Analysis of ratios of propulsion energy demand for transport by bulk carriers

The article presents the results of calculations and analysis of the eM ratio of the propulsion energy consumption per the nautical mile and the eMt ratio of the propulsion energy demand for the transport of 1-ton cargo per the nautical mile for bulk carriers. The relationship between eM and eMt indicators with the EIV (Estimated Index Value) ratio is shown. The output data for the determination of eM and eMt indicators was taken from the quoted MAN publication, reading (reproducing) the values of power, velocity v and DWT tonnage from the charts included in this publication. Calculations and analyses were made for velocity v between 11-15 knots and for DWT from 5-400 kt (kilo tonnes). The graphs of eM and eMt ratios in the function of speed v and load capacity DWT are presented. Using the stepwise method of least squares, models of statistical dependence of indicators on velocity v and load capacity of bulk carriers were developed. They were based on generalized polynomials with integer exponents. Derivatives deM / dv and deMt / dv and derivatives deM / dDWT and deMt / dDWT were determined. The main observations resulting from the conducted analyses are observed with the increase of DWT (within the range of 80-100 kt) a significant decrease in the value of the eM index. For DWT values> 100 kt, the decrease in eMt is slow − eMt asymptotically tends to a constant value. The results of the analyses carried out can be used at the stage of designing the transport capacity (tonnage) and nominal speed of the ship as well as selection of ship tonnage and travel speed in a given transport situation.