Safety and fast-tracking assessment of an innovative SOFC/GT all-electric ship propulsion system under pulsed load
Xicong Mi, Jiale Wen, Jian Yang, Catalina Spataru, Yiwu Weng, Xiaojing Lv
Abstract
To address the challenges of variable sailing conditions and pulsed loads for future long-endurance, high-efficiency ships, an innovative propulsion system for all-electric ship based on solid oxide fuel cell/gas turbine is proposed, whose validated dynamic model is established to analyze the system transient behavior under design condition, step-down load, and pulsed load considering safety and fast load-tracking. The results indicate that the designed propulsion system’s efficiency reaches 60.65 % at a rated power of 10.27 MW, with a steady-state error below 3.4 %. In the scenario of a continuous 20 % step-down load, propulsion system power decreases from 10.27 MW to 4.11 MW, with a steady time of less than 20 s. Notably, under low-load conditions, the system exhibits temperature instability, with the maximum fuel cell temperature gradient fluctuating between 7.0 K/cm and 7.6 K/cm, which stabilized in 360 s. This phenomenon poses a potential safety risk, as the fluctuating internal temperature distribution exacerbates material fatigue. In the scenario of a rectangular pulsed load, the system faces the dual risks of fuel cell material failure and compressor surge. The maximum fuel cell temperature gradient exceeds 10 K/cm, up to 10.8 K/cm. The compressor surge margin fluctuates between 11.1 % and 19.3 % every 10 s, approaching the 10 % safety threshold. Sensitivity analysis reveals that pyrolyzer temperature exerts the strongest influence on system safety under step-down loads with average correlation coefficient of 0.76, while reformer temperature dominates safety under pulsed loads with average correlation coefficient of 0.69. This work can provide technical support for safe and efficient regulation of SOFC/GT propulsion systems under pulsed loads.