THERMAL STRESSES ANALYSIS OF THERMOELECTRIC MATERIALS BASED ON TURBOJET ENGINE

Thermoelectrical generators (TEGs) require high-temperature differences across thermoelectrical (TE) materials to generate high TE output power. However, the increasing thermal gradient causes thermal stresses on TE materials, which might lead to thermal fatigue. In this study, finite element method-based simulation is presented to quantify the Von Mises stresses on annular TE legs attached to the exhaust pipe of the turbojet engine. The thermal stresses build up on TE elements as the heat transfer coefficient of hot gas flow increases. Therefore, the cascade TEG system is designed to overcome high temperatures that are subjected to TE legs. Besides the cascaded TE model, the unileg (n-n or p-p) cascade TEGs system is also designed to alleviate high thermal stress exposed on the TE materials. Silicon germanium is selected as TE material around the exhaust pipe, and skutterudite is chosen next to the cold side. The design of geometry parameters of annular TE modules is also optimized to decrease stresses. At a heat transfer coefficient of 50 W/m².K, the results showed that the Von Mises stresses of silicon germanium and skutterudite are reduced by 22% and 15%, respectively, when the unileg TE cascade is used compared to an uncouple (conventional)TE cascade system.