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about 60 g humidity per kg air. With this amount of water it is possible to arrive at NOx levels of 3 g/kWh. The HI-FOG nozzles and the water technology are provided by Marioff. For low-speed engines the Water Cooled Rest Gas (WaCoReG) is pursued. This system uti- lizes the same mechanism as an EGR system would, i.e. introducing some rest gas into the combustion space. technologies promoted by Wartsila.

However, these technologies cannot be used for very low NOx, because the evaporation of the water in the combus- tion space will steal some of the com- bustion energy. For the lowest NOx val- ues it is therefore desirable to go anoth- er way, and that is to evaporate the water before it enters the combustion space.

Wartsila created such a system in the 1980s called Combustion Air Humidifi- cation. At that time it was not possible to add very much water into the combus- tion air due to sensitive cylinder liner piston ring technology. Since the intro- duction of the antipolishing ring diesel engines have been virtually insensitive to humidity in the combustion air, Wart- sila decided to take up the development of this system again. Here the Marioff technology to create very small water droplets, HI-FOG, comes in handy because when water is introduced directly after the turbocharger in an environment of more than 200 degrees

C and more than 75 m/s air velocity, the small water droplets will evaporate fast.

Fuel flexibility

Wartsila has given priority to the development of engines capable of operating on Orimulsion and even bot- tom oils. One logic is that these fuels are so cheap that it is possible to apply a considerable amount of exhaust gas cleaning technologies and still deliver energy at a cost-effective price. Geolo- gists and chemists seem to agree that the large salt water seas have unlimited capacity to take sulfur emissions. The trick seems to be to get the emissions to touch the salt water before they touch sensitive vegetation on land. Sea water scrubbing sounds like an interesting opportunity if such a device could be made to work. For this reason Wartsila has taken up the development of a scrubber system together with Marioff.

Minimized waste

Increased efforts on numerous fronts have been designed to minimize diesel engine wastes, including used lubricat- ing oil, used oil filter cartridges, and spare parts scrap. The way to avoid used lubricating oil is never to have to change the oil. That was quite easy in the past when oil consumption was high. With the introduction of the antipolishing ring the threshold became higher. However, the oil companies have responded well to the challenge, and at the moment an oil consumption of 0.4 g/kWh is enough for the best lubricating oils to keep them stable without oil changes. Develop- ment is going on all the time.

Wartsila, Marioff To Cooperate

On Emission Control Technolgy

Wartsila and Marioff, agreed earlier this year to cooperate within the area of emission control technologies for recip- rocating engines. Marioff is a specialist in creating humidity, while Wartsila needs humidity for reduction of NOx in diesel, and perhaps gas engines.

The introduction of water into the combustion space of a diesel engine in one way or another reduces NOx forma- tion. There are two main mechanisms for this phenomenon, one being the addition of mass in the combustion space. The other effect may be evapora- tion of the water in the combustion space during combustion. Both mecha- nisms are utilized in the Direct Water

Injection system, which is one of the

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