题目：Numerical simulations of lithium-ion battery thermal runaway, resulting sparks and fire
时间：2024年6月3日 14：30
地点：工科E330
摘要：
The presentation will summarise the development, validation, and application of in-house modified version of open-source computational fluid dynamics (CFD) code OpenFOAM for predicting safety related issues for lithium-ion battery (LIB). The presentation also include some experimental investigations which were carried out as part of a joint project. It will be divided into the following sections:
- Thermal induced thermal runaway (TR)
This section will report the combined numerical and experimental studies carried out by my team to investigate thermal runaway (TR) of large format 21700 cylindrical lithium-ion battery (LIB) induced by different thermal abuse. The cell was treated as a 3-D block with anisotropic thermal conductivities. Paraell laboratory tests and model validation were conducted using Kanthal wire heaters. The validated model was also used to fill the experimental gaps by predicting the onset temperature for TR in simulated EV-ARC environment, heat generation rate due to different abuse reactions, the influence of heating power and heating arrangement as well as the effect of heat dissipation on TR evolution and the implications for battery thermal management.
- Mechanically induced thermal runaway
This section will report the combined numerical and experimental studies to characterise 21700 cylindrical lithium-ion battery (LIB) thermal runaway (TR) induced by nail penetration. Both radial and axial penetrations are considered for 4.8 Ah 21700 NMC cell under 100% state of charge. Heat generation from the decomposition of the cell component materials will be analysed. Validation with the current measurements shows promising agreement. The predictions also provide insight on the magnitudes of heat generation due to internal short circuit resistance, decompositions of solid electrolyte interphase layer (SEI), anode, cathode and electrolyte. Parametric studies further quantify the effects of cell internal short circuit resistance, contact resistance between the nail and cell, convective heat transfer coefficient and cell surface emissivity on TR evolution.
- TR induced fires
This section will report our efforts to characterize the fire hazard of 4.8 Ah 21700 cylindrical NMC LIBs with the aim was to develop a viable predictive tool for simulating LIB fires. An analytical model has been developed to predict cell LIB internal pressure evolution following vent opening. The model uses the measured cell internal temperature and EV-ARC canister pressure as input data. Its predictions serve as boundary condition in the three-dimensional CFD simulation of TR induced fire. Predictions have also been conducted for an open cluster to assess the likelihood of TR propagation in the absence of cell side rupture.
题目：Exploratory numerical study of ammonia dispersion and jet flame
时间：2024年6月4日 9：00
地点：工科E330
摘要：
Ammonia is an efficient hydrogen carrier and clean alternative fuel for marine transport, power generation and fuel cells. Ammonia transportation by sea and bunkering facilities at ports in densely populated areas are rising rapidly. This raises critical safety concern, for which significant knowledge gaps exist. Being a caustic, water-seeking chemical that attaches itself to moisture, leaked ammonia can cling to a person’s eyes, mouth, lungs, throat or skin. Even very low concentrations in the air of just 30 parts per million (ppm) from a very small leak, or even sometimes regular operation, can cause breathing difficulties if a person is exposed to it for more than 15 minutes. A potential accidental spill of ammonia during bunkering poses serious hazards.
Exploratory numerical study has been conducted about both unignited and ignited large-scale ammonia releases using in-house modified OpenFOAM code, which has previously been used for simulating the releases and dispersion of liquid hydrogen. The unignited releases consider scenarios of pressurized ammonia on land. Simulations were conducted for the subsequent dispersion of the ammonia jets to analyze the extent and duration of the resulting toxic cloud. Subsequently, numerical studies were conducted to evaluate ignition potential of accidentally released ammonia jets, giving particular attention to the effect of ambient temperature as well as the addition of hydrogen. To simulate the resulting jet flames, the source terms are calculated using a notional nozzle model. Three-dimensional multi-component compressible Reynolds-averaged Navier-Stokes equations are formulated for the gas flow. The eddy dissipation concept (EDC) model along with a detailed kinetic scheme for ammonia combustion is used to model the interaction of turbulence with chemical reactions.
