Improved modelling of physics for a thermal runaway simulation of a battery cell using 3D-CFD/CHT methods

To tackle CO2 emissions from the transportation sector, the European Commission is considering banning internal combustion engine vehicles by 2035. Battery electric vehicles (BEV) have emerged as the leading solution for this transition. Among BEV technologies, Li-ion batteries stand out as the most promising due to their favorable energy density compared to other options. However, this higher energy density also increases the risk of severe thermal runaway events. Therefore, understanding the phenomena occurring during these events is crucial for enhancing mobility safety. In this framework simulations play a pivotal role in offering precious insights into the mechanism of a thermal runaway. The objective of this work, undertaken at Porsche AG, is to develop a new methodology in Star-CCM+, a 3D-CFD (Computational Fluid Dynamics) software developed by Siemens. This methodology aims to accurately describe the heat release, mass loss, gas, and particle flows generated during a thermal runaway event. Specifically, the new methodology applies functions based on Arrhenius law instead of available empirical temperature-dependent functions for the heat release. Input parameters are calibrated through experimental tests conducted in an autoclave filled with inert gas (N2), where thermal runaway in a prismatic cell is triggered by a heating plate. Subsequently, the methodology is applied in a nail penetration test, where thermal runaway is mechanically triggered by a nail, and a cell-to-cell propagation test, where the thermal runaway of the first cell triggers that of a second cell. Results demonstrate the novel methodology’s capability to describe global phenomena, such as average temperature and pressure, and its relative simplicity allows for fast calibration and customization to different setups. However, some local effects remain inadequately described, and experimental results are highly influenced by the employed setup, impeding the validation of calibration to new scenarios. Chapter 1 provides a general overview and literature review on thermal runaway. Chapter 2 details the methodology development and calibration using the heater-triggered cell setup. Chapters 3 and 4 present the comparison of experimental and simulation results obtained with the new methodology in nail penetration and cell-to-cell propagation tests, respectively.