KRYVORUCHKO Y. Improvement of Fire Extinguishing Techniques Using Fine Water Spray.

The dissertation is devoted to solving an important scientific and practical problem in the field of fire safety, namely: improving the efficiency of fire extinguishing through the use of a fine water spray generated by a periodically-impulsive fire suppression system. In the first section analyzes the physicochemical properties of water as a fire extinguishing agent, including the thermodynamic properties of water that are important in firefighting. The feasibility of using continuous, sprayed, and fine water mist streams for fire suppression is reviewed and substantiated. It is established that the highest extinguishing efficiency is achieved when water is applied in the form of fine mist; in this case, the extinguishing effectiveness of water depends on the droplet size (dispersion) and the intensity of the agent's application. The second section presents the research on water atomization by a shock wave within the barrel of a periodic-impulse fire suppression unit, as well as the investigation of fine water mist distribution within a model room. Mathematical models were substantiated and developed, and subsequently processed using specialized software for simulating the processes of water pressurization into the barrel of the periodic-impulse fire suppression unit, its subsequent atomization by a shock wave, and the dispersion of fine water mist in the model room. The third section presents research on a fire suppression unit utilizing a gas-detonation principle for accelerating liquid. Studies were conducted to determine the operational parameters of the unit and its tactical and technical characteristics during the formation of a fine water mist stream. The development of impulse systems for firefighting using fine water mist was investigated. It was established that, at a propane-oxygen charge pressure of 0.1 MPa and a barrel inclination angle of 30°, the range of the water jet exceeded 15 meters, with a maximum spray cone radius of up to 3 meters. The fourth section presents research on fire suppression using a fine water mist generated by water atomization through detonation products within the barrel of a periodic-impulse fire suppression unit. In this fine water mist suppression system, water is supplied to the barrel continuously, while pulsed atomization by detonation products occurs at a frequency of 23-24 Hz. The process of continuously supplied water being atomized by pulsed gas flows generated by detonation constitutes a subject of significant scientific and practical interest. The fifth section presents experimental research on the formation of a fine water mist stream under the influence of a shock wave. The experiments determined that the dispersion length of the fine water mist stream was 34 meters, with a height of 2.1 meters. It was also found that the most intense droplet deposition occurred at a distance of 3 meters from the barrel of the periodic-impulse fire suppression unit, forming a deposition area with dimensions of 8×1.9 meters. The root mean square water flow rate during the discharge of the fine mist stream was 5.51 ± 1.9140.9 l/min. The research further determined the delay time for mist discharge from the pipeline depending on its total length, as well as the amount of water that condensed inside the pipeline. Practical recommendations were developed for the use of the periodic-impulse fire suppression unit in delivering fine water mist for fire extinguishing. Scientific Novelty of the Obtained Results: 1. For the first time, the features of filling a model room with a fine water mist stream with a droplet size of 5 μm have been identified, including the determination of the propagation velocity of the extinguishing capacity of the fine water mist in the model environment. 2. For the first time, based on theoretical calculations, it has been established that the main water atomization process occurs not under the influence of the shock wave itself, but under the action of a high-velocity gas flow trailing the shock wave. 3. The methods of delivering extinguishing agents to the fire source have been improved by generating a fine water mist stream through pipelines of complex geometry, and the proportion of water condensed within the pipeline has been determined. 4. The method of forming a fine water mist stream has been improved through continuous water supply to the nozzle and periodic exposure of water filaments inside the barrel to intense shock waves at a frequency of 23 Hz or higher, leading to efficient atomization of water flowing along the inner walls of the periodic-impulse fire suppression unit. 5. The technique of fire suppression using a fine water mist stream has been further developed through the application of a gas-detonation-based liquid acceleration principle, which significantly reduces the charge consumption required to accelerate the extinguishing agent.