Design and off-design models of single and two-stage ORC systems on board a LNG carrier for the search of the optimal performance and control strategy

摘要

A diesel-electric propulsion system is generally used in large scale ships to allow a free placement of Internal Combustion Engines (ICES), to acoustically decouple engines and hull, and reduce total weight and volume. On long voyages, the speed of a vessel can be more or less constant. Thus, to a first approximation, it can be considered that the engines operate most of the time at steady-state conditions. On this basis, Organic Rankine Cycle (ORC) systems can be conveniently installed aboard to generate additional electric power by recovering ICEs waste heat and increase in turn the overall system efficiency. The ICEs-ORC combined cycle system has to be designed properly to maximize the work production and guarantee at the same time a stable operation during both transient and steady-state working conditions.