The analysis of fuel cells can be divided into two modes, steady-state modeling, and dynamic modeling. Our previous paper [1] focused on steady state operation of solid oxide fuel cell for aircraft APU. The purpose of this paper is to evaluate the transient behavior of the jet fuel external reforming solid oxide fuel cell system plus one heat exchanger (for air preheating) to sudden current load changes. The present model solves the mass, energy, and electrochemical equations for a solid oxide fuel cell, and calculates the thermal response time of the heat exchanger. In this paper, the SOFC heat-up stage and the output voltage and efficiency response to a sudden load change at regional jet flight cycle are investigated.

The results show that heat exchanger temperature variations will reach steady state after about 50 seconds. The heat transfers to anode interconnector layer are almost double and the more current load changes, the more impact the system performance will be. Also by sudden load current changes, the activation and ohmic voltage variations are the highest in the main engine start stage and conversely, concentration voltage and double layer charging variations are the lowest.