part-load regions, see Fig. 8 [31].