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- ItemUSE OF MILLIGRAM-SCALE FLAME CALORIMETRY FOR CHARACTERIZING FLAMMABILITY OF FABRIC SAMPLES WITH FLAME RETARDANT TREATMENTS(2023) Roche, Thomas William; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The fire hazard associated with fabrics threatens everyone’s safety, and the current standards used to reduce those hazards are expensive and time-consuming. Fabrics are a key component in clothing, upholstery, and carpentry and are present in nearly every built environment. The inherent flammability of fabrics leads to the application of flame-retardant treatments on nearly all commercial fabric products. Recently, environmental, economic and performance concerns have driven research to develop new flame retardants across a variety of materials. The military industry in particular has focused recent research efforts on flame retardant treatments for fabrics, given the challenging environments that military uniforms must endure. Current methods for testing performance of novel flame retardants, such as the Cone Calorimeter and Microscale Combustion Calorimeter can be prohibitively expensive or only provide a limited understanding of flame-retardant action. Fabrics present additional testing challenges due to their low density and thickness, effectively reducing the amount of fuel available for testing. A novel apparatus, the Milligram-scale Flame Calorimeter (MFC), has been used to test flame retardants in polymeric materials, successfully capturing gas-phase activity and with favorable comparison to Cone Calorimeter results. This study aims to expand the use of the MFC to the testing of fabrics and flame-retardant treated fabrics. Optimization tests were run to find the optimal number of fabric layers and best method for preparing samples for use in MFC. Subsequently, cotton fabrics (untreated and treated with phosphoric acid), as well as Nylon fabrics (untreated and treated with tannic acid) were characterized with MFC, and results were compared to those from the Microscale Combustion Calorimeter and Cone Calorimeter. The MFC showed similar trends in the onset of ignition, peak heat release rate, average heat release rate, char yield, and heat of combustion for the untreated fabrics with the Cone Calorimeter and Microscale Combustion Calorimeter results. The results for the flame-retarded fabrics are inconclusive and require additional testing, though the observations of the condensed-phase and gas-phase activity for the MFC samples does provide important insights on how the mechanism for the flame retardants operate.
- ItemDEVELOPING A VELOCITY-DENSITY CURVE FOR HIGH-DENSITY CROWD SIMULATION BY ANALYZING FOOTAGE VIDEOS(2023) Zhang, Zilin; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Crowds with densities higher than 2 persons/m2 can be defined as high-density crowds. High-density crowds presenting in daily life like concerts and sports events can lead to serious people and property loss. This research work focuses on developing a new speed-density relationship for high-density crowds. The applicability of the new speed-density relationship is tested in Pathfinder, an agent-based evacuation simulation software developed by Thunderhead Engineering, to determine the impact of updating such data on the model's performance. This research also discusses several parameters and functions in Pathfinder including acceleration time and reduction factor to help model high-density crowds.Previous work is available for analyzing crowds with densities lower than 3 persons/m2. However, densities as high as 9 persons/m2 are common in many high-density crowd scenarios. The disparity between previous work and real-world situations presents a challenge for engineers to understand the crowd dynamics of high-density crowds. Developing evacuation models to predict the behavior of high-density crowds is crucial to improving the predictive ability of crowd simulation. By doing so, it helps to reduce the number of casualties in future emergencies. Real-world footage videos are analyzed in this research. With the open-source experimental footage videos provided by Jülich, a national research institution, a new speed-density curve is summarized by collecting and analyzing data from the videos. The assessment of the applicability of the new speed-density in Pathfinder focuses on four aspects: evacuation time, flow density, flow velocity, and occupants’ arrangement. Per case examined, by applying the new speed-density curve, the predicted evacuation time from Pathfinder simulation is improved from 12.6% to within 4.9% of the experimental video time. The predicted flow density is improved from 6.2% to within 0.7% of the average video density. The predicted flow velocity is improved from 25.9% to within 3.3% of the average video velocity. At the same time, it is observed that occupants in the model behave more realistically.
- ItemEVALUATION OF LOW-PRESSURE WATER-BASED TRENCH DRAIN FIRE SUPPRESSION SYSTEMS IN AIRCRAFT HANGARS USING FDS MODELING(2023) Braddock, Sofia Le; Milke, James A; Trouve, Arnaud; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The 2020 National Defense Authorization Act (NDAA) prohibition of PFAS-containing AFFF fire protection systems by 2024 has motivated the U.S. Department of Defense to study other alternatives. In this study, the current low-expansion AFFF foam fire suppression systems with trenches layout in NAVFAC facilities are modeled as water-based systems to determine the scale, coverage, and extinguishment times that can be expected from such systems. A reduced spacing of the trenches is then simulated to determine how spacing of the floor nozzles affects fire suppression and control. Additionally, a model of a previously identified floor-level low-pressure water mist nozzle with the incorporation of trenches is studied to validate its possibility of being a replacement option for the current NAVFAC systems. Each simulation consists of three components: fire model, sprinkler/water mist model, and extinction model. Each model is evaluated separately before inputting into the final simulations to determine the most accurate representation and minimize uncertainties. The final simulations with sprinkler nozzles show successful extinguishment up to 23 MW and better performance at earlier activation time and in setups with the current trench spacing. Little to no difference is observed between the two fuel spill fire scenarios at the same activation time and trench spacing. On the other hand, the low-pressure water mist systems do not meet adequate performance in the final hangar simulations.
- ItemCOMPARISON OF IGNITION AND COMBUSTION CHARACTERISTICS OF PRESSURE TREATED WOOD AND TREX EXPOSED TO THERMALLY CHARACTERIZED GLOWING FIREBRAND PILES(2023) Lauterbach, Alec; Stoliarov, Stanislov I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In recent decades, the intensity of wildfires worldwide has escalated, leading to a rise in the destruction of structures and loss of lives within the Wildland-Urban Interface (WUI). Firebrands are small fragments of ignited vegetation or structural material that are carried by the plume of a wildfire, traveling in advance of the main fire front. Firebrand exposure has been recognized as the primary mechanism for the propagation of wildfires as well as a source of ignition of structural elements. However, this complex ignition process of structural elements in the WUI has yet to be fully understood. The ignition and combustion characteristics of a thermoplastic-wood composite (Trex) and Pressure Treated Wood (PTW), two frequently used WUI decking materials, when exposed to glowing firebrand piles were studied using a bench scale wind tunnel. An inert insulation material, ii Kaowool PM, was also used as a deposition substrate to quantify the heat feedback and combustion characteristics of solely the firebrand pile. Firebrand pile densities of 0.16 g cm-2 and 0.06 g cm-2 were deposited on each substrate in rectangular 10 cm x 5 cm orientations and exposed to air flow velocities of 0.9 m s-1, 1.4 m s-1, 2.4 m s-1, and 2.7 m s-1. Infrared camera measurements were used to determine the back surface temperatures of Kaowool PM tests. Using DSLR cameras, surface ignitions of the decking material in front of the firebrand pile (preleading zone ignition events), ignitions on top of the firebrand pile (pile ignition events), and surface ignitions of the decking material behind the firebrand pile (downstream ignition events) were visually quantified via their probability of ignition, time to ignition, and burn duration at each testing condition. A gas analyzer was used to compare combustion characteristics of Trex, PTW, and Kaowool PM tests through heat release rate (HRR) and modified combustion efficiency (MCE). Peak back surface temperatures of the firebrand pile were found to increase with increased air flow up to 2.4 m s-1, and then plateau. The same trend was observed for the ignition probabilities of preleading zone and pile ignition events. The probability of downstream ignition events increased with increasing air flow velocity. Peak HRR increased with increasing air flow velocity. Trex exhibited significantly less smoldering combustion than PTW yet was prone to more intense flaming combustion. When the rectangular 5 cm x 10 cm firebrand pile (10 cm edge facing the airflow), of which the majority of tests were conducted on, was rotated 90 degrees so that the 5 cm edge faced the airflow, the result was a significant decrease in the probability of ignition for both Trex and PTW, along with notable reductions in their HRR and MCE profiles.
- ItemPredicting the Ignition Time and Burning Rate of Thermoplastics in the Cone Calorimeter(1995) Hopkins, Donald Jr.; Quintiere, James G.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)Ignition and burning rate data are developed for Nylon 6/6, Polyethylene, and Polypropylene in a Cone Calorimeter heating assembly. The objective is to examine a testing protocol that leads to the prediction of ignition and burning rate for thermoplastics from Cone data. The flame heat flux is not measured, but is inferred from Cone data. The constancy of the flame heat flux for thermoplastics in the Cone calorimeter is due to the geometry of the flame. The burning rate model is shown to yield good accuracy in comparison to measured transient values. Ignition and burning rate data are developed for Redwood and Red Oak in a Cone Calorimeter heating assembly. Measurements of the flame plus external heat flux are presented. The data is intended to be used for future work to develop a testing protocol and burning rate model for charring materials.