Design of a radiant panel test at reduced scale for the high throughput development of artificial turf structures

Artificial turf structures are increasingly used in closed areas and have to comply with the European fire standard for building products (EN ISO 13501-1). The main test to evaluate the fire performance of flooring products is the EN ISO 9239-1 radiant panel test. The test principle is to determine the critical heat flux of floorings exposed to a forced ignition and a specific heat flux profile. As large amounts of material are needed to perform the test, the development of a radiant panel test at reduced scale was considered. The experimental design methodology was implemented to mimic the heat flux profile. The fire performance of artificial turf structures was evaluated at both scales and the results were compared. The burnt lengths of the specimens and thus the critical heat flux are similar for both scales. Thus, the downscaled device could advantageously be used for high throughput development of artificial turf structures.

In-depth temperature and smoke production of charring wood under a constant external heat flux

The combustion characteristics of charring wood have been studied experimentally in a well-ventilated environment of a smoke chamber. A numerical simulation has also been performed for a limited case, with the Fire Dynamics Simulator, to estimate the burning environment. A horizontally placed specimen (ponderosa pine) with a moisture content of 0% or 20% is exposed to a radiant flux (25 kW/m2), with or without flaming ignition. Simultaneous measurements of the specimen’s in-depth temperature and the mass loss determine the charring front (rate) at 300 °C and the gasification rate, respectively. These condensed-phase conditions relate directly to real-time variations of gas-phase quantities: the specific optical density of smoke and the concentrations of toxic gases measured by a Fourier transform infrared gas analyzer. In-depth temperature trends are similar whether the flame exists, whereas the smoke and toxicants’ concentrations are substantially different. After the charring front moves through the specimen, the oxidative pyrolysis continues under the irradiation at high temperatures (up to ∼550 °C). Carbon monoxide and acrolein are produced continuously throughout the test, and the results indicate strong correlations. Although char formation of wood is favorable for fire safety, consequent incomplete combustion produces smoke and toxicants.

Mine conveyor belt fire classification

This article presents a conveyor belt fire classification model that allows for the determination of the most effective firefighting strategy. In addition, the effect of belt design parameters on the fire classification was determined. A methodology that involves the use of numerical simulations and artificial neural networks was implemented. An approach previously proposed for modeling fires over conveyor belts was used. With the objective of obtaining some required modeling input parameter and verifying the capacity of this approach to get realistic results, computational fluid dynamics model calibration and validation were carried out using experimental test results available in the literature. Results indicated that scenarios with belt positions closer to the mine roof and greater tunnel heights require a higher longitudinal air velocity to be attacked directly. Furthermore, the belt fire classification model provided by the artificial neural network had an accuracy around 95% when test scenarios were classified.

Simulation of the burning and dripping cables in fire using the particle finite element method

The behavior of the cable jacket in fire characterized by the tendency to melt and drip constitutes a major source of fire hazard. The reason is that the melted material may convey the flame from one point to another, expanding fire and contributing to the fire load. In this article, the capability of a new computational strategy based on the particle finite element method for simulating a bench-scale cables burning test is analyzed. The use bench-scale test has been previously used to simulate the full-scale test described in EN 50399. As the air effect is neglected, a simple combustion model is included. The samples selected are two cables consisting of a copper core and differently flame retarded thermoplastic polyurethane sheets. The key modeling parameters were determined from different literature sources as well as experimentally. During the experiment, the specimen was burned under the test set-up condition recording the process and measuring the temperature evolution by means of three thermocouples. Next, the test was reproduced numerically and compared with a real fire test. The numerical results show that the particle finite element method can accurately predict the evolution of the temperature and the melting of the jacket.

Performance optimization of thin fire blankets by varying their radiative properties

In using thin fire blankets to protect structures in wildfires, heat rejections by radiation (reflection and emission) are essential for good performance. By varying the radiative properties of the front and back surfaces of the blankets, this article offers an optimization study of several scenarios of incident heat flux including pure convection, pure radiation, and combinations of the two. Two types of blanket heat-blocking efficiencies are studied in the optimization scheme. An overall efficiency is defined as the amount of incident heat blocked to the total amount of incident heat in specified wildfire scenarios. An instantaneous heat-blocking efficiency is defined as the instantaneous heat flux blocked to the instantaneous incident total heat flux which provides good understanding of the physics of heat-blocking mechanisms of fire blanket under quasi-steady conditions. In addition to maximizing these heat-blocking efficiencies, there are other optimization objectives, including the minimization of the blanket backside temperature. A genetic algorithm is used for the multi-objective optimization schemes. For the transient heat incidence, the optimization for the entire time sequence is performed with the possibility of a change of blanket radiative properties during the fire sequence, accounting for changes to the fire-facing surface caused by the incident heat.

Bench-scale experimental study on the fire behavior of electric cable arrays by considering different layouts

The effect of different cable layouts on the fire behavior of electric cable arrays was experimentally studied. The influence of external heat flux on cable fire characteristics was investigated. Several parameters for electrical cables such as the post-burning morphology, ignition time, heat release rate, peak heat release rate and total heat release were obtained. The results show that cable layouts could affect cable charring degrees according to the post-burning morphology. A linear relationship was found in the transformed form of time to ignition and radiant heat flux, and the critical radiant heat flux value for the single cable array appeared smaller than that for the other two layouts. The peak heat release rate for Cables A–D with the single array presents the increasing trend with an increase in radiant heat flux, while the two parallel and intersectional cable arrays present the different trends. Moreover, the total heat release values of Cables A–D in the different cable layouts were analyzed. This work provides the basic data and preliminary investigation to fire engineering of cable arrays with the different layouts.

Jetfire lab: Jetfire at reduced scale

This article addresses the development of a bench-scale test (jetfire lab) mimicking the fire exposure of the large-scale jetfire facility. An experimental approach was addressed to develop direct correlation and to validate the similitude between bench-scale test and large-scale jetfire. Comparisons were made by testing Zaltex passive fire protection material in the form of panels. Novel setups were designed to make the jetfire lab able to measure time/temperature curves similar to those obtained at a large scale. The assembly of the tested samples was also investigated. An experimental protocol was elaborated to consider the junction between parts of the sample at the reduced scale. Direct correlation was found between the large and the bench scale and it was evidenced that jetfire lab can be used for preliminary study and development of new thermal barriers for fire protection.

Evaluation of propane explosion with applied water mist

This article discusses the overpressure of a gas explosion and the performance of applying water mist for explosion suppression. According to the experimental results, the larger the opening area, the more difficult it is for pressure to accumulate, resulting in lower overpressure of a gas explosion. When the opening was opened under a high air speed environment, the amount of entrained air was greater. Consequently, the occurrence time of the explosion was shorter than at a low air speed. Despite the water mist nozzle being installed outside the enclosure, a propane gas explosion still occurred regardless of the amount of water mist used, failing to suppress the explosion. However, the water mist nozzle installed inside the enclosure supplied an adequate amount of water mist that could wash a part of the propane, resulting in the fuel concentration dropping below the lower explosion limit, hindering the occurrence of an explosion.

Polylactic acid flame-retarded by nano-compound of form II ammonium polyphosphate with montmorillonite

It is reported a convenient method to obtain flame-retardant polylactic acid composite by adding low amount of crystal form II ammonium polyphosphate (APP-II) or nano-compound of crystal form II ammonium polyphosphate with calcium-based montmorillonite. The structures and thermal properties of the crystal form II ammonium polyphosphate and crystal form II ammonium polyphosphate with calcium-based montmorillonite were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Crystallography and morphologies of the polylactic acid and its composites with the crystal form II ammonium polyphosphate and crystal form II ammonium polyphosphate with calcium-based montmorillonite were measured through differential scanning calorimeter and scanning electron microscopy. In flame retardancy of the polylactic acid composites, the 5 wt% crystal form II ammonium polyphosphate could make the polylactic acid achieve the UL-94 vertical burning V-0 rating and limited oxygen index 27.3%. When using crystal form II ammonium polyphosphate with calcium-based montmorillonite in flame-retarding polylactic acid, only 3 wt% nano-compound can result in the same V-0 rating level and the limited oxygen index of 28.0%. Meanwhile, polylactic acid with crystal form II ammonium polyphosphate or crystal form II ammonium polyphosphate with calcium-based montmorillonite still keeps the good mechanical properties. The developed systems are environmentally friendly and highly effective flame retarding, which show a promising future in practical large-scale polylactic acid application.

Development of a pyrolysis model for oriented strand board: Part II—Thermal transport parameterization and bench-scale validation

Oriented strand board is a widely used construction material responsible for a substantial portion of the fire load of many buildings. To accurately model oriented strand board fire response, kinetics and thermodynamics of its thermal decomposition and combustion were carefully characterized using milligram-scale testing in part I of this study. In the current work, Controlled Atmosphere Pyrolysis Apparatus II tests were performed on representative gram-sized oriented strand board samples at a range of radiant heat fluxes. An automated inverse analysis of the sample temperature data obtained in these tests was employed to determine the thermal conductivities of the undecomposed oriented strand board and condensed-phase products of its decomposition. A complete pyrolysis model was formulated for this material and used to predict the mass loss rates measured in the Controlled Atmosphere Pyrolysis Apparatus II experiments. These mass loss rate profiles were predicted well with the exception of the second mass loss rate peak observed at 65 kW m−2 of radiant heat flux, which was underpredicted. To further validate the model, cone calorimeter tests were performed on oriented strand board at 25 and 50 kW m−2 of radiant heat flux. The results of these tests, including both mass loss rate and heat release rate profiles, were predicted reasonably well by the model.