Optimal Power Allocation Strategy and Characteristic Analyze of Parallel Irgt/Sofc System for Large Ocean-Going Vessel Under Multi-Scenario Operation

Abstract

To improve the long-endurance and high-efficiency performance when the large ocean-going vessel faces the multi-mission scenario, this study innovatively proposes an all-electric propulsion system consisting of parallel intercooled reheat gas turbine (IRGT)/solid oxide fuel cell (SOFC). The coordination switching characteristics and power ratio relationship between IRGT and SOFC of hybrid system under full speed, mobile cruise, economic cruise, and silent sailing typical ship scenarios are studied. The optimized power allocation strategies considering efficient and safe factors for wider load range are developed.Results show that the validated 68 MW hybrid system of IRGT/SOFC designed for large ocean-going vessel achieves 50.1% efficiency with a maximum error of 2.5% at design point, demonstrating high accuracy. When ship is navigating in full speed scenario, the hybrid system operates at 2.11 power ratio (IRGT: SOFC) with 50.1% efficiency. To avoid catalytic combustion chamber overtemperature, fuel flow is limited larger than 0.967 kg/s. While ship switch to mobile cruise scenario, the power range is from 29MW-56MW, in which the lowest efficiency is 44.8%. By regulating fuel and air split ratio to 0.99 and 0.58, the main power source is IRGT under 106.1 power ratio with the highest efficiency of 45.8%. Subsequently ship move to economic cruise scenario with power range from 27MW-39MW, in which the lowest efficiency is 41.9%. By increasing the fuel and air split ratio to 0.04 and 1, IRGT of unit 1 transfer to SOFC-dominant mode under 0.05 power ratio with highest 50.1% efficiency, while the overtemperature of SOFC is avoided. Finally, ship transfer to silent scenario with power ranger from 6MW-10MW, in which the lowest efficiency is 48.2%. By regulate the fuel and air split ratio to 0 and 0.42, dual units operate on pure SOFC optimal condition achieving 49.9% highest efficiency. Notably, the proposed optimal power allocation strategy makes this ship propulsion system has a wider operation zone from 10% to 108% and highly efficient of 44.3%-50.5%, which enlarge by 38.5% operation zone compared to referenced ship systemThis work provides a technical insight for the next-generation marine power systems of long endurance, flexible load response, low noise, and multi-scenario adaptability.

Keywords: All-electric propulsion system, Dual unit IRGT/SOFC, Multiple scenario coordination, Optimal power allocation strategy, Large ocean-going vessel