大形タンカーにおける船体抵抗増加が船速と燃料消費量に及ぼす影響についての一考察

抄録

In general, it is widely recognized that the rate of fuel consumption of the vessel (output of main engine) is proportional with the“cube”of vessel speed (revolutions per minute of screw) . However, the vessel speed against a certain rate of fuel consumption is lowered little by little because of deterioration of hull's body, that is inevitable according to the passage of period of time, and soil, which occurs on hull's body.
Therefore, was researched the relationship related with the individual stages on days after inauguration between the vessel speed (R.P.M. of screw) and rate of fuel consumption, while considering the vessel speed and rate of fuel consumption at the official trial operation on the sea, which was made immediately after her inauguration.
On such a research, it was found that the amount of cube shown as the index of speed above is lowered in accordance as the time after inauguration is increased.
So, presuming that such index of speed is“x”and also, presuming the primary function of‘days of passage’ (t), the relative formulas shown below between rate of fuel consumption and speed (R.P.M. of screw) were obtained for the individual vessels on research, “A-Maru”, “B-Maru”and“C-Maru”and by acquiring the amount “x”respectively on these vessels.
“A-Maru”-------F_tA=153×(r_t/90)^{2.841-0.001153t}
“B-Maru”-------F_tB=150×(r_t/90)^{2.799-0.000533t}
“C-Maru”-------F_tC=148×(r_t/90)^{2.742-0.00104t}
By use of these formulas, the rate of fuel consumption (F_tA, F_tB and F_tC) against the revolutions per minute of screw required at any optional time (t) after inauguration could be obtained.
Although some problems still exist on the range of application by such revolutions per minute, the tendency of soils on hull's bottom area influenced by the vessel's age, voyage route, etc. can be supposed with these formulas.