The influence of oxygenated fuels on transient and steady-state engine emissions

This research studies the influence of oxygenated fuels on transient and steady-state engine performance and emissions using a fully instrumented, 6-cylinder, common rail turbocharged compression ignition engine. Beside diesel, the other tested fuels were based on waste cooking biodiesel (primary fuel) with triacetin (highly oxygenated additive). A custom test was designed for this study to investigate the engine performance and emissions during steady-state, load acceptance and acceleration operation modes. Furthermore, to study the engine performance and emissions during a whole transient cycle, a legislative cycle (NRTC), which contains numerous discrete transient modes, was utilised. In this paper, the turbocharger lag, engine power, NOx, PM, PN and PN size distribution were investigated. During NRTC the brake power, PM and PN decreased with fuel oxygen content. During steady-state operation, compared to diesel, the oxygenated fuels showed lower indicated power, while they showed higher values during acceleration and turbocharger lag. During acceleration and load increase modes, NOx, PM and PN peaked over the steady-state counterpart, also, the accumulation mode count median diameter moved toward the larger particle sizes. Increasing the fuel oxygen content increased the indicated specific NOx and PN maximum overshoot, while engine power, PM, PN and PM maximum overshoot decreased. Also, the accumulation mode count median diameter moved toward the smaller particle sizes.