Investigating the influence of injection timing on the performance of a RCCI engine

Reactivity-Controlled Compression Ignition (RCCI) is one of the attractive low-temperature combustion strategies because of its high efficiency, reduced fuel consumption, and good potential in reducing emissions. This type of combustion has gained attention in recent years due to global concerns regarding environmental degradation, strict emission regulations, reduction of oil reserves, and rising fossil fuel prices. In this research, an RCCI engine, with a fuel mixture of diesel and gasoline, simulated with the aid of computational fluid dynamics coupled with chemical kinetics. The AVL FIRE software employed for the simulations. The aim was to investigate the impacts of changing the diesel fuel injection timing on combustion and emissions. In this regard, the effects of changing the diesel fuel injection timing in the range of 20 to 40° bTDC on the in-cylinder pressure, heat release rate, combustion phase, and the amount of carbon monoxide, carbon dioxide, nitrogen oxides, and unburned hydrocarbons emissions investigated at a constant engine speed of 1150 rpm. One of the most important results of this study is the reduction of NOX emissions by advancing fuel injection timing to 40° bTDC. Furthermore, with the advancement of diesel fuel injection timing, the combustion starts earlier. By raising the injection duration, the maximum in-cylinder pressure decreases, and the start of combustion delayed. As the fuel injection advances from 20 to 30° bTDC, the produced carbon monoxide decreases, and a further advancement from 30 to 40° bTDC, raises the amount of this pollutant. It is worth noting that the amount of CO2 greenhouse gas has an almost negative relationship with carbon monoxide production.