The effect of varying EGR and intake air boost on hydrogen-diesel co-combustion in CI engines

The results showed that while H2 can be favourable in reducing CO2 and particulate emissions, it causes an increase in NOx emissions when the intake energy contribution from H2 is increased. A reduction in the number of fine and ultrafine particles (diameter 0.05-0.2 μm) was observed when H2 was added to the engine, especially at the low and intermediate intake air boost levels. At high EGR levels (equivalent to 2% intake O2 concentration reduction) significant reductions in exhaust particulate mass of up to 75% were observed at 15% energy from H2. An attempt was made to identify the optimum H2 operating window at the different engine loads, intake air boost and EGR levels.