Downward Flame Spread over PMMA Spheres

Experiments were conducted to measure downward flame spread over PMMA spheres, and an underpinning theoretical basis was developed to explain the relevant mechanisms governing flame spread over spherical geometries. Flame spread over a sphere was classified into two distinct regimes, that being spread over the upper and lower hemispheres. Experiments were conducted using cast PMMA spheres 40 and 50 mm in diameter. Samples were ignited at the top of the sphere and the progression of the flame front was determined using video analysis. The time resolved flame spread rate was found to increase nearly linearly in time while the flame spread across the upper hemisphere of the sample (at rates ranging from approximately 2.0–3.5 mm/min). Flame spread on the lower hemisphere was observed to accelerate nonlinearly reaching instantaneous flame spread rates greater than 15 mm/min. The flame spread rates were found to be unsteady (i.e., continuously increasing) throughout each experiment. A Stokes flow solution was found to adequately characterize the opposed flame spread rate over the upper hemisphere with respect to the induced buoyant flow. Flame spread rates in the lower hemisphere were found to be controlled by a combination of increasing velocity of the ambient flow and increased heat transfer through the interior of the solid. Flame spread rates for each diameter tested were normalized and presented as a function of the relative angle of inclination at the flame front, . Thus, the two regimes of flame spread identified in this work are largely independent across sphere size for the diameters used in this study. The study of flame spread over spheres provides a unique condition to observe the transition from spread dictated by a well-defined flow condition to one in which heat transfer effects through the solid become increasingly significant

3-Dimensional Automated Heat Flux Calibration Device

This document aims to describe the problems in current radiant heat source heat flux calibration techniques and the approach our team took to solve them through automation. The following sections outline the basic premise of the problem we addressed and who our end product benefited. The proceeding sections addresses the research that we have performed regarding heat flux measurements and automation. This research includes current solutions – mostly partial solutions for problems that are similar but not exactly like ours. Following the background research, we define objectives, with specific details that outline how we evaluated different possible solutions, and how we decided upon our final approach. We discuss our detailed plan used to accomplish each of these objectives, the design process leading to a final design, and the analysis that led to and verified this design. Finally the results and conclusions of the completed project are included

Evaluation of pyrolysis processes and biochar quality in the operation of flame curtain pyrolysis kiln for sustainable biochar production

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The Effect of Orientation on the Ignition of Solids

The ignition of a solid is an inherently complex phenomenon influenced by heat and mass transport mechanisms that are, even to this day, not understood in entirety. In order to use ignition data in meaningful engineering application, significant simplifications have been made to the theory of ignition. The most common way to classify ignition is the use of material specific parameters such as such as ignition temperature (Tig) and the critical heat flux for ignition (CHF). These parameters are determined through standardized testing of solid materials – however, the results of these tests are generally used in applications different from the environments in which these parameters were actually determined. Generally, ignition temperature and critical heat flux are used as material properties and are presented readily in sources such as the SFPE Handbook. However, these parameters are not truly material properties; each are inherently affected by the environment in which they are tested. Ignition parameters are therefore system dependent, tied to the conditions in which the parameters are determined. Previous work has demonstrated that ignition parameters (such as Tig or CHF) for the same material can vary depending on whether the sample is tested in a vertical or horizontal orientation. While the results are clear, the implications this may have on the use of ignition data remains uncertain. This work outlines the fundamental theory of ignition as well as a review of studies related to orientation. The aim of this study it to analyze the influence of sample orientation on ignition parameters. All experimental work in this study was conducted using cast black polymethyl methacrylate (PMMA or commonly referred to as acrylic). This study explores ignition parameters for PMMA in various orientations and develops a methodology through which orientation can be incorporated into existing ignition theory. An additional study was also conducted to explore the statistical significance of current flammability test methodologies. Ultimately, this study outlines the problem of the system dependency of ignition and provides commentary on the use of ignition data in engineering applications

Systematic evaluation of pyrolysis processes and biochar quality in the operation of low-cost flame curtain pyrolysis kiln for sustainable biochar production

Low-cost pyrolysis units such as flame curtain pyrolysis kilns are gaining popularity for biochar production. However, the processes that govern the working of such units are not well understood. Here, emissions, temperatures and mass loss are monitored in real-time during kiln operation, followed by extensive biochar sampling. We found that by adjusting the layering rates of feedstock during kiln operation, we can obtain a biochar yield (28 wt% with a fixed carbon content of 65 wt%) comparable to that produced from the same feedstock in a continuous-scale pyrolysis unit, highlighting the importance of systematic guidelines for optimal kiln operation

Performance de protection passive de CLT lors d'essais au feu standardisés et d'essais au feu naturel

peer reviewedThis paper presents the results of an experimental campaign designed to compare and understand the performance of passive protection under exposure to standard furnace tests and natural fires. As part of this campaign, five natural fire experiments were performed with partially protected cross-laminated timber (CLT) compartments under a range of ventilation conditions. In all the tests, only one side wall was left completely unprotected, and all other timber surfaces were protected with either two layers of 18 mm standard gypsum boards (GB) or two layers of 25 mm standard GBs. The structural CLT ceilings were subjected to a superimposed dead load of 1.35 kN/m² during the natural fire tests, and the fire load was (on average) 950 MJ/m²; chosen to represent the Eurocode 1991-1-2 characteristic value for dwellings. The performance of the passive protection was mainly evaluated with regards to the time to reach a protected timber surface temperature of 250°C. The testing confirms that the resulting fire protection performance of a given gypsum board layout depends on the ventilation conditions of the fire compartment, with more severe (and closest to ISO testing) outcomes when testing under ventilation-controlled scenarios. This paper provides data that sheds light on the co-dependency of the passive protection design and compartment fire dynamics and underlines the importance of considering the safety objectives of a building when defining the performance criteria of its structural elements.Zpernon fire tests programm