Studying the effect of fire retardant coating on the fire hazard characteristics of wood using infrared thermography

This paper represents a study concerning the effect of fire retardant treatment «FUKAM» on the fire hazard characteristics of pine, aspen and larch. The front of model ground fire was investigated to estimate its effect on the surface of wood samples. Infrared thermography was used as a diagnostic method. The surface temperature distribution was obtained for the test wood samples after exposure to a fire front that was modeled using pine needles. The probability of ignition was estimated for the chosen experimental parameters for each kind of wood. The fire hazard characteristics of wood after fire retardant treatment showed a significant reduction in the surface temperature and the resistance to fire for the chosen parameters of the experiment compared to the same untreated samples

Experimental study of the influence of ignition source position on the parameters of peat fire propagation

The penetration of smoldering combustion into the peat layer was experimentally studied taking into account a different botanical peat composition typical in the Tomsk region of Russia. The laboratory tests allowed us to obtain and analyze the temperature of the peat samples versus time, and also to estimate the velocity of the smoldering combustion in the horizontal and vertical directions. The results showed the faster penetration of smoldering combustion into the grass-sphagnum peat compared with the pine-cotton peat. The botanical composition and the flow of oxidizers in the combustion zone have a significant effect on the smoldering combustion, especially on the penetration of smoldering front into the peat layer. The chaotic distribution of the fuel particles contributes to the propagation of smoldering combustion both in the horizontal and vertical direction and influences on the spread of the smoldering front

Laboratory investigation of fire exposure on wood by thermal imagery and thermocouple approach

The impact of spot fire on wood different-shaped samples (flat and cylindered sample) is studied under laborator

Estimation of the influence of wood-fire retardants on fire behavior of some types of wood construction materials

In this paper the effect of fire front on the surface of wood samples (pine, aspen and larch) was presented to estimate the effect of different wood-fire retardants. Infrared thermography was used as a diagnostic method. Modern methods of IR-diagnostics and the use of thermal imagers eliminate the need for a large number of thermocouples, which perturb the investigated medium during measurements. At the same time, a much better resolution in space and time can be obtained using infrared diagnostics. The surface temperature distribution was obtained for the test wood samples after exposure to a fire front that was modeled using pine needles. The ignition probability was estimated for the chosen experimental parameters for each kind of wood. In the infrared region the sample surface characteristics were recorded using a thermal imager JADE J530SB with a 2.5–2.7 micron optical filter that allowed a temperature to be measured in the range of 500–850 K. In order to record a temperature in the range of 293–550 K, the recording was conducted without a filter. The fire hazard characteristics of wood after fire retardant treatment showed a significant reduction in the surface temperature and the resistance to fire for the chosen parameters of the experiment compared to the same untreated sample

Investigation of the ignition of wood structural materials (with and without fire retardant treatment) under the influence of a model fire of irregular intensity

In this paper the effect of fire front on the surface of wood samples (plywood and oriented strand board) was considered to estimate the effect of different wood-fire retardants. Infrared thermography was used as a diagnostic method. The ignition probability was estimated for the chosen experimental parameters for each kind of wood The fire hazard characteristics of wood after fire retardant treatment showed a significant reduction in the surface temperature and the resistance to fire for the chosen parameters of the experiment compared to the same untreated samples. The charring depth of the wood samples was determined depending on the type of wood, as well as on the type of the fire retardant used

Experimental investigation of surface litter ignition by bark firebrands

Probability and conditions for ignition of surface litter (pine needles) caused by firebrands is studied in the laboratory conditions. For modeling of firebrands, pine bark of various sizes 10×10, 15×15, 20×20, 25×25, 30×30 mm2 and 5 mm in thickness is used. The experiment was conducted in the absence of wind and at different wind velocities: 1, 1.5, 2 and 3 m/s. To conduct investigations, an experimental setup was constructed for generation of firebrands and their impact on surface litter. The results of experiments have shown that the increase in air velocity leads to the increase in probability of surface litter ignition. Thus, wind plays a role of catalyst in the ignition process, bringing an oxidizing agent to firebrands and supporting the process of smoldering. However, if the wind velocity is insufficient for ignition, then there is only the process of smoldering. The area of “uncertainty”, where there is smoldering of surface litter without transition to ignition, is found to decrease with increasing the wind velocity. Based on the received results, it can be concluded that the ignition curve of surface liter by firebrands is nonlinear and depends on the wind velocity. At the same time, there is no smoldering and ignition of surface litter for all the wind velocities and the particles with a size of 10 × 10 mm2, regardless of their number

Modeling of wood surface ignition by wildland firebrands

The probability of structural ignition is dependent both on physical properties of materials and the fire exposure conditions. In this study, the effect of firebrand characteristics (i.e., firebrand size, number of firebrands) on wood ignition behavior was considered. Mathematical modeling and laboratory experiment were conducted to better understand the conditions of wood ignition by a single or group of firebrands with different geometry. This model considers the heat exchange between the firebrands, wood layer and the gas phase, moisture evaporation in the firebrands and the diffusion gases of water vapor in the pyrolysis zone. In order to test and verify the model, a series of experiments to determine probability and conditions for ignition of wood-based materials (plywood, oriented strand board, chipboard) caused by wildland firebrands (pine twigs with a diameter of 6–8 mm and a length of 40 ± 2 mm) were conducted. The experiments investigated the firebrand impact on the wood layer under different parameters, such as firebrand size and quantity, wind speed, and type of wood. The results of experiments showed that the increase in wind speed leads to the increase in probability of wood ignition. Based on the received results, it can be concluded that the ignition curve of wood samples by firebrands is nonlinear and depends on the wind speed and firebrand size as well as their quantity. At the same time, there is no ignition of wood samples in the range of wind speed of 0–1 m/s. The ignition of wood is possible with a decrease in the distance between the firebrands with a decrease in the firebrand length. This result agrees more closely with the model

Effect of wood structure geometry during firebrand generation in laboratory scale and semi-field experiments

As the set of experiments result, statistically substantiated data were obtained on the laws of ignition of a model angular structure under conditions of a point source of heat exposure. The use of IR diagnostics made it possible to control the thermal picture in the experimental area, as well as to capture areas of the highest and lowest heating. In the Large Aerosol Chamber of IAO SB RAS, preliminary experiments were carried out on a “firebrand shower” model exposure, which is naturally occurring firebrands (flaming or glowing embers) with some types of construction materials (chipboards). The exposure of the samples to firebrands stream was provided using a firebrand generator of own original design. It was experimentally confirmed that particle size plays a significant role in the ignition of a building structure. If the characteristic particle size, which can be defined as the ratio of its volume to the surface area in contact with the wood, is less than a certain characteristic value, then the ignition mode with a sharp temperature maximum near the phase interface is not fulfilled. This can be explained by the prevailing heat removal into the external environment in comparison with the amount of heat coming from a heat gun and resulting from chemical reactions

Improvement of firebrand tracking and detection software

Burning and glowing firebrands generated by wildland and urban fires may lead to the initiation of spot fnes and the ignition of structures. One of the ways to obtain this infonnation is to process tliennal video files. Earlier, a number of algorithms were developed for the analysis of the characteristics of fu'ebrands under field conditions. However, they had certain disadvantages. In this regard, this work is devoted to the development of new algorithms and their testing