An experimental study of acoustically driven medium-scale pool fires

A set of experiments has been conducted on a medium-scale propane fueled pool fire acoustically forced in order to facilitate repeatable measurements defining the flame’s transient behavior. The fuel flow was slightly perturbed at the pool fire’s natural frequency by a sine waveform driven with a loudspeaker which was installed under the burner. As a result of the perturbation, the puffing behavior of the pool fire and the fire shape were modified. As the magnitude of the sine wave was increased larger perturbations were clearly observed, based on the measurement of the radiative heat flux and image analysis. Temperature and soot volume fractions were measured along the center line and throughout a slice of the flame. The soot volume fractions in the flame region are in good agreement with the data of other researchers. The reproducibility of these measurements was established through several experiments. The acoustically driven flame provides the possibility of more repeatable measurements of the transient behavior of these pool fires.     

Sensors and Machine Learning Models to Prevent Cooktop Ignition and Ignore Normal Cooking

Fire Technology - Cooking equipment is involved in nearly half of home fires in the United States, with cooktop fires the leading cause of deaths and injuries in cooking-related fires. In this...     

Investigation of velocity boundary conditions in counterflow flames

The effects of velocity boundary conditions on the structure of methane-air nonpremixed counterflow flames were investigated by two-dimensional numerical simulation. Two low global strain rates, 12 s⁻¹ and 20 s⁻¹, were considered for comparison with measurements. Buoyancy was confirmed to have strong effects on the flame structure at a low global strain rate. It was shown that the location where a top hat velocity profile was imposed is sensitive to the flame structure, and that the computed temperature along the centerline agrees well with the measurements when plug flow was imposed at the inner surface of the screen nearest the duct exit.     

Meaningful performance evaluation conditions for fire service thermal imaging cameras

Thermal imaging cameras (TIC) are rapidly becoming integral equipment for the fire service for use in structure fires and other emergencies. The Building and Fire Research Laboratory (BFRL) at the National Institute of Standards and Technology has conducted research to establish test conditions that best represent the environment in which TIC are used. Firefighters may use TIC for field operations ranging from fire attack, search/rescue, hot spot detection, overhaul activities, to detecting the location of hazardous materials.To develop standardized TIC performance metrics and test methods that capture the harsh environment in which TIC may be used, information was collected from users, the literature, and from fire tests conducted at BFRL. A workshop was held to facilitate knowledge transfer from the fire service and TIC manufacturers. Full-scale and bench-scale experimental work focused on temperature extremes and the presence of obscuring media such as smoke, dust and water. Consolidation of fire environment data with fire fighting operations and imaging needs resulted in a set of performance metrics and test methods that relate to the conditions and tasks encountered by firefighters in structural fire fighting applications. This work is included in a new draft standard on fire service TIC.     

Volume rendering of pool fire data

In a pool fire, an ignited puddle or pool of liquid fuel burns in the atmosphere. Understanding pool fires is important to devising methods to control the hazards resulting from spilled fuels. In this case study, we consider techniques for visualizing the data measured in pool fires and for computing the radiative transfer from pool fires. We used basic tools to image fire data and to compute irradiation-efficient ray casting and radiometrically accurate line integrations. Visualization techniques help answer a number of questions about pool fires     

Energy balance in a large compartment fire

The National Institute of Standards and Technology (NIST) and the Nuclear Regulatory Commission (NRC) are collaborating to assess and validate fire computer codes for nuclear power plant applications. This evaluation is being conducted through a series of benchmarking and validation exercises. The goal of the present study was to provide data from a large-scale fire test of a simulated nuclear power plant cable room. The experiments consisted of a hydrocarbon spray fire with a 1 MW heat release rate, burning in a single compartment 7 m wide, 22 m long, and 4 m high. Measurements included the vertical temperature profiles, heat flux to the compartment surfaces, the velocity and temperature at the compartment doorway, and the total heat release rate. From these measurements, an energy balance was considered, in which it was determined that nearly 74% of the fire's energy went to heat compartment surfaces, 22% escaped through the doorway, and 4% heated gases in the compartment.     

Performance of liquid‐crystal displays for fire‐service thermal‐imaging cameras

Abstract— As use of handheld thermal‐imaging cameras (TICs) becomes more prevalent in the first‐responder community, it is important that standard test metrics be available to characterize imaging performance. A key performance consideration is the quality of the image presented on the TIC display. This paper focuses on TICs that use liquid‐crystal displays to render an image for the user. Current research on TIC performance for first‐responder applications makes use of trained observers and/or composite‐video‐output‐signal measurements. Trained observer tests are subjective and composite video output tests do not evaluate the performance of the complete imaging system. A non‐destructive objective method was developed that tests the performance of the entire thermal‐imaging system, from the infrared sensor to the display. A thermal target was used to correlate the measured thermal imager composite video output signal with the luminance of the display. A well‐characterized charge‐coupled‐device (CCD) camera and digital recording device were used to measure the display luminance. An electro‐optical transfer function was determined that directly relates the composite video output signal to the luminance of the display, providing a realistic characterization of system performance.     

Reconstruction of the Fires and Thermal Environment in World Trade Center Buildings 1, 2, and 7

The National Institute of Standards and Technology (NIST) conducted an extensive investigation of the collapse of the three tall World Trade Center (WTC) buildings. A central part of this investigation was the reconstruction and understanding of the initiation and spread of the fires. This paper describes the reconstruction of the fires, the thermal environment they created within the buildings, and the raising of the temperatures of the structural components. NIST analyzed thousands of documents, interviews, photographs, and videos to obtain information on the layout of the floors and the progress of the fires. Experiments provided information on the factors likely to have determined the fire growth. Simulations using the Fire Dynamics Simulator gave good agreement with the fire spread as observed at the windows. Imposition of the probable thermal environment on the structural steel produced maps of the probable temperature profile of the steel as the fires progressed. For WTC 1 and WTC 2, even in the vicinity of the fires, it was unlikely that the columns and floor trusses with intact insulation heated to temperatures where significant loss of strength occurred. This was in part due to the short time between aircraft impact and building collapse. There were regions of the towers in which the loss of structural strength of floors and columns, whose insulation had been damaged by aircraft impact, was likely. For WTC 7, even though the insulation was intact, the long periods of heating resulted in floor components whose temperatures exceeded 600°C, but columns did not exceed 300°C.     

Performance and failure mechanism of fire barriers in full-scale chair mock-ups

The effectiveness and the failure mechanism of fire barriers in a residential upholstered furniture (RUF) were investigated by full-scale flaming tests on upholstered chair mock-ups. Six commercial fire barriers were tested in this study. Fire barriers were screened for the presence of elements that are typically used in fire retardants and the presence of commonly used fire retardants. For each fire barrier, triplicate flammability tests were run on chair mock-ups, where polyurethane foam and polyester fiber fill were used as the padding materials, and each chair component was fully wrapped with the fire barrier of choice and a polypropylene cover fabric. The ignition source was an 18 kW square propane burner, impinging on the top surface of the seat cushion for 80 seconds. Results showed all six fire barriers reduced the peak heat release rate (as much as ≈64%) and delayed its occurrence (up to ≈19 minutes) as compared to the control chair mock-ups. The heat release rate remained at a relatively low plateau level until liquid products (generated by either melting or pyrolysis of the padding material) percolated through the fire barrier at the bottom of the seat cushion and ignited, while the fire barrier was presumably intact. The flaming liquid products dripped and quickly formed a pool fire under the chair, and the peak heat release rate occurred shortly thereafter. Ultimately, the ignition of the percolating liquid products at the bottom of the seat cushion was identified as the mechanism triggering the failure of the fire barrier.