Application of Computational Fluid Dynamics in Multi-Physics Modeling
Abstract: Computational fluid dynamics (CFD) is a technology that simulates the flow of liquids and gases by performing millions of numerical calculations. CFD analysis is carried out early in the design process, even before the first prototype is made. It enables scientists and engineers to perform "numerical experiments" in a "virtual flow laboratory." Multi-physics is advanced CFD involving multiple physics coupled to mimic the real behavior as accurately as possible.
In this presentation, two applications of CFD in multi-physics modeling and simulation will be discussed, which includes the topics of large-eddy simulation (LES) of emulsified canola oil combustion in swirl-promoted combustion chamber and safety modeling of lithium-ion batteries under thermal abuse conditions.
- Recent studies have revealed that LES as a CFD technique is capable of capturing the unstable features of two-phase swirling flows during the combustion of straight vegetable oil (SVO) emulsions. In this study, blends of canola oil and methanol were selected as emulsified SVO fuels for simulation purposes. To fully understand the effects of swirl geometry on the combustion characteristics of emulsified canola oil, a numerical approach based on the discrete phase model (DPM), stochastic model, and Taylor analogy breakup (TAB) model were adopted to simulate SVO blend droplets in a swirl-promoted environment. Moreover, the comprehensive numerical approach was validated by using experimental LDA droplet size distribution data. A two-step chemical reaction mechanism and the eddy-dissipation model were implemented. The results of simulation emission data show the same trends as the experimental results even though the simulations depict higher combustion temperatures in absence of heat losses. The study reveals that turbulent flow and combustion characteristics are affected by the geometry of swirler significantly.
- Thermal runaway and its propagation is a big concern for in application of lithium-ion batteries. It is known that potential safety risks of lithium-ion batteries limit their applications. Thermal abuse, which is induced by internal short circuit, is the most dangerous scenario among various safety risks. Numerous studies of internal short circuit have been done by the experimental approach. However, experimental methods cannot provide sufficient information to show the mechanism of thermal runaway propagation during internal shorting. Recently, a comprehensive three-dimensional safety model for lithium-ion cells, which is based on a multiscale multi-dimensional (MSMD) battery modeling methodology, was developed. This safety model, which includes an electrochemical model, an internal short circuit model, and a thermal abuse model, provides a unique capability to investigate the effects of internal short circuit on thermal runaway propagation in a lithium-ion battery. In this study, the numerical approach was validated by an experiment utilizing an internal short circuit device. The propagation of thermal runaway in a single cell is compared with the results of computed tomography scan as well. This talk addresses the mechanism of thermal runaway propagation in detail. Moreover, the dominant parameters to prevent propagation in battery module are identified.