Numerical Simulation of Impacts of Water Injection on Performance of Natural Gas Engines

Abstract:

This paper focused on the effects of water injection on combustion and emission characteristics in heavyduty natural gas engines by numerical methods. The results show that water injection has no significant effects on the stage of low-temperature reactions, but the generation rate of OH radicals is limited in the stage of high-temperature reactions. Therefore, there is not enough oxidant to oxidize CO. The combustion duration is extended, and the temperature during the combustion is reduced. Moreover, the flame propagation speed and fuel heat released rate slow down with the increase of water injection quantity. The combustion duration and phase are delayed, and the maximum temperature decreases with the water quantity increasing. Besides, the spray position closer to the combustion chamber contributes to the effect of water evaporation on reducing the temperature in the combustion chamber, which is beneficial to increasing the charging density in the intake stroke. Water injection can significantly limit the thermal load of engines and the formation of nitrogen oxides in the combustion chamber, thereby providing the possibility of equivalence ratio combustion in natural gas engines.

Key words:internal combustion engines; natural gas; water injection; numerical simulation