貨物船の推進係數の推定法
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The easy estimation of the speed and power of ships is always quite necessary in the early stages of ship design, and with this purpose several methods have been already published. Among these, Dr.Yamagata's method which was indicated in his paper entitled "An Approximate Method of Estimating the Requisite Horse Power of Propelling Machineries of Cargo Ships" (Jour. of the Soc. of N.A. of Japan, Vol.LXIII.) seems to be the most successful one. But this papar is only concerned to neighbourhoods of normal speed attained at the normal horse power of propelling machinery at full load condition. Generally, speed trials and other tests on ships are carried out at light condition or 1/5 load condition, except special cases as on oil tankers, and various guarantees in building contract are chiefly appointed on such light load conditions. Therefore, when the principal dimensions of ship and principal particulars of propelling machinery are decided for a new design, it is also a matter of great importance to estimate the horse power-speed curve at such light load condition of the ship. Since effective horse power-speed curve at any load condition of a ship can be estimated with sufficient accuracy by means of several methods by papers already published, such as Taylor's, Ayre's, Volker's, Koning's etc., the estimation of shaft horse power-speed curve for a newly designed ship at any load condition may be replaced by the estimation of suitable propulsive coefficient curve for that ship. The author analysing the results of self-propulsion tests at the Teisinsyo Ship Experiment Tank during past several years, obtained a new method of estimating the propulsive coefficient of cargo ships at full and light load conditions. In the present paper, the values of propulsive coeffi ient are presented corresponding to the adopted standards of cargo ship forms and propellers, and supplemented with correctional values for differences between standards and those which may be applied to a particular vessel. Symbols Used 1) L ……Length between perpendiculars, in m. 2) B ……Breadth including twice the mean thickness of shell plating, in m. 3) T ……Full load draught including the mean thickness of shell plating, in m. 4) T' ……Mean draught of light load condition including the mean thickness of shell plating, in m. 5) T_0 ……Mean draught of standard light load condition including the mean thickness of shell plating, in m. 6) ∂ ……Block coefficient at full load draught. 7) ∂' ……Block coefficient at mean draught of light load condition. 8) η ……Propulsive coefficient=[numerical formula], obtained by model experiment referring to the ideal condition such as clean bottom, smooth water and no wind. 9) η_r ……Propulsive coefficient at full load condition. 10) η_r' ……Propulsive coefficient at light load condition. 11) Δ_η ……Difference of propulsive coefficient between at full load and standard light load conditions, calculated referring to those at full load and light load conditions, by assuming that propulsive coefficient varies in proportion to draught ; the positive sign representing that propulsive coefficient increases with the decrease of draught. 12) Δη_r' ……Difference of propulsive coefficient between at full load and light load conditions. 13) D ……Diameter of propeller, in m. 14) S.H.P. ……Normal shaft horse power of propelling machinery. S.H.P.=η_t・B.H.P. for diesel engine, S.H.P.=η_t・η_m・B.H.P. for reciprocating engine, where η_t=transmission efficiency, and η_m=mechanical efficiency. 15) N ……Normal revolutions per minute of propeller for normal horse power of propelling machinery. 16) q……S.H.P./N^3 Standard Ships and Propellers Adopted. The standard ships adopted are single screw cargo ships with cruiser sterns whose length dealt with in this paper is from 50m to 100m, and the standards for breadth, full load draught, and longitudinal centre of buoyancy are the same as those adopted in Dr.Yamagata's paper menti
- 社団法人日本船舶海洋工学会の論文
- 1941-02-25