Modern marine steam-turbine feed systems 1

Depending on the auxiliary loads, the method of auxiliary drive, and the amount of regenerative heating employed, a range of 10 per cent. in fuel rate is found on analysing a number of tanker designs of similar power. In a specific design with given loads, alteration to the auxiliary drive and feed heating can alter the fuel rate by 6 to 7 per cent. The methods of auxiliary drive are examined and similarly the use of regenerative heating is evaluated. These are combined to give a “Cycle Ratio” which affords a useful criterion of the efficiency of a system. The cycle ratios of a number of feed circuits are compared and their relative first costs are briefly examined. While the more complex cycles are generally more efficient than the simpler ones, their cost is higher and this tends to lessen the saving from their adoption. Fairly simple cycles can be evolved that are both cheap and efficient, while in other cases the quest for simplicity may lead to too great an increase in fuel rate and hence an appreciable increase in cost taken over the life of the ship.