Both operating current and ambient temperature have a great impact on heat generation and the available residual capacity of the lithium ion battery. The thermal response of the lithium ion battery is investigated under isothermal conditions. Six currents from 1 A to 6 A, with a 1 A interval, are investigated in order to discuss the effect of current under 25 °C; four temperatures from 10 °C to 55 °C, with a 15 °C interval, are investigated to study the effect of temperature under the current of 2 A. The heat generation rate increases with the current increasing during both the charge and discharge stage, but the charge capacity remains independent of current, while the discharge capacity decreases with increasing current. Heat generation decreases with increasing temperature in both the charge and discharge stage, while charge capacity and discharge capacity increase. with the temperature increasing from 10 °C to 55 °C. Heat generation of per charge/discharge capacity is also discussed, and in most cases, the heat generation of per charge capacity during the constant voltage charge stage is larger than that during the constant current charge stage. Heat generation increases at the expense of available capacity, during the discharge stage.

Non-premixed hydrogen flame is solved to investigate turbulent transport characteristic using direct numerical simulation with768 computing cores. Local and statistical transport behaviors are observed in nonbuoyant and buoyant flames. The absence of buoyancy results in a simplified flow field which can serve as a “cheaner” test to provide an improved understanding of transport process and assess the numerical models. Results show that a wider flame front and a lateral shift of temperature are observed in nonbuoyant flame, where diffusional transport is dominant to mixing process. While, both diffusion and convection are the principal factors in a buoyant flame, which makes flame wrinkle and results in a thinner flame. Besides, statistical information indicates that both gradient transport and counter-gradient transport are observed in hydrogen non-premixed flames, and a transition from gradient transport to counter-gradient transport is captured. A large pressure gradient associated with thermal expansion is responsible for counter-gradient transport in diffusion-controlled flames. However, convective transport is inferred to promote the occurrence of counter-gradient transport in buoyancy-driven flames. It is worth noting that traditional gradient transport model fails to completely describe the intricate scalar transport behaviors in non-premixed hydrogen flames, whether diffusion-driven or buoyancy-driven flames.

Lithium ion battery is widely used in electronic products with the advantages of its high specific energy, high theoretical capacity and long span life. The thermal runaway of lithium ion battery is rare in probability, but the thermal runaway caused fires and explosions always occur with the huge used numbers. It is necessary to find how the thermal runaway developing in a single battery. The thermal runaway processes under external heating mode and internal heating mode were investigated in an extended volume accelerating rate calorimeter (EV-ARC) in this work, respectively. The batteries were charged to 0, 25, 50, 75 and 100% SOC, and then they were put into a 150 °C cavity to simulate the external heat conditions, respectively. The results show that the time to thermal runaway decrease with the SOC increasing. The discharging was used to simulate the internal heat influence on the thermal runaway, and the discharging rates were set from 1 A to 5 A with 1 A interval. The results show that the normal cycle number decreases with the current increasing before the thermal runaway, and the time to thermal runaway is shortened. The thermal runaway always occurs at the end of constant voltage charge stage during internal heat experiments. The experimental results indicate that the SOC plays an important role in the process of thermal runaway. The internal exothermal reactions process of battery during thermal runaway could be summarized as the SEI decomposition, anode reaction consumption of Li, separator melting, reactions between internal materials, and then inner short circuit, followed by temperature rising rapidly.