“…There are various methods so as to reduce NOx emissions such as exhaust gas recirculation (EGR), the water usage methods (direct water injection (DWI), fumigation, emulsion). Since EGR decrease the engine performance considerably [31,32], classical water usage methods lower the quality of lubrication oil and increase the attrition rate of moving parts of the engine [33], recently, steam injection method has been proposed and used by engine researchers [33][34][35][36][37][38][39][43][44][45] in order to reduce NOx emissions and improve the engine performance.…”