Experiments were carried out to confirm the modeling
accuracy in terms of maximum cylinder pressure. The
detailed experimental setup and procedures were described
in our previous report of a biogas-fueled gas engine generator
[25]. The experiments were performed at an EAR of 1.2,
1820 rpm, and a boost pressure of 1.2 bar. The experimental
conditions are summarized in Table 3. To prevent mechanical
damage to the engine (such as breakdown due to a sharp
increase in power output or a rapid increase in-cylinder
pressure caused by too much hydrogen additive and/or
excessive retardation of spark timing), the generator was
operated at a fixed power output of 15 kW, even though its
maximum power output was 30 kW. The experiments were
conducted without hydrogen at spark timings of 18e13CA
BTDC, and with 10% hydrogen by volume (equivalent to 5%
hydrogen in terms of heating value) at a spark timing of 10CA
BTDC. The seven resulting experimental data points for
maximum cylinder pressure were compared to the numerical
results obtained by DOE analysis.