| 研究実績の概要 |
The organic electrolyte solvents contribute to the main fuel in the fire hazard of lithium ion batteries (LIBs), quantitative flammability evaluation of LIB electrolytes is essential to a safer battery design. This research has developed the wick-LOC method to measure the limiting oxygen concentration of organic electrolyte solutions. To clarify the flame extinction mechanism and near limit flame behaviors of electrolyte solvents, the wick burner was utilized for the simplification of combustion configuration through experimental and numerical approaches.
In the first fiscal year, the experimental setup was upgraded. The near extinction phenomena have been investigated for dimethyl carbonate with different loading of organophosphorus compounds (OPC) as flame retardant. With the presence of OPC, the flammability limit can be significantly improved; but the thermal feedback from the flame to the wick was enhanced, which led to a larger near-limit burning rate. The mechanism was explained the near-limit flame oscillation study presented in the International combustion symposium 2021. In addition, the 2-D CFD model was developed to simulate the wick flame extinction. Global reaction mechanism of common fuels was applied to validate the simulation conditions. The two-step, quasi-global and detailed reaction mechanisms are under investigation. The current progress shows the feasibility of obtaining the reaction parameters of electrolytes by reproducing the experimental extinction limits. Further investigation will be conducted in the next fiscal year.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
In this year, the experimental setup was upgraded according to the original plan. The materials of fueling system was changed to improve its resistance for special chemicals in battery electrolytes. The chamber and wick burner were optimized to allow the temperature measurement of wick surface under the flame envelope. The fine R-type thermocouple was used to measure the wick surface temperature under steady combustion and near-extinction conditions. The experimental work on near-extinction flame oscillation has been presented in International combustion symposium, where we clarified the enhanced heat feedback from the flame to the wick with the addition of OPC flame retardant. The temperature measurement in experiments is also used to determine the wick boundary condition of numerical model.
For the numerical model, the validation works have been conducted using common fuels like ethanol and methanol. As references with developed mechanism data of combustion reactions, the simulation conditions with proper mesh and time resolutions were achieved. More validations with wider scenarios are under way.
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| 今後の研究の推進方策 |
As applying the detailed reaction model in a specific CFD model is not efficient with a huge computation cost, the reduced mechanism will be applied in CFD model. The detailed mechanism will be used in a simpler flame model in CHEMKIN to validate the reduced reaction mechanism. The wick flame extinction will be simulated using common fuel like ethanol. The near limit flame behaviors are planned to be reproduced. The framework about connecting the wick-LOC experiment with fuel reaction parameters will be organized as research article in next year. The simplified reaction mechanisms of different electrolytes (dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate) will be derived by further simulations under comparison with wick-LOC experiments.
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