Springer Science and Business Media LLC

Measuring flame lengths and areas from turbulent flame flares developing from lithium-ion battery failures is complex due to the varying directions of the flares, the thin flame zone, the spatially and temporally rapid changes of the thermal runaway event, as well as the hazardous nature of the event. This paper reports a novel methodology for measuring heat release rate from flame flares resulting from thermal runaway of electric vehicle lithium-ion modules comprising eight 56.3Ah lithium nickel manganese cobalt (NMC) pouch cells using digital cameras and a newly developed numerical code to process the distortion of the flame size based on distance, direction, and shape. The model is tested with a set of experiments using lithium-ion battery packs and validated with a reference set of measurements using calibration boxes, a method commonly used in the reconstruction of flame areas. The experiments showed that the effect of calibration is large, and thus digital imaging without the appropriate calibration can give very large errors in measurement of flames. The combined imaging and processing method proposed in this work allows the determination of heat release rates from lithium-ion battery packs, one of the most challenging variables to quantify during the failure of a battery pack outside the laboratory. In the example experiment that this method was applied to, almost double the heat released was accounted for, meaning 50% of the total heat released would not have been accounted for without this image processing method.

Thermocouple probes have long been standard equipment for wildland fire scientists. But despite substantial advancements in the electronic datalogger technology necessary to read and store data from thermocouples, the effective cost per thermocouple sensor of commercial systems has not decreased such that most researchers can afford to deploy enough sensors to account for the high degree of variability in wildland fire behavior. Because the equipment must endure the extreme conditions of wildland fire, is unlikely that any thermocouple datalogger system will be considered “cheap.” However, the growing number of applications of open-source, do-it-yourself (DIY) microcontroller systems in scientific research suggests these products might be employed in thermocouple datalogging systems if (1) their performance can be shown to be comparable to commercial systems and (2) they can be protected from exposure in the wildland fire environment. In this paper, we compare the performance of an Arduino MEGA microcontroller board relative to a Campbell Scientific CR1000, reading standard K-type metal overbraided ceramic fiber insulated thermocouple probes, under the constant temperature of a drying oven and the variable flame of a Bunsen burner. In both comparisons, we found that the variability among individual thermocouples, which are known to have a $$\pm\, 2\,^{\circ }\hbox {C}{-}6\,^{\circ }\hbox {C}$$ margin of error, was greater than between the dataloggers. We also describe a compact and mobile Arduino-based system capable of recording wildland fire flame temperatures in agris. In considering these three systems, it is clear that Arduino-based open-source, DIY components can support a compact, low-cost datalogger that accommodates more sensors for lower cost than proprietary commercial systems with no sacrifice in data quality. The combination of low-cost, multi-sensor units can contribute to better understanding of variability in wildland fire behavior.

Fire throttling is the increase in flow resistance due to a large fire in a longitudinally ventilated tunnel. Although the fire throttling effect has been been known and studied for tunnels over the last 40 years, there is not yet a consistent one-dimensional (1D) model that can describe this behaviour or a framework suitable for practical application. We propose a semi-empirical model, based upon pipe flow engineering principles, to describe this effect by separating the resistance to flow, or pressure loses in three parts: upstream of the fire, locally at the fire, and downstream of the fire. The proposed 1D model called TE1D is derived from a simple steady one-dimensional momentum balance in which a semi-empirical mean temperature distribution is assumed across the tunnel. We verify the model by comparing the pressures losses it predicts with those calculated in CFD simulations based on OpenFOAM and Fire Dynamics Simulator. The comparison shows good agreement between the CFD codes for the range of fires sizes considered from 5 to 50 MW and good agreement between TE1D and the CFD results with the proposed 1D model for fire sizes below 30 MW. However, for values above there are large discrepancies between the results obtained by the TE1D and CFD. We posit as a potential explanation that these differences are due to flow and temperature stratification which is not accounted for in the 1D model. The model using pipe flow principles allows engineers to adopt this model for design, together with other pressure losses considered in tunnel ventilation.

Kết quả của hơn một thập kỷ nghiên cứu tại Đại học Victoria về hiệu quả của các tín hiệu báo khói khác nhau đối với việc đánh thức người ngủ đã được trình bày và so sánh. Các kết quả cho thấy mức độ tín hiệu (độ lớn âm thanh, cường độ ánh sáng, v.v.) và loại âm thanh hoặc tín hiệu ảnh hưởng đến khả năng người được đánh thức bởi cảnh báo. Âm thanh sóng vuông 520 Hz là hiệu quả nhất trong số các âm thanh được thử nghiệm, đánh thức hầu hết (thường là tất cả) những người tham gia. Các báo khói hiện đang được sử dụng ở Úc và Hoa Kỳ phát ra âm thanh khoảng 3,100 Hz. Nhiều người tham gia không thức dậy với những tông âm như vậy ngay cả khi rất to ở gối (95 dBA). Trong tất cả các nhóm được thử nghiệm, âm thanh cao là tồi tệ nhất và trong hầu hết, đặc biệt là trẻ em, người lớn trẻ (tỉnh táo và 0.05 BAC) và người lớn tuổi, nó tồi tệ hơn nhiều so với tín hiệu sóng vuông 520 Hz. Ở người lớn có khiếm thính, nó hiệu quả hơn bảy lần so với tín hiệu hiện tại và hiệu quả hơn cả máy rung ở giường và gối. Đèn nháy được phát hiện có hiệu quả đánh thức rất kém. Cảnh báo bằng giọng nói khá hiệu quả với các nhóm tuổi trẻ nhưng không phù hợp với người lớn tuổi. Cảnh báo bằng giọng nói cũng gặp vấn đề thực sự trong việc đánh thức những người tham gia có trình độ tiếng Anh hạn chế. Được khuyến nghị rằng âm thanh sóng vuông 520 Hz theo mẫu T-3 nên được áp dụng thay thế cho âm thanh báo khói hiện tại.