Water works for NOx

A combined injection valve uses one needle for fuel and another for water, allowing individual control of each. Water injection (at 200 to 400 bar) is started before the fuel (in order to cool the combustion chamber and lower the NOx) and can be turned on or off at any time.

Investment costs are said to be around $20-25/kW while operational and maintenance cost are put at about 4-5 per cent of the fuel cost. Normal tap water can be used and the system can be retrofitted to older Wartsila 32 and 46 engines, although a new drilling has to be made in the heads for the water supply.

The order, for four 12-cylinder and three 16-cylinder Wartsila 46 engines, comes from German yard J J Sietas to power a series of roro vessels to be chartered by Transfennica