Ship weight reduction and efficiency enhancement through combined power cycles

This work describes a tool for configuring and analyzing the weight of combined cycle power plant, designed for shipboard applications. The effects that varying selected combined cycle parameters have on the weight and the efficiency are presented. The combined cycle configuration is limited to a simple Rankine cycle bottoming plant recovering power from a gas turbine prime mover in order to increase efficiency. Although the Rankine cycle analysis could be used to design a steam turbine cycle whose HRSG absorbs power from the waste heat from any prime mover, the weight analysis provided constricts the use of the tool to gas turbines. Unlike much of the weight analysis performed in contemporary literature, this work includes fuel weight as part of the power plant weight, and the analysis results in net weight savings as compared to simple cycle gas turbines operating alone. The model was developed using heat transfer and thermodynamic analysis, turbine scaling techniques, and data from commercially available hardware to size the major power plant components. The analysis reveals that the point of optimal weight does not always coincide with the point of optimal efficiency.