Pyrotechnically actuated fuses, referred to as pyrofuses, are a promising technology for the DC distribution system protection of the future hybrid-electric aircraft. The device developed for this application contains, in addition to the pyrotechnic element responsible for the disconnection under fault conditions, an auxiliary spring that generates a constant tensile load over the silver fuse-element even under normal or overload operating conditions. To analyze and improve the fuse-element behavior for the overload regime, the present publication focuses on the numerical treatment of the quartz sand and its effect on the fuse temperature evolution by using multiphysics numerical models and experimental data.
The experiments are carried out for different input currents with the fuse element fully embedded in quartz sand and subjected to a constant tensile preload force of 10 N. The fuse-element input current, voltage drop and temperature at different locations are recorded throughout the test duration to characterize the temperature front development and to determine the breaking current. A three-dimensional electro-thermal finite element model is developed, in which the surrounding quartz sand is represented using different porous-medium formulations with temperature dependent thermal conductivity and employed to compute the spatial-temporal temperature field development.
Based on the experimental and simulated results comparison, the most suitable model to represent the heat conduction in the surrounding quartz sand for this specific setup is identified. The numerical model provides a basis for future design and optimization of pyrofuses for hybrid-electric aircraft DC distribution systems.

Temperature Evolution,Electro-Thermal Model,Porous-Medium Sand,Overload Conditions,Tensile Preload