High-temperature Turbine Machinery for Marine Propulsion

Abstract

The lecturer examines present practice in steam turbines for ship propulsion and describes some of the high-temperature marine installations in Great Britain and overseas. High-temperature land installations are considered and particular note is made of high-temperature high-pressure turbines used. Properties of materials available are given in Appendix I and are used in the main text of the lecture to determine the upper limit of temperature to be explored. Reheating by steam, gas, and liquid metal, are mentioned, and the latter is recommended. Temperatures are then examined at various pressure levels up to 1,500 deg. F. without reheat and with up to two stages of reheat. The maximum gains are assessed and the possible type of future marine propulsion-turbine is discussed. Some of the problems of uncooled gas turbines are described in particular relation to the Pametrada 3,500 s.h.p. unit. The possibility of cooled gas turbines is discussed and calculations are made as to the efficiency attainable in relation to cooling at various temperatures. The results are contrasted with those possible with high-temperature steam-turbine machinery. The cooled gas turbine would appear to have the greater potentiality for improvement. The argument is summarized by stating that the alloy materials required for high-temperature operation amount to under 2 per cent of the ‘steam up’ weight, but that the fuel used during the lifetime of the ship is 25,000 per cent of this weight.