The wide flammability limits of hydrogen in air
suggest that this fuel is suitable for a diesel combustion
process. However, the main challenge for realizing
compression ignition arises from the high spontaneous
ignition temperature of hydrogen, 585 C (Table 1).
Assuming direct injection at ambient temperature, the
temperature at the end of compression would need to be
around 1100 K in order to guarantee sufficient heat input
[38]. Simply raising the compression ratio does not allow
such temperatures to be achieved. Additional measures