Prospective designs of self-extinguishing devices for spills of burning engine fuels

Проведены теоретические и экспериментальные исследования процессов горения и прекращения горения моторных топлив в трубчатых вертикальных каналах без применения средств пожаротушения. Разработаны технические решения, обеспечивающие локализацию проливов горящих жидкостей и эффективное прекращение горения проливов бензина, летнего, зимнего и арктического дизельных топлив. По результатам проведенных исследований разработаны перспективные конструкции устройств, обеспечивающие самотушение моторных топлив за время не более 300 с. В данных конструкциях реализуется принцип подавления естественной конвекции с помощью ряда конструктивных приемов, которые нарушают взаимосвязь пламени с испаряющейся жидкостью и воздушной средой, создавая тем самым условия прекращения горения. There were found technical solutions for localization of spills of burning liquids and effective flame suppression, called self-extinguishing devices for spills of flammable liquids (USP) on the basis of researches conducted by FGBU VNIIPO EMERCOM of Russia (VNIIPO). Currently there are developed several types of USP differ from each other in design solutions due to the conditions of their practical application. The efficiency of devices is confirmed by numerous experiments on self-extinguishing of burning spills of transformer and turbine oils, conducted by VNIIPO and LLC “SKB” Tensor” in the interests of electric power companies. A number of copyright certificates and patents for inventions were obtained. The principle of suppressing natural convection is implemented in the configuration of USP by a number of design techniques that violate the connection of flame with evaporating liquid thereby creating burnout conditions. This paper presents investigation results on development of self-extinguishing devices for spills of burning motor fuels. The conducted theoretical studies of possibility of extinguishing motor fuels in the channels of USP devices allowed us to determine the critical height of the channels at which self-extinguishing of motor fuels occurs. The results of theoretical studies were confirmed experimentally. The experiments were conducted in two stages. There were tested 15 experimental samples of grids of modular USP assemblies with a ratio of lengths and diameters of vertical channels of 3.8 at the first stage of experiments. At the second stage there were tested 4 mock-up samples of USP for motor fuels manufactured by LLC “SKB “Tensor” with a ratio of lengths and diameters of vertical channels from 3.8 to 6 with grid elements and with flat and volumetric hydraulic locks. There were identified the most promising USP designs that provide self-extinguishing of engine fuel spills with the necessary parameters.

Analysis of Flame Suppression Capabilities Using Low-Frequency Acoustic Waves and Frequency Sweeping Techniques

Symmetry plays a key role in the processing and analysis of not only visual but also acoustic signals in various multidisciplinary areas. New innovative and environmentally friendly methods for extinguishing flames are still being sought worldwide. One of these techniques appears to be the acoustic method. A laboratory stand was built for this purpose, which was coupled with the tested prototype of a high-power acoustic extinguisher, and then the original experiments and analyses of extinguishing effectiveness were carried out. For extinguishing, waveforms with specified parameters selected symmetrically around the frequency for which the extinguisher was designed were used. The aim of this article is to present and discuss selected measurement results concerning the possibility of flame extinguishing with the use of sinusoidal acoustic waves of low frequency (below 21 Hz), as well as with the use of frequency sweeping techniques with set parameters. Such an extinguisher can be equipped with an intelligent module so that the extinguisher may be activated automatically (without human intervention) when flames are detected. The benefits of this combination as well as the importance of image processing for flame detection are also presented in this paper. This solution, with its good fire detection and fast response, may be applicable for extinguishing firebreaks in particular.

Modeling of the mechanism of heterogeneous inhibition of the active flame centers of a jet burning system by fire extinguishing powder particles

The relevance of the work is due to the lack of a physical interpretation of the process of extinguishing jet burning systems with fire extinguishing powders, which is important for ensuring effective fire extinguishing at gas and oil complexes and hazardous chemical industries. A mathematical model of the reaction kinetics of heterogeneous inhibition of active flame centers of a jet burning system by fire extinguishing powder particles in an unsteady mode is considered in the approximation of a purely molecular transfer of matter in the reaction zone. The regularities of the mechanism of heterogeneous inhibition of the active flame centers by the particles of the extinguishing powder under conditions when the active particles of the combustion products participate not only in diffuse, but also in convective transport are established. It is shown, that the convective motion of the active flame centers increases the reaction rate of heterogeneous inhibition of their particles of the extinguishing agent. The results obtained allow us to optimize the conditions for the supply of fire extinguishing powder to the jet burning medium for effective flame suppression.

Introduction of a flame suppression pattern into integrated and zone models used to analyze the dynamics of hazardous factors of indoor fires

Introduction. Fire risk calculation is performed to substantiate the compliance of space planning solutions of buildings and structures with fire safety requirements. The calculation of time needed for hazardous factors of fire to block evacuation routes is performed with account for unlimited fire propagation. The only system, whose operation is taken into account if the fire risk value is exceeded, is the smoke ventilation system. The operation of other fire safety systems is disregarded due to the unavailability of reliable engineering methods of analysis of their influence on fire escalation. The problem of development of modified mathematical models, used to analyze the fire escalation pattern, with account to be taken of the process of fire extinguishing and its influence on fire propagation, is relevant. The purpose of this research is to develop common principles that allow to take account of the pattern of fire suppression in solid materials and combustible liquids by fire extinguishing substances having various origins and degrees of dispersion, if the fire extinguishing substances are added to integrated and zone models of development of hazardous factors of fire escalation.Calculation methodology. The calculations are based on the equation compiled in furtherance of principles of conservation of mass and energy in the flame zone above the surface of the combustible material.Research results. The co-authors suggest general principles for the introduction of a flame suppression pattern into integrated and zone models used to analyze the evolution of hazardous factors of indoor fires. The coauthors present the main provisions and parameters needed to modify integrated and zone models in case of different methods of fire extinguishing. The co-authors have analyzed hazardous factors of fire with account for the flame suppression pattern.Conclusions. The co-authors applied the research findings to develop the modified integrated and zone models that allow to analyze the dynamics of hazardous factors of fire with account for the extinguishing of solid materials and combustible fluids by fire extinguishing substances having various origins and degrees of dispersion.

wUUNet: Advanced Fully Convolutional Neural Network for Multiclass Fire Segmentation

This article describes an AI-based solution to multiclass fire segmentation. The flame contours are divided into red, yellow, and orange areas. This separation is necessary to identify the hottest regions for flame suppression. Flame objects can have a wide variety of shapes (convex and non-convex). In that case, the segmentation task is more applicable than object detection because the center of the fire is much more accurate and reliable information than the center of the bounding box and, therefore, can be used by robotics systems for aiming. The UNet model is used as a baseline for the initial solution because it is the best open-source convolutional neural network. There is no available open dataset for multiclass fire segmentation. Hence, a custom dataset was developed and used in the current study, including 6250 samples from 36 videos. We compared the trained UNet models with several configurations of input data. The first comparison is shown between the calculation schemes of fitting the frame to one window and obtaining non-intersected areas of sliding window over the input image. Secondarily, we chose the best main metric of the loss function (soft Dice and Jaccard). We addressed the problem of detecting flame regions at the boundaries of non-intersected regions, and introduced new combinational methods of obtaining output signal based on weighted summarization and Gaussian mixtures of half-intersected areas as a solution. In the final section, we present UUNet-concatenative and wUUNet models that demonstrate significant improvements in accuracy and are considered to be state-of-the-art. All models use the original UNet-backbone at the encoder layers (i.e., VGG16) to demonstrate the superiority of the proposed architectures. The results can be applied to many robotic firefighting systems.