Wartsila has published on their web site an outline of the latest developments in the area of environmentally friendly engines. Common Rail fuel injection appears to be the most effective way to achieve a smokeless diesel engine. It offers flexibility to choose injection pressure and timing totally independently of the engine load. In addition, a computerized control makes it possible to consider several engine parameters and optimize the injection and combustion in each load situation.
CO2 emissions are considered to be more important in the future than NOx emissions, and therefore Wärtsilä has chosen to develop methods that all the time keep fuel consumption low.The introduction of water in one form or another into the engine cylinder seems to be the feasible way forward. The methods chosen by Wärsilä are Direct Water Injection, Combustion Air Humidification and Steam Injection. Fuel-water emulsion certainly is an opportunity, but it has been postponed until common rail injection systems are introduced in all engines because fuel-water emulsion in a conventional injection system causes considerable problems.
The hottest new development at the moment is the Combustion Air Saturation System, where a special HI-FOG nozzle is used to introduce water after the turbocharger in the form of very small droplets.
These droplets evaporate fast, and further heat is introduced in the air cooler, which now acts as an air heater, resulting in combustion air with about 60 g humidity per kg air. With this amount of water it is possible to arrive at NOx levels of 3 g/kWh.