Design and Optimization of a Full-Generation System for Marine LNG Cold Energy Cascade Utilization

This paper took a 100,000 DWT LNG fuel powered ship as the research object. Based on the idea of "temperature matching, cascade utilization" and combined with the application conditions of the ship, a horizontal three-level nested Rankine cycle full-generation system which combined the high-temperature waste heat of the main engine flue gas with the low-temperature cold energy of LNG was proposed in this paper. Furthermore, based on the analysis and selection of the parameters which had high sensitivity to the system performance, the parameters of the proposed system were optimized by using the genetic algorithm. After optimization, the exergy efficiency of the marine LNG gasification cold energy cascade utilization power generation system can reach 48.06%, and the thermal efficiency can reach 35.56%. In addition, this paper took LNG net power generation as the performance index, and compared it with the typical LNG cold energy utilization power generation system in this field. The results showed that the unit mass flow LNG power generation of the system proposed in this paper was the largest, reaching 457.41 k W.