Annotation of the results obtained in 2023
1. All design experimental studies, numerical modeling and testing at the test site planned for the third year have been completed in full. Below are the main conclusions from the research: 1.1. For rooms with an area of up to 10 m^3, it is possible to determine current decomposition and fire at an early stage using modern commercially produced fire detectors (smoke, gas analytical, flame). The operating time of the detectors can range from 10 s to 90 s, depending on the method of initiating the thermal decomposition of the flammable material. 1.2. Identification of the type of material or group of materials, the response area, and the cause of the fire can be reliably carried out using dynamic characteristics: changes over time in the concentrations of CO, CO2, O2 or additional specific gas components (%/s); change in time of temperature in the control zone (K/s); reaching threshold values for triggering smoke and flame detectors. Effective types of sensors, their combinations, as well as factors that make it possible to reliably identify its location in the room, the size of the active zone, the type of pyrolyzed material, and the cause of the fire at an early stage of the origin of a fire, have been determined. 1.3. The most rational location for sensors to monitor changes over time in the concentrations of CO, CO2, O2 or additional specific gas components (%/s); changes in temperature over time in the control zone (K/s); reaching the threshold values for triggering smoke detectors is the ceiling. It is important to position flame sensors in such a way as to provide maximum viewing area. This is due to the fact that, due to diffusion and convection, the resulting products of thermal decomposition and flame combustion rise upward at maximum speed. 1.4. With continuous processing of data from a video camera in the form of luminosity units of each pixel in the frame, it is possible to reliably separate: smoke, steam, dust, flame, etc. In the experiments carried out, the value of the average normalized intensity of the image of objects in rooms was established. 1.5. The determining influence on the speed of sensor response is exerted by natural ventilation from elements of buildings and structures (doors, windows, etc.), as well as forced convection during the operation of supply and exhaust ventilation. A scheme and algorithm for controlling the characteristics of the fire safety system of buildings and structures by varying the input parameters of supply and exhaust ventilation is proposed. 1.6. For each cause of fire and material, the growth rates of carbon monoxide and carbon dioxide concentrations (respectively, a decrease in oxygen concentration) have been established, taking into account the volume of the room and the surface area of the pyrolyzed material. When generalizing the experimental results, predictive approximation expressions for the corresponding functional connections were established. 1.7. The geometry of the premises has a significant impact on the inertia and frequency of operation of fire detectors. For typical room layouts, coefficients have been established for recalculating the sensor response characteristics. 1.8. Based on experimental data, physical and mathematical models of heat and mass transfer have been developed to study the thermal decomposition and combustion of finishing materials in premises for various purposes. A comparison of the results of experiments and mathematical modeling substantiates the adequacy of the developed model. 1.9. When comparing the results of recording trends in the components of the gas-air environment in rooms, it was found that the further the gas analytical sensors are located from the ceiling of the room to the source of the fire, the larger the fluctuations in their readings were recorded. 1.10. When constructing systems with feedback, it is necessary to control: changes over time in the concentrations of CO, CO2, O2 or additional specific gas components (%/s); change in time of temperature in the control zone (K/s). When spraying water or another fire extinguishing agent into a fire zone, the concentrations of CO and CO2 change abruptly during the duration of the spray. Therefore, it is advisable to cover the surface area of the material with a minimum spray duration and pause to stabilize the concentrations of CO, CO2, O2 or additional specific gas components (reach close to 0%/s). Then pause for 5 seconds and update the survey. If the concentrations of flammable gases increase, then carry out a spray pulse. If they do not change or decrease, then the process of thermal decomposition is localized. The duration of liquid spraying and the time pause for polling sensors to receive feedback should be 5-7 s, since these times correspond to the average polling times for most sensors of fire safety systems. 2. A system for monitoring the fire hazard of buildings and structures with neural network algorithms, which has no analogues in the world, has been developed, which allows you to identify the location, area, type of reacting material, the current stage of the process, cause, consequences. The system has been trained for more than 1000 experiments. The system includes: (1) a module for working with experimental data (creation, modification and analytics); (2) a module for receiving readings from sensors installed in the room in real time; (3) a neural network fire detection module that solves the problem of binary classification; (4) neural network module for determining the main characteristics of a fire; (5) neural network module of recommendations for fire prevention, localization and fire suppression; (6) notification module. 3. The main elements of a feedback system for identifying, localizing and eliminating fires in premises have been developed. The essence of the feedback algorithm of the system is taking into account the initial minimization criterion (response time and fire suppression, volume of fire extinguishing agent, number and type of sensors, number and type of sprayers, surface area affected by fire, concentration of asphyxiating gases, etc.), a weighting coefficient for significance, the polling time of sensors is adjusted and their number and type, location are designed, the dispersion of spraying, flow rate, type, temperature and other parameters of the liquid are changed. 4. Practical recommendations for using the results of completed research have been developed; educational and methodological materials for additional courses on training and retraining of specialists in the field of fire safety. The corresponding attached technological solutions are presented in the collective monograph “Low-inertia identification of fires in premises and their suppression using feedback”, which is intended for publication in the publishing house of the SB RAS. 5. Articles have been published in leading Russian and international peer-reviewed publications. 2 applications have been prepared for patenting a method and system for low-inertia identification of conditions preceding fires and fires, as well as a feedback system that allows fires to be localized using minimal time and material resources based on a trained neural network. 2 certificates of state registration of computer programs with the main developed program codes were received. The research results were tested at more than 4 scientific international and all-Russian events. Master's (Alexander Sviridenko, “Automated fire extinguishing system for residential premises based on an intelligent feedback algorithm”) and candidate’s (Svetlana Sergeevna Kropotova, “Thermal decomposition of building and finishing materials during fires in premises”) dissertations with the results of design research have been prepared. All project indicators were fulfilled taking into account the assumed obligations.

 

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Annotation of the results obtained in 2021
All planned work on the project was completed in full, the expected results were obtained, in particular: 1. Experimental methods have been developed, a unique stand has been created for testing and various-scale studies of the characteristics of the processes of detecting fires of materials and substances typical for closed and isolated rooms using a group of sensors: temperature, pressure, heat fluxes, concentration of fuels, oxidizer, flue gases and water vapor. The control systems for the processes of extinguishing fires have been designed, taking into account the receipt of up-to-date information from the sensors used with the use of various water supply schemes. - The concentrations of the components of the gas mixture are determined at three temperatures for each material, corresponding to its ignition, average combustion temperature and typical fire temperature. The possibility of identifying the source of ignition and the type of material dominating in the source by the concentration of gases in the products of pyrolysis and combustion has been substantiated. - The data were generalized and an approximate dependence of the attenuation coefficient of the radiant heat flux on the total surface area of the water curtain droplets was obtained. Using the obtained approximation, it becomes possible to predict the attenuation coefficient of the radiant heat flux from the parameters of the water curtain - the dispersion of drops, the volume concentration of drops, the geometric dimensions of the curtain itself. - Based on the results of the analysis of known experimental data, a physical formulation of the problem of optimizing fire extinguishing with the participation of solid combustible materials by means of water supply was formulated. On the basis of this statement, it is proposed to divide the cooling process (extinguishing of combustible materials) into three phases: heating, cooling, and cooling. A mathematical model has been built that describes the cooling process of combustible materials in order to search for optimization conditions. Examples of optimization of extinguishing fires with hearths based on wood, rubber and other materials have been obtained. 2. Model experiments and bench tests were carried out to establish feedback in fire extinguishing systems, which consists in transmitting relevant information from a group of sensors to a system for generating control signals for spraying water. - Determined the characteristics of the deposition of solid particles of combustion products of a group of typical building and finishing materials in enclosed spaces: wood, linoleum, rubber, etc. The distribution of solid particles - products of pyrolysis in size and concentration. The values of the coefficients of smoke production, extinction and sedimentation rate of smoke aerosol particles without and with the use of water aerosol have been determined. The ranges of variation of the optical properties of the smoke aerosol are highlighted. Variation of the time of action of distributed water on the smoke aerosol was performed in order to assess its effect on the mass deposition rate of solid particles of combustion products. The characteristics of the processes of absorption of laser radiation with different wavelengths in flue gases have been determined in order to establish the most promising colors of reflector materials used for the manufacture of direction indicators when people are taken out of the combustion zone. - Determined the characteristics of the deposition of solid particles of combustion products of a group of typical building and finishing materials in enclosed spaces: wood, linoleum, rubber, etc. The distribution of solid particles - products of pyrolysis in size and concentration. The values of the coefficients of smoke production, extinction and sedimentation rate of smoke aerosol particles without and with the use of water aerosol have been determined. The ranges of variation of the optical properties of the smoke aerosol are highlighted. Variation of the time of action of distributed water on the smoke aerosol was performed in order to assess its effect on the mass deposition rate of solid particles of pyrolysis and combustion products. The characteristics of the processes of absorption of laser radiation with different wavelengths in flue gases have been determined in order to establish the most promising colors of reflector materials used for the manufacture of direction indicators when people are taken out of the combustion zone. - The best combinations of technical means necessary and sufficient for early identification of the moments of the beginning and end of extinguishing in conditions corresponding to fires in a closed room have been determined. It is shown that for error-free and low-response identification of pyrolysis and ignition of various materials (and, as a consequence, the beginning of the extinguishing process), it is advisable to use at least two different types of sensors (thermal, smoke or flame radiation sensors), which makes it possible to increase the probability of fire detection to almost 100 %. It has been substantiated that information on the concentration of O2, CO2 and CO in the air (obtained using a gas analysis system) should be used as a signal confirming the fact of a fire. It has been determined that, under feedback conditions, to determine that the extinguishing process is proceeding successfully (the extinguishing composition interacts with the fire source), it is effective to use the gas analysis system and thermal sensors (in the event of their preliminary triggering). It is shown that information from video recording equipment (video cameras) should be used in real time as an additional parameter confirming the fact of the extinguishing process - a graph of changes in the normalized intensity of images. It has been established that, under feedback conditions, a flame radiation sensor can be used quite effectively to determine the moment of complete cessation of flame combustion. As an additional technique to confirm the fact of complete cessation of flame combustion, one should use the graph of changes in the average normalized intensity of the image from the video camera in real time. It has been established that the moment of complete extinguishing of the fire (cessation of smoldering) and, as a consequence, stopping the process of supplying the extinguishing composition can be determined by analyzing the graph of changes in the average normalized intensity of the image from the video camera. Starting and stopping the fire extinguishing system, taking into account the above criteria, factors and features established in the course of experimental studies, can significantly reduce the spraying time of the extinguishing composition and, as a result, reduce its volume spent. The specific volumes of water per unit are of the fire source required for complete extinguishing with this approach are: wood - 8.7 l/m^2; linoleum - 0.9 l/m^2; paper - 3.6 l/m^2; cardboard - 7.2 l/m^2. 3. The results of experimental determination and analysis of the influence of a group of factors and parameters on the performance of systems for detecting and suppressing the combustion of fires in rooms have been obtained: - the defining parameters for the operation of the thermal sensor are the rate of increase in the air temperature, the air temperature, and the time sufficient for the operation of the air temperature sensor; - the limited value of the minimum temperatures for the operation of thermal sensors was 50-55 ºC (at a rate of air temperature rise of at least 0.7-0.8 ºC/s); - when the paper burns, the rapid growth and, as a consequence, the drop in temperature leads to the fact that even at high rates of temperature rise (more than 1 ºC/s) and air temperature (more than 55-60 ºC), heat sensors do not work at about 42% cases; - the most efficient location of the heat sensor - directly above the combustion center; - when the combustion source is located in the sensor's visibility zone in the presence of a flame, the flame sensors are triggered in 100% of cases for all investigated combustible materials; - with stable combustion of the hearth (after ignition), the response times of the flame sensors do not depend on the weight of the sample of combustible material; - when the flame sensor is removed from the hearth in the range of 1-6 m, the flame height required for the sensor to operate increases nonlinearly in the range of 2-25 cm; - the probability (relative frequency) of smoke detectors triggering for all investigated combustible materials increases with an increase in the weight of the sample of combustible material and the size of the hearth. At the same time, the response times of smoke detectors practically do not depend on the mass of the combustible material; - the most effective use of smoke detectors when detecting foci consisting of linoleum, rubber and other materials, which are characterized by intense smoke generation; - the most effective is the installation of smoke detectors around the perimeter of the room. Using the example of wired sensors connected via a loop, it was registered that the times of fire detection in this case are 20% lower than when the sensors are placed along the wall; - with the switched on smoke exhaust system and other conditions being equal, the relative frequency of the smoke detectors is reduced by 2-4 times; - the use of feedback for the investigated model fire sources made it possible to reduce the operating time of spray systems by 2-6 times, the size of the combustion zone by 3-5 times, the volume of used liquid by 5-8 times; it is substantiated that in the future it is possible to significantly optimize the operation of systems with feedback according to a group of criteria (liquid volume, time of identification, localization and suppression of combustion, the number and layout of sensors and irrigation installations). 4. The maps of regimes were constructed and the integral characteristics of combustion, suppression and localization were established under different conditions. Based on the results of the experiments, the limiting capabilities of the sensors (fire detectors) were established when they operate in the feedback mode. It was found that the flame sensors effectively signal the presence of a flame in the feedback mode (the reaction time was 5-10 s): the sensors can be used to determine the moment when the flame combustion of the material stops. It is shown that heat sensors can be effectively used to identify the combustion and extinguishing process: when the temperature in the vicinity of the sensor drops below 80 ° C, the signal from the detector disappears, which signals the successful course of the extinguishing process. Smoke detectors can be used in the feedback mode only at the initial stage of the extinguishing process: at the beginning of extinguishing the fire, smoke emission intensifies, which leads to a cascade triggering of smoke detectors and indicates the interaction of the extinguishing liquid with the fire. 5. Based on the results of experiments, the optimal (from the point of view of water consumption, spraying time and achievable temperature reduction) specific irrigation densities were calculated. So, for example, the maximum value of the irrigation density corresponds to wood and chipboard (11-18 l/m^2), and the minimum value corresponds to linoleums, PVC panels and lamellar blinds, for which ψ values must be at least 2.2 l/m^2. The minimum value of the irrigation density (ψ) required to extinguish the model hotbed corresponded to the minimum specific irrigation density. In a comprehensive analysis (i.e., taking into account the significant characteristics of extinguishing - extinguishing time and total consumed volume of water), it was found that for most types of foci, the most effective extinguishing is achieved when using pulsed spraying. In the experiments carried out, the effective parameters of the operation of pulsed systems for extinguishing materials typical for premises for various purposes were established. It has been substantiated that the algorithms for the operation of spray systems must be adjusted not only for the localization and extinguishing of fires, but also for effective smoke deposition and smoke removal. For this purpose, a series of experiments were carried out, in which it was found that the linear deposition rate of smoke aerosol particles can vary in the range 0.01–2 cm/s. The experiments carried out proved that the light indication of evacuation tables and signs in the building should be green, yellow or orange (530-600 nm). The supply of a water aerosol into a smoke-filled room for 60 s leads to an increase in the specific mass deposition rate of smoke aerosol particles by a factor of 6 for linoleum on a heat-insulating base and by a factor of 4 for rubber, i.e. Even for fires with intense smoke in the premises, it is possible to significantly accelerate the settling of solid particles from combustion products when spraying water over a limited period of time. 6. Specific characteristics of the processes under study have been determined to ensure the possibility of transferring the research results to different conditions of the propagation of the combustion front in the premises. In particular, an experimental database was obtained with the size distributions of droplets in different sections of the movement after the drop. An assessment of the influence on the data of the distribution of the concentration of components, the initial dimensions, the reset pattern, and other parameters has been carried out. The obtained distributions can be used to develop models used to describe the characteristics of the formation of aerosol clouds over the combustion zone during the operation of fire aviation. Based on the results of the generalization of the experimental data, the influence of a group of factors on the size of the formed droplets in the aerosol cloud was established when typical fire extinguishing compositions move from different discharge heights and with three supply schemes. The contribution of all these factors can be taken into account by varying the values of the three empirical constants in the expression formulated by fire service specialists for average droplet sizes during local discharge of unsprayed massifs. It is shown that this expression can be applied to schemes with jets and sprayed liquid flows. 7. Research results have been published in leading international journals, some articles are under review and are being prepared for submission to journals. Articles published and accepted for publication: 7.1. Process Safety and Environmental Protection. Article "Impact of scattered radiation on thermal radiation shielding by watercurtains". Q1 (IF=6.158). Status: published. 7.2. Powder Technology. Article "Influence of the component composition of extinguishing fluids on the droplet distribution in an aerosol cloud". Q1 (IF=5.134). Status: published. 7.3. Journal of Engineering Physics and Thermophysics. Article "Investigation of the characteristics of a typical fire source in a room." Status: accepted for publication. The editorial note indicates the expected output data: T. 95, No. 6. 2022. 7.4. Journal of Engineering Physics and Thermophysics. The article "On the relationship between the mutual arrangement of the nozzle devices and the dispersion of the generated aerosol". Status: accepted for publication. The editorial note indicates the expected output data: T. 96, No. 1.2023. 8. Two applications for patenting the developed techniques have been prepared, in particular, the first invention relates to methods of preventing fires, containing fires and extinguishing fires at special facilities or localities, namely, to a method for detecting fires in premises for various purposes (residential, warehouse, office, specialized ) and subsequent adaptive localization of the fire source. The second invention relates to methods of saving lives in the event of a fire in various categories of premises through the use of special lighting sources and spray devices located on the escape routes, which form a water curtain in the evacuation passages, providing intensive deposition of smoke and a temporary increase in visibility. 9. The research results were tested at 6 scientific international and Russian events. Oral reports were made at the XXXIII scientific-practical conference "Actual problems of fire safety", the VI All-Russian scientific conference "Thermal physics and physical hydrodynamics" Scientific youth school "Thermophysics and physical hydrodynamics: modern challenges" (TFGSV2021), XXXVII Siberian thermophysical seminar dedicated to the Year and technologies of the Russian Federation (STS-37), International multidisciplinary conference on industrial engineering and modern technologies FarEastCon-2021, VIII international conference "Heat and mass transfer and hydrodynamics in swirling flows", XI All-Russian conference with international participation "Fuel combustion: theory, experiment, applications ". 10. The report on the implementation of the project in 2021 was prepared and the work plan for 2022 was updated. An additional file with a detailed description of the work performed, the project results obtained in 2021 and their analysis is attached to the report.

 

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Annotation of the results obtained in 2022
All planned tasks of the project were solved in full. Goals have been achieved. The most valuable research results are as follows: 1. Characteristics of a typical source of ignition in rooms at the stages of initiation and combustion have been established. The main stages of combustion of model foci are identified. It is shown that the stages can be determined both by the characteristics of thermocouple trends and by the results of gas analysis: the stages of ignition and combustion of the hearth are characterized by an increase in the concentrations of CO2, CO, a decrease in the concentration of O2, and an increase in the temperature in the room; the smoldering stage is characterized by a decrease in the CO2 concentration, reaching constant values of the CO concentration, a slight increase in the O2 concentration, as well as a decrease in the temperature in the room. 2. A comparative analysis of promising methods for the chemical analysis of the composition of gaseous products of pyrolysis and combustion of synthetic and natural materials that make up the fire load of residential and public buildings has been carried out. The techniques are based on the use of gas and gas-liquid chromatography, mass spectrometry, infrared and ultraviolet spectroscopy, and spectroscopy in the visible region. Data were obtained on the qualitative and quantitative composition of the combustion products of wood, textile and finishing products. The toxicity indices of the components of combustion products have been determined. 3. Efficient (in terms of extinguishing time and spent volume of extinguishing composition) layouts of nozzle devices are determined. It has been established that in a room layout corresponding to a rectangular truncated pyramid, it is inappropriate to place the nozzle on the side surface, since in this case a blind zone arises, which increases with the height of the nozzle relative to the base of the room. 4. When conducting experimental studies with a wide group of materials and substances, it was found that the highest yield of toxic substances corresponds to the thermal decomposition of leather, wool, foam rubber and paper. The concentrations of some toxic substances (in particular, C2H6, C2H4, CO) formed during the thermal decomposition of the listed materials are 1.1–3.3 times higher than in the case of wood. These indicators allow you to quickly and accurately identify the relevant materials in the composition of the fire in the room. 5. It has been experimentally substantiated that in the presence of feedback to determine that the extinguishing process is proceeding successfully, it is advisable to use a gas analysis system and thermal sensors (in case of their preliminary operation). It has been established that the concentration of CO during the interaction of the extinguishing liquid with the fire source increases to 0.7-1.2%, which indicates a slowdown in flame combustion, and thermal sensors stop working when the temperature of the gas medium drops below 80 ºC, which indicates a gradual decrease in the heat release of the fire source. It has been established that as an additional parameter confirming extinguishing, information from the video recording equipment (camera) should be used in real time. 6. Approximation expressions are formulated for predicting the delay time of fire safety sensors at different distances from the source of fire with different materials. The formulated expressions take into account the defining parameters: the distance of the sensors from the surface of the material, the area and volume of the premises. 7. The times for extinguishing fires in a room were determined using different fire extinguishing compositions (foaming agent, bentonite, bischofite, OS-5, FR-Les 01, Mig-09). It has been established that a decrease in the surface tension of fire-extinguishing compositions contributes to a 2-3-fold reduction in the time to extinguish a fire. It is shown that the use of OS-5 solution and bentonite suspension is ineffective in extinguishing model fires consisting of cardboard. It has been experimentally substantiated that the delay time for the operation of fire detectors, as well as the value of the irrigation density of the combustion center, is reduced by almost 2 times with the use of chemical additives to water. 8. As a result of the studies performed, the main features and characteristics of shielding the thermal radiation of the fire seat using liquid curtains were established, the ratios of radiant heat fluxes in the absence and presence of a liquid curtain were calculated. 9. The obtained results of numerical studies of the concentration of pyrolysis products and combustion of materials at different distances relative to the potential source are the basis for designing fire safety systems for buildings, taking into account gas analytical systems. The calculations performed made it possible to establish a relationship between the dimensions of the premises and the source of ignition and the ranges of concentrations of gaseous pyrolysis products. It has been established that the achievement of the threshold level of CO concentrations when the gas sensor is located at a distance of 0.9 m (the height of the room (compartment) is 1 m) occurs 49 s faster relative to the height of the location of the sensors at a height of 1.5 m (the height of the room is 2.5 m). 10. Efficient conditions for the use of different types of ventilation of premises have been established to exclude the conditions for the formation of a fire-explosive mixture of pyrolysis products, evaporation, combustion, an oxidizing agent (air) for different categories of premises. Efficient adaptive approaches to smoke deposition in the early stages of fire development with the use of limited volumes of liquids have been established, and smoke removal methods using a supply and exhaust ventilation system have been considered from the point of view of efficiency. For smoke deposition, it is more efficient to use pulsed water supply rather than continuous spraying. Such a choice in practice helps to reduce the amount of water used, and also minimizes potential losses from the flood of the premises. 11. Models have been created to control the characteristics of the processes of identifying a fire, its localization and suppression at an early stage, smoke deposition and smoke removal, taking into account real-time information from sensors located in the room, for the rational consumption of a fire extinguishing agent (water, solution, emulsion, suspension) and optimization localization and suppression time. These models are verified by comparative analysis and comparison with data from test experiments on a test bench. 12. 4 applications for patents for inventions of developed methods and devices were prepared (for 2 applications, positive FIPS conclusions were received, 1 application passed a formal examination, 1 application was sent for consideration). 13. Applications for obtaining certificates of state registration of computer programs with developed models have been prepared (for one application, a certificate has been received, the second application is under consideration). 14. Articles with the results of experimental and theoretical studies were prepared for publication in the leading specialized international and all-Russian journals in accordance with the undertaken obligations. 15. Reports were made with the results of research at specialized international and all-Russian conferences. 16. The limits of applicability of scientifically based solutions proposed based on the results of experiments and mathematical modeling are determined. A detailed report on the work done is presented in the attached file with additional materials. A detailed description of all results in Russian is given in an additional file at https://file.tpu.ru/index.php/s/mjJ1alxdkCbSa9O.

 

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