Studies on Handling Conditions of Marine Engine for Minimizing Oil Consumption―I Fundamental Experiments

Since the popularization of the controllable pitch propellers among small-sized and medium-sized ships, the optimum combination to minimize oil consumption of the rate of rotation of engine (rpm) and the angular pitch of propeller blades at various cruising speeds has been an interest of marine engineers. We made a series of experiments to find the optimum combination with the training ship Kakuyo-Maru (1,044.38G/T, 2,800HP) under various cruising speeds of 9～13.5 knots on October 22nd 1983 in the northwestern Pacific. Following results were obtained. i) Cruising speed, V (knot) and consumption of fuel oil, Gm (kg/n.m. running) were expressed by the following experimental formulae, where n is rpm of the main engine; S, slip ratio of propeller; θp, angular pitch of propeller blades. V=0.0241 n-0.15863 S+0.84685・θp-12.4791 Gm=0.04906・n-0.0086・V²+0.52406 S-0.06734・θp-11.91674 ii) The oil consumption was always smaller at the combination of lower rpm and greater pitch within the speed tested. However, when the angular pitch was 17° or greater, the temperature of exhaust gas often reached above its dangerous level. iii) The relative shaft-horse power at a constant rpm varied with pitch, i.e., the horse power at the pitches of 16° or 17° increased by 3.37 or 11.52% compared with the power at 15° of pitch