Transient model and performance evaluation of a polygonal automobile exhaust thermoelectric generator under different driving cycles

Abstract

Considering the steady-state model is difficult to accurately evaluate the transient performance of the automobile exhaust thermoelectric generator (AETEG) system under practical conditions, an octagonal AETEG system embedded with sickle-shaped fins was designed in this work, and a transient computational fluid dynamics (CFD) model was established to precisely assess the dynamic fluid-thermal coupling characteristic under four driving cycles of China Light-duty Vehicle Test Cycle (CLTC), Highway Fuel Economy Test (HWFET), New European Driving Cycle (NEDC) and Urban Dynamometer Driving Schedule (UDDS). Moreover, the dynamic voltage, power, and conversion efficiency were numerically calculated with a theoretical analytical model based on the transient fluid and thermal distribution. Results indicate that the predicted voltage and power errors between simulation data and experimental results are 4.25 % and 4.73 %, respectively, verifying the feasibility of the constructed transient numerical model. Additionally, both the transient output voltage and power are proportional to exhaust temperature, and the hysteresis effect in the heat transfer affects AETEG’s output performance smoothness and leads to its peak conversion efficiency when the heat absorption plummets. The AETEG system has the best average transient output performance under the HEFET driving cycle due to the continuous high-temperature exhaust flow, and the average transient power and conversion efficiency approach 81.11 W and 2.1 %, respectively. Under the CLTC driving cycle, the AETEG system reaches the best maximum voltage, power, and conversion efficiency of 170.02 V, 144.54 W, and 7.47 %, respectively. This study provides theoretical guidance for transient performance analysis and optimization of AETEG systems during in-vehicle applications.