Introduction. The question of the influence of the configuration of the obstacled space on the dynamics of the emergency explosion development, in particular on the intensity of flame acceleration, has been studied for quite a long time. In many works by experimental and numerical methods combustion in obstacles at their various quantity, mutual location, geometrical forms and other parameters is considered. Nevertheless, in most cases, obstacles arranged in organized and periodical manner are considered. At the same time, explosions of gas clouds can occur in conditions where obstacles represented by building structures and technological equipment are arranged in an unorganized manner.

Objective. To simulate the combustion process with an array of randomly placed obstacles, taking into account the specific parameters of the confined space (the number of obstacles nx, their average size d, blocking ratio BO and volumetric clutter θ) using the developed hydraulic model of explosion development.

Research method. The problem of combustion in a pipe closed at one end with specified geometric parameters is solved. Expressions for calculating the parameters of a confined space are given, as well as the principle according to which these parameters are integrated into a hydraulic model.

Description of the physical model. The system of basic differential and algebraic equations of the developed model is presented.

Results and discussion. Functions of the flame speed (Xf)’ to the path traversed by flame Xf are obtained. The calculation was carried out for obstacles with a size d = 1–4 cm at different θ (0.1–0.25) and BO (0.09–0.37), which were adjusted by changing nx.

Conclusion. With the growth of d or nx, the flame in the obstacled space accelerates more strongly. The growth of BO, like θ, leads to an increasing of the gas flow rate in front of the flame and the effective combustion rate. And, consequently, to more intense flame acceleration. Obtained results are make it possible to verify the model using experimental data and improve it in the future.

Introduction. The provisions of regulatory documents in the field of fire safety contain requirements for limiting the spread of fire along the flat facade of a building into window and door openings of staircases in the form of requirements for the width of blind partitions, but do not contain corresponding requirements for the distances between balconies and windows of staircases. To substantiate these requirements, this paper analyzes the thermal impact on the stairwell windows of a fire that occurred on the balcony of a residential building.

Aims and objectives. The aim of this paper is to calculate the temperature fields and heat flows in the zone of translucent filling of staircase openings, depending on the design of the balconies, the size of the partitions, as well as the possible wind speed in the building area.

Methods. To solve the assigned problems, analytical and mathematical research methods were used, including mathematical methods for modelling the propagation of general physical properties — field (CFD) modelling of fire dynamics.

Results. Calculation data are obtained to evaluate the thermal impact on the stairwell windows of a fire that occurred on the balcony of a residential building, depending on the design of the balconies, the size of the partitions, as well as the possible wind speed in the building area.

Conclusion. Based on the research, calculated data were obtained to assess the thermal impact of a fire that broke out on the balcony of a residential building and spread along the facade to the window openings of the staircase. The data obtained make it possible to evaluate the influence of the design of balconies, wind speed in the area where the facility is located, as well as the size of the partition on the temperature fields and heat flows in the window glazing area of the staircase, and on this basis — to make the necessary additions and clarifications to the requirements of regulatory documents on the issue being analyzed.

Introduction. Improvement of protection and development of an innovative solution using lightweight removable panels made of sandwich panels to protect buildings from internal emergency explosions in the climatic zone of the Arctic region was carried out.
As a result of the research, the influence of the temperature difference between the external environment (from –40 °C and below) and the interior of the building/structure (from +18 °C and above) on the condition of lightweight removable panels at the installation points of destructible frame fastening unit (DFFU) was established. Specifically, ice formation and condensation were identified at the joints of the lightweight removable panels (LRP), as well as inside the DFFU, which negatively affects the efficiency and performance of the building protection system against internal emergency explosions.

Aim. To enhance the explosion resistance of buildings/structures through the use of lightweight removable panels made of sandwich panels, considering the climatic impacts of the Arctic region in case of internal overpressure formation.

Objectives:

• analysis of the production and application of sandwich panels as lightweight removable structures in Russia and abroad;
• review of literature and patent sources on existing LRP used in the Arctic region;
• analysis of the impact of extremely low temperatures on the performance of LRP, particularly on the functionality of the DFFU;
• synthesis of research objects.

Analytical Section. A detailed presentation of the research results (analysis).

Conclusions. The value of the obtained results is substantiated, and recommendations for their implementation are provided. The lightweight removable panels (LRP) currently in use have proved their efficiency in climatic conditions outside the Arctic zone; however, further adaptation and improvement of these LRP are required for application in the extreme climatic conditions of the Arctic.

Introduction. Since the beginning of a special military operation, unmanned aerial vehicles (UAV) have been used to strike industrial, transport, energy and civilian facilities. Currently, a physical method of protecting such objects is actively used — the installation of protective enclosing structures (PES) based on mesh fences. Their function is to prevent the UAV and the charge it carries from contacting the protected object.

Research methods. The main damaging factor in the attack of the UAV is the effect of an air shock wave from the explosion of a charge (munition) on the enclosing structures of buildings and structures. The intensity of the explosive charge at short distances from the charge decreases in proportion to the distance to the third degree, therefore, it is relevant to solve the problem of estimating the minimum distances from the mesh screen to the protected object. In this paper, this problem was solved using computational methods based on empirical relations of M.A. Sadovsky.

Aim. To evaluate the effectiveness of the PES for the protection of buildings and structures from an air shock wave and to assess the possibility of designing and realization of PES in practice.

Objectives. Determination of the minimum distance from the elements preventing the contact of the charge carried by the UAV with the protected object; analysis of the possibility of technical implementation of the PES with the calculated parameters.

Calculation results. As a result of calculations, the values of the minimum distances from the mesh fence of the PES to the protected object were obtained with charges of different masses.

Conclusions. The analysis of the results showed that the use of PES is an effective way to protect buildings and structures from UAV attacks. The existing design solutions and materials of the PES make it possible to implement acceptable security of objects from UAV attacks.

Introduction. To localize fires in electrical cabinets, autonomous thermoactivated gas fire extinguishing devices (ATGFED) have recently become more and more widespread. These devices are produced, subject to mandatory confirmation of conformity in the form of certification, but there are no regulatory requirements and test methods for them. Their certification is carried out according to technical solutions developed on the basis of current standards and containing test methods, which are developed for other products, but applicable to the devices under consideration.

The purpose of this paper is to develop a methodology for determining the extinguishing ability of autonomous thermally activated gas fire extinguishing devices. For this purpose, it is necessary to:

• to develop the design of the fire chamber, allowing to correctly carry out the determination of extinguishing capacity;
• to provide thermoactivation of autonomous devices;
• to carry out approbation of the proposed methodology.

Materials and methods. To determine the fire extinguishing ability was used ATGFED in the form of hermetically sealed at both ends of the polymer tube filled with gas extinguishing agent in the liquid phase. For testing were taken devices with protected volume from 50 to 2,000 dm3. The experiment was conducted in a fire chamber with variable internal volume made of non-combustible material in the form of a cabinet with two doors.

Results and their discussion. The developed methodology makes it possible to determine the fire extinguishing capacity for each unit of the device separately under conditions as close as possible to the operating conditions. A series of tests showed that the fire extinguishing capacity of the considered ATGFED with a protected volume from 50 to 2,000 dm3 is in the range from 48 to 125 seconds.

Conclusions. The design of a fire chamber with a variable volume, allowing to correctly carry out the determination of the fire extinguishing ability of devices with a protected volume from 200 to 2,000 dm3 is proposed. To ensure stable operation, a hearth-initiator is applied, which provides thermal activation of autonomous devices. The fire extinguishing ability of ATGFED is determined.

Introduction. Nowadays, cast-iron is used in the field of metro construction for the production of special products — tubbings of metro tunnel finishing. There is an urgent need to take into account the possibility of a fire in the metro tunnel and its impact on the tubbings. At present, there are no ways to predict the behaviour of tubbings in fire conditions.

Aim. Assessment of the influence of the nature of the cross-section of cast-iron tubbings of metro tunnel lining on their fire resistance.

Objectives. Development of methods and carrying out of experimental and analytical assessments of the fire resistance of cast-iron tubbings; determination of the correlation of fire resistance from the cross-section parameters of cast-iron tubbings lining of metro tunnels.

Objects of research. As an object of research, fragments of tubbings of metro tunnel lining, made of cast-iron SCh20, were considered.

Research methodology. In the course of experimental evaluation the deformation of specimens under fire action was assessed. In the course of analytical evaluation — calculation of the strength of the tubbing cross-section with the assessment of the strength condition fulfillment — the critical temperature at which the bearing capacity is preserved was determined, the limiting load on the tubbing at which the strength is preserved was assessed.

Results and discussion. Experimental and analytical methods on fire resistance were chosen for the study. In the course of the experimental assessment of fire resistance, the deformation of the specimens was assessed, which also served as an indicator of the achievement of the limit state of the specimens, the temperature on the unheated surface of the specimen was estimated for further use in the analytical assessment of fire resistance. During the analytical assessment of fire resistance, the strength of the tubbing section was calculated with an assessment of the fulfillment of the strength condition, the critical temperature at which the bearing capacity is preserved was determined. Based on the calculation, the maximum load on the tubbing was estimated, at which the strength is maintained. As a result of the experimental and analytical assessment of fire resistance, critical load values for the selected specimens were obtained.

Conclusion. Experimental dependencies of deformation and heating of cast-iron lining tubbings on the time of fire exposure, as well as the time of reaching the limit states for the loss of bearing capacity, were obtained. The values of the maximum loads on the tubbings are determined, at which after 90 minutes from the beginning of the fire impact, the limit state for the loss of bearing capacity occurs. The mathematical dependence of the value of the maximum vertical load on the specimens, at which the limit state for the loss of bearing capacity is achieved, on the reduced thickness of the section of the tubbings of metro tunnel lining is obtained.

Introduction. The relevance of the problem considered in the paper is in the need to improve the automation and intellectualization of organizational management of fire and explosion safety at the facilities of the fuel and energy complex. Zero drift due to the influence of a number of parameters in thermochemical sensors reduces their sensitivity, which requires the development of new approaches in the implementation of their maintenance. The sensor readiness class prediction model, based on a convolutional neural network (CNN), allows to adjust the established decision-making process, preventing dangerous situations at early stages of development.

Objective. To increase the efficiency of decision makers (DM) in planning the work of teams performing diagnostics and maintenance of auxiliary equipment used, among other things, to ensure fire safety (FS).

Methods. To calculate the classification values when predicting the readiness class of gas alarm sensors, a strategic planning method based on the importance of features (dynamic strategic planning using mathematical programming) was used. According to it, the readiness class was defined as the sum of the binary values of the features multiplied by the normalized value of their importance.

Results and discussion. To carry out calculations and evaluate the results of the CNN application, the authors developed a programme in the Python programming language. It was used to generate a common data set from which training and test sets were selected in a ratio of 9:1. After their formation, the CNN was trained. Testing showed that the DM can predict the readiness class of gas alarm sensors with a probability of 89 %.

Conclusions. The CNN presented in the paper allows to increase the efficiency of the DM work when planning the work of teams performing diagnostics and technical maintenance of auxiliary equipment for FS. The principle of operation of this CNN can be used to solve other similar planning and management tasks.