Abstract
The experimental tests were carried out on a single cylinder hydrogen fueled spark ignition (SI) generator set with different spark timings (4-20°CA bTDC), exhaust gas recirculation (EGR) up to 28% by volume and water injection up to 1.95 kg/h (maximum water to fuel mass ratio of 8:1). The engine speed was kept constant of 3000 r/min. The NOx emission and thermal efficiency of engine with gasoline and hydrogen fuel operation at 1.4 kW power output are 5 g/kWh and 12.1 g/kWh, and 15% and 20.9% respectively. In order to reduce the NOx emission at source level, retarding spark timing, exhaust gas recirculation (EGR), and water injection techniques were studied. NOx emission decreased with spark timing retardation, EGR, and water injection. NOx emission with hydrogen at 1.4 kW power output decreased from 12.1 g/kWh with maximum brake torque (MBT) spark timing (10°CA bTDC) to 8.1 g/kWh with retarded spark timing (4°CA bTDC) due to decrease in the in-cylinder peak pressure and temperature. The NOx emission decreased to 6.1 g/kWh with 20% EGR due to thermal and chemical dilution effect. However, thermal efficiency decreased about 33% and 17% with spark timing retardation and 20% EGR respectively as compared to that of MBT spark timing. But, in the case of water injection, the NOx emission decreased significantly without affecting the thermal efficiency of the engine and it is 5.6 g/kWh with water-hydrogen ratio of 4:1 (water flow rate of 0.92 kg/h). Water injection is the best suitable method to reduce the NOx emission in a hydrogen fueled engine compared with the spark timing retardation and EGR technique.
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