محمدرضا گل بهار حقیقی

Reducing maintenance costs and the availability of system components is one of the most important components for ship owners, especially in times of economic sanctions. In this paper, the process of changing a variable thrust system of a 40-meter catamaran passenger float to a fixed-step system is studied, and the adaptation status of the components of the drift system is well analyzed. Four 788 kW diesel engines have been replaced with two 1680 kW engines, and the gearbox and shaft and propeller have also been replaced. In the first phase of the change, with the suggestion of foreign companies, the propeller was mounted on a vessel with a step of 60 and a diameter of 48 inches with a 2.5: 1 gearbox, reaching the engine speed up to 1680 rpm and not increasing further and creating a transient state. In the second step, the modification was performed by floating body and impeller simulations, respectively, to calculate the resistance and power of the impeller and to extract the hydrodynamic graphs of the impeller, propose to modify the impeller or to change the gearbox conversion coefficient to the owner, given the gearbox coefficient availability. With a 2.96: 1 conversion, this gearbox was selected with 15% off-road acceptance in the engine. Due to the good buoyancy maneuverability in the separation, mooring and cruising speeds of 20 and 26.5 knots, respectively, the second combination of the propulsion system and its adaptation are satisfactory.