The Thermodynamic Design of a Combined Steam and Gas Turbine Marine Propulsion System

Abstract

The subject of this paper is the thermodynamic design of a 25,000 shp combined steam and gas turbine (COGAS) powerplant for marine propulsion. The plant includes a high-pressure ratio, aircraft-type gas turbine which exhausts into an unfired, low-pressure waste-heat boiler. The paper considers all aspects of the thermodynamic design including selection of the feed heating system, steam conditions, and gas turbine cycle. It considers the different part-throttle operating modes, and describes the major components and machinery arrangements. It is shown that the efficiency of this relatively simple, state-of-the-art system equals or exceeds that of high-pressure marine steam plants, and approaches the efficiency (based on effective horsepower at the propeller) of the low-speed marine diesel.