To prevent water separation from emulsified fuel oil and damage to engine sliding portions economically, and lower the concentration of nitrogen oxides in exhaust while ensuring desirable engine operations.
A waterline 11 in which a variable displacement pump 13 is interposed leads a prescribed quantity of water from a water tank 12 to a mixer 10 interposed in a fuel oil line 9. During an engine operation, based on the output torque, fuel flow rate, charging pressure, fuel rack quantity and engine speed that are from a torque sensor 17, fuel flow rate transmitter 14, charging pressure sensor 16 and rack scale sensor 18, a computer 7 that preliminary stores water mixing ratios as a function of the output torque, fuel flow rate, charging pressure, fuel rack quantity and engine speed refers to the stored water mixing ratios to compute a necessary quantity of water added and outputs a signal indicative of the computed added water quantity to the variable displacement pump 13.
YAMADA TETSUTSUGU
TANABE KENJI
