Environmental performance: A very wide flexibility in optimizing fuel
injection and exhaust valve processes enables RT-flex engines to
comfortably meet IMO limits on NOx emissions. The most visible
benefit cited is smokeless operation at all ship speeds, underwritten
by superior combustion. The common rail system allows the fuel
injection pressure to be maintained at an optimum level irrespective
of engine speed. In addition, at very low speeds, individual fuel injectors
are selectively shut off and the exhaust valve timing adapted to help
keep smoke emissions below the visible limit. In contrast, engines
with traditional jerk-type injection pumps have increasing smoke
emissions as engine speed is reduced because the fuel injection pressure
and volume decrease with speed and power, and they have no means
of cutting off individual injection valves and changing exhaust valve
timing. (Figure 12.34)