This paper presents a study of the performance of a 6-cylinder,
spark-ignited, port-fuel-injected, production engine modified for
hydrogen fueling. The engine modifications include turbo-charging,
multiple fuel injectors per port and charge-dilution control
techniques. Pumping losses are reduced through ultra-lean burn and
throttle-less operation alongside high charge dilution ratio
control achieved by twin independent variable cam timing without
external EGR.
Lean-burn combustion, engine-out emissions and brake thermal
efficiency results are examined in detail. In particular, low NO
emissions and brake thermal efficiencies near 38% are observed
experimentally at the same operating conditions. The former is
explained in terms of the usual thermal NOx pathway.
Usage of throttle position, injection timings and cam timings for
avoiding preignition and knock over the entire engine map are also
discussed. Finally, first law analyses of energy losses for varying
cam timings, varying manifold pressure and varying torque are
presented and used to suggest reasons for values of λ for optimal
BTE in each case.