The Gas Turbine as Applied to Marine Propulsion

Abstract

The paper commences with an historical survey of gas-turbine development, and deals briefly with the constant-volume and constant-pressure principles. Under the latter are included the open, closed, and semi-closed cycles. Notes are added on air heaters and heat exchangers, materials required for gas-turbine components, and systems of control. The latter portion of the paper covers the application to marine purposes, and describes some current marine-turbine installations. In view of the small number of the moving parts, gas turbines should eventually prove as reliable as older forms of propulsion machinery. Life should not be less than 100,000 hours at full load and temperature, but, as creep tests of this duration are impracticable, the designer must at present base his calculation on rather meagre data. Up-keep costs should, once the initial difficulties have been overcome, compare favourably with those of other forms. A gas turbine of 5,000-10,000 s.h.p. per shaft can be constructed to give a fuel consumption of 0·44-0·46 lb. per s.h.p.-hr. (giving a thermal efficiency of more than 30 per cent on the gross calorific value of the fuel), and the figure should improve to 0·38 lb. (comparable with the Diesel consumption) when metallurgical developments allow the initial air temperature to be raised by 150 deg. F. It should be able to burn the cheaper grades of boiler oil. The gas turbine is lighter in weight and occupies less space than the corresponding steam-turbine or Diesel installation. The author concludes that it will earn a fundamental place in marine propulsion during the course of the next few years.