Page 389 - Introduction to Marine Engineering

Appendix 359

modified to provide fuel consumption values. The rate of fuel
consumption is the amount of fuel used in a unit time, e.g. tonne/day.
The specific fuel consumption is the amount of fuel used in unit time to
produce unit power, e.g. kg/kW hr.
since fuel consumption oc power

where power =
Admiralty coefficient

then fuel consumption/day =
fuel coefficient
J2/3V3
or fuel coefficient =
fuel consumption/day
Where the fuel coefficient is considered constant a number of rela-
tionships can be built up to deal with changes in ship speed, displace-
ment, etc.
J2/3 y 3 ^2/3 Y 3
2
i.e. fuel coefficient = —7—~ • = „ *-- - '—
fuel cons.j fuel cons. 2
Where 1 and 2 relate to different conditions,
2 3
fuel cons, j //Jj\ / /V 1\ 3
fuel cons., \^ 0 / \V,
A \ £. I \ 4
Considering the situation on a particular voyage or over some known
distance.
fuel cons./day x number of days = voyage or distance consumption
r i i A voyage distance voyage or distance
o r fuel cons./day x •—— — 7 5
speed x 24 consumption
Where conditions vary on different voyages or over particular dis-
tances, then:
voyage cons.j fuel cons.j voyage distancej speed 2

voyage cons. 2 fuel cons. 2 voyage distance 2 speedj
and from an earlier expression
2 3
fuel cons.. /ZL\ /
—- '— * x
fuel cons. 2 I AJ \V 8
2 3 3
voyage cons^ __ /displacement t \ / /spced^ / speed 2 \
voyage cons. 2 \displacement 2j \speed 2/ \ speedj /
voyage distancej
voyage distance