Combustion characteristics and particles emissions of a pilot-ignited natural gas engine with diesel-dimethyl carbonate blends

Using natural gas in diesel engines has been considered one effectively way to reduce NO_x and particulate matter (PM) emissions, however the reduction in PM emissions results in an increase in the number of ultrafine particles. In order to resolve this problem, Dimethyl carbonate (DMC), which is an oxygenated renewable fuel, was blended with diesel as common pilot fuel to ignite natural gas. The effect of diesel-DMC on combustion characteristics and particles emissions of pilot-ignited natural gas engines was investigated. The results show that when increasing the proportion of DMC of constant pilot mass, the ignition delay period and the heat release rate increase, yet the total combustion duration decreases. The particle size distribution curves all appear unimodal. With the increase of proportion of DMC, the peak of particle number concentration gradually shifts downwards and towards a larger size, while the particle number concentration and the particle mass concentration decrease simultaneously. And the reduction of number concentration is up to 86% at a special load. The results indicate that DMC-diesel as pilot-ignited fuel can improve significantly particles emissions of pilot-ignited natural gas engines.